Note: Descriptions are shown in the official language in which they were submitted.
PF 70291 CA 02787905 2012-07-23
1
Preparing ether carboxylates
The present invention relates to a process for preparing ether carboxylates.
Ether
carboxylates are typically prepared in a batch operation, normally by
initially charging
the alkxoylate, a base such as NaOH and a catalyst such as Raney copper and
bringing this reaction mixture to reaction temperature under superatmospheric
pressure.
The class of ether carboxylates, useful as mild anionic surfactants, is long
known.
US 2,183,853, having a 1934 priority date, describes preparing ether
carboxylates by
reacting alkoxylates with sodium and sodium chloroacetate at temperatures
between
160 and 200 C. To achieve high conversions and low by-product formation, it is
described as advantageous to add the base and chloroacetic acid at different
points of
the reactor with stirring. To remove resulting or added water from the
reaction solution
and to achieve a very quick reaction, the reaction is carried out at 70 to 90
C and a
pressure of about 10 to 50 mbar.
DE 31 35 946 describes the direct oxidation of the alkoxylates with oxygen or
oxygen-
containing gases in an aqueous alkali medium over a platinum or palladium
catalyst as
a further way of preparing ether carboxylates.
The oxidative dehydrogenation of alcohols to carboxylates by thermal reaction
of the
alcohol with alkali metals or alkali metal hydroxides has been known since
1840
(Dumas and Stag, Ann, 35, 129 to 173). This reaction was classically carried
out
without catalyst and at > 200 C. US 2,384,818, issued 1945, employs this
method for
oxidizing amino alcohols.
Similarly, the use of catalysts for the oxidative dehydrogenation is long
known.
US 2,384,817, filed 1942, describes the positive influence of cadmium, copper,
nickel,
silver, lead and zinc compounds on the reaction rate.
EP 0 620 209 describes a process to manufacture carboxylic acid salts by
contacting
an aqueous solution of a primary alcohol with an alkali metal hydroxide in the
presence
of an effective amount of a specific and activated Raney copper catalyst
containing
from 50 to 10 000 ppm of an element selected from the group consisting of
chromium,
titanium, niobium, tantalum, zirconium, vanadium, molybdenum, manganese,
tungsten,
cobalt and mixtures thereof, or from 50 to 10 000 ppm of nickel. The alcohol
may be
aliphatic, aromatic or a polyol. It is stated that both the alcohol - which
necessarily will
have a certain solubility in water - and the resulting carboxylate have to be
stable in the
hot and caustic solution. In addition, superatmospheric pressure is necessary
for the
reaction in order that the reaction temperatures described may be attained.
Amino
alcohols, aromatic alcohols and ethylene glycol are recited as examples.
CA 02787905 2012-07-23
2
EP 1 125 633 describes the use of doped Raney copper (doped with at least one
element from the iron group or with a precious metal), the inactivation of
which by
agglomeration is distinctly reduced and the use cycles are therefore higher.
The
invention relates to the preparation of carboxylic acids from alcohols. Again,
the
oxidative dehydrogenation of diethanolamine under strongly basic conditions at
160 C
and 10 bar pressure is given as an example. The alcohols have to be soluble in
water
and the alcohol and also the carboxylic acid have to be stable to the strongly
basic
solution.
EP 1 125 634 describes a Raney copper fixed bed catalyst (with doping from
iron or a
precious metal), its simple filterability from the reaction solution and its
use in the
context of a continuous process. It is stated to be a prerequisite for the
reaction of the
alcohols that both the reactant and the product have to be stable in the
strongly basic
solutions and the alcohol has to be soluble in water.
US 5,916,840 describes preparing carboxylic acid salts in the presence of a
supported
catalyst consisting of an alkali-resistant support material (activated carbon
for
example), an anchor metal (palladium for example) and a discretely applied
active
metal (copper for example). The reaction takes place in a batch autoclave in
the
presence of water at 160 to 170 C. Continuing this principle, WO 03/033140
describes
further catalysts for preparing iminodiacetic acid from diethanolamine. The
preferred
reaction condition is said to be the use of alkali metal hydroxides (equimolar
use), use
of a solvent and of a catalyst (at least 1% by mass) at temperatures of 120 to
220 C
under superatmospheric pressure.
WO 98/13140 describes a catalyst for dehydrogenation of amino alcohols and
ethylene
glycol derivatives, consisting of zirconium, copper and optionally a further
metal. The
reaction of ethylene glycols such as triethylene glycol with 1 eq of NaOH in
aqueous
solution at 180 C and 10 bar pressure over the described catalyst (30% by
mass) is
disclosed.
US 4,110,371 describes a process for preparing dicarboxylic acid salts from
compounds consisting of 2 to 6 ethylene glycol units with aqueous alkali metal
hydroxide solution at temperatures of 200 to 300 C using a catalyst consisting
of
nickel, copper and chromium.
US 3,717,676 describes a method of preparing alkali metal salts of
oxypolycarboxylates wherein an oxysubstituted or polyoxysubstituted primary
alcohol is
reacted with alkali metal hydroxide, 20% to 60% of water at 190 to 230 C, a
pressure
of 7 to 14 bar over a cadmium catalyst.
PF 70291 CA 02787905 2012-07-23
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JP 10 277 391 finally describes the use of ultra-fine copper catalysts having
particle
sizes of 1 to 20 microns for preparing alkyl ether carboxylates from
polyoxyethylene
alkyl ethers and their use as an anionic surfactant in soap and cosmetic
applications.
The fine state of subdivision of the catalyst gives a distinctly higher
activity than classic
Raney copper or copper-zirconium catalysts (comparative example involving
Raney
copper from Degussa shows a conversion of merely 15% instead of 98% under
otherwise equivalent conditions).
The processes described accordingly all have a number of disadvantages which
it has
proved impossible to overcome despite the many years of research in this
field. A
combination of pressure, high temperatures and strongly alkaline conditions is
as ever
required, imposing a severe stress on the material used (stress corrosion
cracking),
limiting reactivity as well as selectivity, the catalysts used are costly
since they have to
be inconveniently doped and form clumps during the process; only water-soluble
and
hence frequently rather short-chain alcohols can be used; moreover, the
alcohol used
and the product formed have to be base-resistant; and vinyl ethers, frequently
formed
as scissioning products, are not wanted in the product formed, yet are very
difficult to
detect analytically.
It is an object of the present invention to provide a process that reduces
and/or
eliminates the disadvantages mentioned.
We have found that this object is achieved, surprisingly, by a process for
preparing an
ether carboxylate of formula I
0 TOM
O p
R4
M
R3 O
O' Wn
R4 R2 4~_ R2 R2 IR4 1
RO O\ ]~X'X (" /o I J~ oM1
O p ( m 0 n Rl ~ ~lt O ,n` ~ Jm~L`' O p 9
O R3 R3 O
comprising reacting the corresponding alkoxylate of formula II
PF 70291 CA 02787905 2012-07-23
4
OH
Jp
R4
M
R3
OJnL
R4 R2 R2 R2 R4
RO 0 O\1 X( /OH1
p mL O ~nl Rl J LT O 1nl 1 Jm~ O lp q
R3 R3 I I
where independently
R1 is a C1- to C5o-alkyl, mono-, di-, tri-,...polyamine,
0
11
Xis O, COO, CH2-NH-O for r = 0 and q = 1 or N, C -N , N(CH2)tO for r = 0 to 50
and q = 2,
r is an integer from 0 to 50,
R2 is H or C r to Cio-alkyl,
R3 is H or Cr to C,o-alkyl,
R4 is H or C,- to C,o-alkyl,
M is H or a metal, preferably alkali, alkaline earth, ammonium, organic base,
n is from 0 to 50,
m is from 0 to 40,
p is from 0 to 40,
q is from 1 to 20,
s is 0 or 1,
t is from 0 to 20,
provided that n + m + p is at least 1 and
R is C,- to C5o-alkyl, C1- to C5o-alkenyl, C,- to C5o-alkynyl, C6- to C5o-
aryl, C6- to
C5o-alkylaryl, H or a metal, preferably alkali, alkaline earth,
with a base by using a transition metal catalyst, the base being added to the
reaction mixture discontinuously at two or more times or continuously over a
period above 30 minutes.
There are various preferred embodiments; in one, when s is 0, R is C,- to C5o-
alkyl, Cl- to C50-alkenyl, C,- to C5o-alkynyl, C6- to C5o-aryl or C6- to C50-
alkylaryl;
in the other, when s is 1, R is H or a metal, preferably alkali, alkaline
earth.
There are also preferred ranges for r. r is preferably from 1 to 20 and more
preferably
from 2 to 10.
Preference is given to a process for preparing an ether carboxylate of formula
III
PF 70291 CA 02787905 2012-07-23
R2 R4
~X~ f 0 OM J
R Lam' 0~ m O~ q
R3 0 III
comprising reacting the corresponding alkoxylate of formula IV
R2 R4
R ~T" 0~ m O_ Jp q
R3 IV
5 where independently
R is Cl- to C5o-alkyl, Cl- to C5o-alkenyl, Cl- to C5o-alkynyl, C6- to C5o-
aryl, C6- to C5o-
alkylaryl, H or a metal, preferably alkali, alkaline earth,
0
11
X is O, COO, CH2-NH-O for q = 1 or N, C -N, N(CH2)1O for q = 2
R2 is H or Cr to C io-alkyl,
R3 is H or C,- to C,o-alkyl,
R4 is H or Cr to C,o-alkyl,
M is H or a metal, preferably alkali, alkaline earth, ammonium, organic base,
n is from 0 to 50,
m is from 0 to 40,
p is from 0 to 40,
q is from 1 to 2,
t is from 1 to 10,
provided that n + m + p is at least 1,
with a base by using a transition metal catalyst, the base being added to the
reaction
mixture discontinuously at two or more times or continuously over a period
above 30
minutes.
A process for preparing an ether carboxylate of formula V
R2 R4
OM
~1 L R3 0 V
comprising reacting the corresponding alkoxylate of formula VI
R2 IR4
~X/O~}~J /OH
R O n Jm~ O JP
R3 VI
where independently R is C,- to C5o-alkyl, Cl- to C5o-alkenyl, Cl- to C5o-
alkynyl, C6- to
PF 70291
CA 02787905 2012-07-23
6
C5o-aryl, C6- to C5o-alkylaryl, H or a metal, preferably alkali, alkaline
earth,
XisO,
R2 is H or C1- to C1o-alkyl,
R3 is H or Cr to C1o-alkyl,
R4 is H or C1- to C1o-alkyl,
n is from 0 to 50,
m is from 0 to 40,
p is from 0 to 40, preferably from 1 to 20 and more preferably from 5 to 10,
provided that n + m + p is at least 1,
with a base by using a transition metal catalyst, the base being added to the
reaction
mixture discontinuously at two or more times or continuously over a period
above 30
minutes.
There are preferred versions with regard to the alkoxylates used so that a
process is
preferred wherein independently
R is C1- to Cso-alkyl, C1- to Cso-alkenyl, Cl- to C5o-alkynyl, C6- to C5o-
aryl, C6- to C5o-
alkylaryl, H or a metal, preferably alkali, alkaline earth,
Xis0,
R2 is H or C2- to C8-alkyl,
R3 is H or C2- to C8-alkyl,
R4 is H or C2- to C8-alkyl,
n is from 1 to 30,
m is from 1 to 20,
p is from 1 to 20,
n + m + p is atleast2.
Particular preference is given to a process wherein independently
X is 0 or COO,
R is C2- to C1o-alkyl,
R2 is H or C3- to C5-alkyl,
R3 is H or C3- to C6-alkyl,
R4 is H or C3- to C6-alkyl,
n is from 1 to 18,
m is from 1 to 12,
m is from 1 to 12,
n+m+pis at least 5.
R is more particularly methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, 2-
ethylhexyl and
2-propylheptyl, dodecyl, tridecyl, myristyl, lauryl, i-C17, tall oil fat
(C16,18), behenyl.
R2, R3 and R4, if present, are each more particularly and independently
hydrogen,
methyl, ethyl, propyl, butyl, pentyl and isobutyl, of which hydrogen, methyl
and ethyl are
CA 02787905 2012-07-23
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particularly preferred and methyl and ethyl are very particularly preferred.
n is most preferably in the range from 3 to 20.
m is more preferably in the range from 3 to 20.
p is more preferably in the range from 3 to 20.
The sum total of n, m and p is more preferably in the range from 3 to 20. The
individual
alkoxide units can be arranged in various ways, for example randomly, in block
form or
with a gradient. Particular preference is given to processes first using a
higher oxide,
for example propylene oxide, and then EO.
In addition to various alkylene oxides, the process of the present invention
may also
utilize various alkoxylates a, b, c, ..., z being added at one or more times.
For instance,
compounds where Ra = C12,14 to C2o and Rb = C2 to C10 may be used with
advantage.
A useful base is in principle any compound capable of deprotonating the
alkoxylate
used. This includes bases within the meaning of Bjerrum's acid-base
definition. There
are certain preferred bases and hence a process wherein the base is selected
from the
group consisting of NaOH, KOH, Mg(OH)2, Ca(OH)2, ammonium hydroxide, choline
hydroxide and hydrotalcite constitutes a particularly preferred embodiment of
the
present invention. Hydrotalcite is particularly preferred when the product is
to have
narrow molar mass distributions.
The base is added to the reaction mixture during the reaction either batchwise
or
continuously. This means that the base, or portions of the base, are added to
the
reaction mixture at a time at which reaction conditions are present.
A preferred embodiment is accordingly a process wherein the base is added to
the
reaction mixture at 2 to 10 000 times. The number of times at which the base
is added
is preferably in the range from 3 to 1000, more preferably in the range from 4
to 100
and most preferably in the range from 5 to 20.
Another preferred embodiment is a process wherein the base is added to the
reaction
mixture over a period of more than 30 minutes. The period over which the base
is
added to the reaction mixture is particularly advantageous in the range from
more than
2 h to 10 h, preferably in the range from 5 h to 9 h and even more preferably
in the
range from 6 h to 8 h.
In both cases, i.e., in the case of the continuous addition of the base and in
the case of
the batchwise addition of the base, the base can be introduced into the
reaction
PF 70291 CA 02787905 2012-07-23
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mixture at various places. It is particularly preferable when the base is
added to the
reactor at 2 to 10 places and preferably at 3 to 5 places. This procedure can
be used to
reduce the local concentration of base in the reaction mixture still further
and thereby
further suppress the formation of by-products.
As far as the catalyst is concerned, the metals of groups 4 to 12, i.e., from
Ti to Zn and
those thereunder, come into consideration as both main and secondary
constituent,
those of groups 8 to 11, i.e., Fe - Cu and those thereunder, being preferred.
And it is
accordingly the case that a process wherein the transition metal catalyst
comprises at
least one metal selected from the group consisting of Fe, Cu, Co and Ni is
preferred.
The transition metal can be in a variety of forms, such as pure metal or as
metal oxide,
but it is preferably present in activated form, as Raney metal. Raney copper
is
particularly preferred. This Raney copper can also be still further modified,
for example
by doping with other metals. It is an advantage of the process of the present
invention
that such doping is not needed to achieve a good result for the synthesis, but
it may
nevertheless be advantageous to further improve the result of the synthesis.
The
preparation of suitable transition metal catalysts is described for example in
EP 1 125 634 (Degussa), where a simple Raney copper fixed bed catalyst is
disclosed.
EP 1 125 633 (Degussa) describes Raney copper comprising various dopants
[example: 1 % Pt, 3% Fe, 2000 ppm Cr or 1 % V on Raney Cu], and it is shown
that the
doped catalysts deactivate less than conventional Raney copper (Degussa BFX
3113W). WO 96/01146 (Monsato) finally describes C support with a precious
metal, for
example Pt applied as anchor metal on the Cu. This technique is stated to
likewise
prevent the sintering of the Cu. A particularly preferred combination of
transition metals
is that of copper and iron. DMC catalysts are more particularly preferred.
The present process leaves only small amounts of catalyst in the product. In a
preferred process the M content of the product is in the range from 0.1 ppm to
1%,
preferably in the range from 1 to 500 ppm and more preferably in the range
from 10 to
50 ppm.
The process of the present invention can pleasingly also be carried out on a
large
scale. Preference is accordingly given to a process utilizing more than 1 kg,
preferably
more than 10 kg, even more preferably more than 100 kg and most preferably
more
than 1 t (metric ton) of alkoxylate.
The process of the present invention wherein the reaction temperature is in
the range
from 140 C to 220 C is preferred. More preference is given to processes
carried out in
the temperature range from 160 to 200 C and more particularly in the range
from 160
to 190 C, for example at 180 C.
CA 02787905 2012-07-23
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The process of the present invention may in principle employ any solvent that
is stable
under the reaction conditions and does not react with the reactants or with
the
products. Preference is therefore given to solvents selected from the
following list:
Name
NMP
diethylene glycol dimethyl ether
triethylene glycol dimethyl ether
tetraethylene glycol dimethyl ether
diethylene glycol diethyl ether
2- 2-metho ethox ethox acid sodium salt
2- 2- 2-methox ethox ethox etho acetic acid
Decane
Decalin
Dodecane
white oil
1,1,3,3-tetramethyl urea
Tributylamine
y-but rolactone
Undecane
tert-butylbenzene
di ro l carbonate
2,5-dimethyl rrole
2,6-dimethylanisole
3,4-dimethylanisole
1,2-dimeth limidazole
4-ter-but l-1,2-dimeth (benzene
And particular preference is given to the following solvents or suspension
media:
N-methylpyrrolidone, triethylene glycol dimethyl ether, [2-(2-
methoxyethoxy)ethoxy]
acid sodium salt and white oil.
There is also a preferred pressure range. Preference is given to a process
wherein the
pressure in the reaction vessel is less than 10 bar, preferably less than 5
bar and more
preferably less than 2 bar. It is a particular advantage of the process of the
present
invention that it can also be carried out under atmospheric pressure, and that
is in fact
the most preferred embodiment.
Also protected are the ether carboxylates obtainable by this process and
obtained by
this process.
The use of these ether carboxylates in cleaning, crop protection and cosmetic
applications and also as a solubilizer constitutes a further part of the
subject matter of
the present invention.
Compositions comprising ether carboxylates obtained by this process likewise
form
part of the subject matter of the present invention.
Further common constituents of compositions of this kind are mentioned in
CA 02787905 2012-07-23
WO 2008/071582 for example.
The present invention is more particularly elucidated by the following
examples, which
do not restrict the scope of the invention:
5
Examples:
Example 1: Synthesis of nonionic ethoxylate (surfactant A)
10 300 g of a C12114 alcohol mixture of C8 < 0.3% by weight, C,o < 1.0% by
weight, C12
> 65.0% by weight, C14 21.0% to 28.0% by weight, C16 4.0% to 8.0% by weight,
C18
< 0.5% by weight, for example Radianol C12-C161726 from Oleon, were initially
charged
with 2.6 g KOH (45% by weight in water) and dewatered together at 80 C and
reduced
pressure (about 20 mbar). Next 462 g of ethylene oxide were added by metered
addition at 150 C and reacted at that temperature. The end of the reaction was
determined via the drop in pressure. After purging with inert gas and cooling
down to
room temperature, the catalyst was neutralized by addition of 1.25 g of
concentrated
acetic acid.
Example 2: Oxidative dehydrogenation under atmospheric pressure in semi-batch
process
A 21 multi-neck flask equipped with internal thermometer, dropping funnel and
distillation still head with column was initially charged with 498 g of
surfactant A and
also 30 g of Raney copper and the initial charge was heated to 180 C with
stirring.
152 g of aqueous sodium hydroxide solution (25% strength) were added dropwise
over
a period of 8 h during which the water was distilled out of the reaction
mixture. On
completion of the addition of the aqueous sodium hydroxide solution the
reaction
mixture was stirred for a further 30 minutes. The reaction mixture was cooled
down to
140 C and filtered through a frit and the effluent was analyzed.
Strong base titration:
7 mg KOH/g
Weak base titration:
95 mg KOH/g
OH number analysis:
reactant: 119 mg KOH/g
CA 02787905 2012-07-23
11
effluent:13 mg KOH/g, corrected with strong base: 6 mg KOH/g; it follows that
the
conversion was 95%.
NMR (DMSO, CDCI3 = 1/1); 1H NMR, 13C decoupled:
6 = 0.85 (t, 3H, -CH3), 1.25 (s, 20H, CH2), 1.55 (m, 2H, -CH2CH2-O), 3.4 (m,
2H,
CH2-O), 3.6 (m, 24H, O-CH2-CH2-O and CH2-OH of reactant), 3.75 (s, 1.77H,
CH2-COO). It follows that the conversion was 89%.
HPLC: the sample was resolved in a system developed for the determination of
free
polyethylene glycol in nonionic surfactants. The principle of the analysis is
that
molecules having aliphatic moieties are retained on a reversed phase, whereas
polar
substances pass through the column without being retained. A switch valve was
used
to transfer the nonretarded fraction to a size exclusion column, on which the
polymeric
constituents were separated from low molecular weight secondary components.
The
level of scissioning products in the analyzed sample was below 0.5 g/100 g.
Example 3: Oxidative dehydrogenation under superatmospheric pressure in batch
process
A 1.2 I autoclave with pressure maintenance at 15 bar was initially charged
with 249 g
of surfactant A together with 15 g of Raney copper (Degussa) and 76 g of
aqueous
sodium hydroxide solution (25%) and this initial charge was heated to 180 C
for 10 h
with stirring. After removal of the catalyst by filtration, the organic phase
was separated
and titrated for weak base (6 mg KOH/g) and subjected to an OH number
measurement (113 mg KOH/g) to determine conversion (6%).
Example 4: Oxidative dehydrogenation under superatmospheric pressure in semi-
batch
process
A 1.2 I autoclave with pressure maintenance at 15 bar was initially charged
with 249 g
of surfactant A together with 15 g of Raney copper (Degussa) and this initial
charge
was heated to 180 C with stirring. In the course of 7 h, altogether 76 g of
aqueous
sodium hydroxide solution (25%) were metered into the autoclave using an HPLC
pump, followed by a further 30 minutes of stirring. After removal of the
catalyst by
filtration, the organic phase was separated and titrated for weak base (9 mg
KOH/g)
and subjected to an OH number measurement (115 mg KOH/g) to determine
conversion (3.5%).
