Note: Descriptions are shown in the official language in which they were submitted.
l~ti57'7~
This invention relates to the preparation of alkylidene
diesters and more particularly relates to the preparation of
ethylidene diacetate by the action of hydrogen on acetic anhydride.
Ethylidene diacetate is a chemical intermediate of prime
commercial interest in view of its ready convertibili'y to a
number of different tonnage chemicals of commerce. By one known
conversion technique, ethylidene diacetate is readily trans-
formed to vinyl acetate plus acetic acid; see Kirk-Othmer
Encyclopedia of Chemical Technology, (2nd ed.), vol. 21,
page 321, Interscience, New York (1970). By another well-known
conversion process, ethylidene diacetate can be transformed into
acetic anhydride plus acetaldehyde; see Kirk-Othmer Encyclopedia
of Chemical Technology"> (2nd ed.), vol. 8, pages 410-413, Inter-
-
science, New York (1965). Reference is also made to U.S.
Patent No. 2,425,389 as indicative of the flexibility of
ethylidene diacetate as a chemical intermediate.
Various processes have been proposed for the preparation
of ethylidene diacetate. One such process involves the reaction
of acetaldehyde and acetic anhydride, the ethylidene diacetate
being produced as an intermediate in the preparation of vinyl
acetate, a process which has been employed to a limited extent
on a commercial scale; see Hydrocarbon Process 44 (11), 287
(1965). British Patent 1,538,782 discloses another technique
for producing ethylidene diacetate which employs the carbonylation
of methyl acetate or dimethyl ether in the presence of hydrogen.
Fenton U.S. Patent 3,579,566 treats organic acid anyhdrides such
as acetic anhydride with hydrogen in the presence of a catalyst
comprising a complex of a Group VIII noble metal with a biphyllic
~: - 2 -
5~7~7~
ligand from the group consisting of trihydrocarbyl phosphines,
arsines and stihines. The Fenton examples show the preparation
of ethylidene diacetate from acetic anhydride by this technique.
The Fenton examples, however, show that the quantity
of ethylidene diacetate which is produced is relatively small
in relation to the theoretical quantity producible from the
acetic anhydride employed. While Fenton illustrates his generic
process in terms of the following shorthand equation:
o
O-C-R
I
R-C-O-C-R + H2 ~ ~R-C-H
\
O-C-R
the complete equation is as follows:
O O O-C-R O
" ~, /
2 R-C-O-C-R + H2 ~R-C-H ~ R-C-OH
\
O-C-R
In the foregoing equation, when R is -CH3 the treatment of
acetic anhydride with hydrogen is illustrated. In other words,
in such a reaction, one molecule of acetic acid is formed for
each molecule of ethylidene diacetate produced. Competing
reactions tend to form other products such as acetaldehyde and
ethyl acetate to the detriment of the yield of ethylidene
diacetate.
l . - 3 --
~7 ~ ~
Belgian Patent 879,178 converts carboxylic acid anhydrides
to l,l-diesters with hydrogen in the presence of certain supporte
metals, including metals of Group VIII of the Periodic Table, and
in the presence of a strong protonic acid such as hydrochloric
and hydrofluoric acids. The examples show substantial carboxylic
acid formation.
It is accordingly an object of this invention to provide
an improved process for the preparation of alkylidene diesters,
e.g., ethylidene diacetate, from carboxylic acid anhydrides,
e g ~ acetic anhydride, wherein increased proportions of alkylidene
diesters in relation to carboxylic acid can be realized and the
formation of other by-products can be minimized, i.e., the ratio
of alkylidene diester, e.g., ethylidene diacetate to carboxylic
acid, e.g., acetic acid, and the yields of the diester product,
are high.
It is a further object of the invention to provide an im-
proved process for the production of alkylidene diesters from
carboxylic acid anhydrides which does not require the use of
Group VIII noble metals.
In accordance with the invention, these and other objects
are realized by the reaction of a carboxylic acid anhydride,
e.g., acetic anhydride, with hydrogen in the presence of a cobalt
carbonyl. It has been surprisingly disco~ered that a cobalt
carbonyl very effectively catalyzes the reaction and does not
require the presence of a promoter or li~and as in the case of
the process disclosed by Fenton, in addition to not requiring
the presence of a Group VIII noble metal. It also does not re-
quire the presence of an acid of any kind. Although the presence
of an acid may promote the formation of by-products and complicat~
product separation, an acid can be tolerated, if desired, but the
absence of an acid such as used in Belgian patent 879,178, is
preferred.
.
1194 4-
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Thus, in accordance with the invention, hydrogen
is reacted with an acid anhydride in the presence of a cobalt
carbonyl such as dicobalt octacarbonyl ~Co(CO)4]2 or tetra-
cobalt dodecacarbonyl [Co(CO)3~4, although any other cobalt
carbonyl can also be used. Thus, ethylidene diacetate can be
effectively prepared in a representative case by subjecting
acetic anhydride to reaction with hydrogen in the presence
of dicobalt octacarbonyl. In all cases, the reaction is
carried out under anhydrous conditions.
In carrying out the process of the invention, a wide
range of temperatures, e.g., 10 to 250C. are suitable, but
temperatures of 50 to 150C. are preferably employed and the
more preferred temperatures generally lie in the range of
70 to 120C. Temperatures lower than those mentioned can
be used but they tend to lead to reduced react~on rates, and
hlgher temperatures may also be employed but there is no
particular advantage in their use. Preferably the reaction
ls carried out at a substantially constant temperature.
The time of reaction is also not a parameter of the
process and depends largely upon the temperature employed, but
typical reaction or residence times, by way of example, will
generally fall in the range of 0.1 to 6 hours. The reaction
is preferably carried out under super-atmospheric pressures
but excessively high pressures, which require special high-
pressure equipment, are not necessary. In general, the
reaction is effectively carried out by employing a hydrogen
partial pressure which is preferably 50 to 2,000 p.s.i.,
and most preferably 300 to l,000 p.s.i., although hydrogen
partial pressures of l to lO,000 p.s.i. can also be
employed. In the usual case, pressures below about 2,000 psi
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,
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are generally used. ~y maintaining the partial pressure of
hydrogen at the values specified, adequate amounts of this
reactant are always present. The total pressure is preferably
that required to maintain the liquid phase and, in this casel
the reaction can be advantageously carried out in an autoclave
or similar apparatus.
At the end of the desired residence time, the reaction
mixture is separated into its several constituents, as by
distillation. Preferably, the reaction product is introduced
into a distillation zone, which may be a fractional distillation
column, or a series of columns, effective to separate the
unreacted acetic anhydride, acetic acid, other by-products,
from the product ethylidene diacetate. The cobalt carbonyl
is recycled.
The hydrogen is preferably employed in substantially
pure form, as available commercially, but inert diluents
such as carbon monoxide, carbon dioxide, nitrogen, methane,
and noble gases can be present if desired. The presence of
inert diluents does not affect the reaction but their presence
makes it necessary to increase the total pressure in order
to maintain the desired hydrogen partial pressure. The
hydrogen, like other reactants should, however, be essentially
dry, i.e., the hydrogen and the other reactants should be
reasonably free from water. The presence of minor amounts
of water such as may be found in the commercial forms of
the reactants is, however, entirely acceptable.
As previously mentioned, the presence of gaseous
diluents such as carbon monoxide increases the overall
pressure required to provide the desired hydrogen partial
pressure but the presence of carbon monoxide can be effective
to maintain the catalyst for prolonged periods of time.
'7'~
Cobalt car~onyl has a ~endency to decompose in response to ele-
vation of temperature but it has been found that such decompo-
sition is minimized and even completely surpressed when the
temperature is maintained below 100C. under the pressure con-
ditions specified above. The presence of carbon monoxide provides
further insurance against catalyst decomposition.
The amount of cobalt carbonyl is in no way critical and is
not a parameter of the process of the invention and can vary over
a wide range. As is well known to persons skilled in the art,
the amoun~ of catalyst used is that which will provide the desir-
ed suitable and reasonable reaction rate since reaction is in-
fluenced by the amount of catalyst. However, essentially any
amount of catalyst will facilitate the reaction. Typically,
however, the cobalt catalyst is employed in the amount of l mol
per l to lO0,000 mols of carboxylic acid anhydride, preferably 1
1 per 10 to lO,000 mols of carboxylic acid anhydride and most
preferably 1 mol per 50 to 5,000 mols of carboxylic acid anhydride
The anhydrides which can be used in carrying out the process
of the invention are anhydrides of carboxylic acids having up to
10 carbon atoms, preferably lower alkanoic acids having up to 6
carbon atoms. These anhydrides can be represented by the formula:
O O
n n
R ~ C ~ O ~ C ~ R
wherein R i s a hydrocarbyl radical which can be an alkyl group
or a monocyclic aryl group. Representative anhydrides include
acetic anhydride, propionic anhydride, valeric anhydride,
caprylic anhydride, benzoic anhydride, and the like. Acetic
anhydride is preferred.
1194 7-
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The process of this invention can be carried out in the
presence of a solvent or diluent, if desired. Ordinarily, a
solvent is not required. The solvent or diluent can be any
organic solvent which is inert in the environment of the process,
such as hydrocarbons, e.g., octane, benzene, toluene, xylene
and tetralin, or halogenated hydrocarbons such as the chloro-
benzenes, e.g., trichlorobenzene, or carboxylic acids, e.g.,
those containing up to 16 carbon atoms such as acetic acid,
or esters such as methyl acetate and cellosolve acetate, and the
like. Preferred solvents are halogenated hydrocarbons, chloro-
benzenes and high boiling esters. Mixtures of solvents can also
be used, such as mixtures of the solvents named above. In gener-
al, chlorobenzenes have been found to be the most suitable for
use when a solvent is employed in the process. A solvent or
diluent is suitably selected which has a boiling point sufficient-
ly different from the other components in the reaction mixture
that it can be readily separated by distillation, as will be
readily apparent to persons skilled in the art.
It will be apparent that the above-described reaction lends
itself readily to continuous operation in which the reactants
and catalyst are continuously supplied to the appropriate re-
action zone and the reaction mixture continuously distilled to
separate the volatile organic constituents and to provide a net
product consisting essentially of alkylidene diester, with
the other organic components being recycled and, in the case of
liquid-phase reaction, a residual catalyst containing ~raction
also being recycled.
1194 8.
57
It will be apparent that the catalytic reaction in-
volved in the process of the invention can be carried out in the
vapor phase, if desired, by appropriate control of the total
pressure in relati~on to the temperature so that the reactants
are in vapor form when in contact with the catalyst. In the
case of vapor-phase operation, and in the case of liquid-phase
operation, if desired, the catalyst components may be supported,
i.e., they may be dispersed on a carrier of conventional type
such as alumina, silica, silicon carbide, zirconia, carbon,
bauxite, attapulgus clay, solid organic polymers, e.g.,
polyvinyl pyridine and polystyrene and the like. The catalyst
component~ can be applied to the carriers in conventional manner,
e.g., by impregnation of the carrier with a solution of the
catalyst, or the catalyst mixture, followed by drying. Catalyst
component concentrations upon the carrier may vary widely, e.g.,
O.Ol weight percent to lO weight percent, or higher. The support-
ed catalyst is in the active form if it has a hydride or carbonyl
substituent on the supported cobalt. Typical operating conditions
for vapor-phase operation are a temperature of 50 to 300C.,
preferably 70 to 250C. and most preferably 100 to 200C., a
pressure of l to 5,000 p.s.i.a., preferably 50 to 1,500 p.s.i.a.
and most preferably 150 to 500 p.s.i.a., with space velocities
of 50 to lO,000 hr. l, preferably 200 to 6,000 hr. l and most
pre$erably 500 to 4, 000 hr. l ~STP).
The following examples will serve to provide a fuller
understanding of the invention, but it is to be understood that
they are given for illustrative purposes only, and are not to
be construed as limitative of the invention. In the examples,
all parts are by weight and percentages are on a molar basis,
unless otherwise indicated.
1194 9.
~t;'j~7 7~ ;
EXA~PLE 1
In this example, a mAgnetically-stirred Has~elloy Parr
bomb with a glass liner is employed as the reaction vessel. The
bomb is charged with 2 parts of dicobalt octacarbonyl as catalyst,
then with 40 parts of acetic anhydride, is swept out with argon
and pressured to 700 p.~.i.g. with ~ en. The bomb is then placed
in an oil bath at room temperature and brought up to 100C. in
about 1~ minutes. The pressure is maintained at 1,450 p.s.i.g.
by recharging ~2 when needed. ~he reaction is ~hen carried out
at this constant temperature for 3 hours, whereupon the bomb
is cooled to approximately room temperature, vented and opened.
G.C. ~gas chromatography) analysis o, the reaction mixture shows
it to contain 13 parts of ethylidene diacetate and 12.1 parts
acetic anhydride along with 7.4 parts of acetic acid and trace
le~els of ethyl acetate and acetaldehyde by-products. The yield
of ethylidene diacetate is 65% and the ratio of ethylidene di-
acetate to acetic acid i5 72% of theoretical.
~ '`''`' .
1194 10.
il~577~ ~
EXAMPLE 2
A Parr bomb as described in Example 1 is charged with 2
parts of dicobalt octacarbonyl as catalyst, then with 40 parts
of acetic anhydride, is swept out with argon and pressured to
400 psig with hydrogen. The bomb is then placed in an oil bath
at room temperature and brought up to 100C. in about 15 minutes.
The pressure is maintained at 1,200 p.s.i.g. by recharging H2 when
needed. The reaction isithen carried out at ~5 constant ~rature
for 3 hours, whereupon the bomb is cooled to approximately room
temperature, vented and cooled. Gas chromatography analy-
sis of the reaction mixture shows it to contain 10.3 parts of
ethylidene diacetate and 22.7 parts acetic anhydride along with
5.9 parts of acetic acid and trace levels o ethyl acetate and
acetaldehyde by-products. The yield of ethylidene diacetate is
84% and the ratio of ethylidene diacetate to acetic acid is 72
of theoretical.
1194 11.
7 7 ~ ¦
EXAMPLE 3
A reaction vessel as described in Example 1 is charged
with 1 part of tetra cobalt dodecacarbonyl as catalyst, then
with 20 parts of acetic anhydride, is swept out with argon and
pressured to 150 p.s.i.g. with C0 and then to 1,000 p.s.i.g. with
hydrogen. The bomb is then placed in an oil bath at room temper-
ature and grought up to 100C. in about 15 minutes. The pressure
is maintained at 1,000 p.s.i.g. with hydrogen. The reaction is
then carried out at this constant temperature for 3 hours, where-
upon the bGmb is cooled to approximately room temperature, vented
and opened. Gas chromatography analysis of the reaction
mixture shows it to contain 8.2 parts of ethylidene diacetate
and 7.4 parts acetic anhydride along with 3.6 parts of acetic
acid and trace levels of ethyl acetate and ac~taldehyde by-
products. The yield of ethylidene diacetate is 91% and the
ratio of ethylidene diacetate to acetic acid is 93.3% of theo-
retical.
1194 1~.
11~i577~} 1
EXAMPLE 4
In this Example and in the following examples, a stirred
autoclave is used as the xeaction vessel. The autoclave is
charged with 4.1 parts of dicobalt octacarbonyl as catalyst
and 400.4 parts acetic anhydride and pressured with 350 p.s.i.g.
carbon monoxide and 1,150 p.s.i.g. hydrogen. The vessel is then
heated up to 90C. in about lS minutes. During the heating
period, there is absorption of gas and the pressure falls in
spite of the increased temperature. The pressure is returned
to 1,500 p.s.i.g. with hydrogen and is maintained at this
pressure and temperature for 6 ho~rs. G.C. analysis of the
reaction mixture shows it to contain 178.6 parts of ethylidene
diacetate and 134.9 parts acetic anhydride along with 84.8 parts
of acetic acid, 4 parts acetaldehyde and trace levels of ethyl
acetate by-product. The yield of ethylidene diacetate is 94,
and the ratio of ethylidene diacetate to acetic acid is 86.6%
of theoretical. The ratio of ethylidene diacetate plus acet-
aldehyde to acetic acid is 93% of theoretical.
1194 `13.
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EXAMPLE 5
The reaction vessel is charged with 2.1 parts of dicobalt
octacarbonyl, 5 parts p-toluene sulfonic acid and 400 parts acetic
anhydride and pressured with 500 p.s.i.g. carbon monoxide and
1,150 p.s.i.g. hydrogen. The vessel is then heated up to 100C.
in about 15 minutes. The pressure is returned to 1,500 p.s.i.g.
with hydrogen and is maintained at this pressure and temperature
for 4 hours. Gas chrDmatography analysis of the reaction
mixture shows it to contain 83 parts of ethylidene diacetate and
282 parts acetic anhydride along with 36 parts of acetic acid
and trace levels of ethyl acetate and acetaldehyde by-products.
The yield of ethylidene diacetate is 98% and the ratio of ethyl-
idene diacetate to acetic acid is 95% of theoretical.
EXAMPLE 6
The autoclave is charged with 2 parts of dicobalt octa-
carbonyl as catalyst and 400 parts acetic anhydride and pressured
to 200 p.s.i.g.carbon monoxide and 1,300 p.s.i.g.hydrogen. The
vessel is then heated up to 90C. in about 20 minutes. The
pressure is returned to 1,500 p.s.i.g. with hydrogen and is
main~ained at this pressure and temperature for 6 hours.
Gas chromatography analysis of the reaction mixture shows it
to contain 103.6 parts of ethylidene diacetate and 253 parts
acetic anhydride along with 44.3 parts of acetic acid and trace
levels of ethyl acetate and acetaldehyde by-products. The yield
of ethylidene diacetate is 98.5 and the ratio of ethylidene di-
acetate to acetic acid is g6.1% of theoretical.
1194 14.
1~L65~7~
EXAMPLE 7
Into the reaction vessel are charged 4 parts of dicobalt
octacarbonyl as catalyst and 400 parts acetic anhydride and
the vessel is pressured with 130 p.s.i.g.carbon monoxide and
870 p.s.i.g.hydrogen. The vessel is then heated up to 90C.
in about 15 minutes. The pressure is returned to 1,000 p.s.i.g.
with hydrogen and is maintained at this pressure and temperature
for 1 hour. Gas chrom~tography analysis of the reaction
mixture shows it to contain 74 parts of ethylidene diacetate
and 296.6 parts acetic anhydride along with 30 parts of acetic
acid and trace levels of ethyl acetate and acetaldehyde by-
products. The yield of ethylidene diacetate is 100% and the
ratio of ethylidene diacetate to acetic acid is 100% of theo-
retical.
EXAMPLE 8
Into the autoclave are charged 4.0 parts of dicobalt octa-
carbonyl as catalyst and 400 parts acetic anhydride and the
vessel is pressured with 750 p.s.i.g. carbon monoxide and 750
p.s.i.g. hydrogen. The vessel is then heated up to 90C. in
about 15 minutes. The pressure is returned to 1,500 p.s.i.g.
with hydrogen and is maintained at this pressure and temperature
for 7 hours. Gas chromatography analysis of the reaction
mixture shows it to contain 141.8 parts of ethylidene diacetate
and 205.2 parts acetic anhydirde along with 58.5 parts of
acetic acid and trace levels of ethyl acetate and acetaldehyde
by-products. The yield of ethylidene diacetate is 100~ and the
ratio of ethylidene diacetate to acetic acid is 99.6% of theo-
retical.
,~ -
1194 15.
EXAMPLE 9
The stirred pressure vessel is charged with 4.0 parts of
dicobalt octacarbonyl as catalyst and 400 parts acetic anhydride
and pressured with 350 p.s.i.g. carbon monoxide and 1,150 p.s.i.g.
hydrogen. The ~essel is then heated up to 100C. in about 15
minutes. The pre~sure is returned to 1,500 p.s.i.g. with
hydrogen and is maintained at this pressure and temperature for
2 hours. Gas chromatography analysis of the reaction
mixture shows it to contain 97.6 parts of ethylidene diacetate
and 263.3 parts acetic anhydride along with 40.1 parts of acetic
acid and trace levels of ethyl acetate and acetaldehyde by-
products. The yield of ethylidene diacetate is 99.8% and the
ratio of ethylidene diacetate to acetic acid is 100% of
theoretical.
EXAMPLE 10
The stirred pressure vessel is charged with 20 parts of
dicobalt octacarbonyl as catalyst and 400 parts acetic anhydride
and pressured with 400 p.s.i. carbon monoxide. The vessel is
then heated up to 100C. in about 15 minutes. The pressure is
increased to 1,200 p.s.i.g. with hydrogen and is maintained at
thi~ pressure and temperature for 7 hours. Gas chroma-
tography analysis of the reaction mixture shows it to contain
197 parts of ethylidene diacetate and 22.4 parts acetic anhydride
along with 119.8 parts of acetic acid and 17.1 parts acetaldehyde
and trace levels on ethyl acetate by-product. The yield of
ethylidene diacetate is 73% and the ratio of ethylidene di-
acetate to acetic acid is 68% of theoretical. The ratio of
ethylidene diacetate and acetaldehyde to acetic acid is 87% of
theoretical. '
1194 16.
~ ti'~7'7~
EXAMPLE 11
The reaction vessel is charged with 20 parts of dicobalt
octacarbonyl as catalyst, 12 parts acetic acid and 388 parts
acetic anhydride and pressured with 200 p.s.i. carbon and 700
p.s.i. hydrogen. The vessel is then heated up to 100C. in
about 30 minutes. ~he pressure is increased to 1,000 p.s.i.g.
with hydrogen and is maintained at this pressure and temperature
for 2 hours. Gas chromatography analysis of the reaction
mixture shows it to contain 153.5 parts of ethylidene diacetate
and 198.9 parts acetic anhydride along with 88.3 parts of
acetic acid, 2.4 parts acetaldehyde and trace levels on ethyl
acetate by-product. The yield of ethylidene diacetate is 95.7%
and the ratio of ethylidene diacetate to acetic acid is 83%
of theoretical. The ratio of ethylidene diacetate plus acet-
aldehyde to acetic acid is 87% of theoretical.
EXAMPLE 12
A reaction vessel as described in Example 1, is charged
with 1 part of tetra cobalt dodecarbonyl as catalyst, then with
20 parts of propionic anhydride and the reaction is carried out
as described in Example 3, producing results comparable to those
obtained in Example 3, except that propionic acid and the corre-
sponding alkylidene diester are produced.
1194 17.
11 i jl ~'7'~)'1 ;
ExAMæLE 13
Example 12 is repeated but there are employed 20 parts of
valeric anhydride, and similar results are obtained, except that
valeric acid and the corresponding alkylidene diester are pro-
duced.
EXAMPLE 14
Example 12 is again repeated but the propionic anhydride
is replaced by 20 parts benzoic anhydride. Again, results
comparable to those obtained in Exampie 3 are realized, except
that benzoic acid and the corresponding alkylidene diester are
produced.
1194 18.
