Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR THE PREPARATION OF FORMIC ACID BY REACTING CARBON
DIOXIDE WITH HYDROGEN
Description
The invention relates to a process for preparing formic acid by reacting
carbon dioxide with
hydrogen in a hydrogenation reactor in the presence of a catalyst comprising
an element
of group 8, 9 or 10 of the Periodic Table, a tertiary amine and a polar
solvent to form
formic acid-amine adducts which are subsequently dissociated thermally into
formic acid
and tertiary amine.
Adducts of formic acid and tertiary amines can be dissociated thermally into
free formic
acid and tertiary amine and therefore serve as intermediates in the
preparation of formic
acid.
Formic acid is an important and versatile product. It is used, for example,
for acidification
in the production of animal feeds, as preservative, as disinfectant, as
auxiliary in the textile
and leather industry, as a mixture with its salts for deicing aircraft and
runways and also as
synthetic building block in the chemical industry.
The abovementioned adducts of formic acid and tertiary amines can be prepared
in
various ways, for example (i) by direct reaction of the tertiary amine with
formic acid, (ii) by
hydrolysis of methyl formate to formic acid in the presence of the tertiary
amine, (iii) by
catalytic hydration of carbon monoxide in the presence of the tertiary amine
or (iv) by
hydrogenation of carbon dioxide to formic acid in the presence of the tertiary
amine. The
last-named process of catalytic hydrogenation of carbon dioxide has the
particular
advantage that carbon dioxide is available in large quantities and is flexible
in terms of its
source.
EP 0 095 321 decribes a process for preparing trialkylammonium formates, i.e.
an adduct
of formic acid and a tertiary amine, by hydrogenation of carbon dioxide in the
presence of
a tertiary amine, a solvent and a transition metal catalyst of transition
group VIII of the
Periodic Table (groups 8, 9, 10 according to the IUPAC nomenclature).
Ruthenium
trichloride is preferably used as catalyst. As tertiary amine and solvent,
preference is given
to triethylamine and a mixture of isopropanol and water. The reaction is
carried out in an
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autoclave at 82 bar and 80 C. The reaction mixture is worked up by
distillation to give a
first fraction comprising isopropanol, water and triethylamine and a second
fraction
comprising the adduct of formic acid and triethylamine. The thermal
dissociation of the
adduct of formic acid and triethylamine to form formic acid is not described
in EP 0 095
321.
EP 0 151 510 likewise describes a process for preparing adducts of formic acid
and
triethylamine, in which a rhodium-comprising complex catalyst is used as
catalyst. The
reaction is likewise carried out in an autoclave, and, as in EP 0 095 321, the
work-up of the
reaction mixture obtained is carried out by distillation.
EP 0 126 524 and EP 0 181 078 describe a process for preparing formic acid by
thermal
dissociation of adducts of formic acid and a tertiary amine. According to EP 0
181 078, the
process for preparing formic acid comprises the following steps:
i) reaction of carbon dioxide and hydrogen in the presence of a volatile
tertiary amine
and a catalyst to give the adduct of formic acid and the volatile tertiary
amine,
ii) separation of the adduct of formic acid and volatile tertiary amine
from the catalyst
and the gaseous components in an evaporator,
iii) separation of the unreacted volatile tertiary amine from the adduct of
formic acid
and the volatile tertiary amine in a distillation column or in a phase
separation
apparatus,
iv) base exchange of the volatile tertiary amine in the adduct of formic acid
and the
volatile tertiary amine by a less volatile and weaker nitrogen base, for
example
1-n-butylimidazole,
v) thermal dissociation of the adduct of formic acid and the less volatile and
weaker
nitrogen base to give formic acid and the less volatile and weaker nitrogen
base.
In EP 0 126 524 and EP 0 181 078, the volatile tertiary amine in the formic
acid adduct
must be replaced by a less volatile and weaker nitrogen base, for example 1-n-
butylimidazole, before the thermal dissociation. The processes according to EP
0 126 524
and EP 0 181 078 are therefore very complicated, especially in respect of the
base
exchange which is absolutely necessary.
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A further significant disadvantage of the processes according to EP 0 126 524
and
EP 0 181 078 is the fact that the isolation of the adduct of formic acid and
volatile tertiary
amine is carried out in an evaporator in the presence of the catalyst in
accordance with the
above-described step ii) of EP 0 126 524 and EP 0 181 078.
This catalyzes the redissociation of the adduct of formic acid and volatile
tertiary amine
into carbon dioxide, hydrogen and volatile tertiary amine according to the
following
reaction equation:
H CO OH -1\1 R3 Cat C 02 + H2+ N R3
The redissociation leads to a significant decrease in the yield of adduct of
formic acid and
volatile tertiary amine and thus to a reduction in the yield of the target
product formic acid.
In EP 0 329 337 the addition of an inhibitor which reversibly inhibits the
catalyst is
proposed as a solution to this problem. As preferred inhibitors, mention is
made of
carboxylic acids, carbon monoxide and oxidants. The preparation of formic acid
therefore
comprises the steps i) to v) described above for EP 0 126 524 and EP 0 181
078, with the
addition of the inhibitor being carried out after step i) and before or during
step ii).
Disadvantages of the process according to EP 0 329 337 are not only the
complicated
base exchange (step iv)) but also the fact that the inhibitor goes together
with the
recirculated tertiary amine into the hydrogenation (step (i)) and there
interferes in the
synthesis to form the adduct of formic acid and volatile tertiary amine. A
further
disadvantage of EP 0 329 337 is that a major part of the catalyst present in
the process is
inhibited. The inhibited catalyst therefore has to be reactivated in the
process according to
EP 0 329 337 before renewed use in the hydrogenation (step i)).
WO 2010/149507 describes a process for preparing formic acid by hydrogenation
of
carbon dioxide in the presence of a tertiary amine, a transition metal
catalyst and a high-
boiling polar solvent having an electrostatic factor of 200'10-3 Cm, for
example ethylene
glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,3-
propanediol, 2-methyl-
1,3-propanediol, 1,4-butanediol, dipropylene glycol, 1,5-pentanediol, 1,6-
hexanediol and
glycerol. A reaction mixture comprising the formic acid-amine adduct, the
tertiary amine,
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the high-boiling polar solvent and the catalyst is obtained. The reaction
mixture is,
according to WO 2010/149507, worked up according to the following steps:
1) phase separation of the reaction mixture to give an upper phase comprising
the
tertiary amine and the catalyst and a lower phase comprising the formic acid-
amine adduct, the high-boiling polar solvent and catalyst residues;
recirculation
of the upper phase to the hydrogenation,
2) extraction of the lower phase with the tertiary amine to give an extract
comprising the tertiary amine and catalyst residues and a raffinate comprising
the high-boiling polar solvent and the formic acid-amine adduct; recirculation
of
the extract to the hydrogenation,
3) thermal dissociation of the raffinate in a distillation column to give a
distillate
comprising the formic acid and a bottoms mixture comprising the free tertiary
amine and the high-boiling polar solvent; recirculation of the high-boiling
polar
solvent to the hydrogenation.
The process of WO 2010/149507 has the advantage over the processes of
EP 0 095 321, EP 0 151 510, EP 0 126 524, EP 0 181 078 and EP 0 329 337 that
it makes
do without the complicated base exchange step (step (iv)) and allows isolation
and
recirculation of the catalyst in its active form.
However, the process of WO 2010/149507 has the disadvantage that the isolation
of the
catalyst is not always complete despite the phase separation (step 1)) and
extraction (step
2)), so that traces of catalyst comprised in the raffinate can, in the thermal
dissociation in
the distillation column in step 3), catalyze the redissociation of the formic
acid-amine
adduct into carbon dioxide and hydrogen and the tertiary amine. A further
disadvantage is
that in the thermal dissociation of the formic acid-amine adduct in the
distillation column,
esterification of the formic acid formed with the high-boiling polar solvents
(diols and
polyols) occurs. This leads to a reduction in the yield of the target product
formic acid.
It was an object of the present invention to provide a process for preparing
formic acid by
hydrogenating carbon dioxide, which process does not have the abovementioned
disadvantages of the prior art or has them only to a significantly reduced
extent and leads
to concentrated formic acid in high yield and high purity. Furthermore, the
process should
be carried out more simply than described in the prior art, in particular
should allow a
simpler process concept for the work-up of the output from the hydrogenation
reactor,
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simpler process steps, a lower number of process steps or simpler apparatuses.
Furthermore, the process should also be able to be carried out with a very low
energy
consumption. Since complete separation of the homogeneously dissolved active
catalyst
from the product stream can be achieved only with a very high outlay and even
small
5 amounts of catalyst in the thermal dissociation would lead to significant
losses of formic
acid because of the high temperatures, it should also be ensured that traces
of catalyst are
converted into inactive species before the distillation, without the
hydrogenation being
adversely affected.
The object is achieved by a process for preparing formic acid, which comprises
the steps
(a) homogeneously catalyzed reaction of a reaction mixture (Rg)
comprising carbon
dioxide, hydrogen, at least one catalyst comprising at least one element
selected
from groups 8, 9 and 10 of the Periodic Table, at least one polar solvent
selected
from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-
butanol,
2-butanol, 2-methyl-1-propanol and water and also at least one tertiary amine
of
the general formula (Al)
NR1R2R3 (Al),
where
R1, R2, R3 are each, independently of one another, an unbranched or branched,
acyclic or cyclic, aliphatic, araliphatic or aromatic radical having in each
case from
1 to 16 carbon atoms, where individual carbon atoms may, independently of one
another, also be replaced by a heterogroup selected from among the groups -0-
and >N- and two or all three radicals can also be joined to one another to
form a
chain comprising at least four atoms,
in a hydrogenation reactor
to give, optionally after addition of water, a two-phase hydrogenation mixture
(H)
comprising
an upper phase (U1), which comprises the at least one catalyst and the at
least
one tertiary amine (Al) and
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a lower phase (L1) which comprises the at least one polar solvent, residues of
the
at least one catalyst and also at least one formic acid-amine adduct of the
general
formula (A2),
NR1R2R3* x, HCOOH (A2),
where
x, is in the range from 0.4 to 5 and
R1, R2, R3 are as defined above,
(b) work-up of the hydrogenation mixture (H) obtained in step (a)
according to one of
the following steps
(bl) phase separation of the hydrogenation mixture (H) obtained in step (a)
into
the upper phase (U1) and the lower phase (L1) in a first phase separation
apparatus
or
(b2) extraction of the at least one catalyst from the hydrogenation mixture
(H)
obtained in step (a) by means of an extractant comprising at least one
tertiary amine (Al) in an extraction unit to give
a raffinate (R1) comprising the at least one formic acid-amine adduct (A2)
and the at least one polar solvent and
an extract (El) comprising the at least one tertiary amine (Al) and the at
least one catalyst
or
(b3) phase separation of the hydrogenation mixture (H) obtained in step (a)
into
the upper phase (U1) and the lower phase (L1) in a first phase separation
apparatus and extraction of the residues of the at least one catalyst from the
lower phase (L1) by means of an extractant comprising the at least one
tertiary amine (Al) in an extraction unit to give
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a raffinate (R2) comprising the at least one formic acid-amine adduct (A2)
and the at least one polar solvent and
an extract (E2) comprising the at least one tertiary amine (Al) and the
residues of the at least one catalyst,
(c) at least partial separation of the at least one polar solvent from the
lower phase
(L1), from the raffinate (R1) or from the raffinate (R2) in a first
distillation unit to
give
a distillate (D1) comprising the at least one polar solvent, which is
recirculated to
the hydrogenation reactor in step (a), and
a two-phase bottoms mixture (S1) comprising
an upper phase (U2) which comprises the at least one tertiary amine (Al) and
a lower phase (L2) which contains the at least one formic acid-amine adduct
(A2),
(d) optionally work-up of the first bottoms mixture (S1) obtained in step
(c) by phase
separation in a second phase separation apparatus to give the upper phase (U2)
and the lower phase (L2),
(e) dissociation of the at least one formic acid-amine adduct (A2)
comprised in the
bottoms mixture (S1) or optionally in the lower phase (L2) in a thermal
dissociation unit to give the at least one tertiary amine (Al), which is
recirculated
to the hydrogenation reactor in step (a), and formic acid, which is discharged
from
the thermal dissociation unit,
wherein at least one inhibitor selected from the group consisting of
carboxylic acids other
than formic acid, carboxylic acid derivatives other than formic acid
derivatives and oxidants
is added to the lower phase (L1), the raffinate (R1) or the raffinate (R2)
directly before
and/or during step (c).
It has been found that formic acid can be obtained in high yield by means of
the process of
the invention. It is particularly advantageous that the base exchange (step
(iv)) as per the
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processes of EP 0 126 524 and EP 0 181 078 can be saved in the process of the
invention. The process of the invention allows effective isolation of the
catalyst in its active
form and also recirculation of the catalyst which has been separated off to
the
hydrogenation reactor in step (a). In addition, the use of an inhibitor
prevents the
redissociation of the formic acid-amine adduct (A2), which leads to an
increase in the
formic acid yield. Furthermore, the removal of the polar solvent used
according to the
invention prevents esterification of the formic acid obtained in the thermal
dissociation unit
in step (e), which likewise leads to an increase in the formic acid yield. In
addition, it has
surprisingly been found that the use of the polar solvent according to the
invention leads to
an increase in the concentration of the formic acid-amine adduct (A2) in the
hydrogenation
mixture (H) obtained in step (a) compared to the polar solvents used in
W02010/149507.
This makes the use of smaller reactors possible, which in turn leads to a cost
saving.
The terms "step" and "process step" are used synonymously in the following.
Preparation of the formic acid-amine adduct (A2): process step (a)
In process step (a) of the process of the invention, a reaction mixture (Rg)
which
comprises carbon dioxide, hydrogen, at least one catalyst comprising at least
one element
selected from groups 8, 9 and 10 of the Periodic Table, at least one polar
solvent selected
from the group consisting of methanol, ethanol, 1-propanol, 1-butanol, 2-
butanol, 2-methyl-
1-propanol and water and also at least one tertiary amine of the general
formula (Al) is
reacted in a hydrogenation reactor.
The carbon dioxide used in process step (a) can be solid, liquid or gaseous.
It is also
possible to use industrially available gas mixtures comprising carbon dioxide,
as long as
these are largely free of carbon monoxide (proportion by volume of <1% of CO).
The
hydrogen used in the hydrogenation of carbon dioxide in process step (a) is
generally
gaseous. Carbon dioxide and hydrogen can also comprise inert gases such as
nitrogen or
noble gases. However, the content of these is advantageously below 10 mol%,
based on
the total amount of carbon dioxide and hydrogen in the hydrogenation reactor.
Although
large amounts may likewise be tolerable, they generally result in the use of a
higher
pressure in the reactor, which makes further compression energy necessary.
Carbon dioxide and hydrogen can be introduced as separate streams into process
step
(a). It is also possible to use a mixture comprising carbon dioxide and
hydrogen in process
step (a).
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In the process of the invention, at least one tertiary amine (Al) is used in
the
hydrogenation of carbon dioxide in process step (a). For the purposes of the
present
invention, the term "tertiary amine (A1)" refers to both one tertiary amine
(Al) and also
mixtures of two or more tertiary amines (Al).
The tertiary amine (Al) used in the process of the invention is preferably
selected or
matched to the polar solvent in such a way that the hydrogenation mixture (H)
obtained,
optionally after addition of water, in process step (a) is an at least two-
phase mixture. The
hydrogenation mixture (H) comprises an upper phase (U1), which comprises the
at least
one catalyst and the at least one tertiary amine (Al), and a lower phase (L1),
which
comprises the at least one polar solvent, residues of the catalyst and at
least one formic
acid-amine adduct (A2).
The tertiary amine (Al) should be enriched in the upper phase (U1), i.e. the
upper phase
(U1) should comprise the major part of the tertiary amine (Al). For the
purposes of the
present invention, "enriched" or "major part" in respect of the tertiary amine
(Al) means a
proportion by weight of the free tertiary amine (Al) in the upper phase (U1)
of > 50%
based on the total weight of the free tertiary amine (Al) in the liquid
phases, i.e. the upper
phase (U1) and the lower phase (L1) in the hydrogenation mixture (H).
For the present purposes, free tertiary amine (Al) is the tertiary amine (Al)
which is not
bound in the form of the formic acid-amine adduct (A2).
The proportion by weight of the free tertiary amine (Al) in the upper phase
(U1) is
preferably > 70%, in particular > 90%, in each case based on the total weight
of the free
tertiary amine (Al) in the upper phase (U1) and the lower phase (L1) in the
hydrogenation
mixture (H).
The tertiary amine (Al) is generally selected by a simple test in which the
phase behavior
and the solubility of the tertiary amine (Al) in the liquid phases (upper
phase (U1) and
lower phase (L1)) are determined experimentally under the process conditions
in process
step (a). In addition, nonpolar solvents such as aliphatic, aromatic or
araliphatic solvents
can be added to the tertiary amine (Al). Preferred nonpolar solvents are, for
example,
octane, toluene and/or xylenes (o-xylene, m-xylene, p-xylene).
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The tertiary amine which is preferably to be used in the process of the
invention is an
amine of the general formula
NR1R2R3 (Al)
5
in which the radicals R1, R2, R3 are identical or different and are each,
independently of
one another, an unbranched or branched, acyclic or cyclic, aliphatic,
araliphatic or
aromatic radical having in each case from 1 to 16 carbon atoms, preferably
from 1 to 12
carbon atoms, where individual carbon atoms can also be, independently of one
another,
10 replaced by a heterogroup selected from among the groups -0- and >N-
and two or three
radicals can also be joined to one another to form a chain comprising at least
four atoms.
In a particularly preferred embodiment, a tertiary amine of the general
formula (Al) is
used, with the proviso that the total number of carbon atoms is at least 9.
As suitable tertiary amines of the formula (Al), mention may be made by way of
example
of:
= tri-n-propylamine, tri-n-butylamine, tri-n-pentylamine, tri-n-hexylamine,
tri-n-
heptylamine, tri-n-octylamine, tri-n-nonylamine, tri-n-decylamine, tri-n-
undecylamine,
tri-n-dodecylamine, tri-n-tridecylamine, tri-n-tetradecylamine, tri-n-
pentadecylamine,
tri-n-hexadecylamine, tri(2-ethylhexyl)amine.
= dimethyldecylamine, dimethyldodecylamine, dimethyltetradecylamine,
ethyldi(2-
propyl)amine, dioctylmethylamine, dihexylmethylamine.
= tricyclopentylamine, tricyclohexylamine, tricycloheptylamine,
tricyclooctylamine and
derivatives thereof substituted by one or more methyl, ethyl, 1-propyl, 2-
propyl,
1-butyl, 2-butyl or 2-methyl-2-propyl groups.
= dimethylcyclohexylamine, methyldicyclohexylamine, diethylcyclohexylamine,
ethyldicyclohexylamine, dimethylcyclopentylamine, methyldicyclopentylamine.
= triphenylamine, methyldiphenylamine, ethyldiphenylamine,
propyldiphenylamine,
butyldiphenylamine, 2-ethylhexyldiphenylamine,
dimethylphenylamine,
diethylphenylamine, dipropylphenylamine, dibutylphenylamine, bis(2-ethylhexyl)-
phenylamine, tribenzylamine, methyldibenzylamine, ethyldibenzylamine and
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derivatives thereof substituted by one or more methyl, ethyl, 1-propyl, 2-
propyl,
1-butyl, 2-butyl or 2-methyl-2-propyl groups.
= N-C1-C12-alkylpiperidines, N,N-di-C1-C12-alkylpiperazines, N-C1-C12-
alkylpyrrolidones,
N-C1-C12-alkylimidazoles and derivatives thereof substituted by one or more
methyl,
ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl or 2-methyl-2-propyl groups.
= 1 ,8-diazabicyclo[5.4.0]undec-7-ene
("DBU"), 1 ,4-diazabicyclo[2.2.2]octane
("DABCO"), N-methyl-8-azabicyclo[3.2. 1 ]octane
("tropane"), N-methy1-9-
azabicyclo[3.3.1 ]nonane ("granatane"), 1-azabicyclo[2.2.2]octane
("quinuclidine").
Mixtures of two or more different tertiary amines (Al) can also be used in the
process of
the invention.
Particular preference is given to using an amine in which the radicals R1, R2,
R3 are
selected independently from the group consisting of C1-C12-alkyl, C5-C8-
cycloalkyl, benzyl
and phenyl as tertiary amine of the general formula (Al) in the process of the
invention.
Particular preference is given to using a saturated amine, i.e. an amine
comprising only
single bonds, of the general formula (Al) as tertiary amine in the process of
the invention.
Very particular preference is given to using an amine of the general formula
(Al) in which
the radicals R1, R2, R3 are selected independently from the group consisting
of C5-C8-alkyl,
in particular tri-n-pentylamine, tri-n-hexylamine, tri-n-heptylamine, tri-n-
octylamine,
dimethylcyclohexylamine, methyldicyclohexylamine, dioctylmethylamin and
dimethyldecylamine, as tertiary amine in the process of the invention.
In an embodiment of the process of the invention, one tertiary amine of the
general
formula (Al) is used.
In particular, an amine of the general formula (Al) in which the radicals R1,
R2, R3 are
selected independently from among C5- and C8-alkyl is used as tertiary amine.
Tri-n-
hexylamine is most preferably used as tertiary amine of the general formula
(Al) in the
process of the invention.
The tertiary amine (Al) is preferably present in liquid form in all process
steps in the
process of the invention. However, this is not an absolute requirement. It
would also be
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12
sufficient if the tertiary amine (Al) were to be at least dissolved in
suitable solvents.
Suitable solvents are in principle those which are chemically inert in respect
of the
hydrogenation of carbon dioxide, in which the tertiary amine (Al) and the
catalyst dissolve
readily and in which, conversely, the polar solvent and the formic acid-amine
adduct (A2)
are sparingly soluble. Possibilities are therefore in principle chemically
inert, nonpolar
solvents such as aliphatic, aromatic or araliphatic hydrocarbons, for example
octane and
higher alkanes, toluene, xylenes.
In the process of the invention, at least one polar solvent selected from the
group
consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol,
2-methyl-1-
propanol and water is used in the hydrogenation of carbon dioxide in process
step (a).
For the purposes of the present invention, the term "polar solvent" refers
both to one polar
solvent and also mixtures of two or more polar solvents.
The polar solvent used in the process of the invention is preferably selected
or matched to
the tertiary amine (Al) in such a way that the phase behavior in the
hydrogenation reactor
in process step (a) preferably satisfies the following criteria: the polar
solvent should
preferably be selected so that the hydrogenation mixture (H) obtained in
process step (a)
is an at least two-phase mixture. The polar solvent should be enriched in the
lower phase
(L1), i.e. the lower phase (L1) should comprise the major part of the polar
solvent. For the
purposes of the present invention, "enriched" or "major part" in the context
of the polar
solvent means a proportion by weight of the polar solvent in the lower phase
(L1) of > 50%
based on the total weight of the polar solvent in the liquid phases (upper
phase (U1) and
lower phase (L1)) in the hydrogenation reactor.
The proportion by weight of the polar solvent in the lower phase (L1) is
preferably
> 70%, in particular > 90%, in each case based on the total weight of the
polar solvent in
the upper phase (U1) and the lower phase (L1).
The choice of the polar solvent which satisfies the abovementioned criteria is
generally
made by means of a simple experiment in which the phase behavior and
solubility of the
polar solvent in the liquid phases (upper phase (U1) and lower phase (L1)) are
determined
experimentally under the process conditions in process step (a).
The polar solvent can be a pure polar solvent or a mixture of two or more
polar solvents,
as long as the polar solvent or mixture of polar solvents satisfies the
abovementioned
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criteria in respect of phase behavior and solubility in the upper phase (U1)
and the lower
phase (L1) in the hydrogenation reactor in process step (a).
In an embodiment of the process of the invention, a single-phase hydrogenation
mixture is
firstly obtained in step (a) and this is converted by addition of water into
the two-phase
hydrogenation mixture (H).
In a further embodiment of the process of the invention, the two-phase
hydrogenation
mixture (H) is obtained directly in step (a). The two-phase hydrogenation
mixture (H)
obtained according to this embodiment can be passed directly to the work-up
according to
step (b). It is also possible for water to be additionally added to the two-
phase
hydrogenation mixture (H) before the further work-up in step (b). This can
lead to an
increase in the partition coefficient PK.
When a mixture of alcohol and water is used as polar solvent, the ratio of
alcohol to water
is selected so that, together with the formic acid-amine adduct (A2) and the
tertiary amine
(Al), an at least two phase hydrogenation mixture (H) comprising the upper
phase (U1)
and the lower phase (L1) is formed.
It is also possible, for the case where a mixture of alcohol (selected from
the group
consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol
and 2-
methyl-1-propanol) and water is used as polar solvent, that the ratio of
alcohol to water is
selected so that, together with the formic acid-amine adduct (A2) and the
tertiary amine
(Al), a single-phase hydrogenation mixture is initially formed and is
subsequently
converted into the two-phase hydrogenation mixture (H) by addition of water.
In a further particularly preferred embodiment, water, methanol or a mixture
of water and
methanol is used as polar solvent.
The use of diols and formic esters thereof, polyols and formic esters thereof,
sulfones,
sulfoxides and open-chain or cyclic amides as polar solvent is not preferred.
In a preferred
embodiment, these polar solvents are not present in the reaction mixture (Rg).
The molar ratio of the polar solvent or solvent mixture used in process step
(a) of the
process of the invention to the tertiary amine (Al) used is generally from 0.5
to 30 and
preferably from 1 to 20.
CA 02838907 2013-12-10
14
The catalyst used in process step (a) of the process of the invention for
hydrogenating
carbon dioxide comprises at least one element selected from groups 8, 9 and 10
of the
Periodic Table (nomenclature according to IUPAC). Groups 8, 9 and 10 of the
Periodic
Table comprise Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt. In process step (a), it
is possible to
use one catalyst or a mixture of two or more catalysts. Preference is given to
using one
catalyst. For the purposes of the present invention, the term "catalyst"
refers to both one
catalyst and mixtures of two or more catalysts.
The catalyst preferably comprises at least one element selected from the group
consisting
of Ru, Rh, Pd, Os, Ir and Pt, particularly preferably at least one element
from the group
consisting of Ru, Rh and Pd. The catalyst very particularly preferably
comprises Ru.
Preference is given to using a complex-type compound (complex catalyst) of the
abovementioned elements as catalyst. The reaction in process step (a) is
preferably
carried out homogeneously catalyzed.
For the purposes of the present invention, homogeneously catalyzed means that
the
catalytically active part of the complex-type compound (the complex catalyst)
is at least
partly present in solution in the liquid reaction medium. In a preferred
embodiment, at least
90% of the complex catalyst used in process step (a) is present in solution in
the liquid
reaction medium, more preferably at least 95%, particularly preferably more
than 99%, and
the complex catalyst is most preferably entirely present in solution in the
liquid reaction
medium (100%), in each case based on the total amount of the complex catalyst
present
in the liquid reaction medium.
The amount of the metal components of the complex catalyst in process step (a)
is
generally from 0.1 to 5000 ppm by weight, preferably from 1 to 800 ppm by
weight and
particularly preferably from 5 to 800 ppm by weight, in each case based on the
total liquid
reaction mixture (Rg) in the hydrogenation reactor. The complex catalyst is
selected so
that it is enriched in the upper phase (U1), i.e. the upper phase (U1)
comprises the major
part of the catalyst. For the purposes of the present invention, "enriched" or
"major part" in
the context of the complex catalyst means a partition coefficient of the
complex catalyst PK
= [concentration of the complex catalyst in the upper phase (U1)] /
[concentration of the
complex catalyst in the lower phase (L1)] of > 1. Preference is given to a
partition
coefficient PK > 1.5 and particular preference is given to a partition
coefficient PK > 4. The
choice of the complex catalyst is generally made by means of a simple
experiment in
which the phase behavior and the solubility of the complex catalyst in the
liquid phases
CA 02838907 2013-12-10
(upper phase (U1) and lower phase (L1)) are determined experimentally under
the process
conditions in process step (a).
Owing to their good solubility in tertiary amines, homogeneous catalysts, in
particular a
5 metal-organic complex comprising an element of group 8, 9 or 10 of the
Periodic Table
and at least one phosphine group having at least one unbranched or branched,
acyclic or
cyclic, aliphatic radical having from 1 to 12 carbon atoms, where individual
carbon atoms
may also be substituted by >P-, are preferably used as catalysts in the
process of the
invention. The term "branched cyclic aliphatic radicals" also encompasses
radicals such as
10 ¨CH2-C61-111. Suitable radicals are, for example, methyl, ethyl, 1-
propyl, 2-propyl, 1-butyl, 1-
(2-methyl)propyl, 2-(2-methyl)propyl, 1-pentyl, 1-hexyl, 1-heptyl, 1-octyl, 1-
nonyl, 1-decyl,
1-undecyl, 1-dodecyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl,
methylcyclopentyl, methylcyclohexyl, 1-(2-methyl)pentyl,
1-(2-ethyl)hexyl, 1-(2-
propyl)heptyl and norbornyl. The unbranched or branched, acyclic or cyclic,
aliphatic
15 radical preferably comprises at least 1 and preferably not more than 10
carbon atoms. In
the case of an exclusively cyclic radical in the abovementioned sense, the
number of
carbon atoms is from 3 to 12 and preferably at least 4 and preferably not more
than 8
carbon atoms. Preferred radicals are ethyl, 1-butyl, sec-butyl, 1-octyl and
cyclohexyl.
The phosphine group can comprise one, two or three of the abovementioned
unbranched
or branched, acyclic or cyclic, aliphatic radicals. These can be identical or
different. The
phosphine group preferably comprises three of the abovementioned unbranched or
branched, acyclic or cyclic, aliphatic radicals, with particular preference
being given to all
three radicals being identical. Preferred phosphines are P(n-CnH2,1)3 where n
is from 1 to
10, particularly preferably tri-n-butylphosphine, tri-n-octylphosphine and 1,2-
bis(dicyclohexylphosphino)ethane.
As mentioned above, individual carbon atoms in the abovementioned unbranched
or
branched, acyclic or cyclic, aliphatic radicals can also be substituted by >P-
. Polydentate,
for example bidentate or tridentate, phosphine ligands are thus also
comprised. These
preferably comprise the groups
>P-CH2CH2-P< or >P-CH2CH2-P-CH2CH2-P<
If the phosphine group comprises radicals other than the abovementioned
unbranched or
branched, acyclic or cyclic, aliphatic radicals, these generally correspond to
those which
CA 02838907 2013-12-10
16
are otherwise customarily used in phosphine ligands for metal-organic complex
catalysts.
Examples which may be mentioned are phenyl, tolyl and xylyl.
The metal-organic complex can comprise one or more, for example two, three or
four, of
the abovementioned phosphine groups having at least one unbranched or
branched,
acyclic or cyclic, aliphatic radical. The remaining ligands of the metal-
organic complex can
vary in nature. Illustrative examples which may be mentioned are hydride,
fluoride,
chloride, bromide, iodide, formate, acetate, propionate, carboxylate,
acetylacetonate,
carbonyl, DMSO, hydroxide, trialkylamine, alkoxide.
The homogeneous catalysts can be produced directly in their active form or
only under
reaction conditions from conventional standard complexes such as [M(p-
cymene)Cl2]2,
[M(benzene)C12], [M(COD)(allyI)], [MCI3 x H20], [M(acetylacetonate)3],
[M(COD)C12]2,
[M(DMS0)4C12] where M is an element of group 8, 9 or 10 of the Periodic Table
with
addition of the appropriate phosphine ligand(s).
Homogeneous catalysts which are preferred in the process of the invention are
[Ru(PnBu3)4(H)2], [Ru(Pnocty13)4(H)2],
[Ru(PnBu3)2(1,2-bis(dicyclohexylphosphino)-
ethane)(H)2], [Ru(pnocty13)2(1,2-bis(dicyclohexylphosphino)ethane)(H)2],
[Ru(PEt3)4(H)2],
[Ru(Pnocty13)(1,2-bis(dicyclohexylphosphino)ethane)(C0)(H)2],
[Ru(Pnocty13)(1,2-bis(dicyclohexylphosphino)ethane)(C0)(H)(HC00)],
[Ru(Pnbuty13)(1,2-bis(dicyclohexylphosphino)ethane)(C0)(H)2],
[Ru(Pnbuty13)(1,2-bis(dicyclohexylphosphino)ethane)(C0)(H)(HC00)],
[Ru(P ethy13)(1,2-bis(dicyclohexylphosphino)ethane)(C0)(H)2],
[Ru(P ethy13)(1,2-bis(dicyclohexylphosphino)ethane)(C0)(H)(HC00)],
[Ru(Pnocty13)(1,1-bis(dicyclohexylphosphino)methane)(C0)(H)2],
[Ru(Pnocty13)(1,1-bis(dicyclohexylphosphino)methane)(C0)(H)(HC00)],
[Ru(Pnbuty13)(1,1-bis(dicyclohexylphosphino)methane)(C0)(H)2],
[Ru(Pnbuty13)(1,1-bis(dicyclohexylphosphino)methane)(C0)(H)(HC00)],
[Ru(P ethy13)(1,1-bis(dicyclohexylphosphino)methane)(C0)(H)2],
[Ru(P ethy13)(1,1-bis(dicyclohexylphosphino)methane)(C0)(H)(HC00)],
[Ru(Pnoctyl3)(1,2-bis(diphenylphosphino)ethane)(C0)(H)2],
[Ru(Pnocty13)(1,2-bis(diphenylphosphino)ethane)(C0)(H)(HC00)],
[Ru(Pnbuty13)(1,2-bis(diphenylphosphino)ethane)(C0)(H)2],
[Ru(Pnbuty13)(1,2-bis(diphenylphosphino)ethane)(C0)(H)(HC00)],
[Ru(P ethy13)(1,2-bis(diphenlyphosphino)ethane)(C0)(H)2],
[Ru(P ethy13)(1,2-bis(diphenylphosphino)ethane)(C0)(H)(HC00)],
CA 02838907 2013-12-10
17
[Ru(Pnocty13)(1,1-bis(diphenylphosphino)methane)(C0)(H)2],
[Ru(Pnocty13)(1,1-bis(diphenylphosphino)methane)(C0)(H)(HC00)],
[Ru(Pnbuty13)(1,1-bis(diphenylphosphino)methane)(C0)(H)2],
[Ru(Pnbuty13)(1,1-bis(diphenylphosphino)methane)(C0)(H)(HC00)],
[Ru(P ethy13)(1,1-bis(diphenlyphosphino)methane)(C0)(H)2],
[Ru(P ethy13)(1,1-bis(diphenylphosphino)methane)(C0)(H)(HC00)].
TOF (turnover frequency) values of greater than 1000 h-1 can be achieved in
the
hydrogenation of carbon dioxide by means of these catalysts.
The hydrogenation of carbon dioxide in process step (a) occurs in the liquid
phase,
preferably at a temperature in the range from 20 to 200 C and a total pressure
in the range
from 0.2 to 30 MPa abs. The temperature is preferably at least 30 C and
particularly
preferably at least 40 C and preferably not more than 150 C, particularly
preferably not
more than 120 C and very particularly preferably not more than 80 C. The total
pressure is
preferably at least 1 MPa ohs and particularly preferably at least 5 MPa abs
and preferably
not more than 15 MPa abs.
In a preferred embodiment, the hydrogenation in process step (a) is carried
out at a
temperature in the range from 40 to 80 C and a pressure in the range from 5 to
15 MPa
abs.
The partial pressure of carbon dioxide in process step (a) is generally at
least 0.5 MPa and
preferably at least 2 MPa and generally not more than 8 MPa. In a preferred
embodiment,
the hydrogenation in process step (a) is carried out at a partial pressure of
carbon dioxide
in the range from 2 to 7.3 MPa.
The partial pressure of hydrogen in process step (a) is generally at least 0.5
MPa and
preferably at least 1 MPa and generally not more than 25 MPa and preferably
not more
than 10 MPa. In a preferred embodiment, the hydrogenation in process step (a)
is carried
out at a partial pressure of hydrogen in the range from 1 to 10 MPa.
The molar ratio of hydrogen to carbon dioxide in the reaction mixture (Rg) in
the
hydrogenation reactor is preferably from 0.1 to 10 and particularly preferably
from 1 to 3.
The molar ratio of carbon dioxide to tertiary amine (Al) in the reaction
mixture (Rg) in the
hydrogenation reactor is preferably from 0.1 to 10 and particularly preferably
from 0.5 to 3.
CA 02838907 2013-12-10
18
As hydrogenation reactors, it is in principle possible to use all reactors
which are suitable
for gas/liquid reactions at the given temperature and the given pressure.
Suitable standard
reactors for gas-liquid reaction systems are described, for example, in K. D.
Henkel,
"Reactor Types and Their Industrial Applications", in Ullmann's Encyclopedia
of Industrial
Chemistry, 2005, Wiley-VCH Verlag GmbH & Co. KGaA, DOI:
10.1002/14356007.b04_087, chapter 3.3 "Reactors for gas-liquid reactions".
Examples
which may be mentioned are stirred tank reactors, tube reactors and bubble
column
reactors.
The hydrogenation of carbon dioxide can be carried out batchwise or
continuously in the
process of the invention. In the case of a batch process, the reactor is
charged with the
desired liquid and optionally solid starting materials and auxiliaries, after
which carbon
dioxide and the polar solvent are injected to the desired pressure at the
desired
temperature. After the reaction is complete, the reactor is generally
depressurized and the
two liquid phases formed are separated from one another. In a continuous
process, the
starting materials and auxiliaries, including the carbon dioxide and hydrogen,
are
introduced continuously. Accordingly, the liquid phases are discharged
continuously from
the reactor so that the liquid level in the reactor remains, on average,
constant. Preference
is given to the continuous hydrogenation of carbon dioxide.
The average residence time of the components comprised in the reaction mixture
(Rg) in
the hydrogenation reactor is generally from 5 minutes to 5 hours.
The homogeneously catalyzed hydrogenation in process step (a) gives a
hydrogenation
mixture (H) which comprises the catalyst, the polar solvent, the tertiary
amine (Al) and the
at least one formic acid-amine adduct (A2).
For the purposes of the present invention, the term "formic acid-amine adduct
(A2)" refers
to both one formic acid-amine adduct (A2) and mixtures of two or more formic
acid-amine
adducts (A2). Mixtures of two or more formic acid-amine adducts (A2) are
obtained in
process step (a) when two or more tertiary amines (Al) are used in the
reaction mixture
(Rg).
In a preferred embodiment of the process of the invention, a reaction mixture
(Rg)
comprising one tertiary amine (Al) is used in process step (a) to give a
hydrogenation
mixture (H) comprising one formic acid-amine adduct (A2).
CA 02838907 2013-12-10
19
In a particularly preferred embodiment of the process of the invention, a
reaction mixture
(Rg) comprising tri-n-hexylamine as tertiary amine (Al) is used in process
step (a) to give
a hydrogenation mixture (H) comprising the formic acid-amine adduct of tri-n-
hexylamine
and formic acid, corresponding to the formula (A3) below
N(n-hexy1)3* x, HCOOH (A3).
In the formic acid-amine adduct of the general formula (A2) or (A3), the
radicals R1, R2, R3
have the meanings given above for the tertiary amine of the formula (Al), with
the
preferences indicated there applying analogously.
In the general formulae (A2) and (A3), x, is in the range from 0.4 to 5. The
factor x,
indicates the average composition of the formic acid-amine adduct (A2) or
(A3), i.e. the
ratio of bound tertiary amine (Al) to bound formic acid in the formic acid-
amine adduct
(A2) or (A3).
The factor x,= can be determined, for example, by determining the formic acid
content by
acid-base titration with an alcoholic KOH solution against phenolphthalein.
The factor x,
can also be determined by determining the amine content by gas chromatography.
The
precise composition of the formic acid-amine adduct (A2) or (A3) is dependent
on many
parameters such as the concentrations of formic acid and tertiary amine (Al),
the
pressure, the temperature and the presence and nature of further components,
in
particular the polar solvent.
The composition of the formic acid-amine adduct (A2) or (A3), i.e. the factor
x,, can
therefore also alter over the individual process steps. Thus, for example, a
formic acid-
amine adduct (A2) or (A3) having a relatively high formic acid content is
generally formed
after removal of the polar solvent, with the excess bound tertiary amine (Al)
being
eliminated from the formic acid-amine adduct (A2) and a second phase being
formed.
Process step (a) generally gives a formic acid-amine adduct (A2) or (A3) in
which x, is in
the range from 0.4 to 5, preferably in the range from 0.7 to 1.6.
The formic acid-amine adduct (A2) is enriched in the lower phase (L1), i.e.
the lower phase
(L1) comprises the major part of the formic acid-amine adduct. For the
purposes of the
present invention, "enriched" or "major part" in the context of the formic
acid-amine adduct
(A2) means a proportion by weight of the formic acid-amine adduct (A2) in the
lower phase
CA 02838907 2013-12-10
(L1) of > 50% based on the total weight of the formic acid-amine adduct (A2)
in the liquid
phases (upper phase (U1) and lower phase (L1)) in the hydrogenation reactor.
The proportion by weight of the formic acid-amine adduct (A2) in the lower
phase (L1) is
5 preferably > 70%, in particular > 90%, in each case based on the total
weight of the formic
acid-amine adduct (A2) in the upper phase (U1) and the lower phase (L1).
Work-up of the hydrogenation mixture (H); process step (b)
10 The hydrogenation mixture (H) obtained in the hydrogenation of carbon
dioxide in process
step (a) preferably has two liquid phases and is worked up further in process
step (b)
according to one of the steps (b1), (b2) or (b3).
Work-up according to process step (b1)
In a preferred embodiment, the hydrogenation mixture (H) is worked up further
according
to step (b1). The invention therefore also provides a process for preparing
formic acid,
which comprises the steps
(a) homogeneously catalyzed reaction of a reaction mixture (Rg) comprising
carbon
dioxide, hydrogen, at least one catalyst comprising at least one element
selected
from groups 8, 9 and 10 of the Periodic Table, at least one polar solvent
selected
from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-
butanol,
2-butanol, 2-methyl-l-propanol and water and also at least one tertiary amine
of
the general formula (Al)
NR1R2R3 (Al),
where
R1, R2, R3 are each, independently of one another, an unbranched or branched,
acyclic or cyclic, aliphatic, araliphatic or aromatic radical having in each
case from
1 to 16 carbon atoms, where individual carbon atoms may, independently of one
another, also be replaced by a heterogroup selected from among the groups -0-
and >N- and two or all three radicals can also be joined to one another to
form a
chain comprising at least four atoms,
in a hydrogenation reactor
CA 02838907 2013-12-10
21
to give, optionally after addition of water, a two-phase hydrogenation mixture
(H)
comprising
an upper phase (U1), which comprises the at least one catalyst and the at
least
one tertiary amine (Al) and
a lower phase (L1) which comprises the at least one polar solvent, residues of
the
at least one catalyst and also at least one formic acid-amine adduct of the
general
formula (A2),
NR1R2R3* x, HCOOH (A2),
where
x, is in the range from 0.4 to 5 and
R1, R2, R3 are as defined above,
(b1) phase separation of the hydrogenation mixture (H) obtained in step (a)
into the upper
phase (U1) and the lower phase (L1) in a first phase separation apparatus
(c) at least partial separation of the at least one polar solvent from the
lower phase
(L1) in a first distillation unit to give
a distillate (D1) comprising the at least one polar solvent, which is
recirculated to
the hydrogenation reactor in step (a), and
a two-phase bottoms mixture (Si) comprising
an upper phase (U2) which comprises the at least one tertiary amine (Al) and
a lower phase (L2) which contains the at least one formic acid-amine adduct
(A2),
(d) optionally work-up of the first bottoms mixture (Si) obtained in step
(c) by phase
separation in a second phase separation apparatus to give the upper phase (U2)
and the lower phase (L2),
(e) dissociation of the at least one formic acid-amine adduct (A2)
comprised in the
bottoms mixture (Si) or optionally in the lower phase (L2) in a thermal
CA 02838907 2013-12-10
22
dissociation unit to give the at least one tertiary amine (Al), which is
recirculated
to the hydrogenation reactor in step (a), and formic acid, which is discharged
from
the thermal dissociation unit,
wherein at least one inhibitor selected from the group consisting of
carboxylic acids other
than formic acid, carboxylic acid derivatives other than formic acid
derivatives and oxidants
is added to the lower phase (L1) directly before and/or during step (c).
Here, the hydrogenation mixture (H) obtained in process step (a) is worked up
further by
phase separation in a first phase separation apparatus to give a lower phase
(L1)
comprising the at least one formic acid-amine adduct (A2), the at least one
polar solvent
and residues of the at least one catalyst and also an upper phase (U1)
comprising the at
least one catalyst and the at least one tertiary amine (Al).
In a preferred embodiment, the upper phase (U1) is recirculated to the
hydrogenation
reactor. The lower phase (L1) is, in a preferred embodiment, fed to the first
distillation
apparatus in process step (c). Recirculation of a further liquid phase which
comprises
unreacted carbon dioxide and is present over the two liquid phases and also of
a gas
phase comprising unreacted carbon dioxide and/or unreacted hydrogen to the
hydrogenation reactor may also be advantageous. It may be desirable, for
example to
discharge undesirable by-products or impurities, to discharge part of the
upper phase (U1)
and/or part of the liquid or gaseous phases comprising carbon dioxide or
carbon dioxide
and hydrogen from the process.
The separation of the hydrogenation mixture (H) obtained in process step (a)
is generally
carried out by gravimetric phase separation. Suitable phase separation
apparatuses are,
for example, standard apparatuses and standard methods as may be found, for
example,
in E. Muller et al., "Liquid-liquid Extraction", in Ullman's Encyclopedia of
Industrial
Chemistry, 2005, Wiley-VCH Verlag GmbH & Co. KGaA, DOI:
10.1002/14356007.b93_06,
chapter 3 "Apparatus". In general, the liquid phase enriched in the formic
acid-amine
adducts (A2) and the polar solvent is heavier and forms the lower phase (L1).
The phase separation can, for example, be effected by depressurization to
about or close
to atmospheric pressure and cooling of the liquid hydrogenation mixture, for
example to
about or close to ambient temperature.
CA 02838907 2013-12-10
23
In the context of the present invention, it has been found that in the present
system, i.e. a
lower phase (L1) enriched in the formic acid-amine adducts (A2) and the polar
solvent and
an upper phase (U2) enriched in the tertiary amine (Al) and the catalyst, the
two liquid
phases separate very well, even at significantly elevated pressure, when a
suitable
combination of the polar solvent and the tertiary amine (Al) is selected. For
this reason,
the polar solvent and the tertiary amine (Al) in the process of the invention
are selected so
that the separation of the lower phase (L1) enriched in the formic acid-amine
adducts (A2)
and the polar solvent from the upper phase (U1) enriched in tertiary amine
(Al) and
catalyst and also the recirculation of the upper phase (U1) to the
hydrogenation reactor
can be carried out at a pressure of from 1 to 30 MPa abs. Corresponding to the
total
pressure in the hydrogenation reactor, the pressure is preferably not more
than 15 MPa
abs. It is thus possible to separate the two liquid phases (upper phase (U1)
and lower
phase (L1)) from one another without prior depressurization in the first phase
separation
apparatus and to recirculate the upper phase (U1) to the hydrogenation reactor
without an
appreciable increase in pressure.
It is also possible to carry out the phase separation directly in the
hydrogenation reactor. In
this embodiment, the hydrogenation reactor simultaneously functions as the
first phase
separation apparatus and the process steps (a) and (b1) are both carried out
in the
hydrogenation reactor. Here, the upper phase (U1) remains in the hydrogenation
reactor
and the lower phase (L1) is fed to the first distillation apparatus in process
step (c).
In one embodiment, the process of the invention is carried out with the
pressure and the
temperature in the hydrogenation reactor and in the first phase separation
apparatus being
the same or approximately the same, with approximately the same meaning, for
the
present purposes, a pressure difference of up to +/- 0.5 MPa or a temperature
difference
of up to +/-10 C.
It has surprisingly also been found that in the case of the present system,
the two liquid
phases (upper phase (U1) and lower phase (L1)) separate from one another very
readily
even at an elevated temperature corresponding to the reaction temperature in
the
hydrogenation reactor. In this case, no cooling for the phase separation in
process step
(b1) and subsequent heating of the recirculated upper phase (U1) is necessary,
which
likewise saves energy.
Work-up according to process step (b3)
CA 02838907 2013-12-10
24
In a further preferred embodiment, the hydrogenation mixture (H) is worked up
further
according to step (b3). The invention therefore also provides a process for
preparing
formic acid, which comprises the steps
(a) homogeneously catalyzed reaction of a reaction mixture (Rg) comprising
carbon dioxide, hydrogen, at least one catalyst comprising at least one
element selected from groups 8, 9 and 10 of the Periodic Table, at least one
polar solvent selected from the group consisting of methanol, ethanol,
1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-l-propanol and water
and also at least one tertiary amine of the general formula (Al)
NR1R2R3 (Al),
where
R1, R2, R3 are each, independently of one another, an unbranched or branched,
acyclic or cyclic, aliphatic, araliphatic or aromatic radical having in each
case from 1 to 16 carbon atoms, where individual carbon atoms may,
independently of one another, also be replaced by a heterogroup
selected from among the groups -0- and >N- and two or all three radicals
can also be joined to one another to form a chain comprising at least four
atoms,
in a hydrogenation reactor
to give, optionally after addition of water, a two-phase hydrogenation mixture
(H)
comprising
an upper phase (U1), which comprises the at least one catalyst and the at
least
one tertiary amine (Al) and
a lower phase (L1) which comprises the at least one polar solvent, residues of
the
at least one catalyst and also at least one formic acid-amine adduct of the
general
formula (A2),
NR1R2R3* x, HCOOH (A2),
where
CA 02838907 2013-12-10
x, is in the range from 0.4 to 5 and
1:21, R2, R3 are as defined above,
(b3) phase separation of the hydrogenation mixture (H) obtained in step (a)
into
5 the upper phase (U1) and the lower phase (L1) in a first phase
separation
apparatus and extraction of the residues of the at least one catalyst from the
lower phase (L1) by means of an extractant comprising the at least one
tertiary amine (Al) in an extraction unit to give
10 a raffinate (R2) comprising the at least one formic acid-
amine
adduct (A2) and the at least one polar solvent and
an extract (E2) comprising the at least one tertiary amine (Al) and
the residues of the at least one catalyst,
(c) at least partial separation of the at least one polar solvent
from the raffinate
(R2) in a first distillation unit to give
a distillate (D1) comprising the at least one polar solvent, which is
recirculated to the hydrogenation reactor in step (a), and
a two-phase bottoms mixture (S1) comprising
an upper phase (U2) which comprises the at least one tertiary amine (Al)
and
a lower phase (L2) which contains the at least one formic acid-amine adduct
(A2),
(d) optionally work-up of the first bottoms mixture (S1) obtained in step (c)
by
phase separation in a second phase separation apparatus to give the upper
phase (U2) and the lower phase (L2),
(e) dissociation of the at least one formic acid-amine adduct (A2)
comprised in
the bottoms mixture (S1) or optionally in the lower phase (L2) in a thermal
dissociation unit to give the at least one tertiary amine (Al), which is
CA 02838907 2013-12-10
26
recirculated to the hydrogenation reactor in step (a), and formic acid, which
is discharged from the thermal dissociation unit,
wherein at least one inhibitor selected from the group consisting of
carboxylic acids
other than formic acid, carboxylic acid derivatives other than formic acid
derivatives
and oxidants is added to the raffinate (R2) directly before and/or during step
(c).
Here, the hydrogenation mixture (H) obtained in process step (a) is, as
described above
for process step (b1), separated in the first phase separation apparatus into
the lower
phase (L1) and the upper phase (U1) which is recirculated to the hydrogenation
reactor.
With regard to the phase separation in process step (b3), what has been said
in respect of
process step (b1), including preferences, applies analogously. In the work-up
according to
step (b3), too, the phase separation can be carried out directly in the
hydrogenation
reactor. In this embodiment, the hydrogenation reactor simultaneously
functions as first
phase separation apparatus. The upper phase (U1) then remains in the
hydrogenation
reactor and the lower phase (L1) is fed to the extraction unit.
The lower phase (L1) obtained after phase separation is subsequently subjected
to an
extraction with at least one tertiary amine (A1) as extractant to separate off
the residues of
the catalyst in an extraction unit to give a raffinate (R2) comprising the at
least one formic
acid-amine adduct (A2) and the at least one polar solvent and an extract (E2)
comprising
the at least one tertiary amine (A1) and the residues of the catalyst.
In a preferred embodiment, the same tertiary amine (A1) comprised in the
reaction mixture
(Rg) in process step (a) is used as extractant, so that what has been said in
respect of
process step (a), including preferences, in respect of the tertiary amine (Al)
applies
analogously to process step (b3).
The extract (E2) obtained in process step (b3) is, in a preferred embodiment,
recirculated
to the hydrogenation reactor in process step (a). This makes efficient
recovery of the
expensive catalyst possible. The raffinate (R2) is, in a preferred embodiment,
fed to the
first distillation apparatus in process step (c).
The tertiary amine (Al) which is obtained in the thermal dissociation unit in
process step
(e) is preferably used as extractant in process step (b3). In a preferred
embodiment, the
tertiary amine (Al) obtained in the thermal dissociation unit in process step
(e) is
recirculated to the extraction unit in process step (b3).
CA 02838907 2013-12-10
27
The extraction in process step (b3) is generally carried out at temperatures
in the range
from 30 to 100 C and pressures in the range from 0.1 to 8 MPa. The extraction
can also
be carried out under hydrogen pressure.
The extraction of the catalyst can be carried out in any suitable apparatus
known to those
skilled in the art, preferably in countercurrent extraction columns, mixer-
settler cascades or
combinations of mixer-settler cascades and countercurrent extraction columns.
Optionally, not only the catalyst but also proportions of individual
components of the polar
solvent from the lower phase (L1) to be extracted are dissolved in the
extractant, viz, the
tertiary amine (Al). This is not a disadvantage for the process since the
amount of polar
solvent which has been extracted does not have to be fed to solvent removal
and thus
may save vaporization energy in some circumstances.
Work-up according to process step (b2)
In a further preferred embodiment, the hydrogenation mixture (H) is worked up
further
according to step (b2). The invention therefore also provides a process for
preparing
formic acid, which comprises the steps
(a) homogeneously catalyzed reaction of a reaction mixture (Rg) comprising
carbon dioxide, hydrogen, at least one catalyst comprising at least one
element selected from groups 8, 9 and 10 of the Periodic Table, at least one
polar solvent selected from the group consisting of methanol, ethanol,
1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol and water
and also at least one tertiary amine of the general formula (Al)
NR1R2R3 (Al),
where
R1, R2, R3 are each, independently of one another, an unbranched or
branched, acyclic or cyclic, aliphatic, araliphatic or aromatic radical
having in each case from 1 to 16 carbon atoms, where individual carbon
atoms may, independently of one another, also be replaced by a
heterogroup selected from among the groups -0- and >N- and two or all
CA 02838907 2013-12-10
28
three radicals can also be joined to one another to form a chain
comprising at least four atoms,
in a hydrogenation reactor
to give, optionally after addition of water, a two-phase hydrogenation mixture
(H) comprising
an upper phase (U1), which comprises the at least one catalyst and the at
least one tertiary amine (Al) and
a lower phase (L1) which comprises the at least one polar solvent, residues of
the at least one catalyst and also at least one formic acid-amine adduct of
the
general formula (A2),
NR1R2R3* x, HCOOH (A2),
where
x, is in the range from 0.4 to 5 and
R1, R2,
K are as defined above,
(b2) extraction of the at least one catalyst from the hydrogenation mixture
(H)
obtained in step (a) by means of an extractant comprising the at least one
tertiary amine (Al) in an extraction unit to give
a raffinate (R1) comprising the at least one formic acid-amine adduct
(A2) and the at least one polar solvent and
an extract (El) comprising the at least one tertiary amine (Al) and the
at least one catalyst
(c) at least partial separation of the at least one polar solvent from the
raffinate
(R1) in a first distillation unit to give
a distillate (D1) comprising the at least one polar solvent, which is
recirculated
to the hydrogenation reactor in step (a), and
CA 02838907 2013-12-10
29
a two-phase bottoms mixture (Si) comprising
an upper phase (U2) which comprises the at least one tertiary amine (Al) and
a lower phase (L2) which contains the at least one formic acid-amine adduct
(A2),
(d) optionally work-up of the first bottoms mixture (Si) obtained in step (c)
by
phase separation in a second phase separation apparatus to give the upper
phase (U2) and the lower phase (L2),
(e) dissociation of the at least one formic acid-amine adduct (A2) comprised
in the
bottoms mixture (Si) or optionally in the lower phase (L2) in a thermal
dissociation unit to give the at least one tertiary amine (Al), which is
recirculated to the hydrogenation reactor in step (a), and formic acid, which
is
discharged from the thermal dissociation unit,
wherein at least one inhibitor selected from the group consisting of
carboxylic acids
other than formic acid, carboxylic acid derivatives other than formic acid
derivatives
and oxidants is added to the raffinate (R1) directly before and/or during step
(c).
Here, the hydrogenation mixture (H) obtained in process step (a) is fed
directly, without
prior phase separation, to the extraction unit. What has been said above in
respect of the
extraction for process step (b3), including preferences, applies analogously
to process
step (b2).
The hydrogenation mixture (H) is subjected to an extraction with at least one
tertiary amine
(Al) as extractant to separate off the catalyst in an extraction unit to give
a raffinate (R1)
comprising the at least one formic acid-amine adduct (A2) and the at least one
polar
solvent and an extract (El) comprising the at least one tertiary amine (Al)
and residues of
the catalyst.
In a preferred embodiment, the same tertiary amine (Al) comprised in the
reaction mixture
(Rg) in process step (a) is used as extractant, so that what has been said
above in respect
of the tertiary amine (Al) for process step (a), including preferences,
applies analogously
to process step (b2).
CA 02838907 2013-12-10
The extract (El) obtained in process step (b2) is, in a preferred embodiment,
recirculated
to the hydrogenation reactor in process step (a). This makes efficient
recovery of the
expensive catalyst possible. The raffinate (R1) is, in a preferred embodiment,
fed to the
first distillation apparatus in process step (c).
5
The tertiary amine (Al) obtained in the thermal dissociation unit in process
step (e) is
preferably used as extractant in process step (b2). In a preferred embodiment,
the tertiary
amine (Al) obtained in the thermal dissociation unit in process step (e) is
recirculated to
the extraction unit in process step (b2).
The extraction in process step (b2) is generally carried out at temperatures
in the range
from 30 to 100 C and pressures in the range from 0.1 to 8 MPa. The extraction
can also
be carried out under hydrogen pressure.
The extraction of the catalyst can be carried out in any suitable apparatus
known to those
skilled in the art, preferably in countercurrent extraction columns, mixer-
settler cascades or
combinations of mixer-settler cascades and countercurrent extraction columns.
Optionally, not only the catalyst but also proportions of individual
components of the polar
solvent from the hydrogenation mixture (H) to be extracted are dissolved in
the extractant,
viz, the tertiary amine (Al). This is not a disadvantage for the process since
the amount of
polar solvent which has been extracted does not have to be fed to solvent
removal and
thus may save vaporization energy in some circumstances.
Inhibition of traces of the catalyst
At least one inhibitor is added to the lower phase (L1) obtained according to
process step
(bl), the raffinate (R1) obtained according to process step (b2) or the
raffinate (R2)
obtained according to process step (b3) immediately before and/or during step
(c).
Although the work-up of the hydrogenation mixture (H) makes effective
isolation and
recirculation of the catalyst to the hydrogenation reactor in step (a)
possible, residues of
the catalyst are still comprised in the lower phase (L1) in the work-up
according to process
step (bl). In the work-up according to process step (b2), the raffinate (R1)
still comprises
traces of the catalyst. In the case of the work-up according to process step
(b3), too, the
raffinate (R2) still comprises traces of the catalyst.
CA 02838907 2013-12-10
31
The lower phase (L1) obtained according to process step (b1) comprises
residues of the
catalyst in amounts of < 100 ppm, preferably <80 ppm and in particular < 60
ppm, in each
case based on the total weight of the lower phase (L1).
The raffinate (R1) obtained according to process step (b2) comprises traces of
the catalyst
in amounts of < 5 ppm, preferably < 3 ppm and in particular < 1 ppm, in each
case based
on the total weight of the raffinate (R1).
The raffinate (R2) obtained according to process step (b3) comprises traces of
the catalyst
in amounts of < 5 ppm, preferably <3 ppm and in particular < 1 ppm, in each
case based
on the total weight of the raffinate (R2).
The residues or traces of the catalyst in the lower phase (L1), the raffinate
(R1) or the
raffinate (R2) lead to redissociation of the formic acid-amine adduct (A2)
into tertiary amine
(Al), carbon dioxide and hydrogen in the further work-up. The redissociation
of free formic
acid, which may be comprised in the lower phase (L1), the raffinate (R1) or
the raffinate
(R2) or is formed from the formic acid-amine adduct (A2) in the further work-
up, is also
catalyzed by the residues or traces of the catalyst. The formic acid is in the
case
dissociated into carbon dioxide and hydrogen.
To prevent or minimize this redissociation, at least one inhibitor is added to
the lower
phase (L1), the raffinate (R1) or the raffinate (R2) directly before and/or
during step (c).
In an embodiment of the present invention, the at least one inhibitor is added
either directly
before or during step (c). In a further embodiment of the present invention,
the at least one
inhibitor is added directly before and during step (c). In a further
embodiment, the at least
one inhibitor is added only directly before step (c). In a further embodiment,
the at least
one inhibitor is added only during step (c).
For the purposes of the present invention, "directly before step (c)" refers
to an addition of
the inhibitor to the lower phase (L1), the raffinate (R1) or the raffinate
(R2) after this has
been taken from the first phase separation apparatus or the extraction unit
and before it is
fed to the first distillation apparatus in process step (c). The addition of
the inhibitor can be
carried out continuously or discontinuously.
For the purposes of the present invention, the term inhibitor encompasses both
one
inhibitor and also mixtures of two or more inhibitors. The inhibitor converts
the catalyst into
CA 02838907 2013-12-10
32
an inactive form so that it can no longer catalyze the redissociation of the
formic acid-
amine adduct (A2) or the free formic acid.
The inhibitor is selected from the group consisting of carboxylic acids other
than formic
acid, carboxylic acid derivatives other than formic acid derivatives and
oxidants.
In one embodiment, a mixture of at least one carboxylic acid and at least one
oxidant is
used as inhibitor.
The inhibitor is used in a molar ratio of from 0.5 to 1000, preferably from 1
to 30, based on
the catalytically active metal component of the catalyst which is comprised in
the lower
phase (L1), the raffinate (R1) or the raffinate (R2).
Preferred carboxylic acids are those which have at least one carboxy group (-
COOH) and
a further functional group such as hydroxy groups (-OH), carboxy groups or
thiol groups (-
SH), since such carboxylic acids effectively bind to the metal component of
the catalyst
due to the chelating effect and convert the catalyst into an inactive form.
Particularly useful carboxylic acids are, for example, oxalic acid, lactic
acid, maleic acid,
phthalic acid, tartaric acid, citric acid, iminodiacetic acid,
ethylenediaminetetraacetic acid
(EDTA), nitriloacetic acid, methylglycinediacetic acid,
diethylenetriaminepentaacetic acid
(DTPA), dimercaptosuccinic acid.
For the purposes of the present invention, carboxylic acid derivatives are
organic
compounds whose functional groups are formally derived from the carboxy group
(-COOH). Suitable carboxylic acid derivatives are, for example, carboxylic
esters,
carboxamides, carboxylic acid halides (e.g. carboxylic acid chlorides),
carboxylic acid salts
(e.g. lithium, sodium, potassium, trialkylammonium and ammonium salts of
carboxylic
acids), carboxylic anhydrides, carboxylic hydrazides, carboxylic azides,
dithiocarboxylic
acids, thiocarboxylic acids, hydroxamic acids, ketenes, imidocarboxylic acids,
imidocarboxylic esters, amidines, amitrazones and nitriles.
Preference is given to carboxylic acid derivatives which can be prepared from
the above-
described carboxylic acids, so that the preferences described above for
carboxylic acids
apply analogously to the carboxylic acid derivatives. Particularly suitable
carboxylic acid
derivatives are carboxylic acid salts and carboxylic anhydrides of the
abovementioned
CA 02838907 2013-12-10
33
carboxylic acids, with alkali metal salts and trialkylammonium salts being
particularly
preferred among the carboxylic acid salts.
As particularly suitable carboxylic acid derivatives, mention may be made by
way of
example of maleic anhydride, phthalic anhydride, the trisodium salt of
methylglycinediacetic acid (obtainable as Trilon M ) and thioacetamide.
The carboxylic acids can thus be added either in the form of the free acid or
in the form of
derivatives thereof (carboxylic acid derivatives), with alkali metal
carboxylates or
trialkylammonium carboxylates being preferred among the carboxylic acid
derivatives. The
carboxylic acids and/or carboxylic acid derivatives can be added neat or in
the form of a
solution.
As suitable oxidants, mention may here be made of hydrogen peroxide,
peroxycarboxylic
acids, diacyl peroxides and trialkyl N-oxides. Preferred oxidants are hydrogen
peroxide,
peroxoformic acid and trihexyl N-oxide since these oxidants decompose under
the process
conditions in step (c) and/or the process conditions in step (e) to form
substances which
are in any case present in the process of the invention for preparing formic
acid. The
inhibitor is preferably selected so that it is enriched in the phase which
also comprises the
formic acid-amine adduct (A2).
In a preferred embodiment, thioacetamide is used as inhibitor.
In a preferred embodiment, a mixture of hydrogen peroxide and EDTA is used as
inhibitor.
In a preferred embodiment, a mixture of hydrogen peroxide and
diethylenetriaminepentaacetic acid is used as inhibitor.
In a preferred embodiment, EDTA is used as inhibitor.
In a preferred embodiment, Trilon M is used as inhibitor.
In a preferred embodiment, meso-dimercaptosuccinic acid is used as inhibitor.
In a preferred embodiment, a mixture of hydrogen peroxide and meso-
dimercaptosuccinic
acid is used as inhibitor.
CA 02838907 2013-12-10
34
In the context of the inhibitor, "enriched" means, in respect of process step
(c), a partition
coefficient
= [concentration of inhibitor in the lower phase (L2)] / [concentration of
inhibitor in the
upper phase (U2)]
of > 1. The partition coefficient PI(c) is preferably 2 and particularly
preferably ?. 5.
In the context of the inhibitor, "enriched" in respect of the optional process
step (d) means
a partition coefficient
Pi(d) = [concentration of inhibitor in the lower phase (L2)] / [concentration
of inhibitor in the
upper phase (U2)]
of > 1. The partition coefficient Pi(d) is preferably ?. 2 and particularly
preferably 5.
In the context of the inhibitor, "enriched" in respect of the process step (e)
means a
partition coefficient
Pi(e) = [concentration of inhibitor in the lower phase (L3)] / [concentration
of inhibitor in the
upper phase (U3)]
of > 1. The partition coefficient Pi(e) is preferably 2 and particularly
preferably 5.
This makes recirculation of the upper phase (U2) or the upper phase (U3) to
the
hydrogenation reactor possible without considerable amounts of the inhibitor
being
recirculated to the hydrogenation reactor and interfering in process step (a)
in the
hydrogenation reactor.
Removal of the polar solvent: process step (c)
In process step (c), the polar solvent is at least partly separated off from
the lower phase
(L1), from the raffinate (R1) or from the raffinate (R2) in a first
distillation apparatus. A
CA 02838907 2013-12-10
distillate (D1) and a two-phase bottoms mixture (S1) are obtained from the
first distillation
apparatus. The distillate (D1) comprises the polar solvent which has been
separated off
and is recirculated to the hydrogenation reactor in step (a). The bottoms
mixture (Si)
comprises the upper phase (U2), which comprises the tertiary amine (Al), and a
lower
5 phase (L2), which comprises the formic acid-amine adduct (A2). In an
embodiment of the
process of the invention, the polar solvent is partly separated off in the
first distillation
apparatus in process step (c) so that the bottoms mixture (Si) still comprises
polar solvent
which has not yet been separated off. In process step (c), it is possible to
separate off, for
example, from 5 to 98% by weight of the polar solvent comprised in the lower
phase (L1),
10 in the raffinate (R1) or in the raffinate (R2), with preference being
given to from 50 to 98%
by weight, more preferably from 80 to 98% by weight and particularly
preferably from 80 to
90% by weight, being separated off, in each case based on the total weight of
the polar
solvent comprised in the lower phase (L1), in the raffinate (R1) or in the
raffinate (R2).
15 In a further embodiment of the process of the invention, the polar
solvent is completely
separated off in the first distillation apparatus in process step (c). For the
purposes of the
present invention, "completely separated off" means a removal of more than 98%
by
weight of the polar solvent comprised in the lower phase (L1), in the
raffinate (R1) or in the
raffinate (R2), preferably more than 98.5% by weight, particularly preferably
more than
20 99% by weight, in particular more than 99.5% by weight, in each case
based on the total
weight of the polar solvent comprised in the lower phase (L1), in the
raffinate (R1) or in the
raffinate (R2).
The distillate (D1) which has been separated off in the first distillation
apparatus is, in a
25 preferred embodiment, recirculated to the hydrogenation reactor in step
(a). When a
mixture of one or more alcohols and water is used as polar solvent, it is also
possible to
take off a low-water distillate (D1,a) and a water-rich distillate (Dlwr) from
the first
distillation apparatus. The water-rich distillate (Dlwr) comprises more than
50% by weight
of the water comprised in the distillate (D1), preferably more than 70% by
weight,
30 particularly preferably more than 80% by weight, in particular more than
90% by weight.
The low-water distillate (Dlwa) comprises less than 50% by weight of the water
comprised
in the distillate D1, preferably less than 30% by weight, particularly
preferably less than
20% by weight, in particular less than 10% by weight.
35 In a particularly preferred embodiment, the low-water distillate (Dlwa)
is recirculated to the
hydrogenation reactor in step (a). The water-rich distillate (Dlwr) is added
to the upper
phase (U1).
CA 02838907 2013-12-10
36
The separation of the polar solvent from the lower phase (L1), the raffinate
(R1) or the
raffinate (R2) can, for example, be carried out in an evaporator or in a
distillation unit
comprising a vaporizer and column, with the column being provided with ordered
packing,
random packing elements and/or trays.
The at least partial removal of the polar solvent is preferably carried out at
a temperature
at the bottom at which no free formic acid is formed from the formic acid-
amine adduct
(A2) at the given pressure. The factor x, of the formic acid-amine adduct (A2)
in the first
distillation apparatus is generally in the range from 0.4 to 3, preferably in
the range from
0.6 to 1.8, particularly preferably in the range from 0.7 to 1.7.
In general, the temperature at the bottom of the first distillation apparatus
is at least 20 C,
preferably at least 50 C and particularly preferably at least 70 C, and
generally not more
than 210 C, preferably not more than 190 C. The temperature in the first
distillation
apparatus is generally in the range from 20 C to 210 C, preferably in the
range from 50 C
to 190 C. The pressure in the first distillation apparatus is generally at
least 0.001 MPa
abs, preferably at least 0.005 MPa abs and particularly preferably at least
0.01 MPa abs,
and generally not more than 1 MPa abs and preferably not more than 0.1 MPa
abs. The
pressure in the first distillation apparatus is generally in the range from
0.0001 MPa abs to
1 MPa abs, preferably in the range from 0.005 MPa abs to 0.1 MPa abs and
particularly
preferably in the range from 0.01 MPa abs to 0.1 MPa abs.
In the removal of the polar solvent in the first distillation apparatus, the
formic acid-amine
adduct (A2) and free tertiary amine (Al) can be obtained at the bottom of the
first
distillation apparatus, since formic acid-amine adducts having a low amine
content are
formed during the removal of the polar solvent. As a result, a bottoms mixture
(Si)
comprising the formic acid-amine adduct (A2) and the free tertiary amine (Al)
is formed.
The bottoms mixture (Si) comprises, depending on the amount of polar solvent
separated
off, the formic acid-amine adduct (A2) and possibly the free tertiary amine
(Al) formed in
the liquid phase of the first distillation apparatus. For further work-up, the
bottoms mixture
(Si) is optionally worked up further in process step (d) and subsequently fed
to process
step (e). It is also possible to feed the bottoms mixture (S1) from process
step (c) directly
to process step (e).
In the process step (d), the bottoms mixture (Si) obtained in step (c) can be
separated into
the upper phase (U2) and the lower phase (L2) in a second phase separation
apparatus.
CA 02838907 2013-12-10
37
The lower phase (L2) is subsequently worked up further according to process
step (e). In a
preferred embodiment, the upper phase (U2) from the second phase separation
apparatus
is recirculated to the hydrogenation reactor in step (a). In a further
preferred embodiment,
the upper phase (U2) from the second phase separation apparatus is
recirculated to the
extraction unit. What has been said in respect of the first phase separation
apparatus,
including preferences, applies analogously to process step (d) and the second
phase
separation apparatus.
In one embodiment, the process of the invention thus comprises the steps (a),
(b1), (c), (d)
and (e). In a further embodiment, the process of the invention comprises the
steps (a),
(b2), (c), (d) and (e). In a further embodiment, the process of the invention
comprises the
steps (a), (b3), (c), (d) and (e). In a further embodiment, the process of the
invention
comprises the steps (a), (b1), (c) and (e). In a further embodiment, the
process of the
invention comprises the steps (a), (b2), (c) and (e). In a further embodiment,
the process
of the invention comprises the steps (a), (b3), (c) and (e).
In one embodiment, the process of the invention consists of the steps (a),
(b1), (c), (d) and
(e). In a further embodiment, the process of the invention consists of the
steps (a), (b2),
(c), (d) and (e). In a further embodiment, the process of the invention
consists of the steps
(a), (b3), (c), (d) and (e). In a further embodiment, the process of the
invention consists of
the steps (a), (b1), (c) and (e). In a further embodiment, the process of the
invention
consists of the steps (a), (b2), (c) and (e). In a further embodiment, the
process of the
invention consists of the steps (a), (b3), (c) and (e).
Dissociation of the formic acid-amine adduct (A2): process step (e)
The bottoms mixture (Si) obtained according to step (c) or the lower phase
(L2) optionally
obtained after the work-up according to step (d) is fed to a thermal
dissociation unit for
further reaction.
The formic acid-amine adduct (A2) comprised in the bottoms mixture (Si) or
optionally in
the lower phase (L2) is dissociated into formic acid and tertiary amine (A1)
in the thermal
dissociation unit. The formic acid is discharged from the thermal dissociation
unit. The
tertiary amine (Al) is recirculated to the hydrogenation reactor in step (a).
The tertiary
amine (Al) from the thermal dissociation unit can be recirculated directly to
the
hydrogenation reactor. It is also possible firstly to recirculate the tertiary
amine (Al) from
the thermal dissociation unit to the extraction unit in process step (b2) or
process step (b3)
CA 02838907 2013-12-10
38
and subsequently pass it on from the extraction unit to the hydrogenation
reactor in step
(a); this embodiment is preferred.
In a preferred embodiment, the thermal dissociation unit comprises a second
distillation
apparatus and a third phase separation apparatus, with the dissociation of the
formic acid-
amine adduct (A2) occurring in the second distillation apparatus to give a
distillate (D2),
which is discharged (taken off) from the second distillation apparatus, and a
two-phase
bottoms mixture (S2) comprising an upper phase (U3), which comprises the at
least one
tertiary amine (Al), and a lower phase (L3), which comprises the at least one
formic acid-
amine adduct (A2) and the at least one inhibitor.
The formic acid obtained in the second distillation apparatus can, for
example, be taken off
(i) via the top, (ii) via the top and via a side offtake or (iii) only via a
side offtake from the
second distillation apparatus. If the formic acid is taken off via the top,
formic acid having a
purity of up to 99.99% by weight is obtained. When it is taken off via a side
offtake,
aqueous formic acid is obtained, with a mixture comprising about 85% by weight
of formic
acid being particularly preferred here. Depending on the water content of the
bottoms
mixture (S1) or optionally the lower phase (L2) fed to the thermal
dissociation unit, the
formic acid can be taken off mostly as overhead product or mostly via the side
offtake. If
necessary, it is also possible to take off formic acid only via the side
offtake, preferably
with a formic acid content of about 85% by weight, in which case the required
amount of
water may also be provided by addition of additional water to the second
distillation
apparatus. The thermal dissociation of the formic acid-amine adduct (A2) is
generally
carried out at the process parameters in respect of pressure, temperature and
configuration of the apparatus known from the prior art. These are described,
for example,
in EP 0 181 078 or WO 2006/021 411. Suitable second distillation apparatuses
are, for
example, distillation columns which generally comprise random packing
elements, ordered
packing and/or trays.
In general, the temperature at the bottom of the second distillation apparatus
is at least
130 C, preferably at least 140 C and particularly preferably at least 150 C,
and generally
not more than 210 C, preferably not more than 190 C, particularly preferably
not more
than 185 C. The pressure in the second distillation apparatus is generally at
least 1 hPa
abs, preferably at least 50 hPa abs and particularly preferably at least 100
hPa abs, and
generally not more than 500 hPa, particularly preferably not more than 300 hPa
abs and
particularly preferably not more than 200 hPa abs.
CA 02838907 2013-12-10
39
The bottoms mixture (S2) obtained at the bottom of the second distillation
apparatus is a
two-phase mixture. In a preferred embodiment, the bottoms mixture (S2) is fed
to the third
phase separation apparatus of the thermal dissociation unit and separated
there into the
upper phase (U3), which comprises the tertiary amine (Al), and the lower phase
(L3),
which comprises the formic acid-amine adduct (A2) and the inhibitor. The upper
phase
(U3) is discharged from the third phase separation apparatus of the thermal
dissociation
unit and recirculated to the hydrogenation reactor in step (a). The
recirculation can be
carried out directly to the hydrogenation reactor in step (a) or the upper
phase (U3) is
firstly fed to the extraction unit in step (b2) or step (b3) and from there
passed on to the
hydrogenation reactor in step (a). The lower phase (L3) obtained in the third
phase
separation apparatus is then fed back into the second distillation apparatus
of the thermal
dissociation unit. The formic acid-amine adduct (A2) comprised in the lower
phase (L3) is
again subjected to dissociation in the second distillation apparatus, once
again with formic
acid and free tertiary amine (Al) being obtained and with a two-phase bottoms
mixture
(S2) again being formed at the bottom of the second distillation apparatus of
the thermal
dissociation unit and then being fed again to the third phase separation
apparatus of the
thermal dissociation unit for further work-up.
As indicated above, the inhibitor preferably remains in the phase which also
comprises the
formic acid-amine adduct (A2), i.e. in the lower phase (L3). This has the
advantage that
the upper phase (U3) comprising the tertiary amine (Al) can be recirculated to
the
hydrogenation reactor without appreciable amounts of inhibitor being
recirculated with the
upper phase (U3) to process step (a) and there being able to hinder the
hydrogenation
reaction.
The introduction of the bottoms mixture (51) or optionally of the lower phase
(L2) into the
thermal dissociation unit in process step (e) can be effected into the second
distillation
apparatus and/or the third phase separation apparatus. In a preferred
embodiment, the
bottoms mixture (51) or optionally the lower phase (L2) is introduced into the
second
distillation apparatus of the thermal separation unit. In a further
embodiment, the bottoms
mixture (51) or optionally the lower phase (L2) is introduced into the third
phase
separation vessel of the thermal dissociation unit.
In a further embodiment, the bottoms mixture (51) or optionally the lower
phase (L2) is
introduced both into the second distillation apparatus of the thermal
dissociation unit and
into the third phase separation apparatus of the thermal dissociation unit.
For this purpose,
the bottoms mixture (51) or optionally the lower phase (L2) is divided into
two substreams
CA 02838907 2013-12-10
of which one substream is introduced into the second distillation apparatus
and one
substream is introduced into the third separation apparatus of the thermal
dissociation unit.
The drawings show in detail:
5
Figure 1 a block diagram of a preferred embodiment of the process of the
invention,
Figure 2 a block diagram of a further preferred embodiment of the process of
the
invention,
Figure 3 a block diagram of a further preferred embodiment of the process of
the
invention,
Figure 4 a block diagram of a further preferred embodiment of the process of
the
invention,
Figure 5 a block diagram of a further preferred embodiment of the process of
the
invention,
Figure 6 a block diagram of a further preferred embodiment of the process of
the
invention.
In Figures 1 to 6, the reference numerals have the following meanings:
Figure 1
1-1 hydrogenation reactor
11-1 first distillation apparatus
111-1 third phase separation apparatus (of the thermal dissociation
unit)
IV-1 second distillation apparatus (of the thermal dissociation unit)
1 stream comprising carbon dioxide
2 stream comprising hydrogen
3 stream comprising formic acid-amine adduct ((A2), residues of the
catalyst,
polar solvent; (lower phase (L1))
4 stream comprising inhibitor
5 stream comprising polar solvent; (distillate (D1))
CA 02838907 2013-12-10
41
6 stream comprising tertiary amine (Al) (upper phase (U2)) and
formic acid-
amine adduct (A2) (lower phase (L2)); bottoms mixture (Si)
7 stream comprising formic acid-amine adduct (A2) and inhibitor;
lower phase
(L3)
8 stream comprising tertiary amine (Al) (upper phase (U3)) and also formic
acid-
amine adduct (A2) and inhibitor (lower phase (L3)); bottoms mixture (S2)
9 stream comprising formic acid; (distillate (D2))
stream comprising tertiary amine (Al); upper phase (U3)
10 Figure 2
1-2 hydrogenation reactor
11-2 first distillation apparatus
111-2 third phase separation apparatus
1V-2 second distillation apparatus
V-2 first phase separation apparatus
V1-2 extraction unit
11 stream comprising carbon dioxide
12 stream comprising hydrogen
13a stream comprising hydrogenation mixture (H)
13b stream comprising lower phase (L1)
13c stream comprising raffinate (R2)
14 stream comprising inhibitor
15 stream comprising distillate (D1)
16 stream comprising bottoms mixture (Si)
17 stream comprising lower phase (L3)
18 stream comprising bottoms mixture (S2)
19 stream comprising formic acid; (distillate (D2))
20 stream comprising upper phase (U3)
21 stream comprising extract (E2)
22 stream comprising upper phase (U1)
Figure 3
1-3 hydrogenation reactor
11-3 first distillation apparatus
CA 02838907 2013-12-10
42
111-3 third phase separation apparatus
IV-3 second distillation apparatus
V-3 first phase separation apparatus
VI-3 extraction unit
31 stream comprising carbon dioxide
32 stream comprising hydrogen
33a stream comprising hydrogenation mixture (H)
33b stream comprising lower phase (L1)
33c stream comprising raffinate (R2)
34 stream comprising Inhibitor
35 stream comprising distillate (D1)
36 stream comprising bottoms mixture (Si)
37 stream comprising lower phase (L3)
38 stream comprising bottoms mixture (S2)
39 stream comprising formic acid; (distillate (D2))
40 stream comprising upper phase (U3)
41 stream comprising extract (E2)
42 stream comprising upper phase (U1)
Figure 4
1-4 hydrogenation reactor
11-4 first distillation apparatus
111-4 third phase separation apparatus
IV-4 second distillation apparatus
V-4 first phase separation apparatus
VI-4 extraction unit
V11-4 second phase separation apparatus
51 stream comprising carbon dioxide
52 stream comprising hydrogen
53a stream comprising hydrogenation mixture (H)
53b stream comprising lower phase (L1)
53c stream comprising raffinate (R2)
54 stream comprising Inhibitor
55 stream comprising distillate (D1)
CA 02838907 2013-12-10
43
56a stream comprising bottoms mixture (Si)
56b stream comprising lower phase (L2)
56c stream comprising upper phase (U2)
57 stream comprising lower phase (L3)
58 stream comprising bottoms mixture (S2)
59 stream comprising formic acid; (distillate (D2))
60 stream comprising upper phase (U3)
61 stream comprising extract (E2)
62 stream comprising upper phase (U1)
1-5 hydrogenation reactor
11-5 first distillation apparatus
111-5 third phase separation apparatus
IV-5 second distillation apparatus
V-5 first phase separation apparatus
VI-5 extraction unit
71 stream comprising carbon dioxide
72 stream comprising hydrogen
73a stream comprising hydrogenation mixture (H)
73b stream comprising lower phase (L1)
73c stream comprising raffinate (R2)
74 stream comprising inhibitor
75 stream comprising low-water distillate (D1wa)
76 stream comprising bottoms mixture (Si)
77 stream comprising lower phase (L3)
78 stream comprising bottoms mixture (S2)
79 stream comprising formic acid; (distillate (D2))
80 stream comprising upper phase (U3)
81 stream comprising extract (E2)
82 stream comprising upper phase (U1)
83 stream comprising water-rich distillate (D1wr)
Figure 6
1-6 hydrogenation reactor
CA 02838907 2013-12-10
44
11-6 first distillation apparatus
111-6 third phase separation apparatus
IV-6 second distillation apparatus
VI-6 extraction unit
91 stream comprising carbon dioxide
92 stream comprising hydrogen
93a stream comprising hydrogenation mixture (H)
93c stream comprising raffinate (R1)
94 stream comprising Inhibitor
95 stream comprising distillate (D1)
96 stream comprising bottoms mixture (Si)
97 stream comprising lower phase (L3)
98 stream comprising bottoms mixture (S2)
99 stream comprising formic acid; (distillate (D2))
100 stream comprising upper phase (U3)
101 stream comprising extract (El)
In the embodiment of Figure 1, a stream 1 comprising carbon dioxide and a
stream 2
comprising hydrogen are fed to a hydrogenation reactor 1-1. It is possible to
feed further
streams (not shown) to the hydrogenation reactor 1-1 in order to compensate
any losses of
the tertiary amine (Al) or the catalyst.
In the hydrogenation reactor 1-1, carbon dioxide and hydrogen are reacted in
the presence
of a tertiary amine (Al), a polar solvent and a catalyst comprising at least
one element of
groups 8, 9 and 10 of the Periodic Table. This gives a two-phase hydrogenation
mixture
(H) which comprises an upper phase (U1) comprising the catalyst and the
tertiary amine
(Al) and a lower phase (L1) comprising the polar solvent, residues of the
catalyst and the
formic acid-amine adduct (A2).
The lower phase (L1) is fed as stream 3 to the distillation apparatus 11-1.
The upper phase
(U1) remains in the hydrogenation reactor 1-1. In the embodiment of Figure 1,
the
hydrogenation reactor 1-1 simultaneously serves as first phase separation
apparatus.
The inhibitor is added continuously or discontinuously as stream 4 to the
stream 3. In the
first distillation apparatus, the lower phase (L1) is separated into a
distillate (D1)
comprising the polar solvent, which is recirculated as stream 5 to the
hydrogenation
CA 02838907 2013-12-10
reactor 1-1, and a two-phase bottoms mixture (Si) comprising an upper phase
(U2), which
comprises the tertiary amine (Al), and the lower phase (L2), which comprises
the formic
acid-amine adduct (A2), inhibited residues of the catalyst and the inhibitor.
5 The bottoms mixture (Si) is fed as stream 6 to the third phase separation
apparatus 111-1
of the thermal dissociation unit.
In the third phase separation apparatus III-1 of the thermal dissociation
unit, the bottoms
mixture (Si) is separated to give an upper phase (U3) comprising the tertiary
amine (Al)
10 and a lower phase (L3) comprising inhibited residues of the catalyst,
the inhibitor and the
formic acid-amine adduct (A2).
The upper phase (U3) is recirculated as stream 10 to the hydrogenation reactor
1-1. The
lower phase (L3) is fed as stream 7 to the second distillation apparatus 1V-1
of the thermal
15 dissociation unit. The formic acid-amine adduct (A2) comprised in the
lower phase (L3) is
dissociated into formic acid and free tertiary amine (Al) in the second
distillation
apparatus IV-1. A distillate (D2) and a two-phase bottoms mixture (S2) are
obtained in the
second distillation apparatus 1V-1.
20 The distillate (D2) comprising formic acid is discharged as stream 9
from the distillation
apparatus IV-1. The two-phase bottoms mixture (52) comprising the upper phase
(U3),
which comprises the tertiary amine (Al), and the lower phase (L3), which
comprises the
formic acid-amine adduct (A2), inhibited residues of the catalyst and the
inhibitor, is
recirculated as stream 8 to the third phase separation apparatus 111-1 of the
thermal
25 dissociation unit. In the third phase separation apparatus 111-1, the
bottoms mixture (82) is
separated into upper phase (U3) and lower phase (L3). The upper phase (U3) is
recirculated as stream 10 to the hydrogenation reactor 1-1. The lower phase
(L3) is
recirculated as stream 7 to the second distillation apparatus 1V-1.
30 In the embodiment of Figure 2, a stream 11 comprising carbon dioxide and
a stream 12
comprising hydrogen are fed to a hydrogenation reactor 1-2. It is possible to
feed further
streams (not shown) to the hydrogenation reactor 1-2 in order to compensate
any losses of
the tertiary amine (Al) or the catalyst.
35 In the hydrogenation reactor 1-2, carbon dioxide and hydrogen are
reacted in the presence
of a tertiary amine (Al), a polar solvent and a catalyst comprising at least
one element of
groups 8, 9 and 10 of the Periodic Table. This gives a two-phase hydrogenation
mixture
CA 02838907 2013-12-10
46
(H) which comprises an upper phase (U1) comprising the catalyst and the
tertiary amine
(Al) and a lower phase (L1) comprising the polar solvent, residues of the
catalyst and the
formic acid-amine adduct (A2).
The hydrogenation mixture (H) is fed as stream 13a to a first phase separation
apparatus
V-2. In the first separation phase apparatus V-2, the hydrogenation mixture
(H) is
separated into the upper phase (U1) and the lower phase (L1).
The upper phase (U1) is recirculated as stream 22 to the hydrogenation reactor
1-2. The
lower phase (L1) is fed as stream 13b to the extraction unit V1-2. In this,
the lower phase
(L1) is extracted with the tertiary amine (Al) which is recirculated as stream
20 (upper
phase (U3)) from the third phase separation apparatus 111-2 to the extraction
apparatus VI-
2.
A raffinate (R2) and an extract (E2) are obtained in the extraction unit V1-2.
The raffinate
(R2) comprises the formic acid-amine adduct (A2) and the polar solvent and is
fed as
stream 13c to the first distillation apparatus 11-2. The extract (E2)
comprises the terrtiary
amine (Al) and the residues of the catalyst and is recirculated as stream 21
to the
hydrogenation reactor 1-2.
The inhibitor is added continuously or discontinuously as stream 14 to the
stream 13c. In
the first distillation apparatus 11-2, the raffinate (R2) is separated into a
distillate (D1)
comprising the polar solvent, which is recirculated as stream 15 to the
hydrogenation
reactor 1-2, and a two-phase bottoms mixture (Si).
The bottoms mixture (Si) comprises an upper phase (U2), which comprises the
tertiary
amine (Al), and a lower phase (L2), which comprises the formic acid-amine
adduct (A2),
inhibited residues of the catalyst and the inhibitor. The bottoms mixture (Si)
is fed as
stream 16 to the second distillation apparatus 1V-2.
The formic acid-amine adduct comprised in the bottoms mixture (S1) is
dissociated into
formic acid and free tertiary amine (Al) in the second distillation apparatus
IV-2. A distillate
(D2) and a bottoms mixture (S2) are obtained in the second distillation
apparatus IV-2.
The distillate (D2) comprising formic acid is discharged as stream 19 from the
second
distillation apparatus IV-2. The two-phase bottoms mixture (S2) comprising the
upper
phase (U3), which comprises the tertiary amine (Al), and the lower phase (L3),
which
CA 02838907 2013-12-10
47
comprises the formic acid-amine adduct (A2), inhibited residues of the
catalyst and the
inhibitor, is recirculated as stream 18 to the third phase separation
apparatus 111-2 of the
thermal dissociation unit.
In the third phase separation apparatus 111-2 of the thermal dissociation
unit, the bottoms
mixture (S2) is separated to give an upper phase (U3) comprising the tertiary
amine (Al)
and a lower phase (L3) comprising inhibited residues of the catalyst, the
inhibitor and the
formic acid-amine adduct (A2).
The upper phase (U3) from the third phase separation apparatus 111-2 is
recirculated as
stream 20 to the extraction unit VI-2. The lower phase (L3) is fed as stream
17 to the
second distillation apparatus IV-2 of the thermal dissociation unit. The
formic acid-amine
adduct (A2) comprised in the lower phase (L3) is dissociated into formic acid
and free
tertiary amine (Al) in the second distillation apparatus IV-2. As indicated
above, a distillate
(D2) and a bottoms mixture (S2) are then again obtained in the second
distillation
apparatus IV-2.
In the embodiment of Figure 3, a stream 31 comprising carbon dioxide and a
stream 32
comprising hydrogen are fed to a hydrogenation reactor 1-3. It is possible to
feed further
streams (not shown) to the hydrogenation reactor 1-3 in order to compensate
any losses of
the tertiary amine (Al) or the catalyst.
In the hydrogenation reactor 1-3, carbon dioxide and hydrogen are reacted in
the presence
of a tertiary amine (Al), a polar solvent and a catalyst comprising at least
one element of
groups 8, 9 and 10 of the Periodic Table. This gives a two-phase hydrogenation
mixture
(H) which comprises an upper phase (U1) comprising the catalyst and the
tertiary amine
(Al) and a lower phase (L1) comprising the polar solvent, residues of the
catalyst and the
formic acid-amine adduct (A2).
The hydrogenation mixture (H) is fed as stream 33a to a first phase separation
apparatus V-3. In the first phase separation apparatus V-3, the hydrogenation
mixture (H)
is separated into the upper phase (U1) and the lower phase (L1).
The upper phase (U1) is recirculated as stream 42 to the hydrogenation reactor
1-3. The
lower phase (L1) is fed as stream 33b to the extraction unit VI-3. In this,
the lower phase
(L1) is extracted with the tertiary amine (Al) which is recirculated as stream
40 (upper
CA 02838907 2013-12-10
48
phase (U3)) from the third phase separation apparatus 111-3 of the thermal
dissociation unit
to the extraction unit V1-3.
A raffinate (R2) and an extract (E2) are obtained in the extraction unit VI-3.
The raffinate
(R2) comprises the formic acid-amine adduct (A2) and the polar solvent and is
fed as
stream 33c to the first distillation apparatus 11-3. The extract (E2)
comprises the tertiary
amine (Al) and the residues of the catalyst and is recirculated as stream 41
to the
hydrogenation reactor 1-2.
The inhibitor is added continuously or discontinuously as stream 34 to the
stream 33c. In
the first distillation apparatus 11-3, the raffinate (R2) is separated into a
distillate (D1)
comprising the polar solvent, which is recirculated as stream 35 to the
hydrogenation
reactor 1-3, and a two-phase bottoms mixture (S1).
The bottoms mixture (Si) comprises an upper phase (U2), which comprises the
tertiary
amine (Al), and a lower phase (L2), which comprises the formic acid-amine
adduct (A2),
inhibited residues of the catalyst and the inhibitor.
The bottoms mixture (Si) is fed as stream 36 to the third phase separation
apparatus 111-3
of the thermal dissociation unit.
In the third phase separation apparatus 111-3 of the thermal dissociation
unit, the bottoms
mixture (Si) is separated to give an upper phase (U3) comprising the tertiary
amine (Al)
and a lower phase (L3) comprising inhibited residues of the catalyst, the
inhibitor and the
formic acid-amine adduct (A2).
The upper phase (U3) is recirculated as stream 40 to the extraction unit V1-3.
The lower
phase (L3) is fed as stream 37 to the second distillation apparatus IV-3 of
the thermal
dissociation unit. The formic acid-amine adduct (A2) comprised in the lower
phase (L3) is
dissociated into formic acid and free tertiary amine (Al) in the second
distillation
apparatus IV-3. A distillate (D2) and a bottoms mixture (S2) are obtained in
the second
distillation apparatus IV-3.
The distillate (D2) comprising formic acid is discharged as stream 39 from the
distillation
apparatus 1V-3. The two-phase bottoms mixture (S2) comprising the upper phase
(U3),
which comprises the tertiary amine (Al), and the lower phase (L3), which
comprises the
CA 02838907 2013-12-10
49
formic acid-amine adduct (A2), inhibited residues of the catalyst and the
inhibitor, is
recirculated as stream 38 to the third phase separation apparatus 111-3 of the
thermal
dissociation unit. In the third phase separation apparatus 111-3, the bottoms
mixture (S2) is
separated. The upper phase (U3) is recirculated to the extraction unit V1-3.
The lower
phase (L3) is recirculated to the second distillation apparatus IV-3.
In the embodiment of Figure 4, a stream 51 comprising carbon dioxide and a
stream 52
comprising hydrogen are fed to a hydrogenation reactor 1-4. It is possible to
feed further
streams (not shown) to the hydrogenation reactor 1-4 in order to compensate
any losses of
the tertiary amine (Al) or the catalyst.
In the hydrogenation reactor 1-4, carbon dioxide and hydrogen are reacted in
the presence
of a tertiary amine (Al), a polar solvent and a catalyst comprising at least
one element of
groups 8, 9 and 10 of the Periodic Table. This gives a two-phase hydrogenation
mixture
(H) which comprises an upper phase (U1) comprising the catalyst and the
tertiary amine
(Al) and a lower phase (L1) comporising the polar solvent, residues of the
catalyst and the
formic acid-amine adduct (A2).
The hydrogenation mixture (H) is fed as stream 53a to a first phase separation
apparatus V-4. In the first phase separation apparatus V-4, the hydrogenation
mixture (H)
is separated into the upper phase (U1) and the lower phase (L1).
The upper phase (U1) is recirculated as stream 62 to the hydrogenation reactor
1-4. The
lower phase (L1) is fed as stream 53b to the extraction unit VI-4. In this,
the lower phase
(L1) is extracted with the tertiary amine (Al) which is recirculated as stream
60 (upper
phase (U3)) from the third phase separation apparatus 111-4 of the thermal
dissociation unit
and as stream 56c from the second phase separation apparatus VII-4 to the
extraction unit
VI-4.
A raffinate (R2) and an extract (E2) are obtained in the extraction unit VI-4.
The raffinate
(R2) comprises the formic acid-amine adduct (A2) and the polar solvent and is
fed as
stream 53c to the first distillation apparatus 11-4. The extract (E2)
comprises the tertiary
amine (Al) and the residues of the catalyst and is recirculated as stream 61
to the
hydrogenation reactor 1-4.
CA 02838907 2013-12-10
The inhibitor is added continuously or discontinuously as stream 54 to the
stream 53c. In
the first distillation apparatus 11-4, the raffinate (R2) is separated into a
distillate (D1)
comprising the polar solvent, which is recirculated as stream 55 to the
hydrogenation
reactor 1-4, and a two-phase bottoms mixture (S1).
5 The bottoms mixture (Si) comprises an upper phase (U2), which comprises
the tertiary
amine (Al), and a lower phase (L2), which comprises the formic acid-amine
adduct (A2),
inhibited residues of the catalyst and the inhibitor. The bottoms mixture (Si)
is fed as
stream 56a to the second phase separation apparatus V11-4.
In the second phase separation apparatus V11-4, the bottoms mixture (Si) is
separated
10 into the upper phase (U2) and the lower phase (L2). The upper phase (U2)
is recirculated
from the second phase separation apparatus VII-4 as stream 56c to the
extraction unit
VI-4.
The lower phase (L2) is fed as stream 56b to the second distillation apparatus
IV-4.
The formic acid-amine adduct (A2) comprised in the lower phase (L2) is
dissociated into
15 formic acid and free tertiary amine (Al) in the second distillation
apparatus IV-4. A distillate
(D2) and a bottoms mixture (S2) are obtained in the second distillation
apparatus IV-4.
The distillate (D2) comprising formic acid is discharged as stream 59 from the
second
distillation apparatus IV-4. The two-phase bottoms mixture (S2) comprising the
upper
phase (U3), which comprises the tertiary amine (Al), and the lower phase (L3),
which
20 comprises the formic acid-amine adduct (A2), inhibited residues of the
catalyst and the
inhibitor, is recirculated as stream 58 to the third phase separation
apparatus 111-4 of the
thermal dissociation unit.
In the third phase separation apparatus 111-4 of the thermal dissociation
unit, the bottoms
mixture (S2) is separated to give an upper phase (U3) comprising the tertiary
amine (Al)
25 and a lower phase (L3) comprising inhibited residues of the catalyst,
the inhibitor and the
formic acid-amine adduct (A2).
The upper phase (U3) is recirculated from the third phase separation apparatus
III-4 as
stream 60 to the extraction unit VI-4. The lower phase (L3) is fed as stream
57 to the
second distillation apparatus IV-4 of the thermal dissociation unit. The
formic acid-amine
CA 02838907 2013-12-10
51
adduct (A2) comprised in the lower phase (L3) is dissociated into formic acid
and free
tertiary amine (Al) in the second distillation apparatus IV-4. A distillate
(D2) and a bottoms
mixture (S2) are, as indicated above, then again obtained in the second
distillation
apparatus 1V-4.
In the embodiment of Figure 5, a stream 71 comprising carbon dioxide and a
stream 72
comprising hydrogen are fed to a hydrogenation reactor 1-5. It is possible to
feed further
streams (not shown) to the hydrogenation reactor 1-5 in order to compensate
any losses of
the tertiary amine (Al) or the catalyst.
In the hydrogenation reactor 1-5, carbon dioxide and hydrogen are reacted in
the presence
of a tertiary amine (Al), a polar solvent and a catalyst comprising at least
one element of
groups 8, 9 and 10 of the Periodic Table. This gives a two-phase hydrogenation
mixture
(H) which comprises an upper phase (U1) comprising the catalyst and the
tertiary amine
(Al) and a lower phase (L1) comprising the polar solvent, residues of the
catalyst and the
formic acid-amine adduct (A2).
The hydrogenation mixture (H) is fed as stream 73a to a first phase separation
apparatus V-5. In the first phase separation apparatus V-5, the hydrogenation
mixture (H)
is separated into the upper phase (U1) and the lower phase (L1).
The upper phase (U1) is recirculated as stream 82 to the hydrogenation reactor
1-5. The
lower phase (L1) is fed as stream 73b to the extraction unit VI-5. Here, the
lower phase
(L1) is extracted with the tertiary amine (Al) which is recirculated as stream
80 (upper
phase (U3)) from the third phase separation apparatus of the thermal
dissociation unit to
the extraction unit V1-5.
A raffinate (R2) and an extract (E2) are obtained in the extraction unit VI-5.
The raffinate
(R2) comprises the formic acid-amine adduct (A2) and the polar solvent and is
fed as
stream 73c to the first distillation apparatus 11-5. The extract (E2)
comprises the tertiary
amine (Al) and the residues of the catalyst and is recirculated as stream 81
to the
hydrogenation reactor 1-5.
The inhibitor is added continuously or discontinuously as stream 74 to the
stream 73c. In
the first distillation apparatus 11-5, the raffinate (R2) is separated into a
water-rich distillate
CA 02838907 2013-12-10
52
(D1wr), a low-water distillate (D1wa) and a two-phase bottoms mixture (Si).
The water-
rich distillate (D1wr) is added as stream 83 to the stream 73a. The low-water
distillate
(D1wa) is recirculated as stream 75 to the hydrogenation reactor 1-5. A
prerequisite of the
embodiment of Figure 5 is that a mixture of one or more alcohols with water is
used as
polar solvent.
The bottoms mixture (Si) comprises an upper phase (U2), which comprises the
tertiary
amine (Al), and a lower phase (L2), which comprises the formic acid-amine
adduct (A2),
inhibited residues of the catalyst and the inhibitor.
The bottoms mixture (Si) is fed as stream 76 to the third phase separation
apparatus 111-5
of the thermal dissociation unit.
In the third phase separation apparatus 111-5 of the thermal dissociation
unit, the bottoms
mixture (Si) is separated to give an upper phase (U3) comprising the tertiary
amine (Al)
and a lower phase (L3) compirising inhibited residues of the catalyst, the
inhibitor and the
formic acid-amine adduct (A2).
The upper phase (U3) is recirculated as stream 80 to the extraction unit IV-5.
The lower
phase (L3) is fed as stream 77 to the second distillation apparatus IV-5 of
the thermal
dissociation unit. The formic acid-amine adduct (A2) comprised in the lower
phase (L3) is
dissociated into formic acid and free tertiary amine (Al) in the second
distillation
apparatus IV-5. A distillate (D2) and a bottoms mixture (S2) are obtained in
the second
distillation apparatus IV-5.
The distillate (D2) comprising formic acid is discharged as stream 79 from the
distillation
apparatus IV-5. The two-phase bottoms mixture (S2) comprising the upper phase
(U3),
which comprises the tertiary amine (Al), and the lower phase (L3), which
comprises the
formic acid-amine adduct (A2), inhibited residues of the catalyst and the
inhibitor, is
recirculated as stream 78 to the third phase separation apparatus 111-5 of the
thermal
dissociation unit. The bottoms mixture (S2) is separated in the third phase
separation
apparatus 111-5. The upper phase (U3) is recirculated as stream 80 to the
extraction unit VI-
5. The lower phase (L3) is recirculated as stream 77 to the second
distillation apparatus
IV-5.
In the embodiment of Figure 6, a stream 91 comprising carbon dioxide and a
stream 92
comprising hydrogen are fed to a hydrogenation reactor 1-6. It is possible to
feed further
CA 02838907 2013-12-10
53
streams (not shown) to the hydrogenation reactor 1-6 in order to compensate
any losses of
the tertiary amine (Al) or the catalyst.
In the hydrogenation reactor 1-6, carbon dioxide and hydrogen are reacted in
the presence
of a tertiary amine (Al), a polar solvent and a catalyst comprising at least
one element of
groups 8, 9 and 10 of the Periodic Table. This gives a two-phase hydrogenation
mixture
(H) which comprises an upper phase (U1) comprising the catalyst and the
tertiary amine
(Al) and a lower phase (L1) comprising the polar solvent, residues of the
catalyst and the
formic acid-amine adduct (A2).
The hydrogenation mixture (H) is fed as stream 93a to the extraction unit VI-
6.
In this, the hydrogenation mixture (H) is extracted with the tertiary amine
(Al) which is
recirculated as stream 100 (upper phase (U3)) from the third phase separation
apparatus
111-6 of the thermal dissociation unit to the extraction unit VI-6.
A raffinate (R1) and an extract (El) are obtained in the extraction unit VI-6.
The raffinate
(R1) comprises the formic acid-amine adduct (A2) and the polar solvent and is
fed as
stream 93c to the first distillation apparatus 11-6. The extract (El)
comprises the tertiary
amine (Al) and the catalyst and is recirculated as stream 101 to the
hydrogenation reactor
1-6.
The inhibitor is added continuously or discontinuously as stream 94 to the
stream 93c. In
the first distillation apparatus 11-6, the raffinate (R1) is separated into a
distillate (D1)
comprising the polar solvent, which is recirculated as stream 95 to the
hydrogenation
reactor 1-6, and a two-phase bottoms mixture (Si).
The bottoms mixture (Si) comprises an upper phase (U2), which comprises the
tertiary
amine (Al), and a lower phase (L2), which comprises the formic acid-amine
adduct (A2),
inhibited residues of the catalyst and the inhibitor.
The bottoms mixture (81) is fed as stream 96 to the third phase separation
apparatus 111-6
of the thermal dissociation unit.
In the third phase separation apparatus 111-6 of the thermal dissociation
unit, the bottoms
mixture (81) is separated to give an upper phase (U3) comprising the tertiary
amine (Al)
CA 02838907 2013-12-10
54
and a lower phase (L3) comprising inhibited residues of the catalyst, the
inhibitor and the
formic acid-amine adduct (A2).
The upper phase (U3) is recirculated as stream 100 to the extraction unit VI-
6. The lower
phase (L3) is fed as stream 97 to the second distillation apparatus IV-6 of
the thermal
dissociation unit. The formic acid-amine adduct (A2) comprised in the lower
phase (L3) is
dissociated into formic acid and free tertiary amine (Al) in the second
distillation
apparatus IV-6. A distillate (D2) and a bottoms mixture (S2) are obtained in
the second
distillation apparatus IV-6.
The distillate (D2) comprising formic acid is discharged as stream 99 from the
distillation
apparatus IV-6. The two-phase bottoms mixture (S2) comprising the upper phase
(U3),
which comprises the tertiary amine (Al), and the lower phase (L3), which
comprises the
formic acid-amine adduct (A2), inhibited residues of the catalyst and the
inhibitor, is
recirculated as stream 98 to the third phase separation apparatus III-6 of the
thermal
dissociation unit. The bottoms mixture (S2) is separated in the third phase
separation
apparatus III-6. The upper phase (U3) is recirculated as stream 100 to the
extraction unit
VI-6. The lower phase (L3) is recirculated as stream 97 to the second
distillation apparatus
IV-6.
The invention is illustrated below by means of examples and a drawing.
Examples
Examples A-1 to A-17 according to the invention (hydrogenation and phase
separation,
work-up of the output from the hydrogenation reactor)
A 250 ml Hastelloy C autoclave equipped with a magnetic stirrer bar was
charged under
inert conditions with tertiary amine (Al), polar solvent and homogeneous
catalyst. The
autoclave was subsequently closed and CO2 was injected at room temperature. H2
was
then injected and the reactor was heated while stirring (700 rpm). After the
desired
reaction time, the autoclave was cooled and the hydrogenation mixture (H) was
depressurized. Unless indicated otherwise, a two-phase hydrogenation mixture
(H) was
obtained, with the upper phase (U1) being enriched in the still free tertiary
amine (Al) and
the homogeneous catalyst and the lower phase (L1) being enriched in the polar
solvent
and the formic acid-amine adduct (A2) formed. The total content of formic acid
in the
CA 02838907 2013-12-10
formic acid-amine adduct (A2) was determined by potentiometric titration with
0.1 N KOH
in Me0H using a "Mettler Toledo DL50" titrator. The turnover frequency (=TOF;
for the
definition of the TOF see: J.F. Hartwig, Organotransition Metal Chemistry, 1st
edition,
2010, University Science Books, Sausalito/California p.545) and the reaction
rate were
5 calculated therefrom. The composition of the two phases was determined by
gas
chromatography. The ruthenium content was determined by atomic adsorption
spectroscopy (=AAS). The parameters and results of the individual experiments
are shown
in Tables 1.1 to 1.5.
10 Examples A-1 to A-17 show that high to very high reaction rates of up to
0.98 mol kg-1 h-1 are achieved in the process of the invention even with
variation of the
tertiary amine (Al), the polar solvent, the catalyst in respect of the ligands
and the metal
component, the amount of the catalyst and the amount of water added. All
systems
examined formed two phases, with the upper phase (U1) in each case being
enriched in
15 the still free tertiary amine (Al) and the homogeneous catalyst and the
lower phase (L1) in
each case being enriched in the polar solvent and the formic acid-amine adduct
(A2)
formed.
Table 1.1
Example A-1 Example A-2 Example A-3
Example A-4
Tertiary amine (Al) 75 g of trihexylamine 75 g of
trihexylamine 75 g of tripentylamine 75 g of tripentylamine
Polar solvent 17.8 g of 1-propanol 21.7 g of 2-propanol
17.8 g of 1-propanol 17.8 g of 1-propanol
(used) 7.3 g of water 3.3 g of water 7.3 g of
water 7.3 g of water
Catalyst 0.2 g of [Ru(rE3u3)4(H)2] 0.2 g of
[Ru(PnI3u3)4(H)2] 0.3 g of [Ru(PnOct3)4(H)2] 0.2 g of [Ru(PnI3u3)4(H)2]
Injection of CO2 19.6 g to 2.4 MPa abs 20.0 g to 2.3 MPa abs
20.0 g to 2.5 MPa abs 20.3 g to 2.5 MPa abs
Injection of H2 to 10.4 MPa abs to 10.3 MPa
abs to 10.6 MPa abs to 10.5 MPa abs
Heating to 50 C to 50 C to 50 C
to 50 C
Pressure change to 10.0 MPa abs to 10.5 MPa
abs to 11.4 MPa abs to 11.5 MPa abs 0
I.)
Reaction time 1 hour 1 hour 1 hour
1 hour co
Special feature - - -
cow
ko
Upper phase (U1) 57.5g 62.3g 75.6g
63.8g (y, 0
-A
8.0% of 1-propanol 15.4% of 2-propanol 10.9% of 1-
propanol 5.7% of 1-propanol cs) I.)
0
0.9% of water 1.7% of water 0.9% of
water 0.5% of water H
u.)
91.1% of trihexylamine 82.9% of trihexylamine
88.2% of tripentylamine 93.8% of tripentylamine I
H
Lower phase (L1) 43.6 g 37.3 g 22.9 g
38.4 g "
1
5.9% of formic acid 4.7% of formic acid 3.4% of
formic acid 6.8% of formic acid H
0
30.3% of 1-propanol 32.4% of 2-propanol 41.7% of 1-
propanol 36.7% of 1-propanol
15.6% of water 5.9% of water 28.9% of water
18.2% of water
48.3% of trihexylamine 56.8% of trihexylamine 26% of tripentylamine
38.3% of tripentylamine
kR, (cRu in upper phase 1.60 1.02 85
2.7
(U1)/ cRL, in lower phase
(L1)) _
TOF 252 h-1 175 1.1-1 81 h-1
250 h-1
_
Reaction rate 0.54 mol kg-1 h-1 0.38 mol kg-
1 h-1 0.17 mol kg-1 h-1 0.56 mol kg-1 h-1
Table 1.2
Example A-5 Example A-6 Example
A-7 Example A-8
Tertiary amine (Al) 75g of tripentylamine 75 g of tripentylamine
75g of tripentylamine 75 g of tripentylamine
Polar solvent 21.8 g of 2-propanol 17.8 g of 1-propanol 17.8 g
of 1-propanol 18.8 g of methanol
(used) 3.3 g of water 7.3 g of water 7.3 g
of water 6.3 g of water
Catalyst 0.2 g of [Ru(PnBu3)4(H)2] 0.2 g of
[Ru(In3u3)4(H)2], 0.2 g of [Ru(PnBu3)4(H)2], 0.2 g of [Ru(PnBu3)4(H)2]
0.2 g of 1,2-bis(dicylcohexyl- 0.2 g of 1,2-bis(dicylcohexyl-
phosphino)ethane
phosphino)ethane
Injection of CO2 20.1 g to 2.4 MPa abs 20.2 g to 2.8 MPa abs
20.0 g to 2.5 MPa abs 20.0 g to 2.3 MPa abs
Injection of H2 to 10.4 MPa abs to 8.1 MPa abs to 10.5
MPa abs to 10.3 MPa
0
Heating to 50 C to 50 C
to 50 C to 50 C
Pressure change to 11.0 MPa abs to 8.5 MPa abs
to 10.9 MPa abs. to 10.5 MPa 0
I.)
Reaction time 1 hour 1 hour
1 hour 1 hour co
u.)
co
Special feature -
- ko
0
Upper phase (U1) 65.79 60.6 g
51.4 g 60.5 g -V
oi
11.5% of 2-propanol 5.1% of 1-propanol
3.9% of 1-propanol 3.1% of methanol -4 N.)
0
1.0% of water 94.9% of tripentylamine 96.1%
of tripentylamine 96.9% of tripentylamine H
LO
I
87.5% of tripentylamine
H
IV
Lower phase (L1) 35.0 g 40.8 g
50.1 g 40.8 g I
H
5.6% of formic acid 7.0% of formic acid
8.4% of formic acid 7.3% of formic acid 0
40.6% of 2-propanol 36.0% of 1-propanol 31.5% of
1-propanol 41.5% of methanol
7.5% of water 17.9% of water 14.6%
of water 15.4% of water
46.3% of tripentylamine 39.1% of tripentylamine 45.5%
of tripentylamine 35.8% of tripentylamine
kRu (cRu in upper phase 1.4 2.2 2.5
4.8
(U1) / cRu in lower phase
(L1))
TOE 195 h-1 282 h-1
413 h-1 290 h-1
Reaction rate 0.43 mol kg-111-1 .
0.61 mol kg"1 h-1 0.90 mol kg-1 11-1 0.64 mol kg-1 h-1 '
Table 1.3
Example A-9 Example A-10 Example A-
11 Example A-12
Tertiary amine (Al) 70 g of trihexylamine 75 g of
tripentylamine 75 g of tripentylamine 75 g of trihexylamine
Polar solvent 15.0 g of ethanol 21.5 g of
methanol 24.0 g of methanol 22.0 g of methanol
(used) 5.0 g of water 3.6 g of water 1.0 g of
water 3.0 g of water
Catalyst 0.2 g of [Ru(Pn131-13)4(H)2] 0-2 9 of [Ru(r13113)4(H)21
0-16 g of [Ru(PnOct3)4(H)2] 0.16 g of [Ru(rOct3)4(H)2],
0.08 g of 1,2-bis(dicyclohexyl-
phosphino)ethane
Injection of CO2 20.2 g to 2.5 MPa abs 20.0 g to 2.2
MPa abs 19.9 g to 2.3 MPa abs 20.0 g to 2.5 MPa abs n
Injection of H2 to 10.9 MPa abs to 10.5 MPa
abs to 10.3 MPa abs to 10.5 MPa abs 0
Heating to 50 C to 50 C to
50 C to 50 C "
co
Pressure change to 11.8 MPa abs to 10.3 MPa
abs to 10.2 MPa abs to 10.6 MPa abs u.)
co
ko
Reaction time 1 hour 1 hour 1
hour 1 hour 0
-A
Special feature - -
- I.)
Upper phase (U1) 52.0 g 49.5 g
63.3 g 46.7 g cri 0
co
H
4.6% of ethanol 2.5% of methanol 8.4% of methanol
4.1% of methanol u.)
,
H
95.4% of trihexylamine 77.5 g of tripentylamine
91.6% of tripentylamine 95.9% of trihexylamine "
1
Lower phase (L1) 38.4 g 52.8 g
35.9 g 54.2 g H
0
7.3% of formic acid 8.7% of formic acid 4.5% of formic acid 7.2%
of formic acid
32.8% of ethanol 38.5% of methanol 52.1% of methanol 37.1%
of methanol
13.0% of water 6.8% of water 2.8% of water 5.5% of
water
46.9% of tripentylamine 46.0% of tripentylamine
40.7% of tripentylamine 50.2% of trihexylamine
kR, (cR, in upper phase 1.9 2.5 14.0
1.7
(U1) / cRi, in lower phase
(L1)) .
TOF 271 h-1 446 h-1 343
h-1 806 h-1
Reaction rate 0.67 mol kg-1 h-1 0.98 mol kg-
1 h-1 0.35 mol k_g-1 h-1 0.84 mol kg-1 h-1
Table 1.4
Example A-13 Example A-14 Example A-15
Example A-16
Tertiary amine (Al) 75 g of trihexylamine 75 g of
trihexylamine 75 g of trihexylamine 75 g of trihexylamine
Polar solvent 24.0 g of methanol 25.0 g of ethanol 25.0 g of 1-
propanol 25.0 g of ethanol
(used) 6.7 g of water 6.0 g of water 6.0 g of
water 8.0 g of water
Catalyst 0.18 g of [Ru(PnBu3)4(H)2] 0.16 g of 0.16 g of
[Ru(PnOct3)4(H)2], 0.16 g of [Ru(PnOct3)4(H)2],
[Ru(PnOct3)4(H)2], 0.08 g of 1,2-
bis(dicyclo- 0.08 g of 1,2-bis(dicyclohexyl-
0.08 g of 1,2-bis(dicyclo-
hexylphosphino)ethane phosphino)ethane
hexylphosphino)ethane
Injection of CO2 20.2 g to 3.5 MPa abs 19.9 g to 2.5 MPa abs
19.9 g to 2.5 MPa abs 19.5 g to 2.6 MPa abs
Injection of H2 to 11.5 MPa abs to 11.5 MPa abs , to 10.5 MPa
abs to 10.7 MPa abs n
Heating to 50 C to 50 C to 50 C
to 50 C 0
Pressure change to 11.0 MPa abs to 10.5 MPa abs to 11.3 MPa
abs to 11.6 MPa abs I.)
co
u.)
Reaction time 1 hour 1 hour 1 hour
2 hours co
ko
Special feature - -
0
csi
-A
Upper phase (U1) 44.1 g 60.2 g 46.4 g
48.9 g
2.7% of methanol 0.7% of water 2.0% of
water 0.6% of water 0
F-,
LO
97.3% of trihexylamine 6.6% of ethanol 6.2% of 1-
propanol 4.5% of ethanol I
H
92.7% of trihexylamine 91.8% of
trihexylamine 94.9% of trihexylamine I.)
1
Lower phase (L1) 65.9g 51.3g 60.6g
61.9g H
0
7.5% of formic acid 5.3% of formic acid 5.6% of
formic acid 6.0% of formic acid
10.2% of water 9.3% of water 8.4% of
water 12.4% of water
34.6% of methanol 41.0% of ethanol 36.5% of 1-
propanol 36.8% of ethanol
47.7% of trihexylamine 44.4% of trihexylamine 49.5% of
trihexylamine 44.8% of trihexylamine
KRu (cRi, in upper 1.9 1.6 1.5
3.2
phase (U1)/ cRu in
lower phase (L1))
TOF 551 h-1 569 h-1 726 h-1
351 h-1
Reaction rate 0.98 mol kg-1 h-1 0.53 mol kg-1 h-1 0.68 mol kg-1
h-1 0.37 mol kg-1 h-1
CA 02838907 2013-12-10
Table 1.5
Example A-17
Tertiary amine (Al) 75 g of trihexylamine
Polar solvent 25.0 g of 1-propanol
ji.Js,0) 8.0 g of water
Catalyst 0.16 g of [Ru(PnOct3)4(H)2],
0.08 g of 1,2-
bis(dicyclohexylphosphino)ethane
Injection of CO2 20.3 g to 2.5 MPa abs
Injection of H2 to 10.5 MPa abs
Heating to 50 C
Pressure change to 11.4 MPa abs
Reaction time 2 hours
Special feature
Upper phase (U1) 37.1 g
2.6% of water
3.9% of 1-propanol
93.5% of trihexylamine
Lower phase (L1) 74.5 g
6.2% of formic acid
9.4% of water
31.5% of 1-propanol
52.9% of trihexylamine
KRu (CRu in upper phase 3.9
(U1) / cRi, in lower phase
(L1))
TOE 437 h-1
Reaction rate 0.45 mol kg-1 h-1
CA 02838907 2013-12-10
61
Examples A-18 to A-21 (hydrogenation using diols and methanol as solvent)
A 100 ml or 250 ml Hastelloy C autoclave equipped with a blade or magnetic
stirrer was
charged under inert conditions with the tertiary amine (Al), polar solvent and
the
catalyst. The autoclave was subsequently closed and CO2 was injected at room
temperature. H2 was then injected and the stirrer was heated while stirring
(700-
1000 rpm). After the reaction time, the autoclave was cooled and the
hydrogenation
mixture (H) was depressurized. After the reaction, water was added where
applicable to
the reaction output and the mixture was stirred for 10 minutes at room
temperature. A
two-phase hydrogenation mixture (H) was obtained, with the upper phase (U1)
being
enriched in the tertiary amine (Al) and the homogeneous catalyst and the lower
phase
(L1) being enriched in the polar solvent and the formic acid-amine adduct (A2)
formed.
The phases were subsequently separated and the formic acid content of the
lower
phase (L1) was determined. The total content of formic acid in the formic acid-
amine
adduct (A2) was determined by potentiometric titration with 0.1 N KOH in Me0H
using a
"Mettler Toledo DL50" titrator. The parameters and results of the individual
experiments
are shown in Table 1.1
Examples A-18 to A-21 show that, under comparable conditions, higher formic
acid
concentrations in the lower phase can be achieved when using methanol/water
mixtures
as polar solvent compared to dials as polar solvent.
Table 1.6
Comparative Example Example A-19 according to
Comparative Example Example A-21 according to
A-18 the invention A-20 the
invention
Autoclave 250 ml 250 ml 250 ml
100 ml
Tertiary amine (Al) trihexylamine 50.0 g trihexylamine 85.0 g
trihexylamine 50.0 g trihexylamine 37.5 g
Polar solvent 2-methyl-1,3-propanediol methanol 25.0 g
1,4-butanediol 50.0 g methanol 12.0 g
(used) 50.0 g water 2.0 g
water 0.25 g
Catalyst [Ru(PnBu3)4(H)21100 mg [Ru(PnOcty13)4(H)2] 320 mg
[Ru(PnBu3)4(H)21 100 mg [Ru(PnOcty13)4(H)2] 160mg n
1,2-bis(dicyclohexylphos- 1,2-bis(dicyclohexyl-
1,2-bis(dicyclohexyl- 1,2-bis(dicyclohexyl- 0
phino)ethane 90 mg phosphino)ethane 90 mg
phosphino)ethane 90 mg phosphino)ethane 82 mg I.)
co
Injection of CO2 20.4 g to 3.6 MPa 26.2 g to 2.8 MPa 15.5 g to
3.1 MPa 7.9 g to 2.9 MPa
co
Injection of H2 to 11.1 MPa to 12.0 MPa to 8.1
MPa to 8.0 MPa IV to
0
-A
Heating 50 C 50 C 50
C 50 C I.)
Reaction time 1 h 1 h 1 h
1 h 0
H
Formic acid concen- 7.1% 8.5%
2.1% 8.0 u.)
,
H
tration in the lower
I.)
1
phase (L1)
H
0
Water addition after - 2.0 g-
1.0 g
the reaction
CA 02838907 2013-12-10
63
Examples B-1 to B-3 (extraction of the catalyst)
A 100 ml Hastelloy C autoclave equipped with a blade stirrer was charged under
inert
conditions with the tertiary amine (Al), polar solvent and the catalyst. The
autoclave was
subsequently closed and CO2 was injected at room temperature. H2 was then
injected and
the reactor was heated while stirring (1000 rpm). After the reaction time, the
autoclave was
cooled and the hydrogenation mixture (H) was depressurized. This gave a two-
phase
hydrogenation mixture (H), in which the upper phase (U1) was enriched in the
still free
tertiary amine (Al) and the homogeneous catalyst and the lower phase (L1) was
enriched
in the polar solvent and the formic acid-amine adduct (A2) formed. The lower
phase (L1)
was separated off and admixed three times under inert conditions with the same
amount
(mass of amine corresponds to the mass of the lower phase (L1)) of fresh
tertiary amine
(Al) (stir for 10 minutes at room temperature and subsequently separate the
phases) to
extract the catalyst. The total content of formic acid in the formic acid-
amine adduct (A2)
was determined by potentiometric titration with 0.1 N KOH in Me0H using a
"Mettler
Toledo DL50" titrator. The ruthenium content was determined by AAS. The
parameters
and results of the individual experiments are shown in Table 1.6.
Examples B-1 to B-3 show that the amount of ruthenium catalyst in the lower
phase (L1)
can be reduced by extraction with tertiary amine (Al) obtained in process step
(e) in the
process of the invention. This value was able to be reduced further by means
of further
extraction steps or a continuous countercurrent extraction.
Table 1.7
Example B-1 Example B-2
Example B-3
Tertiary amine (Al) 37.5 g of trihexylamine 37.5 g of tripentylamine
37.5 g of trihexylamine
Polar solvent 12.0 g of methanol 10.0 g of methanol
10.0 g of methanol
(used) 0.5 g of water 2.5 g of water
2.5 g of water
Catalyst 0.16 g of [Ru(PnOcty13)4(H)2] 0.1
g of [Ru(PnButy13)4(H)2] 0.1 g of [Ru(PnButy13)4(H)2]
Injection of CO2 to 1.7 MPa abs to 2.3 MPa abs
to 2.5 MPa abs
Injection of H2 to 8.0 MPa abs to 8.0 MPa abs
to 8.0 MPa abs
Heating 50 C 50 C
50 C n
Reaction time 1.5 hours 1 hour
1 hour 0
Upper phase (U1) 23.3g 31.1 g
22.9g "
op
Lower phase (L1) 26.2 g 17.4 g
27.5 g u.)
op
ko
6.1% of formic acid 5.6% of formic acid
7.2% of formic acid 0
cRu in upper phase (U1) 350 ppm 320 ppm
250 ppm o)
N
after the reaction
0
F-,
cR, in lower phase (L1) 33 ppm 80 ppm
170 ppm u.)
,
H
after the reaction
"
,
cRu in lower phase after 21 ppm 50 ppm
75 ppm H
0
the extraction (raffinate
R2)
CA 02838907 2013-12-10
Examples C-1 to C-16 according to the invention (hydrogenation and phase
separation,
addition of water after the reaction)
A 250 ml Hastelloy C autoclave equipped with a magnetic stirrer bar was
charged under
5 inert conditions with tertiary amine (Al), polar solvent and homogeneous
catalyst. The
autoclave was subsequently closed and CO2 was injected at room temperature. H2
was
then injected and the reactor was heated while stirring (700 rpm). After the
desired
reaction time, the autoclave was cooled and the hydrogenation mixture (H) was
depressurized. This gave, unless indicated otherwise, after addition of water
a two-phase
10 hydrogenation mixture (H), with the upper phase (U1) being enriched in
the still free
tertiary amine (Al) and the homogeneous catalyst and the lower phase (L1)
being
enriched in the polar solvent, water and the formic acid-amine adducts (A2)
formed. The
total content of formic acid in the formic acid-amine adduct (A2) was
determined by
potentiometric titration with 0.1 N KOH in Me0H using a "Mettler Toledo DL50"
titrator. The
15 turnover frequency (=TOF; for the definition of the TOF see: J.F.
Hartwig, Organotransition
Metal Chemistry, 1st edition, 2010, University Science Books,
Sausalito/California p.545)
and the reaction rate were calculated therefrom. The ruthenium content was
determined by
atomic absorption spectroscopy. The composition of the two phases was
determined by
gas chromatography and proton NMR spectroscopy. The parameters and results of
the
20 individual experiments are shown in Tables 1.7 to 1.11.
In the embodiments in Experiments C-1 to C-16, unfavorable Ru partition
coefficients kRu
are present after the reaction. The product phase, viz. stream (3, 13a), 33a),
53a), 73a),
93a)), was therefore subsequently admixed with water to form a two-phase
mixture, with
25 the upper phase (U1) comprising mainly amine and the alcohol and the
lower phase (L1)
comprising the formic acid-amine adducts (A2), the alcohol and water and
improved Ru
partition coefficients between these two phases being established as a result
of the
addition of water. In the embodiments in comparative experiments for
comparison with C3,
C7 and C15 (Experiments C-17 to C-19 in Table 1.12), the total amount of water
was
30 added in the reaction. It can clearly be seen here that, in the case of
the solvents and
catalysts used here, the addition of this amount of water in the hydrogenation
leads to
poorer ruthenium partition coefficients after the reaction and/or lower
reaction rates.
Table 1.8
Example C-1 50 g of the lower phase from
Example C-2 50 g of the lower phase
Tertiary amine (Al) 75 g of trihexylamine Example C-2
are admixed 75 g of tripentylamine from Example C-2 are
with 6.1 g of water. Two admixed with 8.3 g of
Polar solvent 25 g of methanol
25 g of methanol
(used)
phases are formed. water. Two phases
are Catalyst 0.18 g of [Ru(PnBu3)4(H)2] 0.18 g of [Ru(PnI3u3)4(H)2]
formed.
Injection of CO2 19.9 g to 1.8 MPa abs 19.7 g to
1.9 MPa abs
Injection of H2 to 9.8 MPa abs
to 9.9 MPa abs
Heating to 50 C
to 50 C n
Pressure change to 9.4 MPa abs
to 9.4 MPa abs 0
Reaction time 1 hour
1 hour "
co
u.)
Special feature
co
ko
Upper phase (U1) 15.9 g 18.8 g
38.5 g 10.4 g 0
-A
12.4% of methanol 2.8% of methanol
4.9% of methanol 1.1% of methanol
87.6% of trihexylamine 97.2% of
trihexylamine 95.1% of tripentylamine 98.9% of tripentylamine cs)
0
,
Lower phase (L1) 87.3 g 36.2 g
64.1 g 46.7 g u.)
1
H
5.9% of formic acid 7.3% of formic
acid 8.1% of formic acid 8.0% of formic acid I.)
1
26.4% of methanol 16.9% of water
36.1% of methanol 17.8% of water H
0
67.7% of trihexylamine 35.0% of methanol
55.8% of tripentylamine 38.5% of methanol
40.8% of trihexylamine 35.7% of tripentylamine
KRu (CRu in upper phase 0.3 4.0 0.7
2.7
(U1)/ cm, in lower phase
(L1))
TOF 560 h-1 -
562 11-1 -
Reaction rate 1.09 mol kg-1 h-1
- 1.09 mol kg-1 h-1 -
Table 1.9
Example C-3 50 g of the lower Example C-4 50 g of the
lower phase from
Tertiary amine (Al) 75 g of trihexylamine phase from Example
75 g of tripentylamine Example C-4 are admixed
C-3 are admixed with with 7.8 g of water. Two
Polar solvent 24 g of methanol
24 g of methanol
Two
5.7 g of water.
phases are formed.
(used) 1 g of water
1 g of methanol
Catalyst 0.18 g of [Ru(P R ) (H)2, 1
. n, phases are formed. 0.18 g of [Ru(PnBu3)4(F1)2]
Injection of CO2 20.1 g to 2.1 MPa abs 20.1 g to 2.2
MPa abs
Injection of H2 to 10.1 MPa abs
to 10.2 MPa abs
Heating to 50 C to 50 C
Pressure change to 9.6 MPa abs
to 10.3 MPa abs n
Reaction time 1 hour 1 hour
0
Special feature - -
I.)
co
Upper phase (U1) 27.4 g 12.3 g 43.9 g
7.3 g cy) u.)
co
9.0% of methanol 2.8% of methanol 3.4% of methanol 1.3% of
methanol --J l0
0
-A
91.0% of trihexylamine 97.2% of trihexylamine
96.6% of tripentylamine 98.7% of tripentylamine I.)
Lower phase (L1) 76.3g 41.7g 59.2g
49.1 g 0
H
7.1% of formic acid 7.8% of formic
acid 8.7% of formic acid 8.3% of formic acid u.)
,
H
1.3% of water 15.2% of water 38.0% of methanol
17.6% of water I.)
,
28.2% of methanol 33.0% of methanol
1.7% of water 38.5% of methanol H
0
63.4% of trihexylamine 44.0% of trihexylamine
51.6% of tripentylamine 35.6% of tripentylamine
KRu (CRu in upper phase 0.6 3.3 1.1
1.7
(U1)/ cRu in lower phase)
TOF 591 h-1 - 551 h-1
-
Reaction rate 1.09 mol kg-1 I-11
- 1.08 mol kg-1 h-1 -
Table 1.10
Example C-5 Example C-6 Example C-7
Example C-8
Tertiary amine (Al) 75 g of tripentylamine 75 g of
trihexylamine 75 g of tripentylamine 75 g of tripentylamine
Polar solvent 25 g of methanol 25 g of methanol 25 g of
methanol 25 g of methanol
(used)
Catalyst 0.16 g of 0.16 g of 0.16 g of
0.33 g of
[Ru(PnOct3)4(H)2] [Ru(PnOct3)4(H)2]
[Ru(PnOct3)4(H)2] [Ru(PnOct3)4(H)2]
Injection of CO2 30.0 g to 2.5 MPa abs 20.0 g to 1.7
MPa abs 19.9 g to 2.1 MPa abs 20.0 g to 2.0 MPa abs
Injection of H2 to 8.0 MPa abs to 9.7 MPa abs to 10.0 MPa abs
to 10.0 MPa abs
Heating to 50 C to 50 C to 50 C
to 50 C
n
Pressure change to 10.5 MPa abs to 10.4 MPa abs to 10.6 MPa abs
to 10.8 MPa abs
Reaction time 1 hour 1 hour 1 hour
1 hour 0
I.)
Special feature addition of 2 g of water addition of 2 g of water
addition of 5 g of water addition of 3 g of water after co
u.)
after the reaction after the reaction after the
reaction the reaction co
ko
0
Upper phase (U1) 55.9 g 43.9 g 55.5 g
40.5 g -A
4.9% of methanol 9.7% of methanol 3.1% of
methanol VH10-44 o) I.)
co
0
95.1% of tripentylamine 92.3% of trihexylamine 96.9% of
tripentylamine H
u.)
1
Lower phase (L1) 44.6 g 49.9 g 45.5 g
61.5 g
IV
6.4% of formic acid 5.7% of formic acid 6.1% of formic
acid 7.0% of formic acid I
H
4.5% of water 41.5% of methanol 51.2% of
methanol 35.9% of methanol 0
50.0% of methanol 4.0% of water 11.0% of water
4.9% of water
39.1% of tripentylamine 48.8% of trihexylamine 31.7% of
tripentylamine 52.2% of trihexylamine
KRu (cR, in upper phase 4.2 6.8 10.9
41.0
(U1) / cRu in lower phase
(L1))
TOF 602 h-1 602 h-1 586 h-1
447 h-1
Reaction rate 0.62 mol kg-1 h-1 0.62 mol kg-1 h-1 0.60 mol kg-1 h-
1 0.91 mol kg-1 h-1
Table 1.11
Example C-9 Example C-10 Example C-11
Example 0-12
Tertiary amine (Al) 75 g of trihexylamine
75 g of trihexylamine 75 g of trihexylamine 75 g of trihexylamine
Polar solvent 25 g of methanol 25
g of methanol 25 g of methanol 25 g of methanol
(used)
Catalyst 0.16 g of 0.16 g of 0.16 g of
0.32 g of [Ru(PnOcty13)4(H)2],
[Ru(PnOcty13)4(H)21, [Ru(PnOcty13)4(H)2]
[Ru(PnOcty13)4(H)2], 0.17 g of 1,2-
0.08 g of 1,2- 0.08 g 1,2-
bis(dicyclohexylphosphino)ethane,
bis(dicyclohexylphosphino)
bis(dicyclohexylphosphino) 0.15 g of PnOcty13
ethane ethane
Injection of CO2 to 2.0 MPa abs to
1.9 MPa abs to 1.8 MPa abs to 2.0 MPa abs
Injection of H2 to 10.0 MPa abs to
9.9 MPa abs to 9.8 MPa abs to 12.0 MPa abs n
Heating 70 C 70 C 40 C
50 C
0
Pressure change to 10.4 MPa abs to
11.1 MPa abs to 10.0 MPa abs to 12.4 MPa abs
co
Reaction time 1 hour 1 hour 1 hour
1 hour
co
Special feature addition of 5 g of water addition of 5 g of
addition of 5 g of water after addition of 5 g of water after the
ko
0
after the reaction water after the the reaction
reaction -A
N
reaction
0
H
Upper phase (U1) 42.5g 55.2g 50.5g
25.9g u.)
1
Lower phase (L1) 58.4 g 43.4 g 49.0 g
78.0 g H
I.)
1
7.3% of formic acid 5.4% of formic acid
6.2% of formic acid 8.5% of formic acid H
KRu (CRu in upper 16.3 100 2.2
19.4 0
phase (U1) / cRu in
lower phase (L1))
TOF 904 1-11 492 h-1 650 h-1
696
Reaction rate 0.92 mol kg-1 h-1
0.52 mol kg-1111 0.62 mol kg-1 h-1 1.38 mol kg-1 h-1
Table 1.12
Example C-13 Example C-14 Example C-
15 Example C-16
Tertiary amine (Al) 75 g of trihexylamine
75 g of trihexylamine 75 g of trihexylamine 75 g of trihexylamine
Polar solvent 25 g of methanol 25 g of
methanol 25 g of methanol 25 g of ethanol
(used)
Catalyst 0.11 g of [Ru(COD)C12]2,
0.32 g of 0.32 g of [Ru(PnOcty13)4(H)2], 0.189 of
[Ru(PnOct3)4(H)2]
0.17 g of 1,2- [Ru(PnOctyl3)4(H)2],
0.08 g of 1,2-
bis(dicyclohexylphos- 0.08 g of 1,2- bis(dicyclohexylphosphino)-
phino)ethane, bis(diphenylphosphino)- ethane
0.15 g of PnOct3 ethane
Injection of CO2 to 1.6 MPa ohs to 1.6 MPa abs to 1.7 MPa
abs 20.0 g to 2.2 MPa abs
Injection of H2 to 12.0 MPa abs to 9.6 MPa
abs to 9.7 MPa abs to 10.2 MPa abs n
Heating 50 C 50 C 50 C
to 50 C
0
Pressure change to 12.1 MPa abs to 8.6 MPa
abs to 9.5 MPa abs to 11.1 MPa abs I.)
co
Reaction time 1 hour 2 hours 2 hours
1 hour u.)
co
Special feature addition of 5 g of water
addition of 5 g of water addition of 5 g of water
after Single-phase reaction ko
0
-A
after the reaction after the reaction the reaction
output;
I.)
addition of 5 g of water after
0
H
the reaction, resulting in
--,1 Lo
a
1
formation of two phases
H
I.)
Upper phase (U1) 16.6 g 36.2 g 26.7 g
66.3 g 1
H
8.8% of ethanol
0
0.8% of water
90.4% of trihexylamine
Lower phase (L1) 88.1 g 66.1 g 74.0 g
29.6 g
9.0% of formic acid 7.3% of formic acid 8.3% of formic acid 2.7% of
formic acid
20.9% of water
64.4% of ethanol
12% of trihexylamine
KRu (cRu in upper phase 12.0 1.4 14
22.5
(U1)/ cRu in lower phase)
TOF 435 h-1 258 h.' 335 h-1
152 h-1
Reaction rate 1.64 mol kg-1 h-1 1.02 mol kg-
1 h-1 1.33 mol kg-1 h-1 0.18 mol kg-1 h-1
Table 1.13: Comparative experiments - addition of water in the reaction
Example C-17 (comparative Example C-18 (comparative
Example C-19 (comparative
experiment for C3) experiment for C15)
experiment for C7)
Tertiary amine (Al) 75 g of trihexylamine 75 g of trihexylamine
75 g of tripentylamine
_
Polar solvent 24 g of methanol 25 g of methanol
25 g of methanol
(used) 6.7 g of water 5.0 g of water
5.0 g of water
Catalyst 0.18 g of [Ru(PnBu3)4(H)2] 0.32 g of
[Ru(PnOcty13)4(H)2], 0.16 g of [Ru(PnOcty13)4(F)2)
0.08 g of 1,2-
_ bis(dicyclohexylphosphino)ethane
Injection of CO2 20.0 g to 3.5 MPa abs 20.0 g to 2.5 MPa abs
20.0 g to 2.1 MPa abs n
_
Injection of H2 to 11.5 MPa absto 10.6 MPa abs
to 10.1 MPa abs 0
_
I.)
Heating to 50 C to 50 C
to 50 C co
u.)
Pressure change to 11.0 MPa abs to 11.0 MPa abs
to 11.3 MPa abs co
ko
0
Reaction time 1 hour 1 hour
1 hour -A
-
Special feature water is added before the reaction water is added before
the reaction water is added before the I.)
--4
0
reaction _, H
.
LO
Upper phase (U1) 44.1 g 64.3g
66.6g I
F-,
IV
Lower phase (L1) 65.9 g 41.7 g
37.6 g I
H
7.5% of formic acid 4.7% of formic acid
2.4% of formic acid 0
,
KRu (Cfzu in upper phase 1.8 1.3
32.5
(U1)/ cRu in lower phase
(L1)) ,
TOF 551 h-1394 h1
187 h-1
-
Reaction rate 0.98 mol kg-1 h-1 0.4 mol kg-1 I-11
0.19 mol kg-1 h-1
CA 02838907 2013-12-10
72
Examples D1-D4 (extraction of the catalyst)
A 100 ml Hastelloy C autoclave equipped with a blade stirrer was charged under
inert
conditions with the tertiary amine (Al), polar solvent and the catalyst. The
autoclave was
subsequently closed and CO2 was injected at room temperature. H2 was then
injected and
the reactor was heated while stirring (1000 rpm). After the reaction time, the
autoclave was
cooled and the hydrogenation mixture (H) was depressurized. After the
reaction, water
was added to the reaction output and the mixture was stirred at room
temperature for 10
minutes. This gave a two-phase hydrogenation mixture (H), with the upper phase
(U1)
being enriched in the still free tertiary amine (Al) and the homogeneous
catalyst, and the
lower phase (L1) being enriched in the polar solvent and the formic acid-amine
adduct (A2)
formed. The lower phase (L1) was separated off and treated three times under
inert
conditions with the same amount (mass of amine corresponds to the mass of the
lower
phase) of fresh trialkylamine (stir at room temperature for 10 minutes and
subsequently
separate the phases). The total content of formic acid in the formic acid-
amine adduct was
determined by potentiometric titration with 0.1 N KOH in Me0H using a "Mettler
Toledo
DL50" titrator. The ruthenium content was determined by AAS. The parameters
and results
of the individual experiments are shown in Table 1.13 .
Examples D-1 to D-4 show that the ruthenium content of the product phase can
be
reduced to less than one ppm of ruthenium by varying the catalyst and the
amount of
water added in the formation of formic acid.
Table 1.14
Example D-1 Example D-2 Example
D-3 Example D-4
Tertiary amine (Al) 37.5 g of 37.5 g of trihexylamine 37.5 g
of trihexylamine 37.5 g of trihexylamine
trihexylamine
Polar solvent 12.0 g of methanol 12.0 g of methanol 12.0 g of
methanol 12.0 g of methanol
(used)
0.5 g of water
Catalyst 0.16 g of 0.16 g of 0.16 g
of 0.1 g of
[Ru(PnOcty13)4(H)21 tRu(PnOcty13)4(H)2]
[Ru(PnOcty13)4(H)2] [Ru(PnButy13)4(11)21
Injection of CO2 to 1.7 MPa abs to 1.6 MPa abs to 1.8
MPa abs to 1.7 MPa abs
Injection of H2 to 8.0 MPa abs to 8.0 MPa to 8.0
MPa to 8.0 MPa n
Heating 50 C 50 C 50 C
50 C
Reaction time 1.5 hours 1.5 hours 16
hours 1.5 hours 0
I.)
Water addition after the 2.5 g 4.7 g 2.5 g
0.8 g co
u.)
co
reaction
ko
0
Upper phase (U1) 26.3g 27.4g 23.2g
17.5 g --.1
Lower phase (L1) 24.7 g 25.5 g 28.1
g 28.9 g "
0
6.6% of formic acid 5.9% of formic acid 6.8% of
formic acid 7.4% of formic acid H
u.)
1
cRu in upper phase (U1) 350 ppm 280 ppm 370
ppm 200 ppm H
IV
I
after the reaction and
H
addition of water
0
cR, in lower phase (L1) after 4 ppm 2 ppm <1 ppm
43 ppm
extraction (raffinate (R2))
CA 02838907 2013-12-10
74
Examples E1-E9 (reuse of the catalyst and catalyst extraction)
A 100 ml Hastelloy C autoclave equipped with a blade stirrer was charged under
inert
conditions with the tertiary amine (Al), polar solvent and the catalyst. The
autoclave was
subsequently closed and CO2 was injected at room temperature. H2 was then
injected and
the reactor was heated while stirring (1000 rpm). After the reaction time, the
autoclave was
cooled and the hydrogenation mixture (H) was depressurized. After the
reaction, water
was added to the reaction output and the mixture was stirred at room
temperature for 10
minutes. This gave a two-phase product mixture, with the upper phase (U1)
being enriched
in the still free tertiary amine (Al) and the homogeneous catalyst and the
lower phase (L1)
being enriched in the polar solvent and the formic acid-amine adduct (A2)
formed. The
phases were subsequently separated and the formic acid content of the lower
phase (L1)
and also the ruthenium content of both phases were determined by the methods
described
below. The upper phase (U1) comprising ruthenium catalyst was then made up to
37.5 g
with fresh tertiary amine (Al) and reused for the hydrogenation of CO2 using
the same
solvent under the same reaction conditions as before. After the reaction was
complete and
water had been added, the lower phase (L1) was separated off and admixed three
times
under inert conditions with the same amount (mass of amine corresponds to the
mass of
the lower phase) of fresh tertiary amine (Al) (stir at room temperature for 10
minutes and
subsequently separate the phases) to extract the catalyst. The total content
of formic acid
in the formic acid-amine adduct (A2) was determined by potentiometric
titration with 0.1 N
KOH in Me0H using a "Mettler Toledo DL50" titrator. The ruthenium content was
determined by AAS. The parameters and results of the individual experiments
are shown
in Tables 1.14 to 1.19.
Examples E-1 to E-9 show that varying the catalyst, the amount of water added
(both
before and after the reaction) and the reaction conditions allows the active
catalyst to be
reused for the hydrogenation of CO2 and allows the ruthenium content of the
product
phase to be reduced to as low as 2 ppm by means of only a single extraction.
Table 1.15
Example E-la (first Example E-1 b (reuse of
Example E-la (first Example E-2b (reuse of
hydrogenation) the catalyst and extraction)
hydrogenation) the catalyst and
extraction)
Tertiary amine (Al) 37.5 g of trihexylamine Upper
phase from E-la 37.5 g of trihexylamine Upper phase from E-2a
made up to 37.5 g with
made up to 37.5 g with
fresh trihexylamine
fresh trihexylamine
Polar solvent 12.0 g of methanol 12.0 g of methanol 12.0 g
of methanol 12.0 g of methanol
(used) 0.5 g of water
0.3 g of water 0.25 g of water
Catalyst 0.16 g of Upper phase from C-la 0.16
g of Upper phase from C-2a
[Ru(PnOcty13)4(H)2],
[Ru(PnOcty13)4(H)2],
0.08 g of 1,2- 0.08 g of 1,2-
n
bis(dicyclohexylphosphino)-
bis(dicyclohexylphosphino)- 0
ethane
ethane I.)
co
Injection of CO2 to 1.6 MPa abs
to 1.5 MPa abs to 1.6 MPa abs to 1.7 MPa abs u.)
co
Injection of H2 to 8.0 MPa abs
to 8.0 MPa to 8.0 MPa abs to 8.0 MPa abs ko
0
-A
Heating 70 C 70 C 70
C 70 C I.)
Reaction time 1.5 hours 1.5 hours 1.5
hours 1.5 hours ---1 0
,
Water addition after the 0.5 g 1.0 g 1.0
g 1.0 g
,
H
reaction
I.)
i
Upper phase (U1) 19.3 g 24.7 g 20.9
g 25.9 g H
0
Lower phase (L1) 30.8 g 25.4 g 29.9
g 24.8 g
6.0% of formic acid 5.9% of formic acid 6.6% of
formic acid 6.4% of formic acid
cR, in upper phase (U1) 250 ppm 170 ppm 200
ppm 140 ppm
after the reaction and
addition of water
cRu in lower phase (L1) 120 ppm- 130
ppm
-
after the reaction and
addition of water
cRu in lower phase after - 9 ppm -
10 ppm
extraction (raffinate (R2))
Table 1.16
Example E-3a (first Example E-3b (reuse of the Example
E-4a (first Example E-4b (reuse of
hydrogenation) catalyst and extraction) hydrogenation)
the catalyst and
extraction)
Tertiary amine (Al) 37.5 g of trihexylamine Upper phase
from E-3a made 37.5 g of trihexylamine Upper phase from E-4a
up to 37.5 g with fresh
made up to 37.5 g with
trihexylamine
fresh trihexylamine
Polar solvent 12.0 g of methanol 12.0 g of methanol 12.0 g of
methanol 12.0 g of methanol
(used) 0.5 g of
water 0.5 g of water
Catalyst 0.16 g of Upper phase from C-3a 0.16 g
of Upper phase from C-4a
[Ru(PnOcty13)4(H)2],
[Ru(PnOcty13)4(H)2], n
0.08 g of 1,2- 0.08 g of 1,2-bis(dicyclo-
bis(dicyclo-
hexylphosphino)ethane 0
I.)
co
hexylphosphino)ethane
u.)
co
Injection of CO2 to 1.8 MPa ohs to 1.6
MPa abs to 1.8 MPa abs to 1.7 MPa abs ko
0
Injection of H2 to 8.0 MPa abs to 8.0 MPa to 8.0
MPa abs to 8.0 MPa abs -A
Heating 70 C 70 C 70 C
70 C I.)
0
Reaction time 16 hours 1.5 hours 16
hours 1.5 hours a) u.)
1
Water addition after the 1.0 g 1.0 g 1.0 g
1.0 g H
I.)
1
reaction
H
Upper phase (U1) 19.9 g 24.7 g 19.7
g 24.0 g 0
Lower phase (L1) 30.8 g 24.4 g 31.1
g 26.8 g
6.8% of formic acid 6.0% of formic acid 7.1% of
formic acid 6.4% of formic acid
CRu in upper phase 205 ppm 135 ppm 250 ppm
175 ppm
(U1) after the reaction
and addition of water
cRu in lower phase (L1) 145 ppm - 125 ppm
-
after the reaction and
addition of water
cRu in lower phase after - 4 ppm -
4 ppm
extraction (raffinate
(R2))
Table 1.17
Example E-5a (first Example E-5b (reuse of the Example E-
6a (first Example E-6b (reuse of the
hydrogenation) catalyst and extraction)
hydrogenation) catalyst and extraction)
Tertiary amine (Al) 37.5 g of trihexylamine upper phase from C-5a made
37.5 g of trihexylamine upper phase from C-6a
up to 37.5 g with fresh
made up to 37.5 g with
trihexylamine
fresh trihexylamine
Polar solvent 12.0 g of methanol 12.0 g of methanol 12.0 g of
methanol
(used)
Catalyst 0.16 g of upper phase from C-5a
0.16 g of [Ru(PnOcty13)4(H)2] upper phase from C-6a
[Ru(PnOcty13)4(H)2]
Injection of CO2 to 1.7 MPa abs to 1.6 MPa abs to 1.7 MPa
abs to 1.7 MPa abs
Injection of H2 to 8.0 MPa abs to 8.0 MPa to 8.0 MPa
abs to 8.0 MPa abs n
Heating 50 C 50 C 50 C
50 C
0
Reaction time 1.5 hours 1.5 hours 1.5
hours 1.5 hours I.)
co
Water addition after 1.0 g 1.0 g 2.5 g
1.0 g u.)
co
the reaction
ko
-,1
0
Upper phase (U1) 22.1 g 27.1 g 23.8 g
28.6 g
Lower phase (L1) 27.8 g 22.1 g 26.9 g
20.6 g I.)
0
H
6.7% of formic acid 4.5% of formic acid 6.2% of
formic acid 4.8% of formic acid u.)
1
cR, in upper phase 420 ppm 310 ppm 400 ppm
310 ppm H
I.)
1
(U1) after the reaction
H
and addition of water
0
cR,, in lower phase (L1) 14 ppm - 4 ppm
-
after the reaction and
addition of water
cRõ in lower phase- 2 ppm -
2 ppm
after extraction
(raffinate R2)
Table 1.18
_
Example E-7a (first Example E-7b (reuse of
the catalyst and
hydrogenation)
extraction)
- Tertiary amine (Al) 37.5 g of trihexylamine upper phase from E-
7a made up to
37.5 g with fresh trihexylamine
Polar solvent 12.0 g of methanol 12.0 g of
methanol
(used) 0.25 g of water 0.25 g of water
Catalyst 0.16 g of [Ru(PnOcty13)4(H)2], upper phase
from C-7a
0.08 g of 1,2-bis(dicyclo-
hexylphosphino)ethane
Injection of CO2 to 1.5 MPa abs to 1.6 MPa abs
n
Injection of H2 to 8.0 MPa abs to 8.0
MPa 0
I.)
Heating 50 C 50 C
co
Reaction time 1.5 hours 1.5
hours co
ko
Water addition after the reaction , 1.0 g
1.0 g 0
-A
Upper phase (U1) 17.5g 19.7g
co
iv
o
Lower phase (L1) 33.0 g 30.6 g
H
LO
I
7.3% of formic acid 7.1% of formic
acid H
CRu in upper phase (U1) after the 370 ppm 260 ppm
I.)
,
H
reaction and addition of water
0
cRu in lower phase (L1) after the 34 ppm -
reaction and addition of water
cRu in lower phase after extraction- 16 ppm
(raffinate (R2))
Table 1.19
Example E-8a (first Example E-8b (reuse of the
Example E-8c (reuse of the
hydrogenation) catalyst and extraction)
catalyst and extraction)
Tertiary amine (Al) 37.5 g of trihexylamine
upper phase from E-8a made upper phase from E-8b made up
up to 37.5 g with fresh
to 37.5 g with fresh trihexylamine
trihexylamine _
Polar solvent 12.0 g of methanol 12.0 g of methanol
12.0 g of methanol
(used)
Catalyst 0.16 g of [Ru(PnOcty13)4(H)2],
upper phase from C-8a upper phase from C-8b
0.08 g of 1,2-
bis(dicyclohexylphosphino)ethane
n
Injection of CO2 to 1.7 MPa abs to 1.8 MPa abs
to 1.6 MPa abs 0
Injection of H2 to 8.0 MPa abs to 8.0 MPa
to 8.0 MPa I.)
co
.
u.)
Heating 70 C 70 C
70 C co
,
ko
Reaction time 16 hours 1.5 hours
1.5 hours 0
_
-A
Water addition after the 1.0 g 1.0 g
1.0 g I.)
0
reaction
-.1 H
-
CO la
I
Upper phase (U1) 20.4 g 27.3 g
23.7 g
_
H
Lower phase (L1) 29.8g 22.3g
25.3g "
1
6.7% of formic acid 5.7% of formic acid
4.9% of formic acid H
0
_
CRu in upper phase (U1) 215 ppm 150 ppm
110 ppm
after the reaction and
addition of water _
cR, in lower phase (L1) 145 ppm 14 ppm
-
after the reaction and
addition of water .
cRi, in lower phase after - -
3 ppm
extraction (raffinate (R2))
Table 1.20
Example E-9a (first Example E-9b (reuse of the
Example E-9c (reuse of the
hydrogenation) catalyst and extraction)
catalyst and extraction)
Tertiary amine 37.5 g of trihexylamine
upper phase from E-9a made upper phase from E-9b made up
up to 37.5 g with fresh
to 37.5 g with fresh trihexylamine
trihexylamine
_
_
Polar solvent 12.0 g of methanol 12.0 g of methanol
12.0 g of methanol
(used) 0.5 g of water
_
Catalyst 0.16 g of [Ru(PnOcty13)4(H)2],
upper phase from C-9a upper phase from C-9b
0.08 g of 1,2-
bis(dicyclohexylphosphino)ethane
n
_
Injection of CO2 to 1.5 MPa abs to 1.6 MPa abs
to 1.6 MPa abs 0
.
I.)
Injection of H2 to 8.0 MPa abs to 8.0 MPa
to 8.0 MPa co
u.)
Heating 70 C 70 C
70 C co
ko
Reaction time 16 hours 1.5 hours
1.5 hours 0
-A
Water addition after the 1.0 g 1.0 g
1.0 g
a
0
reaction
H
LO
I
Upper phase 19.7 g 27.8 g
25.6 g H
Lower phase 31.6 g 22.6 g
24.4 g "
i
7.0% of formic acid 6.1% of formic acid
6.1% of formic acid H
0
-
cRu in upper phase after 235 ppm 155 ppm
125 ppm
the reaction and addition
of water
_
cRu in lower phase after 110 ppm 11 ppm
-
the reaction and addition
of water
_
cRu in lower phase after - -
3 ppm
extraction
_
CA 02838907 2013-12-10
81
Examples F1-F4 (thermal separation of the polar solvent from the
trialkylamine/solvent/formic acid mixtures obtained as product phase after the
extraction)
Alcohol and water are distilled off from the product phase (comprises the
formic acid-
amine adduct; lower phase (L1), raffinate (R1) or raffinate (R2)) under
reduced pressure
by means of a rotary evaporator. A two-phase mixture (trialkylamine and formic
acid-amine
adduct phase; bottoms mixture (Si)), is formed at the bottom, and the two
phases are
separated and the formic acid content of the lower phase (L2) was determined
by
potentiometric titration with 0.1 N KOH in Me0H using a "Mettler Toledo DL50"
titrator. The
amine and alcohol content is determined by gas chromatography. The parameters
and
results of the individual experiments are shown in Table 1.20.
Examples F-1 to F-4 show that various polar solvents can be separated off
under mild
conditions from the product phase (lower phase (L1); raffinate (R1) or
raffinate (R2)) in the
process of the invention, giving a lower phase (L2) which is relatively rich
in formic acid
and an upper phase (U2) comprising predominantly tertiary amine.
Table 1.21
Example F-1 Example F-2 Example F-3
Example F-4
Feed mixture 18.79 19.3g 81.8g
88.6g
(% by weight) 7.2% of formic acid 5.8% of formic acid
7.3% of formic acid 9.2% of formic acid
26.4% of 1-propanol 22.8% of 2-propanol
41.3% of methanol 31.4% of ethanol
15.5% of water 4.1% of water 15.4% of water
11.3% of water
48.3% of 67.2% of 35.9% of
48.1% of
trihexylamine trihexylamine tripentylamine
tripentylamine
Formic acid: amine in 1 : 1.2 1 : 2.0 1 :
1 1 : 1.1
feed mixture
Pressure 20 mbar 20 mbar 200 mbar 200
mbar
Temperature 50 C 50 C 100 C 110
C
Formic acid content of 16.4% 18.0%
23.7% 22.7% n
lower phase after
0
distillation (% by weight)
I.)
co
u.)
Formic acid : amine in 1 : 0.76 1 : 0.78 1 :
0.6 1 : 0.56 co co
lower phase after
0
-A
distillation (molar ratio)
I.)
Recovery of formic acid 95.3% 93.7%
90.4% 95.2% 0
H
LO
after distillation
1
H
IV
I
H
0
CA 02838907 2013-12-10
83
Examples G1 and G2 (thermal separation of the polar solvent from the
trialkylamine/solvent/formic acid mixtures and dissociation of the formic acid-
amine adduct)
Alcohol and water are distilled off from the product phase (comprises the
formic acid-
amine adduct; lower phase (L1), raffinate (R1) or raffinate (R2)) under
reduced pressure
by means of a rotary evaporator. A two-phase mixture (trialkylamine and formic
acid-amine
adduct phase; bottoms mixture (Si)) is formed at the bottom and the two phases
are
separated. The composition of the distillate (comprising the major part of the
methanol and
of the water; distillate (D1)), the upper phase (comprising the free
trialkylamine; upper
phase (U2)) and the lower phase (comprising the formic acid-amine adduct;
lower phase
(L2)) was determined by gas chromatography and by potentiometric titration of
the formic
acid against 0.1 N KOH in Me0H using a "Mettler Toledo DL50" titrator. The
formic acid is
then thermally split off from the tertiary amine (A2) in the lower phase (L2)
from the first
step via a 10 cm Vigreux column in a vacuum distillation apparatus. After all
the formic
acid has been split off, a single-phase bottom fraction (S2) comprising the
pure tertiary
amine (A2) is obtained and can be used for extraction of the catalyst and
recirculation to
the hydrogenation. The formic acid and residual water are present in the
distillate (D2).
The composition of the bottoms (S2) and of the distillate was determined by
gas
chromatography and by potentiometric titration of the formic acid against 0.1
N KOH in
Me0H using a "Mettler Toledo DL50" titrator. The parameters and results of the
individual
experiments are shown in Table 1.21.
Examples G-1 and G-2 show that various polar solvents can be separated off
from the
product phase under mild conditions in the process of the invention, giving a
lower phase
(L3) which is relatively rich in formic acid and an upper phase (U3)
comprising
predominantly tertiary amine (Al). The formic acid can then be split off from
the tertiary
amine (Al) in this lower phase (L3) which is relatively rich in formic acid at
relatively high
temperatures, leaving the free tertiary aminee (Al). The formic acid which has
been
obtained in this way still comprises some water which can be separated off
from the formic
acid by means of a column having a relatively high separating power. The
tertiary amine
(Al) obtained both in the removal of the solvent and in the thermal
dissociation can be
used for extracting the catalyst.
Table 1.22
Example G-1 a Example G-lb
Example G-2a Example GD-2b
(removal of the polar (dissociation of the (removal of
the polar (dissociation of the formic
solvent) formic acid-amine solvent) acid-amine adduct)
adduct)
Feed mixture 199.8 g lower phase from G1-a 199.8
g lower phase from G2-a
( /0 by weight) 8.9% of formic acid 7.8% of formic
acid
28.4% of methanol 33.0% of
methanol
5.6% of water 15.1% of water
57.1% of trihexylamine 44.0% of
trihexylamine
Formic acid: amine in 1 : 1.1 1 : 0.64 1 : 1
1 : 0.89 n
feed mixture
Pressure 200 mbar 90 mbar 200 mbar
90 mbar 0
I.)
Temperature 120 C 153 C 120 C
153 C co
u.)
co
Lower phase in the 79.8 g 63.6 g 69.4
g 55.5 g ko
0
bottoms after distillation 22.1% of formic acid 100% of
trihexylamine 14.9% of formic acid 99.7% of
trihexylamine co
=
I , - V
( % by weight) 1.5% of water 6.9% of water
0.3% of water "
0
76.4% of trihexylamine 78.2% of
trihexylamine H
L J
I
Upper phase in the 50.5 g single-phase 32.7
g single-phase H
I V
bottoms after distillation 100% of
trihexylamine 99.7% of trihexylamine I
H
0.3% of water
0
Distillate 66.6 g 14.9 g 93.1
g 12.9 g
0.3% of formic acid 92.1% of formic acid 70.1% of
methanol 85.0% of formic acid
81.2% of methanol 7.9% of water
29.9% of water 15% of water
18.5% of water
CA 02838907 2013-12-10
Examples H1 to H4 (preferential solubility of the inhibitors used according to
the invention
in a two-phase mixture of formic acid-amine adduct (A2) and tertiary amine
(Al))
5 20 g formic acid-amine adduct derived from formic acid and tri-n-
hexylamine (A3) (20.4%
of HCOOH), 10 g of trihexylamine and in each case 0.5 g of the inhibitors
indicated in the
table are weighed into a vessel and stirred at room temperature for 2 hours.
The two liquid
phases are subsequently separated (in the case of EDTA and Trilon M, a little
solid is
formed and the liquid is decanted off from this) and the content of the
inhibitor in each
10 phase is determined by HPLC (detection limit for EDTA and Trilon M: 0.01
g/100 g, for
citric acid and DL-tartaric acid: 0.1 g/100 g)
Inhibitor EDTA Trilon-M Citric acid DL-tartaric
acid
Content of not detectable not detectable not detectable
not detectable
inhibitor in the
trihexylamine
phase
(corresponds to
the upper
phase (U3) in
the process of
the invention)
Content of 0.028 g; 0.14 g; 0.248 g; 0.23 g;
inhibitor in the (0.14 g/100 g) (0.07 g/100 g) (1.24 g/100 g)
(1.15 g/100 g)
formic acid-
amine adduct
(A3) phase
(corresponds to
the lower phase
(L3) in the
process of the
invention)
15 Examples H-1 to H4 show that the inhibitors accumulate preferentially in
the formic acid-
amine adduct (A3) phase in the process of the invention and thus do not get
into the
hydrogenation step.
CA 02838907 2013-12-10
86
Examples
Examples I1 and 12: Decomposition of formic acid in the hydrogenation mixture
(H) from
the hydrogenation of CO2 without addition of an inhibitor (reference values,
Comparative
Example I1) and with addition (Example Al2 according to the invention) in the
removal of
the solvent.
Comparative Example Ii: A 250 ml Hastelloy C autoclave equipped with a
magnetic stirrer
bar was charged under inert conditions with trihexylamine (65.0 g), methanol
(25.0 g),
water (2.0 g), [Ru(PnOct3)4(H)2] (82 mg) and 1,2-
bis(dicyclohexylphosphino)ethane
(=dcpe, 20 mg). The autoclave was subsequently closed and CO2 (25.0 g) was
injected at
room temperature. H2 was then injected to 120 bar and the reactor was heated
to 70 C
while stirring (700 rpm). After a reaction time of 8 hours, the autoclave was
cooled and the
hydrogenation mixture (M) was depressurized. The total content of formic acid
in the
formic acid-amine adduct (A3) in the lower phase (L1) was determined by
potentiometric
titration with 0.1 N KOH in Me0H using a "Mettler Toledo DL50" titrator and
was 8.1%,
with the hydrogenation mixture (M) (96.2 g) comprising 85.5% of the lower
phase (L1). The
hydrogenation mixture (H) was then heated under reflux at atmospheric pressure
(oil bath
temperature 80 C) in a glass flask, and the ratio of upper phase (U1) to lower
phase (L1)
and the formic acid content by titration were determined every hour.
Example 12 according to the invention: A 250 ml Hastelloy C autoclave equipped
with a
magnetic stirrer bar was charged under inert conditions with trihexylamine
(65.0 g),
methanol (25.0 g), water (2.0 g), [Ru(PnOct3)4(H)2J (82 mg) and 1,2-
bis(dicyclo-
hexylphosphino)ethane (20 mg). The autoclave was subsequently closed and CO2
(25.0 g)
was injected at room temperature. H2 was then injected to 120 bar and the
reactor was
heated to 70 C while stirring (700 rpm). After a reaction time of 8 hours, the
autoclave was
cooled and the hydrogenation mixture (H) was depressurized. The total content
of formic
acid in the formic acid-amine adduct (A3) in the lower phase (L1) was
determined by
potentiometric titration with 0.1 N KOH in Me0H using a "Mettler Toledo DL50"
titrator and
was 8.2%, with the hydrogenation mixture (H) (95.7 g) comprising 83.5% of the
lower
phase (L1). The hydrogenation mixture (H) was admixed with H202 (136 mg of a
30%
strength solution in water) and then heated under reflux at atmospheric
pressure (oil bath
temperature 80 C) in a glass flask. The ratio of upper phase (U1) to lower
phase (L1) and
the formic acid content by titration were determined every hour.
CA 02838907 2013-12-10
87
Figure 7 shows the change in the percentage content of the lower phase (L1)
based on the
total weight of the hydrogenation mixture (H).
Figure 7 and Examples I1 and 12 show that the formic acid comprised in the
formic acid-
amine adduct (A3) in the lower phase (L1) decomposes significantly more slowly
at the
temperatures of the methanol removal (80 C) (removal of the polar solvent)
when small
amounts of an inhibitor such as H202 are added (Example 12). However, the
decomposition rate in the formic acid-amine adduct (A3) dissociation is
significantly faster
than in the step of removal of the polar solvent because of the higher bottoms
temperatures (> 130 C) and is thus more relevant, and the further studies on
inhibitors
therefore relate to process step (e), i.e. the dissociation of the formic acid-
amine adduct
(A3) (Examples 13-125).
Comparative Examples 13 ¨ 15: Decomposition of formic acid in the dissociation
of the
formic acid-amine adduct (A3) without addition of an inhibitor; simulation of
process step
(e) without addition of an inhibitor.
Comparative Examples 13 ¨ 15: 80.0 g of formic acid-amine adduct (A3), i.e.
adduct of
formic acid and tri-n-hexylamine, (1:1.5, 20% by weight of formic acid) and
the ruthenium
catalyst were weighed into a glass flask. The reaction mixture was heated to
130 C in an
open system with reflux cooling, forming an upper phase and a lower phase. The
content
of formic acid in the formic acid-amine adduct (A3) in the lower phase was
determined
every hour by potentiometric titration with 0.1 N KOH in Me0H using a "Mettler
Toledo
DL50" titrator, and the ratio of upper phase to lower phase in the reaction
mixture was also
determined.
Table 1
Comparative Example 13 Comparative Example 14
Comparative Example 15
Ruthenium catalyst [Ru(PnOct3)4(H)2] 80 mg [Ru(PnOct3)4(H)2] 40 mg
RuCI3*H20 (13 mg)
Ligand 1,2-bis(dicyclo- 1,2-bis(dicyclo-
hexylphosphino)ethane hexylphosphino)ethane
20 mg 10 mg
Inhibitor 1
Inhibitor 2
Time after which half of <1 h <I h
<1 h
the formic acid initially
0
present in the formic
CO
UJ
CO
acid-amine adduct (A3)
0
co
has decomposed
03
0
UJ
0
CA 02838907 2013-12-10
89
Examples 13 and 15 show that the formic acid in the lower phase decomposes
very
quickly at the temperatures of the dissociation (> 130 C) (process step (e))
when
ruthenium compounds (with or without phosphane ligand) are present and no
inhibitor has
been added
Examples 16 ¨ 130 according to the invention: Decomposition of formic acid in
the
dissociation of the formic acid-amine adduct (A3) with addition of an
inhibitor; simulation of
process step (e) with addition of an inhibitor
Examples 16 ¨ 130 according to the invention: 80.0 g of formic acid-amine
adduct (A3), i.e.
adduct of formic acid and tri-n-hexylamine, (1:1.5, 20% by weight formic acid)
and the
ruthenium catalyst and also the inhibitor were weighed into a glass flask. The
reaction
mixture was heated to 130 C in an open system with reflux cooling, forming an
upper
phase and a lower phase. The content of formic acid in the formic acid-amine
adduct (A3)
in the lower phase was determined every hour by potentiometric titration with
0.1 N KOH in
Me0H using a "Mettler Toledo DL50" titrator, and the ratio of upper phase to
lower phase
in the reaction mixture was also determined.
Examples 16 and 130 according to the invention show that the decomposition of
formic
acid in the dissociation (> 130 C) (process step (e)) can be slowed
significantly by addition
of inhibitors according to the invention and as a result significally smaller
losses of formic
acid occur in the work-up.
Table 2:
Example 16 Example 17 Example
18 Example 19
Ruthenium catalyst [Ru(PnOct3)4(H)2] 90 mg
[Ru(PnOct3)4(H)2] 47 mg [Ru(PnOct3)4(H)2] 82 mg RuCI3*H20 (16
mg)
Ligand 1,2-bis(dicyclohexyl- 1,2-bis(dicyclohexyl- 1,2-
bis(dicyclohexyl-
phosphino)ethane 20 mg phosphino)ethane 10 mg
phosphino)ethane 20 mg
Inhibitor 1 H202 (30% in H20) 170 F-1202(30% in H20) 90 mg
H202(30% in H20) 150 mg -
mg
Inhibitor 2
oxalic acid 85 mg oxalic acid 82 mg
Time after which half 1 h 1 h 4 h
3 h
the formic acid initially
n
present in the formic
0
I.)
acid-amine adduct
co
u.)
(A3) has decomposed
co
ko
0
-V
IV
Table 3:
CD o
H
0
LO
I
Example 110 Example 111 Example 112
Example 113 H
IV
I
Ruthenium catalyst [Ru(PnOct3)4(H)2] 55 mg
[Ru(PnOct3)4(H)2] 43 mg [Ru(PnOct3)4(H)2] 62 mg
[Ru(PnOct3)4(H)2] 67 mg H
0
Ligand 1,2-bis(dicyclohexyl- 1,2-bis(dicyclohexyl-
1,2-bis(dicyclohexyl- 1,2-bis(dicyclohexyl-
phosphino)ethane 11 mg phosphino)ethane 11 mg
phosphino)ethane 11 mg phosphino)ethane 11 mg
Inhibitor 1 H202(30% in H20) 150 mg H202(30% in H20) 170 mg -
Inhibitor 2 oxalic acid 90 mg maleic anhydride 100 mg EDTA 99
mg lactic acid 320 mg
Time after which half 6 h 2.5 h 20 h
6 h
the formic acid initially
present in the formic
acid-amine adduct
(A3) has decomposed
Table 4:
Example 114 Example 115 Example 116
Example 117
phosphino)ethane 11 mg phosphino)ethane 11 mg
phosphino)ethane 10 mg phosphino)ethane 11 mg
Inhibitor 1 H202(30% in H20) 170 mg H202(30% in H20)
180 mg
230 mg
Time after which half 3 h >23 h 110 h
8 h
the formic acid initially
0
present in the formic
co
co
acid-amine adduct
0
(A3) has decomposed
0
CID
0
Table 5:
Example 118 Example 119 Example
120 Example 121
Ruthenium catalyst [Ru(PnOct3)4(H)2] 51 mg
[Ru(PnOct3)4(H)2] 55 mg [Ru(PnOct3)4(H)2] 44 mg [Ru(PnOct3)4(H)2] 50 mg
Ligand 1,2-bis(dicyclohexyl- 1,2-bis(dicyclohexyl-
1,2-bis(dicyclohexyl- 1,2-bis(dicyclohexyl-
phosphino)ethane 11 mg phosphino)ethane 14 mg
phosphino)ethan 14 mg phosphino)ethane 12 mg
Inhibitor 1
Inhibitor 2 citric acid 230 mg iminodiacetic acid 134 mg
DL-tartaric acid 159 mg thioacetamide 85 mg
Time after which half 12 h 2 h 2 h
10 h
the formic acid initially
present in the formic
0
acid-amine adduct
co
(A3) has decomposed
co
0
(.0
0
0
Table 6:
Example 122 Example 123 Example 124
Example 125
Ruthenium catalyst [Ru(PnOct3)4(H)2] 50 mg
[Ru(PnOct3)4(H)2] 50 mg [Ru(PnOct3)4(H)2] 50 mg [Ru(PnOct3)4(H)2] 57 mg
Ligand 1,2-bis(dicyclohexyl- 1,2-bis(dicyclohexyl-
1,2-bis(dicyclohexyl- 1,2-bis(dicyclohexyl-
phosphino)ethane 10 mg phosphino)ethane 10 mg
phosphino)ethane 10 mg phosphino)ethane 13 mg
Inhibitor 1 H202(30% in H20) 180 mg- H202(30% in
H20) 170 mg H202(30% in H20) 170 mg
Inhibitor 2 iminodiacetic acid 146 mg
diethylenetrianninepenta- diethylenetriaminepenta- DL-tartaric acid 160
mg
acetic acid 433 mg acetic acid
433 mg
n
Time after which half 5 h 3.5 h > 120 h
3 h
0
the formic acid initially
I.)
co
u.)
present in the formic
co
ko
0
acid-amine adduct
-V
I.)
(A3) has decomposed
0
H
LO
I
H
(c)
IV
0.)
I
H
0
Table 7:
Example 126 Example 127
Example 128 Example 129
Ruthenium catalyst [Ru(PnOct3)4(H)2] 50 mg RuCI3*H20 10 mg
[Ru(PnOct3)4(H)2] 45 mg [Ru(PnOct3)4(H)2] 45 mg
Ligand 1,2-bis(dicyclohexyl--
1,2-bis(dicyclohexyl- 1,2-bis(dicyclohexyl-
phosphino)ethane 10 mg phosphino)ethane
12 mg phosphino)ethane 11 mg
Inhibitor 1 H202(30% in H20) 180 mg-
H202(30% in H20) 170 mg -
Inhibitor 2 iminodiacetic acid 146 mg EDTA 350 mg
Trilon M 298 mg meso-dimercaptosuccinic
acid 200 mg
Time after which half the 5 h > 71 h 35 h
50 h
formic acid initially
0
present in the formic acid-
0
amine adduct (A3) has
I.)
co
u.)
decomposed
co
ko
0
-V
IV
Table 8:
0
H
LO
I
Example 130
IV
I
Ruthenium catalyst [Ru(PnOct3)4(H)2] 40 mg
co
.4,
F-,
0
Ligand 1,2-bis(dicyclohexylphosphino)ethane 11 mg
Inhibitor 1 H202(30% in H20) 170 mg
Inhibitor 2 meso-dimercaptosuccinic acid 200 mg
Time after which half the formic acid 96 h
initially present in the formic acid-amine
adduct (A3) has decomposed
