CS195686B2 - Process for preparing acetanhydride - Google Patents

Description

(54) A method for producing acetic anhydride

It is an object of the present invention to provide a process for the preparation of acetic anhydride by carbonylation, i.e. by treatment with carbon monoxide.

Acetic anhydride has long been used as an industrial raw material, and large amounts of this substance have been used in the production of cellulose acetate.

It is usually prepared on an industrial scale by reaction of a ketone with acetic acid. It is also known to prepare acetic anhydride by decomposing ethylidene dithionate and by oxidizing acetaldehyde. Each of these classical processes has well-known drawbacks and still seeks to improve the process for producing acetic anhydride. Methods for preparing anhydrides by treating carbon monoxide with various substances are known; ctzý. (e.g., U.S. Pat. Nos. 2,729,561, 2,730,546, and 2,791,937). However, these proposed processes involving carbonylation require very high pressures. Carbonylation at lower pressures has also been suggested, but only as a way to produce acetic acid. French Patent 1573 130, for example, describes the carbonylation of methanol and mixtures of methanol and methyl acetate in the presence of iridium, platinum, palladium, osmium and ruthenium compounds, and in the presence of bromine and iodine, more mildly.

pressures other than those used in the processes of the US patent specifications. Similarly, according to ZA patent specification 68/2174, acetic acid is prepared from the same reactants as described above. use of a rhodium compound together with bromine and iodine. Recently, U.S. Pat. Nos. 3,689,533 and 3,717,670 disclose a process for the preparation of gaseous acetic acid using various catalysts containing a iodine component dispersed on a support. None of these relatively recent carbonylation processes relates to or describes the preparation of acetic anhydride or other carboxylic anhydrides.

Therefore, there is still a need for an improved process for the production of acetic anhydride, especially one that does not require the high pressures required in the prior art.

The present invention relates to a process for the preparation of acetic anhydride which is characterized by the reaction of carbon monoxide with methyl iodide or methyl bromide. at a partial pressure of 0.68 kPa to 34.32 MPa in the presence of rhodium, iridium or osmium as a catalyst at a temperature of 20 to 200¾, acetyl iodide or acetyl bromide is prepared, which is reacted under anhydrous conditions with methyl acetate. or dimethylether.

: More volatile methyl iodide, unreacted ace195686

5 ³ iodide, and ether or ester in the final reaction mixture can be readily removed ,, for example by distillation and used for further recycling (and the net yield of the reaction is N .produktu substantially almost exclusively expected, acetic anhydride. In the case of reaction in the liquid Faïza It is found that the process according to the invention can be carried out not only in two reaction steps, i.e. in the first stage, when the methyl iodide is carbonylated in the presence of Group VIII noble metal, and in the second stage, where the carbonylation product (i.e., acetyl iodide) is treated with an ester or ether, but that the two stages can be advantageously combined together in a single reaction where the oxide (carbon monoxide, ester or ether, methyl iodide and (a noble metal catalyst) are introduced into the process in such a way that, in fact ... The reactions described above do not produce water, and use either anhydrous or substantially anhydrous (components, since it is important to work in essentially an aqueous environment).

Thus, acetyl iodide was prepared by carbonylation, and the process was carried out in two stages, treating the methyl iodide with carbon monoxide in the first reaction step in the presence of a precious metal catalyst. The acetyl iodide is then introduced into a second reaction zone where the acetyl iodide is treated with methyl acetate or dimethyl ether to form acetic anhydride and regenerate the methyl iodide. (Methyl iodide is separated from the anhydrides as a product, for example by distillation, and recycled to the reaction in the first step for the new carbonyl; unreacted acetyl iodide and ester or ether are also recycled and acetic anhydride is isolated as a single pure product.

Temperatures in the (wide range, for example, 20 to 300 ° C) are suitable for the reaction of methyl iodide with carbon monoxide, but a temperature in the range of 100 to 300 ° C is preferred, and the most preferred range is 125 ° C. to 250 ° C. Lower temperatures than those mentioned above may also be used, but this leads to a reduction in the reaction rate; also higher temperatures can be used, but this is not associated with any apparent advantage. The reaction time is not a parameter of the process, and will largely depend on the temperature used, but the typical time falls within the range of 0.1 to 20 hours. Of course, the reaction is carried out at a pressure higher than atmospheric pressure, but it is one feature of the present invention that excessively high pressures can be avoided, although they can be used if desired. In general, the reaction is carried out at a partial pressure of carbon monoxide which is preferably (0.034 to 13.7 MPa, and most preferably (0.17 to 6.86 MPa), but which may be in the range When operating in the liquid phase reaction, the total pressure is required to maintain the desired liquid phase. Thus, the liquid phase reaction is carried out in an autoclave. At the end of the expected time, the reaction mixture is introduced into the second reaction zone and heated, preferably the reaction product is first fed to the distillation zone, which may be a traction distillation column with the efficiency to separate any proportion of unreacted methyl The catalyst and methyl iodide are then recycled to the first stage of the reaction, otherwise these separations can be omitted, and the reaction mixture as a whole can be introduced. t in the second reaction zone, since it can only methyl iodide, or only the catalyst separated at this point. In the second reaction zone, acetyl iodide is reacted with methyl acetate or dimethyl ether. This reaction can be carried out even after. of heat, if the acetyl iodide has been separated from the catalyst, i.e. the noble metal from Vlil. groups, or. if this separation has not been carried out, the reaction with the ester or the ether can be carried out in the presence of a catalyst. In any event, operating at temperatures ranging from 0 to 300 ^Q C, with a range from 20 to 250 ^q C (it is preferred that <a range of · 50 to 200 ° G 'is especially desirable. During reaction, acetic anhydride and regenerated methyl The resulting reaction mixture then contains acetic anhydride as a product as well as methyl iodide and may also contain unreacted ester or ether or acetyl iodide as well as a noble metal catalyst, unless the catalyst has been separated before the reaction in the second step. they are easily separated from one another by conventional fractional distillation, where methyl iodide is the most volatile substance and acetic anhydride is usually the least volatile, and acetic anhydride is readily distilled off from the inorganic catalyst, if it is still present in the mixture. into the first reaction band for carhonylation, and so on, together with any proportion of regenerated kata Any unreacted ester and either, and / or acetyl iodide can be recycled to the second reaction zone, and the remaining component of the reaction mixture, i.e., acetic anhydride is isolated as a product.

According to a preferred embodiment of the process of the present invention, the two reaction steps described above are combined together, i.e., the process is carried out in a single reaction zone, where methyl iodide is usually fed to the first zone, and methylaceitate or dimethyl ether, two-stage design, to be run jointly by doi ¹ single reaction zone and there. are heated together, preferably in the liquid phase, in the presence of carbon monoxide. and in the presence of a noble metal of the group VIIIa; of the catalyst. It goes without saying that methyl iodide can be prepared in situ.

56 8 6

8 as organic methyl iodide, but can also be added to the reaction mixture in the form of hydrogen iodide or as other inorganic iodide, for example in the form of a salt such as. it is an alkali metal or other metal salt, or optionally in the form of an elemental iodine. After the course of the reaction, several components of the reaction mixture are readily separated from one another, for example by traction distillation.

¹ When oneness, the saw embodiment of the present invention is suitable · wide range of temperatures ·, for example 20 to 500 C, Temperature-but between 100 and 300 ° C is preferably used and the most preferred temperature range • le 'runs in between. 125 DEG-250 ^DEG C. As in the two-stage embodiment, lower temperatures than the above range may be used, but this is associated with a reduction in reaction rates, higher temperatures may be used, but not associated with any particular advantage of the reaction. time -not. it is also not a parameter of the clamping process and depends largely on the temperature used, but typical times, for example, fall within the range of 0.1 to 20 hours. The reaction is carried out at a pressure higher than atmospheric pressure, but it is a particular advantage and object of the present invention that excessively high temperatures requiring special high pressure devices; Generally, the reaction can be carried out efficiently at a carbon monoxide partial pressure of 0.032 to 13.72, most preferably at a carbon monoxide partial pressure of 0.17 to 6.8.6. MPa, although 1 partial pressures of carbon monoxide in the range of 0.68 to 1.5 bar may be used ^. Pa to 34.312 MPa. The total pressure is preferably maintained so as to maintain the reaction mixture in the liquid phase, and in this case the reaction can be advantageously carried out in an autoclave or similar device. At the end of the required time, the reaction mixture is divided into several components which it contains. for example by fractional distillation. Preferably, the reaction product is fed to a distillation zone, which may be a fractional distillation column, or a series of columns with sufficient efficiency to separate methyl iodide, acetyl iodide and methyl acetate and dimethylethe.ru from the product itself; acetic anhydride. Temperatures. The boiling of these few hens are sufficient. Similarly, acetic anhydride can easily be distilled off from the noble metal support catalyst. Methyl iodide and the noble metal catalyst, as well as acetyl iodide, can be combined together with fresh amounts of the tester. , or the .alpha.-carbon monoxide ether, and the reaction yields additional (amounts of acetic anhydride.

^! The final reaction mixture usually comprises tecetyl iodide together with acetic anhydride as the product, and it is an object of the present invention that acetyl iodide after separation from acetic anhydride. may be reused to react with an ester or ether either by recycling the reaction mixture or by separately reacting the tester or ether with acetyl iodide, as is the case. in the second stage of the two-stage embodiment described above. to form additional portions of acetic anhydride. .

The ester or ether to iodide polymers in the reaction system can vary over a wide range. Typically, 1 to 500 equivalents of ester or ether are used, per equivalent of iodide, preferably. up to 200 equivalents per equivalent. Thus, in the case of an ester, typically 1 to 500 moles, preferably 1 to 200 moles, of ester per mole of iodide are used as reactant, and in the case of ether 0.5 to 250, preferably 0.5 to 100 moles, per mole of iodide. Maintaining the partial pressure of carbon monoxide at. the corresponding amounts of reactants for the reaction with methyl iodide are always present.

The carbonylation _of methyl iodide, as discussed above in connection with the two-stage embodiment, is preferably carried out in the presence of a solvent or non-diluent. Although a solvent or diluent from the group of organic solvents inert during the course of the reactions may be used, methyl acetate or a methyl acetate may also be used. dimethyletheř ,. so; acetic anhydride is formed together with acetyl iodide, which is the desired product in such a case. In other words, the reaction of a two-stage embodiment to form acetyl iodide will have the character of a one-stage embodiment. Similarly, the single-stage embodiment is preferably performed in a; the presence of a solvent or diluent, especially if the reactant has a relatively low boiling point, such as ethyl ether. The presence of a higher-boiling solvent or diluent, which may be an anhydride as a product, for example acetic anhydride in the case of ethyl ether, or a corresponding ester, for example methyl acetate, again in the case of methyl ether, will allow a milder total pressure. Alternatively, the solvent or diluent may be an organic solvent that is inert to the process, such as hydrocarbons such as octane, benzene, toluene, or the like. The solvent or diluent is preferably chosen such that its boiling point is sufficiently different from the boiling point of the components in the reaction mixture so that it can be readily separated, as will finally be apparent to those skilled in the art. Precious metal catalyst Vlil. The groups, i.e., iridium, osmium, platinum, palladium, rhodium and ruthenium, can be used, in any suitable form, for example, in the zero degree of valence or in any higher valency form. For example, the catalyst to be added is. it may use the metal as such in finely divided form, or as a carbonate, metal, furthermore an oxide, hydroxide, bromide, iodide, chloride, lower alkoxide (meith oxide, phenoxide or metal carboxylate, wherein the carboxylate ion is derived from an alkanoic acid with one to one. Similarly, metal complexes such as canbonyl compounds such as the carbonyl derivative of iridium and rhodium, as well as other complexes such as carhonylhaiogenides, ice e.g. 3Cl 12 or acetylacetonates such as a rhodium derivative (R 1 H 1 H 2 O 2 O 2) 3.

The carbon monoxide preferably uses substantially pure form, as commercially available, but inert diluents such as carbon dioxide, nitrogen, methane, and noble gases may optionally be present. The presence of inert diluents does not affect the carbonylation reaction, but their presence is associated with the need to increase the total pressure to achieve the desired partial pressure of carbon monoxide. Carbon monoxide, as well as the other components, should be substantially dry, i.e., carbon monoxide and other reactants should be substantially free of water. However, the presence of foamy amounts of water, as can be seen with commercial forms of reactants, is entirely acceptable.

As already. It has been reported that the carbonylation reaction of the process of the present invention can be carried out optionally in the gaseous phase using appropriate control of the total pressure relative to the temperature such that the reactants are in contact with the catalyst in gaseous form . In the case of the gas phase process and the liquid phase process, the catalyst (s) may optionally be of a conventional type, such as alumina, silica, silicon carbide, zirconia, carbon. bauxite, tapulgite clay and the like. The catalyst components may be applied to the support in a conventional manner, for example by impregnating the support with a catalyst solution followed by drying. The concentration of the catalyst component in the carrier may vary considerably, for example from 0.01% to 10% or more by weight.

Further examples serve to better understand this! It is to be understood that they are merely for the purpose of explanation and do not limit the scope of the invention. All parts and percentages in the examples are by weight unless otherwise indicated.

Example 1

A mixture of 3.7 parts of acetic acid methyl ester and 8.5 parts of acetyl iodide was heated at reflux for 4 hours while maintaining the reflux temperature. it is in the range of 45 to 50 ° C, and the steam that does not condense in this cooler condenses in a second cooler maintained at 10 ° C. 2.8 parts of methyl iodide are obtained from the second condenser together with a smaller proportion (about 15%) of methyl acetate, the mixture remaining in the distillation flask containing 20% by weight of acetic anhydride (2.2 parts) as determined by gas. chromatography. The remainder of the reaction mixture in the distillation flask consists of unreacted methyl acetate and acetyl iodide together with minor amounts of methyl iodide. ·. ·· _ · '

Example 2

A mixture of 71 parts of methyl iodide, 0.83 parts of rhodium chloride hydrate and 300 parts of methyl acetate is heated to 175 ° C to 200 ° C in a stirrer stainless steel autoclave under a partial pressure carbon monoxide atmosphere. 5.0 MPa to 4.00 MPa, total pressure 6.9 MPa. After three hours of reaction time, 0.7 mole of carbon monoxide is absorbed per mole of methyl iodide, and according to evaluation? The reaction mixture contains 7.7% acetyl iodide and 8.7% acetic anhydride. The remainder of the reaction mixture consists of reacted components and a catalyst. The autoclave is cooled; the pressure is vented and the reaction mixture is drained, which is diluted by adding 100 parts of n-stear to facilitate separation, and distilled under normal pressure with a fifteen-column column. Methyl iodide and methyl acetic acid distillates as the anterior of rt. v. 45. ^q to 57 C, and 18.7 parts distilled acetyljodidu the TV 108 to 111 ° C, two-phase fraction of acetic anhydride and nonane TV 113 to 127.5 ° C, which were separated from

21.6 parts of the bottom fraction, which is essentially pure acetic anhydride (confirmed by infrared spectroscopy) according to gas chromatography. The resulting acetyl iodide is used most conveniently for the reaction of Example 1.

Example 3

A mixture of 300 parts of methyl esters of toy, 35 parts of methyl iodide and 1.6 parts of rhodium chloride hydrate was heated to 200 DEG C. in a stirrer stainless steel autoclave under a carbon monoxide atmosphere (total pressure of 6.9 MPa, carbon monoxide partial pressure 4.0 MP, a), Two each. hours of reaction, 0.416 moles of carbon monoxide is absorbed per 0.246 moles of methyl iodide; according to gas chromatography, the reaction mixture contained 15.3% acetic anhydride (40 parts) together with 4.5% acetyl iodide (1, 9 parts). The rest of the reaction mixture consists of unreacted reactants and a catalyst.

Example 4

A mixture of 6 parts of acetic acid methyl ester, 0.7 parts of methyl iodide with 0.1 parts of thodium chloride was heated under carbon monoxide atmosphere (initial partial pressure 2.0 M'Pa) for 16 hours to 175 ° C in an acyl-lined rotary autoclave According to the gas chromatography, the reaction mixture contained 10% acetic anhydride (6.0 parts) and 2.8% acetyl iodide (0.17 parts). Residue

19588Β

10 'of the reaction mixture corresponds to the description of Examples 2 and 3.

Example 5

A mixture of 6. parts of methyl acetic acid ester, 0.7 parts of methyl iodide and 0.1 parts of rhodium iodide is heated in an atmosphere of carbon monoxide ¹ (initial partial pressure of 2.4 ^l MPa) to 1175 · for 16 hours in a rotary autoclave ¹ with glass unloading ·. According to gas chromatography, the reaction mixture contained 15% (0.3 part) acetic anhydride and 2.8% (0.17 part acetyl iodide) in a mixture with non-reacting reagents and catalyst.

Example 1 The procedures of Examples 1 to 5 were repeated but using an appropriate amount of dimethyl ether instead of acetic acid methyl ester. Correspondingly, acetic anhydride and acetyl iodide are formed. Example 7

A mixture of 300 parts of methyl acetate, 1 & 2 parts of dimethyl ether, 8.8 parts of lithium iodide, 65 parts of methyl iodide and 3 parts of rhodium chloride hydrate with three parts of chromium powder was heated to 150 ° C in a stainless steel autoclave equipped with a stirrer. , in a carbon monoxide atmosphere (total pressure of 5.5 MPa, initial carbon monoxide partial pressure of 0.9 MPa). After 10 hours of reaction time, the reaction mixture contained 54% (407 parts) acetic anhydride and 31% (233 parts) methyl acetate. The remainder of the reaction mixture consists of unreacted words, reaction intermediates and catalyst components.

Example

Example 7 is repeated, but using an equivalent amount of lithium iodide instead of methyl iodide and powdered amazon. Formation of acetic anhydride and acetic acid methyl ester was observed.

Example 9

A mixture of 187 parts of dimethyl ether, 408 parts of acetic anhydride, 70 parts of lithium iodide and 3 parts. The rhodium chloride hydrate is heated to 150 ° C in a stainless steel autoflave equipped with a stirrer, in an atmosphere of carbon monoxide (total pressure

After 10 hours of reaction time, the reaction mixture contained 64% (498 parts) of acetic anhydride and 21.5 θ / oi (167 parts) of methyl acid ester according to gas chromatography. , acetic.

Example 10 '

A mixture of 150 parts of methyl acetate, 0.75 parts of rhodium chloride hydrate,

18.5 parts of iodine and '3 parts of powdered chromium ^is: heated to 175 ° C in a glass lined autoclave equipped with a stirrer, in an atmosphere of carbon monoxide (total pressure of 2.4 MPa, the initial partial pressure of carbon monoxide' 0.45 MPa ). After 4 hours of the reaction time, the reaction mixture contains a gas mixture; chromatography of 59% acetic anhydride (121 parts). In this example, as well as others where analysis of the anhydride product is reported, the remainder of the reaction mixture is in each case unreacted reagents, intermediates and catalyst components, unless otherwise indicated. Example 11

A mixture of 600 parts of acetic acid methyl ester, 65 parts of methyl iodide, 9 parts of lithium iodide and 3 parts of powdered chromium is heated together with 3 parts of rhodium chloride to 175 ^A C in a stainless steel autoclave under carbon monoxide atmosphere (total pressure)

2.4 MPa, initial carbon monoxide partial pressure 0.45 MPa). After 8 hours of reaction time, according to gas chromatography, the reaction mixture contained 71.1% acetic anhydride (601 parts).

Example 12

A mixture of ISO parts of acetic acid meithyl ester, 0.75 parts of rhodium chloride hydrate, 17.5 parts of aluminum iodide and 1 part of powdered chromium is heated to 175 ° C in a glass-lined autoclave with stirrer under a carbon monoxide atmosphere (total pressure 2, 4 MPa, the initial partial pressure of carbon monoxide is 0.45 MPa). After 4 hours of reaction, the reaction mixture contained 67.6% acetic anhydride (141 parts) according to gas chromatography.

Example 1 a d 13. The reaction mixture, 150 parts of methyl ester (acetic acid, 0.75 parts of rhodium chloride hydrate, 1.7.5 parts of magnesium iodide and 1 part of powdered flavor) was heated to 175 ° C in a glass lined autoclave equipped with a stirrer in a carbon monoxide atmosphere. (total pressure 2.4 MPa, initial carbon monoxide partial pressure 0.45 MPa) After 4 hours of reaction time according to gas chromatography, the reaction mixture contains 40% acetic anhydride (76 parts).

Example. 14 ''; The reaction mixture of 150 parts of acetic acid methyl ester, 0.75 parts of rhodium chloride hydrate and 20 parts of anhydrous chromium i5686 iodide is heated to 175 ¾ in a glass lined autoclave equipped with a stirrer under a carbon monoxide atmosphere (total pressure 2.4 MPa). partial pressure of carbon monoxide 0.45 MPa). After 4 hours of reaction time, the reaction mixture contained ‘52.2% acetic anhydride (104 parts) by gas chromatography. Example 1.5

A mixture of 150 parts of methyl acetate, 0.75 parts of rhodium chloride hydrate,

18.5 parts, ¹ methyl iodide, ¹ part powdered chromium 3 parts of titanium dioxide are heated to 175 ° C in a glass lined autoclave with a stirrer, in a carbon monoxide atmosphere (total pressure of 2.4 MPa, initial partial pressure) of carbon monoxide 0.45 MPa). After 4 hours of reaction time, the reaction mixture contained 39% acetic anhydride (81 dFlft) according to gas analysis. ..

.Example 16

A mixture of 15 parts of methyl acetate,. 0.75 parts of rhodium chloride hydrate, 8.5. of methyl iodide! and 5.7 parts of chromium carbonyl are heated to 175 ¾ in a glass lined autoclave equipped with a stirrer in a carbon monoxide atmosphere (total pressure of 2.4 MPa, initial carbon monoxide partial pressure of 0.45 MPa). After 14 hours of reaction time, the reaction mixture contained 51% anhydride according to gas analysis. acetic acid (103 parts).

Example 17

A mixture of 150 parts of methyl acetate, 0.75 parts of rhodium chloride hydrate,

18.5 parts of methyl iodide and 3 parts of powdered astonishment. is heated to 175 ° C in a glass lined autoclave equipped with a stirrer in an atmosphere of carbon monoxide (total pressure 2.4 MPa, initial partial pressure of carbon monoxide 0.045 MPa). After 4 hours of reaction time, the reaction mixture contained 56.5% acetic anhydride (115 parts) by gas analysis.

Example 18

A mixture of 150 parts of methyl acetate, 0.75 parts of rhodium chloride hydrate, 1 part of powdered chromium. 2.5 parts of aluminum oxide · and 18.5 parts of methyl iodide are heated to 175¾ in a glass lined autoclave equipped with a stirrer under a carbon monoxide atmosphere (total pressure)

2.4 MPa, initial partial pressure of carbon monoxide 0.45 MPa). After 4 hours of reaction time, the reaction mixture contained 59% acetic anhydride (122 parts) according to gas chromatography.

P, k 1 and d 19., .-. · ·, ·.

A mixture of 150 parts of acetic acid methyl ester, 0.75 parts of rhodium chloride hydrate, 37 parts of methyl iodide, 2.2 parts of chromium carbonyl and 1 part of alumina was heated to 175 ° C and a glass lined autoclave equipped with a stirrer, at . carbon monoxide sphere 0.45 M.Pa _; After 3 hours of reaction time, the reaction mixture contained 56% by gas chromatography. acetic anhydride (127 parts). Example 20.

A mixture of 600 parts of acetic acid methyl ester, 140 parts of lithium iodide and 6 parts of rhodium chloride hydrate is heated to. 175 ° C in a glass lined autoclave equipped with a stirrer in a carbon monoxide atmosphere (total pressure 2.4 MPa, initial carbon monoxide pressure 0.45 MPa). After a reaction time of 8 hours, the reaction mixture contained 75.2% acetic anhydride (707 parts) according to gas chromatography. Example 21

A mixture of 600 parts methyl acetate, 315 parts methyl iodide, 70 parts. Iithného iodide and 3 parts .hydrátu, rhodium trichloride · heated to 175 ^Q C in a stainless steel autoclave equipped with a stirrer, in an atmosphere of carbon monoxide (total pressure 2.4 MPa, initial carbon monoxide partial tlalk 0.45 MPa). After 8 hours of reaction time, the reaction mixture contained 78.4% acid anhydride according to gas chromatography. • acetic (7017 parts).

Example 22

A mixture of 600 parts of acetic acid methyl ester, 17 parts of lithium acetate, 35 parts of lithium iodide, and 3 parts of rhodium chloride hydrate is heated to 175 ° C in a stainless steel autoclave equipped with a stirrer in a carbon monoxide atmosphere (total pressure 2.4 MPa) partial pressure of carbon monoxide 0.45 MPa). After 8 hours of reaction time, the reaction mixture contains 68% acetic anhydride (928 parts) according to gas chromatography.

Example 23 • Mixture. 300 parts of acetic acid methyl ester, 35 parts of methyl iodide and 2.2 parts of iridium chloride are heated to 225¾ in a stainless steel stirrer autoclave under a carbon monoxide atmosphere (total system pressure 6,9 MPa, partial carbon monoxide pressure 2,2 MPa) . After 14 hours of reaction time, the reaction mixture contains 22% acetic anhydride according to gas chromatography. The rest of the reaction mixture consists of unreacted reagents, intermediates and a catalyst.

Example 24

A mixture of 6 parts of acetic acid methyl ester, 0.7 parts of lithium iodide and 0.1 parts of platinum (II) bromide is heated in an atmosphere of carbon monoxide (total pressure of 4.3 MPa, initial carbon monoxide partial pressure of 2.4 MPa) to 175 ° C. for 16 hours in a stainless steel autoclave equipped with a stirrer. According to gas chromatography, the reaction mixture contained 1.4% acetic anhydride (0.1 part).

Example 25

A mixture of 6 parts of acetic acid methyl ester, 0.2 parts of lithium iodide and 0.1 parts of osmium chloride is heated in a carbon monoxide atmosphere (total pressure of 4 bar, initial partial carbon monoxide pressure of 2 bar) for 15 hours at 175 ° C. ^d C in a rotary autoclave with glass insert. According to gas chromatography, the reaction mixture contained 4.5 percent acetic anhydride (0.28 parts).

Example 26

A mixture of 150 parts of methyl acetate, 18.5 parts of methyl iodide, 0.75 parts of rhodium chloride hydrate, 1.0 part, 1 part of powdered chromium and 7.0 parts of sodium methoxide was heated to 175 ° C in a glass lined autoclave equipped with a stirrer. , in the atmosphere of carbon monoxide (total pressure

2.4 MPa, initial carbon monoxide partial pressure 0.5 MPa). After 4 hours of reaction time, according to gas chromatography, the reaction mixture contained 22.5% acetic anhydride (41.5 parts).

Example 27

A mixture of 150 parts of acetic acid methyl ester, 0.75 parts of rhodium chloride hydrate, 1.5 parts of hexacarbonylmolybdenum, 16.0 parts of methyl iodide and 2.5 parts of lithium iodide is heated to 175 ° C in a glass lined autoclave equipped with a stirrer, atmosphere carbon monoxide (total pressure 2,4 MPa, partial pressure of carbon monoxide 0,5 MPa). After 4 hours of reaction time, according to gas chromatography, the reaction mixture contained 40.0: 0/0 acetic anhydride (82.7 parts).

Example 28 A mixture of 190 parts of dimethyl ether, 300 parts of methyl acetate, 74 parts of meth, yl iodide and 3 parts of rhodium chloride was heated to 150 ° C in a stainless steel stirrer autoclave under a carbon monoxide atmosphere (total pressure 5.5 MPa, initial). partial pressure of carbon monoxide (0.8 MPa). After 2 hours of reaction time, the reaction mixture contained 76% acetic acid methyl ester (489 parts) and some acetic anhydride as indicated by gas chromatography.

Example 29

A mixture of 375 parts of dimethyl ester, 75 parts of methyl iodide and 3 parts of rhodium chloride hydrate is heated to 110 ° C in a stainless steel autoclave equipped with a stirrer, under a carbon monoxide atmosphere (total pressure 5.5 MPa, partial carbon monoxide pressure)

1.3 MPa). After 2 hours of reaction time, the reaction mixture contained 16.3% acetic acid methyl ester (80 parts) and 2.4% acetic anhydride (12 parts) according to gas chromatography.

Example 30

A mixture of 150 parts of methyl acetate, 0.75 parts of rhodium chloride hydrate,

24.7 parts of cerium iodide ¹ and 1 part of powdered chromium are heated to 175 ° C in a glass-lined autoclave under a carbon monoxide atmosphere (total pressure of 2.4 MPa, initial carbon monoxide pressure of 0.5 MPa). After 8 hours of reaction time, the reaction mixture contained 22.1% acetic anhydride (41.5 parts) by gas chromatography.

Claims (1)

SUBJECT A process for the preparation of acetic anhydride characterized in that carbon monoxide is reacted with methyl iodide or methyl bromide at a partial pressure of 0.68 kPa to 34.32 MPa at a temperature of 20 to 300 ° C in the presence of rho NALE of dia, iridium or osmium. as a catalyst and the resulting acetyl iodide or acetyibromide is reacted under anhydrous conditions with methyl acetate or dimethyl ether. Severography, n.