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Description  |
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This invention relates to the preparation of anhydrides of carboxylic
acids, more particularly mono-carboxylic acids, and especially the
anhydrides of lower alkanoic acids, such as acetic anhydride, by
carbonylation.
Acetic anhydride has been known as an industrial chemical for many years
and large amounts are used in the manufacture of cellulose acetate. It has
commonly been produced on an industrial scale by the reaction of ketene
and acetic acid. It is also known that acetic anhydride can be produced by
the decomposition of ethylidene diacetate, as well as by the oxidation of
acetaldehyde, for example. Each of these "classic" processes has
well-known drawbacks and disadvantages and the search for an improved
process for the production of acetic anhydride has been a continuing one.
Proposals for producing anhydrides by the action of carbon monoxide upon
various reactants (carbonylation) have been described, for example, in
Reppe et al U.S. Pat. Nos. 2,729,561 2,730,546, and 2,789,137. However,
such prior proposals involving carbonylation reactions have required the
use of very high pressures. More recently, carbonylation at lower
pressures has been proposed but only as a route to the preparation of
acetic acid. French Pat. No. 1,573,130, for example, describes the
carbonylation of methanol and mixtures of methanol with methyl acetate in
the presence of compounds of Group VIII noble metals such as iridium,
platinum, palladium, osmium and ruthenium and in the presence of bromine
or iodine under more moderate pressures than those contemplated by Reppe
et al. Similarly, South African Pat. No. 68/2174 produces acetic acid from
the same reactants using a rhodium component with bromine or iodine.
Schultz (U.S. Pat. Nos. 3,689,533 and 3,717,670) has disclosed a
vapor-phase process for acetic acid production employing various catalysts
comprising a rhodium component dispersed on a carrier. None of these later
carbonylation disclosures, however, refers to or contemplates the
preparation of acetic anhydride or other carboxylic acid anhydrides.
Most recently, improved processes for preparing carboxylic acid anhydrides,
including acetic anhydride, have been disclosed in co-pending applications
of Colin Hewlett Ser. No. 394,220, filed Sept. 4, 1973, Ser. No. 467,977,
filed May 8, 1974, and Ser. No. 554,933, filed Mar. 3, 1975 and in the
co-pending application of Nabil Rizkalla, Ser. No. 556,750, filed Mar. 10,
1975. In all of these recent processes, however, a Group VIII noble metal
is an essential catalyst component. Consequently, while entirely
effective, these processes suffer from the need to employ expensive,
relatively rare metals.
It is an object of the present invention to provide an improved process for
the manufacture of carboxylic acid anhydrides, especially lower alkanoic
anhydrides, such as acetic anhydride, which requires neither high
pressures nor Group VIII noble metals.
In accordance with the invention, it has been surprisingly discovered that
a carboxylic ester and/or a hydrocarbyl ether can be carbonylated at
relatively low pressures if the carbonylation is carried out in the
presence of a multiple or co-catalyst comprising a nickel component and a
chromium component in the presence of an iodide, and in the presence of a
promoter comprising an organo-nitrogen compound or an organo-phosphorus
compound wherein the nitrogen and phosphorus are trivalent. It has been
discovered that this nickel-chromium co-catalyst-promoter system makes
possible carbonylation at relatively low pressures, especially carbon
monoxide partial pressures, in contrast to the process disclosed in Reppe
et al U.S. Pat. No. 2,729,651 in which, while employing a
nickel-containing catalyst, the patentees find it necessary to use
pressures of at least 200 atmospheres in their examples.
Thus, in accordance with the invention, carbon monoxide is reacted with a
carboxylate ester, especially a lower alkyl alkanoate, or a hydrocarbyl
ether such as a lower alkyl ether, to produce a carboxylic anhydride, such
as a lower alkanoic anhydride, the carbonylation taking place in the
presence of an iodide e.g., a hydrocarbyl iodide, especially a lower alkyl
iodide, such as methyl iodide. Thus, acetic anhydride, for example, can be
effectively prepared in a representative case by subjecting methyl acetate
or dimethyl ether to carbonylation in the presence of methyl iodide. In
all cases, the carbonylation is carried out under anhydrous conditions in
the presence of the co-catalyst promoter-system described above. Moreover,
an ester-ether mixture can be carbonylated if desired.
It will be understood that the iodine moiety does not have to be added to
the system as a hydrocarbyl iodide but may be supplied as another organic
iodide or as the hydroiodide or other inorganic iodide, e.g., a salt, such
as the alkali metal or other metal salt, or even as elemental iodine.
Following the reaction the organic components of the reaction mixture are
readily separated from one another, as by fractional distillation.
In like manner, other lower alkanoic anhydrides, i.e., anhydrides of lower
alkanoic acids, such as propionic anhydride, butyric anhydrides, and
valeric anhydrides, can be produced by carbonylating the corresponding
lower alkyl alkanoate or a lower alkyl ether. Similarly, other carboxylic
acid anhydrides, e.g., the anhydrides of other alkanoic acids, such as
those containing up to 12 carbon atoms, for example capric anhydrides,
caprylic anhydrides, and lauric anhydrides, and like higher anhydrides are
produced by carbonylating the corresponding ester, e.g., alkyl alkanoates
containing up to 11 carbon atoms in the alkyl group and up to 12 carbon
atoms in the carboxylate group, or aryl esters, or the corresponding
ether, such as heptyl caprylate, nonyl decanoate, undecyl laurate, phenyl
benzoate, heptyl ether, nonyl ether, phenyl ether, and the like.
It is preferred that the reactants be selected to that the resulting
anhydride will be a symmetrical anhydride, i.e., having two identical acyl
groups, viz., wherein R in equations (1) and (2) is the same in each
instance, but it is within the scope of the invention to produce
non-symmetrical or mixed anhydrides and this can be readily effected by
using different combinations of reactants, e.g., by using compounds having
different R groups in the foregoing reactions, as will be obvious to
persons skilled in the art.
The above-described reactions can be expressed as follows:
CO + RCOOR .fwdarw. (RCO).sub.2 O (1)
2co + ror .fwdarw. (rco).sub.2 o (2)
wherein R is a hydrocarbyl radical which may be saturated, e.g., alkyl of 1
to 11 carbon atoms, or monocyclic aryl, e.g., phenyl or aralkyl, e.g.,
benzyl. Preferably, R is lower alkyl, i.e., an alkyl group of 1 to 4
carbon atoms, such as methyl, ethyl, n-propyl, i-propyl, n-butyl,
sec-butyl, and t-butyl.
The hydrocarbyl radical may be substituted with substituents which are
inert in the reactions of the invention.
The more volatile components such as alkyl iodide and unreacted ether or
ester in the final product mixture can be readily removed, as by
distillation, for recycling, and the net yield of product is substantially
exclusively the desired carboxylic anhydride. In the case of liquid-phase
reaction which is preferred, the organic compounds are easily separated
from the metal-containing components, as by distillation. The reaction is
suitably carried out in a reaction zone to which the carbon monoxide, the
ester or ether, the iodide and the nickel-chromium catalyst and the
promoters are fed. No water is produced in the above-described reactions
and anhydrous or substantially anhydrous conditions are employed.
In carrying out the process of the invention, a wide range of temperatures,
e.g., 25.degree. to 350.degree. C are suitable but temperatures of
100.degree. to 250.degree. C are preferably employed and the more
preferred temperatures generally lie in the range of 125.degree. to
225.degree. C. Temperatures lower than those mentioned can be used but
they tend to lead to reduced reaction rates, and higher temperatures may
also be employed but there is no particular advantage in their use. The
time of reaction is also not a parameter of the process and depends
largely upon the temperature employed, but typical residence times, by way
of example, will generally fall in the range of 0.1 to 20 hours. The
reaction is carried out under super-atmospheric pressure but, as
previously mentioned, it is a feature of the invention that excessively
high pressures, which require special high-pressure equipment, are not
necessary. In general, the reaction is effectively carried out by
employing a carbon monoxide partial pressure which is preferably 15 to
1000 psi and most preferably 30 to 200 psi, although carbon monoxide
partial pressures of 1 to 10,000 psi can also be employed. By establishing
the partial pressure of carbon monoxide at the values specified, adequate
amounts of this reactant are always present. The total pressure is, of
course, that which will provide the desired carbon monoxide partial
pressure and preferably it is that required to maintain the liquid phase
and in this case the reaction can be advantageously carried out in an
autoclave or similar apparatus. The final reaction mixture will normally
contain volatile components such as a hydrocarbyl iodide, unreacted ester
or ether along with the product anhydride and these volatile components,
after separation from the anhydride, can be recycled to the reaction. 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 volatile components from the product anhydride and to
separate the product anhydride from the less volatile catalyst and
promoter components of the reaction mixture. The boiling points of the
volatile components are sufficiently far apart that their separation by
conventional distillation presents no particular problem. Likewise, the
higher boiling organic components can be readily distilled away from the
metal co-catalyst components and any organic promoter which may be in the
form of a relatively non-volatile complex. Nickel-chromium catalyst, as
well as promoter can then be combined with fresh amounts of ester or ether
and carbon monoxide and reacted to produce additional quantities of
anhydride.
The ratio of ester or ether to the halide in the reaction system can vary
over a wide range. Typically, there are used 0.1 to 1000 moles of the
ester or ether per mole of halide, preferably 1 to 30 moles per mole.
The process is advantageously carried out in the presence of a solvent or
diluent, particularly when the reactant has a relatively low boiling
point, as in the case of dimethyl ether. The presence of a higher boiling
solvent or diluent, which may be the product anhydride itself, e.g.,
acetic anhydride in the case of dimethyl ether, or which may be the
corresponding ester, e.g., methyl acetate, again in the case of methyl
ether, will make it possible to employ more moderate total pressure.
Alternatively, the solvent or diluent may be any organic solvent which is
inert in the environment of the process such as hydrocarbons, e.g.,
octane, benzene, toluene, or carboxylic acids, e.g., acetic acid, and the
like. The carboxylic acid, when used, should preferably correspond to the
anhydride being produced. A solvent or diluent is suitably selected which
has a boiling point sufficiently different from the desired product in the
reaction mixture so that it can be readily separated, as will be apparent
to persons skilled in the art.
The carbon monoxide is preferably employed in substantially pure form, as
available commercially, but inert diluents such as carbon dioxide,
nitrogen methane, and noble gases can be present if desired. The presence
of inert diluents does not affect the carbonylation reaction but their
presence makes it necessary to increase the total pressure in order to
maintain the desired CO partial pressure. The carbon monoxide, like other
reactants should, however, be essentially dry, i.e., the CO 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. It is preferable that the
amount of moisture be kept to a minimum, since the presence of water has
been found to have an adverse effect upon the activity of the cocatalyst
promoter system. Hydrogen which may be present as an impurity is not
objectionable and even may tend to stabilize the catalyst. Indeed, in
order to obtain low CO partial pressures the CO fed may be diluted with
hydrogen or any inert gas such as those above mentioned.
The nickel and chromium catalyst components can be employed in any
convenient form, viz., in the zero valent state or in any higher valent
form. For example, the nickel and chromium to be added may be the metals
themselves in finely divided form, or a compound, both organic or
inorganic, which is effective to introduce the nickel and chromium into
the reaction system. Thus, typical compounds include the carbonate, oxide,
hydroxide, bromide, iodide, chloride, oxyhalide, hydride, lower alkoxide
(methoxide) phenoxide or chromium and nickel carboxylates wherein the
carboxylate ion is derived from an alkanoic acid of 1 to 20 carbon atoms
such as acetates, butyrates, decanoates, laurates, benzoates, and the
like. Similarly, complexes of nickel or chromium can be employed, for
example, nickel, or chromium carbonyls and metal alkyls as well as
chelates, association compounds and enol salts. Examples of other
complexes include bis-(triphenyl phosphine) nickel dicarbonyl,
tricyclopentadienyl trinickel dicarbonyl, tetrakis (triphenyl phosphite)
nickel, benzene chromium tricarbonyl, cycloheptatriene chromium
tricarbonyl and dicyclopentadienyl chromium.
Included among the catalyst components listed above are complexes of nickel
and/or chromium with organic promoter ligands derived from the organic
promoters hereinafter described. Particularly preferred are the elemental
forms, compounds which are iodides, and organic salts, e.g., salts of the
monocarboxylic acid corresponding to the anhydride being produced. It will
be understood that the foregoing compounds and complexes are merely
illustrative of suitable forms of the nickel-chromium co-catalyst and are
not intended to be limiting.
The nickel and chromium catalyst components employed may contain impurities
normally associated with the commercially available metal or metal
compounds and need not be purified any further.
The organic promoter is an organo-nitrogen or organo-phosphorus compound
wherein the nitrogen and phosphorus are trivalent. Preferably, however,
the organo-nitrogen promoter is a tertiary amine or a polyfunctional
nitrogen-containing compound, such as an amide, a hydroxy amine, a keto
amine, a di-, tri and other polyamine or a nitrogen-containing compound
which comprises two or more other functional groups. Typical
organo-nitrogen promoters include 2-hydroxypyridine, 8-quinolinol,
1-methylpyrrolidinone, 2-imidazolidone, N,N-dimethylacetamide,
dicyclohexylacetamide, dicyclohexylmethylamine, 2,6-diaminopyridine,
2-quinolinol, and N,N-diethyltoluamide.
The organo-phosphorus promoter is preferably a phosphine, e.g., a phosphine
of the formula
##STR1##
wherein R.sup.1, R.sup.2 and R.sup.3 may be the same or different, and are
alkyl, cycloalkyl, aryl groups, amide groups or halogen atoms, preferably
containing up to 1 to 20 carbon atoms in the case of alkyl and cycloalkyl
groups and 6 to 18 carbon atoms in the case of aryl groups. Typical
phosphines include trimethylphosphine, tripropylphosphine,
tricycohexylphosphine and triphenylphosphine.
Although generally the organic promoters are added separately to the
catalyst system, it is also possible to add them as complexes with the
nickel and/or chromium such as bis(triphenyl phosphine) nickel dicarbonyl,
tricyclopentadienyl trinickel, dicarbonyl, and tetrakis (triphenyl
phosphite) nickel. Both free organic promoters and complexed promoters can
also be used. Indeed, when a complex of the organic promoter and nickel
and/or chromium is used, free organic promoter can also be added as well.
The amount of nickel and chromium 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 amount of catalyst
used is that which will provide the desired suitable and reasonable
reaction rate since reaction rate is influenced by the amount of catalyst.
However, essentially any amount of catalyst will facilitate the basic
reaction and can be considered a catalytically-effective quantity.
Typically, however, each component of the co-catalyst is employed in the
amount of 1 mol per 10 to 100,000 mols of ester or ether, preferably 1 mol
per 100 to 10,000 mols of ester or ether, and most preferably 1 mol per
500 to 2000 mols of ester or ether.
The ratio of nickel to chromium can vary. Typically, it is one mol of the
nickel component per 0.1 to 20 mols of chromium component, preferably the
nickel component is used in the amount of 1 mol per 0.5 to 5 mols, most
preferably 1 mol per 2 mols of chromium component.
The quantity of organic promoter can also vary widely but typically it is
used in the amount of 1 mol per 1 to 10,000 mols of ester or ether,
preferably 1 mol per 10 to 1000, most preferably 1 mol per 15 to 200 mols
of ester or ether.
As previously mentioned, in the working up of the reaction mixtures, e.g.,
by distillation, the promoter components can be readily recovered and
recycled to the reaction. The chromium and nickel generally remain as the
least volatile components, and are recycled or otherwise handled together.
They may, however, distill with the volatile components, e.g., in the case
of nickel carbonyl. The same is true of the promoter components.
When an ether is used as the reactant, the corresponding ester is formed as
an intermediate, e.g., methyl acetate is formed when dimethyl ether is
carbonylated in accordance with the invention. This intermediate ester may
be recovered from the reaction mixture, if desired, e.g., by fractional
distillation, for example during the separation of the volatile components
of the reaction mixture as described above.
It will be apparent that the above-described reactions lend themselves
readily to continuous operation in which the reactants and catalyst,
preferably in combination with the promoter, are continuously supplied to
the appropriate reaction zone and the reaction mixture continuously
distilled to separate the volatile organic constituents and to provide the
desired product or products, e.g., carboxylic acid anhydride, with the
other organic components being recycled and, in the case of liquid-phase
reaction, a residual nickel-chromium-containing (and promoter-containing)
fraction also being recycled. It has been observed that hydrogen, e.g.,
used as a CO diluent as indicated above, is of value in maintaining the
catalyst at maximum activity on repeated recycle. During continuous
operation, it will be apparent that the iodine moiety remains in the
system at all times subject only to occasional handling losses or purges.
The small amount of iodine makeup which may be needed from time to time is
preferably effected by supplying the iodine in the form of the hydrocarbyl
iodide but, as pointed out above, the iodine moiety may also be supplied
as another organic iodide or as the hydrogen iodide or other inorganic
iodide, e.g., a salt, such as the alkali metal or other metal salts, or as
elemental iodine.
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 on a molar basis and all percentages are by
weight, unless otherwise indicated. The various reactants and catalyst
components are charged to the reaction vessel which is then closed and
brought to the reaction temperature indicated.
EXAMPLE 1
Methyl acetate (100 parts), methyl iodide (18 parts), nickel acetate (0.8
part), chromium carbonyl (2 parts) and 2-hydroxy pyridine (1.6 parts) are
charged to a glass-lined bomb which is pressured to 400 psig with carbon
monoxide at room temperature and sealed. The bomb is then heated and
stirred for 17 hours at 150.degree. C. At this temperature the initial
total pressure is approximately 750 psig and the initial partial pressure
of carbon monoxide is approximately 550 psi. Analysis of the reaction
mixture by gas chromatography (G. C.) at the end of the 17-hour reaction
period shows it to contain 38 wt. % of acetic anhydride, representing a
conversion of 54%.
EXAMPLE 2
Using the procedure of Example 1, methyl acetate (100 parts), methyl iodide
(18 parts), nickel acetate (0.8 part), chromium carbonyl (2 parts) and
2-quinolinol (1.6 parts) are reacted in a glass-lined bomb which is
pressured to 400 psig with carbon monoxide at room temperature and then
heated and stirred for 17 hours at 150.degree. C. As in Example 1, at this
temperature the initial total pressure is approximately 750 psig and the
initial partial pressure of carbon monoxide is approximately 550 psi. G.
C. analysis of the reaction mixture shows it to contain 19 wt. % acetic
anhydride, representing a conversion of 21%.
EXAMPLE 3
Again using the procedure of Example 1, methyl acetate (100 parts), methyl
iodide (18 parts), nickel acetate (0.8 part), chromium carbonyl (2 parts)
and 1-methyl pyrrolidinone (1.6 parts) are charged to a glass-lined bomb
which is pressured to 400 psig with carbon monoxide at room temperature
and sealed. The bomb is then heated and stirred for 17 hours at
150.degree. C. At this temperature the initial total pressure is
approximately 750 psig and the initial partial pressure of carbon monoxide
is approximately 550 psi. G. C. analysis of the reaction mixture shows it
to contain 9.8 wt. % acetic anhydride, representing a conversion of 10.6%.
EXAMPLE 4
Example 1 is repeated except that the charge includes 1.6 parts of
2-imidazolidone instead of 2-hydroxypyridine. G. C. analysis of the
reaction mixture after the 17-hour reaction period shows it to contain
14.7 wt. % of acetic anhydride, representing a conversion of 16%.
EXAMPLE 5
Example 1 is again repeated except that 1.6 parts of N,N-dimethyl acetamide
are substituted for the 2-hydroxy pyridine. As in the case of the
preceding examples at the 150.degree. C reaction temperature the initial
total pressure is approximately 750 psig and the initial partial pressure
of carbon monoxide is approximately 550 psi. G. C. analysis of the
reaction mixture shows it to contain 8.4 wt. % acetic anhydride,
representing a conversion of 9%.
EXAMPLE 6
Methyl acetate (100 parts), methyl iodine (18 parts), nickel acetate (0.8
part), chromium carbonyl (2 parts) and N, N-dicyclohexyl methyl amine (1.6
parts) are charged to a glass-lined bomb which, as in the preceding
examples, is pressured to 400 psig with carbon monoxide at room
temperature and sealed and then heated and stirred for 17 hours at
150.degree. C. At this temperature the initial total pressure is
approximately 750 psig and the initial partial pressure of carbon monoxide
is approximately 550 psi. G. C. analysis of the reaction mixture shows it
to contain 13.6 wt. % acetic anhydride, representing a conversion of 15%.
EXAMPLE 7
Example 6 is repeated but 1.6 parts of 2,6-diamino pyridine are substituted
for the N,N-dicyclohexyl methyl amine. At the 150.degree. C reaction
temperature the initial total pressure is approximately 750 psig and the
initial partial pressure of carbon monoxide is approximately 550 psi. G.
C. analysis of the reaction mixture shows it to contain 10 wt. % acetic
anhydride, representing a conversion of 11%.
EXAMPLE 8
Example 6 is again repeated but 1.6 parts of N,N-diethyl-m-toluamide are
substituted for the N,N-dicyclohexyl methyl amine. At the 150.degree. C
reaction temperature the initial total pressure is approximately 750 psig
and the initial partial pressure of carbon monoxide is approximately 550
psi. G. C. analysis of the reaction mixture shows it to contain 42 wt. %
acetic anhydride, representing a conversion of 51%.
EXAMPLE 9
Methyl acetate (100 parts), methyl iodide (18 parts), nickel acetate (0.8
part), chromium hexacarbonyl (2 parts) and triphenyl phosphine (1.6 parts)
are charged to a glass-lined bomb which, as in the preceding examples, is
then pressured to 400 psig with carbon monoxide at room temperature and
sealed and then heated and stirred for 17 hours at 150.degree. C. At this
temperature the initial total pressure is approximately 750 psig and the
initial partial pressure of carbon monoxide is approximately 550 psi. G.
C. analysis of the reaction mixture shows it to contain 45 wt. % acetic
anhydride, representing a conversion of 55%.
EXAMPLE 10
Methyl acetate (100 parts), methyl iodide (17 parts), bis-(triphenyl
phosphine) nickel dicarbonyl (0.8 part) and chromium hexacarbonyl (2
parts) are charged into a stirred Hastelloy-C pressure vessel which is
pressured to 275 psig with carbon monoxide and the vessel is then heated
at 153.degree. C for 7 hours. At the reaction temperature the carbon
monoxide has an initial partial pressure of 370 psi, and during the
reaction period carbon monoxide is continuously supplied to maintain a
continuous total pressure in the vessel of 550 psig. After the 7-hour
reaction time, G. C. analysis of the reaction mixture shows it to contain
48 wt. % acetic anhydride, representing a conversion of 64%.
EXAMPLE 11
Methyl acetate (100 parts), methyl iodide (17 parts), bis-(triphenyl
phosphine) nickel dicarbonyl (0.8 part) and chromium hexacarbonyl (2
parts) are charged into a stirred Hastelloy-C pressure vessel which is
pressured to 600 psig with carbon monoxide and the vessel is then heated
at 153.degree. C for 51/2 hours. At the reaction temperature the carbon
monoxide has an initial partial pressure of 850 psi and during the
reaction period, carbon monoxide is continuously supplied to maintain a
continuous total pressure in the vessel of 750 psig. After the 51/2-hour
reaction time, G. C. analysis of the reaction mixture shows it to contain
56 wt. % acetic anhydride, representing a conversion of 70%.
EXAMPLE 12
Methyl acetate (100 parts), methyl iodide (17 parts), nickel tetracarbonyl
(0.8 part), triphenyl phosphine (1.7 parts) and chromium hexacarbonyl (2
parts) are charged into a stirred Hastelloy-C pressure vessel which is
pressured to 370 psig with carbon monoxide and hydrogen (9:1 ratio) and
the vessel is then heated at 153.degree. C for 51/2 hours. At the reaction
temperature the carbon monoxide has an initial partial pressure of 480
psi, and during the reaction period, carbon monoxide is continuously
supplied to maintain a continuous total pressure in the vessel of 725
psig. After the 51/2-hour reaction time, G. C. analysis of the reaction
mixture shows it to contain 58 wt. % acetic anhydride, representing a
conversion of 73%.
EXAMPLE 13
Methyl acetate (100 parts), methyl iodide (17 parts), bis-(triphenyl
phosphine) nickel dicarbonyl (0.8 part), triphenyl phosphine (1.2 parts)
and chromium hexacarbonyl (2 parts) are charged into a stirred Hastelloy-C
pressure vessel which is pressured to 390 psig with carbon monoxide and
hydrogen (9:1 ratio) and the vessel is then heated at 153.degree. C for
61/2 hours. At the reaction temperature the carbon monoxide has an initial
partial pressure of 500 psi, and during the reaction period, carbon
monoxide is continuously supplied to maintain a continuous total pressure
in the vessel of 750 psig. After the 61/2-hour reaction time, G. C.
analysis of the reaction mixture shows it to contain 59.4 wt. % acetic
anhydride, representing a conversion of 77%.
EXAMPLE 14
Methyl acetate (100 parts), methyl iodide (17 parts), bis-(triphenyl
phosphine) nickel dicarbonyl (0.8 part) and triphenyl phosphine (2.4
parts) are charged into a stirred Hastelloy-C pressure vessel which is
pressured to 400 psig with carbon monoxide and hydrogen (9:1 ratio) and
the vessel is then heated at 154.degree. C for 61/2 hours. At the reaction
temperature the carbon monoxide has an initial partial pressure of 525
psi, and during the reaction period, carbon monoxide is continuously
supplied to maintain a continuous total pressure in the vessel of 775
psig. After the 61/2-hour reaction time, G. C. analysis of the reaction
mixture shows it to contain 7.3 wt. % acetic anhydride, representing a
conversion of 8%. Comparison of this example with Example 13 shows the
significance of the presence of the chromium component.
EXAMPLE 15
Methyl acetate (100 parts), iodine (10 parts), nickel acetate (1 part),
chromium carbonyl (2 parts) and triphenyl phosphine (3 parts) were heated
at 150.degree. C for 17 hours under an atmosphere of carbon monoxide (400
psig at room temperature). At this temperature the initial total pressure
is approximately 750 psig and the initial carbon monoxide partial pressure
is approximately 550 psi. After the 17-hour reaction time, G. C. analysis
of the reaction mixture shows it to contain 33 wt. % acetic anhydride,
representing a conversion of 33%.
EXAMPLE 16
Methyl acetate (100 parts), methyl iodide (10 parts), nickel acetate (1
part), chromic iodide (2 parts) and triphenyl phosphine (3 parts) were
heated at 150.degree. C for 17 hours under an atmosphere of carbon
monoxide (400 psig at room temperature). At this temperature the initial
total pressure is approximately 750 psig and the initial carbon monoxide
partial pressure is approximately 550 psi. After the 17-hour reaction
time, G. C. analysis of the reaction mixture shows it to contain 43 wt. %
acetic anhydride, representing a conversion of 49%.
EXAMPLE 17
Methyl acetate (100 parts), methyl iodide (5 parts), nickel iodide (4
parts), chromium hexacarbonyl (2 parts) and triphenyl phosphine (3 parts)
were heated at 150.degree. C for 17 hours under an atmosphere of carbon
monoxide (400 psig at room temperature). At this temperature the initial
total pressure is approximately 750 psig and the initial carbon monoxide
partial pressure is approximately 550 psi. After the 17-hour reaction
time, G. C. analysis of the reaction mixture shows it to contain 39 wt. %
acetic anhydride, representing a conversion of 45%.
EXAMPLE 18
Methyl acetate (40 parts), dimethyl ether (60 parts), bis-(triphenyl
phosphine) nickel dicarbonyl (0.8 part), triphenyl phosphine (0.5 part),
methyl iodide (18 parts) and chromium hexacarbonyl (2 parts) are charged
to a glass-lined bomb which is pressured to 500 psig carbon monoxide at
room temperature. The vessel is closed and then stirred for 14 hours at
145.degree. C. At this temperature the initial total pressure is
approximately 1450 psig and the initial partial pressure of carbon
monoxide is approximately 700 psi. G. C. analysis of the reaction mixture
at the end of the 14-hour reaction period shows it to contain 50 parts
dimethyl ether, 45 parts methyl acetate and 5 parts acetic anhydride.
EXAMPLE 19
Dimethyl ether (100 parts) N, N-diethyl-m-toluamide (18 parts),
bis-(triphenyl phosphine) nickel dicarbonyl (1.3 parts), methyl iodide (14
parts), and chromium hexacarbonyl (2 parts) are charged to a
stainless-steel bomb which is pressured to 500 psig at room temperature
with carbon monoxide. The vessel is then closed, heated and stirred for 14
hours at 150.degree. C. At the reaction temperature the total pressure is
less than 1700 psig and the initial CO partial pressure is less than 800
psi. G. C. analysis of the reaction mixture at the end of the 14-hour
reaction period shows it to contain 13 parts dimethyl ether, 24 parts
methyl acetate and 63 parts acetic anhydride.
EXAMPLE 20
Dimethyl ether (100 parts), N,N-diethyl-m-toluamide (18 parts),
bis-triphenyl phosphine) nickel carbonyl (1.3 parts), methyl iodide (26
parts) and chromium hexacarbonyl (1.5 parts) are charged to a
stainless-steel bomb which is pressured at room temperature to 600 psig
with carbon monoxide and hydrogen (5:1 ratio). The vessel is then closed,
heated and stirred for 16 hours at 150.degree. C. At the reaction
temperature the total pressure is less than 800 psi. G. C. analysis of the
reaction mixture at the end of the 16-hour reaction period shows it to
contain 7 parts dimethyl ether, 54 parts methyl acetate and 38 parts
acetic anhydride.
EXAMPLE 21
Dimethyl ether (75 parts), methyl acetate (25 parts), nickel acetate (0.9
part), triphenyl phosphine (1.2 parts), methyl iodide (10 parts) and
chromium hexacarbonyl (1.4 parts) are charged to a stainless-steel bomb
which is pressured at room temperature to 600 psig with carbon monoxide
and hydrogen (9:1 ratio). The vessel is then closed, heated and stirred
for 14 hours at 150.degree. C. At the reaction temperature the total
pressure is 1800 psig and the initial CO partial pressure is 750 psi. G.
C. analysis of the reaction mixture at the end of the 14-hour reaction
period shows it to contain 38 parts dimethyl ether, 52 parts methyl
acetate and 10 parts acetic anhydride.
EXAMPLE 22
Dimethyl ether (100 parts), ethylene glycol diacetate (30 parts), nickel
acetate (1.2 parts), triphenyl phosphine (4 parts), methyl iodide (17
parts) and chromium hexacarbonyl (2.4 parts) are charged to a
stainless-steel bomb which is pressured at room temperature to 600 psig
with carbon monoxide and hydrogen (9:1 ratio). The vessel is then closed,
heated and stirred for 14 hours at 150.degree. C. At the reaction
temperature the total pressure is 1680 psig and the initial CO partial
pressure is 750 psi. G. C. analysis of the reaction mixture at the end of
the 14-hour reaction period shows it to contain 28 parts dimethyl ether,
44 parts methyl acetate and 28 parts acetic anhydride.
EXAMPLE 23
Dimethyl ether (72 parts), acetic anhydride (28 parts), bis-(triphenyl
phosphine) nickel carbonyl (0.65 part), triphenyl phosphine (1.6 parts),
methyl iodide (13 parts) and chromium hexacarbonyl (1.9 parts) are charged
to a stainless-steel bomb which is pressured at room temperature to 600
psig with carbon monoxide and hydrogen (9:1 ratio). The vessel is closed,
heated and stirred for 13 hours at 150.degree. C. At the reaction
temperature the total pressure is 1750 psig and the initial CO partial
pressure is 750 psi. G. C. analysis of the reaction mixture at the end of
the 13-hour reaction period shows it to contain 25 parts dimethyl ether,
40 parts methyl acetate and 35 parts acetic anhydride.
EXAMPLE 24
Dimethyl ether (100 parts), toluene (54 parts), nickel acetate (1.1 parts),
triphenyl phosphine (4 parts), methyl iodide (17 parts) and chromium
hexacarbonyl (2.4 parts) are charged to a stainless-steel bomb which is
pressured to 600 psig at room temperature with carbon monoxide and
hydrogen (9:1 ratio). The vessel is closed, heated and stirred for 15
hours at 150.degree. C. At the reaction temperature the total pressure is
1630 psig and the initial CO partial pressure is 750 psi. G. C. analysis
of the reaction mixture at the end of the 15-hour reaction period shows it
to contain 49 parts dimethyl ether, 49 parts methyl acetate and 2 parts
acetic anhydride.
EXAMPLE 25
Methyl acetate (100 parts), methyl iodide (17 parts), bis-(triphenyl
phosphine) nickel dicarbonyl (0.8 part) and chromium hexacarbonyl (2
parts) are charged into a stirred Hastelloy-C pressure vessel which is
pressured to 120 psig at room temperature with carbon monoxide and
hydrogen (1:1 ratio) and the vessel is then closed and heated with
stirring at 153.degree. C for 5 hours. At the reaction temperature the
carbon monoxide has an initial partial pressure of 85 psi and during the
reaction period, carbon monoxide is continuously supplied to maintain a
continuous total pressure in the vessel of 350 psig. After the 5-hour
reaction time, G. C. analysis of the reaction mixture shows it to contain
38 wt. % acetic anhydride, representing a conversion of 45%.
EXAMPLE 26
Methyl acetate (100 parts), methyl iodide (17 parts) and nickel diiodide (2
parts) are charged to a glass-lined bomb which is pressured to 550 psig
with carbon monoxide at room temperature and sealed. The bomb is then
heated and stirred for 17 hours at 150.degree. C. At this temperature the
initial total pressure is approximately 970 psig and the initial partial
pressure of carbon monoxide is approximately 775 psi. G. C. analysis of
the reaction mixture at the end of the 17-hour reaction period shows it to
contain no acetic anhydride.
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