Note: Descriptions are shown in the official language in which they were submitted.
~ 11,095
This in~ention relates to the production of
polyhydric alcohols, their ether and ester derivatives,
a~d oligomers of such alcohols. This invention also pro-
duces monohydric alcohols such as methanol and their
ether and es~er derivatives.
Polyhydric alcohols are presently being produced
synthe~ically b~ the oxidation o~ petroleum derived
material~. Owin~ to the limited availability of petxole~m
sourcesj the cost o~ these petroleum derived ma~erials has
been steadily increasing. Many h~.~e raised the dire pre-
dic~ion o~ a significant oil shor~age in the uture. The
consequence of this has been the recognition of the need
for a new low cost source o chemicals which can be
con~erted into such p~lyhydric alcohols.
This in~e~ion is directed to ~he process of
m~king alkane diols and triol~, contain~ng 2, 3 or 4
carbon atoms~ and derivatives such as the~r esters. Key
products of the process of this invention are e~ylene
glycol and its es~er der~vati~es. Byproducts o this
i~ention are the lesser valuable, but valua~le neverthe-
less, monohydric alkanols such as methanol, ethanol and
propan~ls, and their ether and ester derivatives. The
p~oducts of the proc~ss of thi~ ln~ention co~tai~ earbon,
hydrogen and oxygen.
There are described in U.S. Patent 3,833~634,
issued Septem~er 3, 1974, and U.S. Patent 3,957,857,
issued May 18, 1976~ processes for reacting hydrogen and
2~6 1~, 095
oxides of carbon in the presence of rhodium carbonyl com-
plex catalysts. U.S. Patent 3,957,857 is concerned with
a rhodium carbonyl cwmplex which is a rhodium carbonyl
cluster exhibiting a particular infrared spec~rum. The
conditions, broadly speaking, employed in those processes
involve reacting a mîxture of an o~ide of carbon and
hydrogen with a eatalytîc amount of rhodium in complex
combination with carbon monoxide, at a tempera~ure of
between about 100C to abou~ 375~C and a pressure of
between abou~ 500 p.s.i.a. to about 50,000 p~s.i.a~ As
described in these patents, the process ls carried ou~
in a homogeneous liquid phase mixture in the presence of
one or more compounds seleeted from ~mong groups referred
to in the patent, as organic oxygen ligands, org~nic
nitrogen ligands and organic aza-oxa ligands. In
addition to the aforementioned U.S. Patents, the follow-
ing U.S. and Canadian Patents and Canadian applications
amplify the development of the processes for making
alkane polyols from mixtures of hydrogen and oxides of
carbon:
U.S,P. 3,878,292 Patented April 15, 1975
U.S.P. 3,878,290 Patented April 15, 1975
U.S.P. 3,878,214 Patented ApriL 15, 1975
U.S.P. 3,886,364 Patented May 27, 1975
U.S.P~ 3,940,432 Patented February 24, 1976
U.S.P. 3,929,969 Patented December 30, 1975
U.S.P. 3,952,039 Patented April 20, 1976
U.S.P. 3,948,965 Patented April 6, 1976
U.S.P. 3,944~588 Patented March 16, 1976
U.S.P. 3,974~259 Patented August 10, 1976
U.S.P. 3,989,799 Patented November 2, 1976
U.S.P, 4,013,700 Patented March 22, 1977
U.SOP~ 3,968,136 Patented July 6, 1976
U~S~P~ 4~001,289 Patented January 4, 1977
Canadian Pat. 1,058,639 Patented July 179 1979
Canadian Pat. 1,064,968 Patented September 23~ 1979
Canadian Pak. 1,069,540 Patented January 3, 1980
Can. Ser. No. 262,263 Filed September 29, 1976
3 095
Can. S~r. No. 262,265 Filed September 29, 1976
Can. Ser. No. 262,266 Filed September 29, 1976
Can~ Ser. No. 287,745 Filed September 29, 1976
U.S. Patent No. 3,952,039 issued April 20, 1976
to Walker et al descrlbes the use of salts containing
alkali metal cations to improve ~he yield of ~he desired
alkane diols and triols of the învention. The process of
the Walker et al paten~ involves providing a metal salt to
the aorementioned homogeneous liquid phase reaction mix-
~0 ture to promote the production of alkane polyols, ethylene
glycol being the primary product in terms o its c~mmercial
value. The salt promoter provided to ~he mixture is pres-
ent in an amount to achieve the ~ptimum rate of forma~ion
of said alkane polyol at the correlated catalyst concentra-
tion, temperature and pressure of such reaction mix~ure.
A range of 0.5 - 1.5 atoms of cation per six atoms of
rhodium is disclosed in the patent. ~len the amount of
alkali metal cation in the reaction is greater or less
than this 2mo~mt, the productivity of reaction to poly-
hydric alcohol is significantly reduced. This invention~
however, provides for the selection of a salt pr~moter in
terms of its basicity to minimize inhibition of alkane
polyol production by the presence of anexcess of salt.
The follGwing postulate possible mechanisms which
wou~d result in the above-described behavior:
a.) the inhibitor function of the salt is of
higher kinetic order in salt than is the promoter function;
11,095
bo ) the promoter ~unction of the salt has
a stoichiometric limit after which only the inhibitor
function o~ the salt remains.
The tenm "inhibitor func~ion" means the
func~ion of the salt which reæults in a decrease in alkane
polyol yield as salt concentration increases.
An above postulate can be illustrated by the
following reac~ion scheme:
The involvement of salt is described as follows
L0 tRh symbolizes a rhodium~containing ~pecies):
Rh ~ salt (MX)~ h M ~ + M ~ 3
glycol
[NOTE: In the above reaction scheme the charge o~ the
rhodium carbonyl comple~ is no~ showrl; it contains a fixed
or varying number o~ Cûls and H~s; the rate and equilibr~um
constants implicity contain an~ appropriate CO and H2
concentration~.] The salt acts as a promoter because its
anion helps to produce the active catalyst ~nd as an in-
hibitor because its cation has an adverse mass law effect
on the equilibrium concentration o a direct precursor of
the active catalyst. The model sugge~ts the use of a salt
and reaction conditions which produce a reactive anion and
an impotent cation.
The model predicts that the rate will increase
as a function of the stoichiometric concentration of salt
promoter, and then decrease. As K increases, elther
because of an intrinsic property of M+ or use of a sol~ent
of high dielectric constant (for example, suli~olane) or
11,09~
high constant of complexation with M~,(for example, crown
ether, and to a lesser extent tetraglyme) 3 the rate of
decrease decreases. Any complexation of ~he cation by
~he solvent is incorporated implici~y into the deinition
o K as a resuL~ of t~e cu~omary deinition of standard
states. More generally, however, such a microseopic solvent
effect is jus~ one example of the use of a co~plexing agent
to in1uence the ion-pairing abili~y of M+. The simplest
case, since it would not in~olve ~he introduction of an
additional compound,would be complexation of M~ by X~.
This is described by the following equilibra
XlM~ X- ~ M~ (2)
~ ~ ROX ~ ~.i T RO (3)
RO ~ RO- + ~ (4)
Thus, the process of U.S.Patent ~o. 3~952J039
recognizes that there is an optimum concentration for
salt promoters ~o achieve maximum alkane polyol production
~nd that amounts in excess of that optimum concentration
are undesirable. This in~ention contemplates increasing
the concentration o the salt in excess of said opti~um
c~ncentratlon for the purpose of enhancing catalyst
stabilit~ in the reaction. Catalyst stability relates
to the desirable feature of keeping the catalyst in solu-
tion. The invention also recognizes the fact that allow-
ing for some excess of the salt over the optimum concenr
tration will reduce the criticality of having to operate
the process under strict control of salt concentration,
- 11,095
The process of this invention differs from the
process described in U.S. Patent No. 3,952,039, in that
there is provided in the aforementioned homogeneous
liquid phase mixture a concentration of salt promoter
in excess o~ the optimum such that the yield of alkane
polyol is nct decreased from the maximum by more than
50%.
For the purposes of this invention, ~he ultimate
salt promoter selected is one whose cation ion pairs
least with the rhodi~ catalyst. One should employ such
a promo~er in the homogeneous liquid phase reaction mix-
ture in an amount which is greater than the minimum for
producing the maximum amount of alkane polyols, partic-
ularly ethylene glycol 9 using that pr~moter.
The efects of concentration of the salt pro
moter on product formation in the homogeneous liquid phase
mixture of the process o~ this invention has been found to
be dependent upon the tempera~ure, thP rhodium concentra-
tion, the solvent employed and, to a lesser degree, the
pressure.
The precise role of the rhodium carbonyl com-
plexes, such as the rhodium carbonyl clusters, in the
reaction of ~ydrogen with oxides of carbon to produce
polyhydric alcohols is not fully appreciated at present.
Under the reaction conditions of the present process the
carbonyl complexes are believed to be anionic in their
active forms.
11,095
Infrared spectra under reaction conditions of
the present process have shown Rh(C0)4, Rhl3(CO)24H3 2,
Rh6(C0)15~ , Rhl3(co)24H2 , ~nd [Rhl2(CO)34-36] anions~
and other rhodium clusters to be present at various con-
centrations at different times of the reaction. These
may represent the active rhodium carbonyl species re-
sponsible or polyhydric alcohol formation or may be
merely symptomatic of some further intermediate trans-
itory rhodium carbonyL structure which serves to convert
the carbon monoxide and hydrogen to the polyhydric alcohol.
The salt promoters contemplated by the present
invention include any organic or inorganic salt which does
not ~dversely affect the production of polyhydric alcohols.
Experimental wor~ suggest that ~any salts are beneficial as
either a copromoter and/or in aiding in maintaining
rhodium in solu~ion during the reaction. Illustrative
of useful salt promoters are the ammonium salts and the
salts of the metals of Group I a~d Group Il o~ the Periodic
Table (Handbook of Chemistry and Physics 50th Edition)
for instance the halide, hydroxide, alkoxide, phenoxide
and carboxylate salts such as sodium fluoride 3 cesium
fluoride~ cesium pyridinolate, cesium formate, cesium
acetate, cesium benzoate~ cesium ~-me~hylsulfonyl-
benzoa~e (CH3S02C6H4COO)Cs, rubidium ace~ate, magnesium
acetate, strontium acetate, ~mmonium formate, ~mmonium
benzoate and the like. Preerred are the cesium and
ammonium salts.
~9~ 6
11,095
In addition, the anion of the above salt may be
any of the rhodium carbonyl anions. Suitable rhodium
carbonyl anions include ~Rh6(CO)15~2 ; [Rh6(CO)15Y~
wherein Y may be hydrogen or halogen, such as chlorine,
bromine, or iodine, [Rh6(C0)15(COOR"] wherein R" is
lower alkyl or aryl such as methyl, ethyl, or phenyl;
~Rh (CO)14]2 ; [Rh7(C0)16] ; [Rh12(C )30]
Rhl3(C0)24H3 ; and Rhl3(~0)24H2 ; Rhl3(C0)24H .
The capabilities of seven cesium carboxylates
(RC02Cs) as inhibitors of alkane polyol formation in
tetraglyme, 18-crown~6 and sulfolane are shown in Tables
I and III and Figures 1 and 2. They decrease with in-
creasing basicity of RC02 , a result consistent with
~onsideration of equilibria (5)-(8)
Rh Cs~ Rh ~ ~s~ (5)
RC4 Cs+ - ~ RC2 + Cs~ (6)
R~02 + R'OH ~ - > RC02H ~ R'O- (7)
R'O Cs+ ~ ~ R'O ~ Cs+ (8)
within the framework of the previously discussed model:
Since inhibitor capability ~rate of fall-off o a plot
of g glycol vs. n~moles salt (Figures 1 and 2), gO ~5~ gO 75
(Table I)3 depends on K5 , an increase in basicity
Ks ~ [Cs~
of RC02 at fîxed stoichiometric ~Cs+~ leads to a decrease
in ~Cs+3 and in its inhibitory effeGtO Note that ~his depend-
ence on basicLty of RC02 ls not merely a general "basi ity
effect" of added nucleophile (amine or anion) since variatlon
of basicity of amine and anion affects oppositely the degree
ll ~ o9s
C`l~
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11, 095
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12
11,095
of inhibition by the amine and salt, respectively. The effect
of æmine basicity on inhlbition of alkane polyol formation is
disclosed in copending application Canadian Ser. No. 262,263,
$iled September 29, 1976.
Illustrative solvents which are generally suit-
able in making the homogeneous mixture lnclude9 for ex-
ample, e~hers such as ~etrahydrofuran, tetrahydropyran,
crown ethers (see, for example, "S~ruc~ure and Bonding"
vol. 16, 1973, Published by Springer-Verlag), diethyl ether,
1,2-dimethoxybenzene, 1,2-diethoxybenzene, the mono- and
dialkyl ethers of ethylene g7ycol, of propylene glycol,
of butylene glycol, of diethylene glycol, of dipropylene
glycol, of triethylene glycol, of tetraethylene glycol,
of dibutylene glycol, of oxyethylenepropylene glycol, etc.;
alkanols such as methanol, ethanol, propanol, isobutanol,
2-ethylhexanol, etc.; ketones such as acetone, methyl ethyl
ketone, cyclohexanone, cyclopentanone, etc~; esters such as
methyl acetate, ethyl acetate, propyl acetate, butyl
acetate, methyl propionate, ethyl butyrate, methyl laurate,
etc.; water gamma-butyrolactone, deltavalerolactone,
substituted and unsubstituted tetrahydrothiophene-l,l-
dioxides (sulfolanes) as disclosed in Canadian Patent
1,069,540, patented January 8, 1980, at pages 6 and 7
of the specification; and others. The mono dialkyl
ethers of tetraethylene glycol, gamma bu~yrolactone, par-
ticularly sulfolane, 3~4-bis(2-methoxyethoxy) sulfolane,
and crown ethers, are the preferred solvents.
The temperature which may be employed can vary
over a wide range of elevated temperatures. In general,
the process can be conducted at a temperature in the range
of from about 100C and upwards to approximately 375C,
and higher. Temperatures outside this stated rang~ are
13.
~ 11,095
~,
not excluded from the scope of ~he invention. At the
lower end of the temperature range, and lower, the rate
of reaction to desired product becomes mar~edly slow. At
the upper t.emperature range, and beyond, signs of some
catalyst ins~ability are no~ed. Notwithstanding this
factor, reaction continues ant alkane polyols and/or their
derivativPs are producedO Additionally, one should take
notice of the equilibrium re~on for forming ethylene glycol
CO ~ 3H~ ~ HOCH2 CH OH
At relatively high tempera~ures ~he equilibrium inereasing~
ly favors the left hand side of ~he equation. To drive the
reaction to the formation of increased quantities of
ethylene glycol~ higher par~iat pressures of carbon
monoxide and hydrogen are required. Processes based
on correspondingly higher pressures, howeverg do not
represent preferred embodiments of the invention in view
of the high in~estment costs associated with erecting
chemical plants which utilize high pressure utilities
and the necessi~y of fabricating equipment capable of
withstandin~ such enoLmous pressures. Suitable tempera-
tures are between about 150 C to about 320C, and
desirably from about 210C to about 300C.
The novel process is e~fected for a period of
tLme sufficiPnt to produce the alkane po~yols and/or
derivatives thereof. In general, the residence time can
vary from minutes to several hours, e.g., from a few
minutes to approximateLy 24 hours, and longer. It is
readily appreciated that the residence period will be
14
11,095
~19~Z~6
influenced to a significant extent by the reaction te~-
p~rature, the concentration and choice of the catalyst,
the total gas pressure and the partial pressures exerted
by its components, the concentration and choice of
diluent, and other factors. The synthesis of the
desired product(s) by the reaction o~ hydrogen wlth an
oxide of carbon is suitably conducted under operati~e
conditions which give reasonable reaction rates and/or
conversionsO
The relative amounts o~ oxide o carbon
and hydrogen which are lnitially presen~ in ~he
reaction mixture can be ~aried over a wide range.
In general, the mole ratio o CO:H2 is in the
range o from about 20:1 to about 1:20, suitably
from about 10:1 to about 1:10, and pre~erably
from about 5:1 to abou~ 1:5.
It is to be understood, however9 that
molar ratios outside the aforestatP.d broad range
may be emplQyed. Substances or reaction mixtures
which give rise to the formation o carbon monoxide
and hydrogen under the reaction conditions may be
employed ins~ead o mixtures comprising carbon
monoxide and hydrogen which are used in preferr~d r
embodimen~s in the practice of the inven~ion.
For instance, polyhydric alcohols are obtained by
using mixtures containing carbon dioxide and
hydrogen. ~ixtures o~ carbon dioxide, carbon
monoxide and hydrogen c~n also be empLoyed. If
desired, ~he reaction mixture an eompri~e ste~m
a~d car~on monoxide,
11,095
The novel process can be executed in
a batch, semi-continuous, or continuous fashion.
The reaction can b~ conducted in a single reaction
æone or a plurality of reaction zones, in series
o~ in parallel, or it may be conducted inter-
mittently or continuously in an elongated ~ubular
zon~ or series o such zones. The material of
construction should be such that it is inert
during ~he reaction and the fabriea~ion of
the equipment should be able to withstand the
reaction temperature and pressure. Ihe reaction
zone can be fitted with inte~nal and/or external
heat exchanger(s) to thus control undue tempera-
ture fluctuatio~, or to prevent any possibl~
"run-away" reaction temperatures due to the
exothermic nature of the reastlon~, II1 preferred
embodiments o~ the invention, agitation means to
vary the dcgre~ of mixi~g of the reaction mixture
can be suitably employed. Mixing induced by
~ibration~ shaker~ stirrer, ro~atory, oscilla~ion,
ultrasonic, etc., æe all lllus~ra~ive o ~he
typ~s of agitatiQn means which are contemplated.
Such means are available ~nd we~l~known to the ar..
The catalyst may be initlally introduced into the
~ reaction æone batchwise~ or it may be contLnuously
- or intermittently introduced in~o such zone during
the course of the synthesis reaction. Means to
introducs and/or ad~ust the reactants, either
16
11, 095
intermittently or contiIluously, into the reaction
zone during the course of the reaction can be
conveniently utilized ;n ~he novel process especially
to maintain the desired molar ratios of and ~he
partial pressures exerted by the reactants.
As intimated previously, the operative conditions
can be adjusted to optimize the conversion of the desired
product and/or the economics of the novel process. In a
continuous process, for instance, when it is preferred ~o
operate at relatively low conversions, it is generally
desirable to recirculate unreacted synthesis gas with/with-
out make-up carbon monoxide and hydrogen to ~he reaction.
Recovery o~ the desired product can be achieved by methods
well-known in the art such as by distillation, fraction-
ation, extraction, and the like. A fraction comprising
rhodium catalyst~ g~nerally contained in byproduc~s and/or
normally liquid organic diluen~, can be rec~cled to the
reaction zone, if desiredO All or a portion of such .
fraction can be removed for recovery o~ the rhodium ~alues
or regeneration to the active catalys~ and intermittently
added to the recycle stream or directly to the reaction
zone.
The acti~e forms of the rhodium carbonyl clusters
may be prepared by various techniques. They can be
preformed and then introduced into the reaction zone or
they can be formed i~ situ.
11, 095
~Ca9~`96
The equipment arrangement and procedure which
provides the capability for determlning ~he existence of
anionic rhodium carbonyl complexes or clusters having de-
fined infrared spectntm characteristics, during ~he course
of the manufac~ure of polyhydric alcohols from carbon mon-
oxide and hydrogen, pursuant to this invention is disclosed
and schematically depicted ln U.S. Patent application No.
3,957,8S7 3 issued May 18, 1976.
A particularly desirable infrared cell construc-
tion is described in U.S. Patent No. 3,886,364, issued
May 27, 1975. The preferred cell of U.S. Pa~ent No.
3,886,364 is well suited for use in the aforementioned
procedure.
The "oxide of carbon" as covered by the claims
and as used herein is intended to mean carbon monoxide and
mixtures of carbon dioxide and carbon monoxide, elther
introduced as such or formed in the reaction. Preferablyg
the oxide o carbon is carbon monoxide.
Materials used in the followlng examples had
the following characteristics:
11~095
~ 6
Tetraglyme (Ansul), cesium formate (Alfa), and
cesium acetate (Alfa) were used without urther purifica-
tion. Sulfolane (Phillips) was puriied as described in
E.N. Arnett and C.F. Douty, J.Am.Chem.Soc., 86, 409 (1964).
Cesium benzoate,[J H.S. Green, W. Kynaston~ and A.S.
Lindsey, Spec~rochim. Acta, 17, 486 (1961)], (recryst.
H20. Anal. Found: G,32.62; H,l.90. Calcd. for G7H50zCs:
C,33.10; H,1.98) and cesium pivalate ~P.H. Reichenbacher~
M.D. Morris, and P.S. Skell, J.Am.Chem.Soc.~ 90, 3432
(1968)], (washed with PhCl, recryst. H20. Anal. Found:
C,24.75; H,4.20. Calcd. for C5H902Cs: C,25.66; H,3.88)
were prepared by use of literature procedures. Cesium
p-methylsulfonyl benzoate (washed with ether, recryst.
H20. Anal. Found: C,28.26; H,2.05. Calcd. for C8H704SCs:
C,28.90; H,2.13), cesium triphenylacetate (recryst. H20.
Anal. Found: C,56.25; H,3.74. Calcd. for C20H1502Cs:
C,57.16; H,3.60), and cesium isobutyrate (washed with
PhCl, recryst. H20. ~nal. Fou~d: C,21.01; H~3.32.
Calcd. or C4H702Cs: C,21.84; H,3.21) were prepared by
reaction of CsOH and the corresponding acids. ~18] crown-6
solvent was obtained from Pari~h Chemical Company, Pxovo,
Utah, and was heated under vacuum to remove possible
volatile impurities and its purity was checked by vpc,
nmr~ mel~ing point, and elemental analysis.
Pr3cedure employed in examples:
A 150 ml. capacity stainless steel reactor cap-
able of withstanding pressures up to 7,000 atmospheres was
charged with a premix of 75 cubic centimeters (cc) of
19
llgO95
~ g9296
solvent, rhodium dicarbonylacetylacetonate, and promoter(s).
The reactor was sealed and charged with a gaseous mixture,
containin~ equal molar amounts of carbon monoxide and hydro-
gen, to the desired pressure. Heat was applied to the
reactor and its contents; when the temperature of ~he
mixture inside the reactor reached 190C, as measured by
a suitably pla~ed thermocouple, the carbon monoxide and
hydrogen (H2:CO=l:l mole ratio) pressure was adjusted to
maintain the desired gas pressure. During the course of
the reaction additional carbon monoxide and hydrogen was
added whenever the pressure inside the reactor dropped
approximately 500 psi below the desired pressure. With
these added repressurizations, the pressure inside the
reactor was maintained within about 500 psi of the desired
pressure over the en~ire reaction period.
A~ter the reaction p~riod, the vessel and its
contents were cooled to room temperature, the excess gas
vented and the reaction product mixture was removed.
Analysis of the reaction product mixture was made by gas
chromatographic analysis using a Hewlett Packard FM TM
model 81Q Research Chromatograph.
Rhodium recovery was determined by atomîc absorp-
tion analysis of the contents of the reactor after the
~enting of the unreacted gases at the end of the reaction.
The rhodium recovery values recited below are the percent
rhodium based on the total rhodium charged to the reactor
that is soluble or suspended in the reaction mixture after
the specified reaction time.
11,095
g296
The same equipment and procedure were used in
all the ea~amples in the Tables and Figures except or
the reactants and conditions speciied. Table III
illustrates the use of cesium carboxylates in excess of
optimum concentration in ~18~ crown-6 solvent and its
at:tendant inc;ease in rhodium stability.
Figure 1 graphically depicts the inhibitory
effect of the use of various carboxylate salts in excess
of the optimum con~entration. The dissociation constant
o the conjugate acid for each sal~ is also provided.
Figure 2 illustrates ~he inhibitory effect o
PhCQ2Cs promoter in 2 solvents of diferent complexing
ability. The inhibitory effect is shown to be weaker in
the solvent of greater c~mplexing a~ility, i.e.,
[18] crown~6.
11 ~ Og5
~(~9~29~
o~ c~ o ~ oo ~ ~ o ~ o u~ ~ ~ ~ r~ ~1 ~
~ o
o
l ~ ~ 00 0
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