JPS5953440A - Simultaneous preparation of acetic anhydride and acetic acid - Google Patents

Abstract

PURPOSE:To obtain the titled compounds simultaneously at industrially satisfactory speed, by reacting catalytically a mixture of methyl acetate/methanol in a specific molar ratio with a CO-containing gas in the presence of a catalyst consisting of a limited combination comprising rhodium as a main catalyst in a liquid phase. CONSTITUTION:A mixture (especially preferably azeotrope) of methyl acetate/ methanol in a molar ratio of 1/3-3/1 is reacted catalytically with a CO-containing gas in a liquid phase at 120-200 deg.C in the presence of a catalyst consisting of (A) rhodium or its metal compound (e.g., rhodium chloride), (B) tri-substituted phosphine such as trimethylphosphine, triphenylphosphine, etc., (C) chromium or zircon or their metallic compounds, and (D) iodine compound (e.g., methyl iodide, or lithium iodide). The amounts of catalyst components used are 0.1-20mg atom A, 0.05-2mol B, 0.2-2mol D and 0.1-10mol C based on 1 rhodium atom per lliquid reaction mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for the simultaneous production of acetic anhydride and acetic acid, which comprises cocarbonylating methyl acetate and methanol with a generalized carbon-containing gas. It is well known that the method of producing borihinyl alcohol by metathurisis of polyvinyl alcohol convex tahinyl is known from let fortunetelling, and it is well known that borihinyl alcohol li J, +7゜ is produced on a human scale. Methyl acetate, which is produced as a by-product through metatrilysis of polyhinyl acetate, forms a compound i'JIl lt; ``I! First, before recovering methanol, there is a method of first separating 111 fl of methyl acetate from the azeotropic 1111 compound by Sende natural distillation using an oil such as water or ethylene glycol. It is generally used for stirring.The separated methyl acetate is
, t is hydrolyzed under I and finally converted into acetic acid and methanol, each of which is recovered at 6+11 min. Until now, the recovery of acetic acid and methanol from by-product methyl acetate has been carried out using
It is clear from 2a's own explanation that there is a large amount of steam 4r, and this 1 person 1), y (H blasphemous,
This was an issue to be considered starting from the first song.

Based on this background, the present inventors have developed a method for recovering acetic acid and methanol from a mixture of methyl acetate and methanol with reduced energy, and a method for effectively utilizing the mixture of methyl acetate and methanol. We have been conducting intensive studies for some time.

In the course of these various studies, the present inventors recently discovered that fii1M in the presence of a limited combination of catalysts.
? If a mixture of methyl acetate and methanol is brought into contact with carbon monoxide gas, even if the abundance ratio of methyl acetate and methanol is close to the composition of the azeotrope of the two, anhydrous anhydride will be produced in a proportion approximately corresponding to the abundance ratio. The present invention was completed by discovering that a mixture of acetic acid and acetic acid can be obtained.That is, according to the present invention, a) rhodium or its metal compound, b)
trisubstituted phosphine, 0) chromium or zircon, or 11 compounds of these metals, and (1) a molar ratio of methyl acetate/methanol of 1 in the liquid phase in the presence of an iodine compound.
A process for simultaneous 8Iv production of acetic anhydride and acetic acid is provided (1a), characterized in that a mixture of methyl acetate and methanol in the range of 1/3 to 3/1 is brought into contact with a carbon monoxide synthesis gas.

When using the method of the present invention, Y of methyl acetate and methanol
The fact that a mixture of acetic anhydride and acetic acid with a ratio corresponding to 1.1 to the r content can be obtained by the previously proposed method of acetic acid synthesis using the carbonylation reaction of methanol and the synthesis of acetic anhydride using the carbonylation reaction of methyl acetate. H1f of synthesis method
Considering the difference in reaction rate between the two reactions as estimated from the experimental results, this is completely unexpected, and such an effect can only be achieved by using the above-mentioned specific catalyst according to the present invention. If the present invention is carried out in connection with the production of polyvinyl alcohol, the mixture of methyl acetate and methanol or an azeotrope thereof, which is produced as a by-product in the polyvinyl alcohol production process, can be directly processed according to the present invention without being separated into each component. carbonylation t+;
When used as iEl, acetic anhydride and acetic acid with a higher addition 1i11i value can be obtained simultaneously with J':, and M is essential in the conventional recovery process of acetic acid and methanol from the by-product methyl acetate. A large amount of steam (consumption 1
1"L) becomes unnecessary. Thus, the method of the present invention is industrially extremely significant.

Specific examples of rhodium compounds that can be used as the main catalyst in the method of the present invention include rhodium chloride, thalodium vinegar, rhodium oxide, tetrarhodium dodecacarbonyl,
hexalodium hexadecacarbonyl, ■+Ce(1'
lL5)g (l represents an alkyl group or an allyl group), 1. Examples include IHlt(COXPJ13)s, rhodium acetylacetonate, and the like. The concentration of rhodium metal or its compound in reaction III fi frl is generally selected to be within the range of 0.1 to 20 milligram atoms (in the case of a rhodium compound, converted to rhodium atoms) per reaction nl sound solution 11. The trisubstituted phosphine, which is another catalyst component in the process of the present invention, has the general formula tt it 1t i' (where It,
Rin and Ru are *;! 1% of aliphatic hydrocarbons) or aromatic hydrocarbons (h). Specific examples of desirable trisubstituted phosphine include I.limethylphosphine, triethylphosphine, tributylphosphine,
Dibutylphenylphosphine, diphenylpropyl small sphine, triphenylphosphine, etc. can be mentioned. The concentration of 311°-converted phosphine in the reaction mixture is generally selected to be within the range of 0.05 to 2 moles per l j l of the reaction mixture.As will be described later, methyl iodide or 1. , t y The corresponding quaternary phosphide (7) easily obtained by the reaction of the three lf', f, and l phosphides (7) with cetyl iodine as a catalyst component. Using phosphonylim salts in place of trisubstituted phosphines
.

can. In the method of the present invention, chromium "F", taIJ
Zircon or these gold ■ compounds help! Used as l'/component. Specific examples of chromium compounds include chromium acetate, chromium iodide, and chromium hexacal+J+21. Specific examples of the silconi/compounds include zirconium tetrachloride, zirconyl chloride, zirconium acetate, zirconyl acetate, and bis(cyclopentagenyl)zirconium V. These co-catalyst components are 0.1 to 10 per rhodium atom.
Used in the molar range [,1. In the reaction of the present invention, industrially satisfactory J! At one time, anhydrous vinegar and acetic acid are produced. Examples of iodine compounds include methyl iodide, io(Is acetyl, lithium iodide, etc.), and these iodine compounds contain 0 per 111 of the reaction mixture.
．． It is used in 2 to 2 moles of 1111 agricultural products.

As mentioned above, in the method of the present invention,
S compounds, trisubstituted phosphines, chromium or zirconium, or metal compounds thereof, and the elemental compound are all essential catalyst components, and even if any of them is missing, the process of the present invention cannot be carried out. Utility cannot be achieved.

The reaction temperature is within the range of 120-200'C. -f'+4? (As a gas containing 9 carbons,
A gas consisting mainly of carbon monoxide, partially nitrogen, helium, argon, methane, hydrogen, etc., is used. - Hydrogen concentration in the carbon oxide-containing gas depends on the selectivity of the reaction, 1" and /Q!!l L!1.Activity 54F
Because it controls life, it is baking soda, and generally contains 1 to 1 mmol% of carbon monoxide,,! :<lj2.5-7.5 mol%
It is preferable that the range is within the range of . reaction 5-10 n kQ
17ij J11 of the reaction rate and reaction is carried out under the monohydric carbon partial pressure of lad! It is preferable from the viewpoint of sexual orientation. As mentioned above, the purpose of the present invention is to prepare acetic anhydride or acetic acid by introducing a carbon-containing gas into a methyl acetate-methanol mixture or a carbon-containing gas. Therefore, the composition of the methyl acetate-methanol mixture should be in the range of 115 to 3/1 in terms of molar ratio.In particular, it is preferable to use the Jll 6u compound (for both). Industrially, it is the most economical. A methyl acetate-methanol mixture containing a large excess of methanol relative to methyl acetate was used as a reaction raw material. Finally, add 1 tllU of acetic anhydride to the reaction solution.
Methyl acetate-methanol rlj' The compound can be used as a reactant even if it contains water as long as the voltage is as low as 11V.

Reaction 1; t )? ! ! j'l' fl! Industrially, it is preferable to carry out the reaction in a continuous manner in a reactor with a normal air pressure of 9'; H/Qll 1IH9. After the reaction, the reaction mixture is subjected to the usual tY7 operation to finally obtain the method of the present invention. Acetic anhydride and acetic acid, which are the target substances of fleas, each have 1 ii 1 and 11
be done.

EXAMPLES The present invention will be specifically explained below with reference to Examples.

Example 1 160·i Methyl acetate; 171 fl methanol; 41 f (acetic acid) Methyl iodide: 51p, l-butylphosphine methyl iosite; 43F, rhodium trichloride trihydrate: 0,79f1 chromium hexacarbonyl; 1,32p were charged, and the system was evaporated. After sufficient substitution with carbon monoxide, the -carbon oxide partial pressure is approximately 301
Each gas was supplied so as to maintain a hydrogen partial pressure of about 1.5 kQlad/g/crl s, and the reaction was carried out at 180° C. for 2 hours.

After 2 hours - 57 f/ each at temperature and pressure
br of methyl acetate, 14 p/br of methanol, 17
VI+r of methyl iodide, 14.3 y/hr of tributylphosphine methyl iosite, 0.26 p/br of rhodium dichloride trihydrate and 0.44 p/ltr
i consisting of hl corresponding to chromium hex→J carbonyl
Ti! (1) Reaction mixture) 1:(11() was continuously fed into the reactor bottom J: about 13(1(//ltr) (1) Reaction mixture?('f) was continuously withdrawn for 8 hours. i, (r
+It.

Production of acetic anhydride and acetic acid from analysis of effluent i1j Iu
are respectively acetic anhydride: 62 y/br S f'iM
'++ <; When not using anhydrous vinegar r+! This example shows that the generation chain [ of < is relatively slow. Using Rota 1, in which no chrono-hexacarbonyl was added in Example 1, the reaction of Example 1 was repeated under the same conditions as in Example 1 and by the same procedure. (The lS mixture was continuously withdrawn from the bottom of the reactor). 7 from the analysis of the effluent after 8 hours! IC hydrochuic acid, 1 ゛bi vinegar rr->
The production rate of acetic anhydride is 25 y/llr, respectively.
, acetic acid; 28y/11r, and it can be seen that the production rate of acetic anhydride is significantly slower than that of Example 1 compared to the production rate of acetic acid.

Comparative Example 2 This ratio i11. ! The /' example illustrates that the rate of acetic anhydride production is significantly slower when no trisubstituted phosphine is used.

Methyl acetate in the same reactor as in Example 1; 171 p.

Methanol 141y, methyl iodide; 56p, chromium hexacarbonyl', 1. S2f and rhodium trichloride
After charging 0.79p of trihydrate and thoroughly replacing the inside of the system with carbon monoxide, raise the temperature to 180°C and reduce the CO partial pressure to 50 kq/cnl.
The reaction was carried out for 2 hours while maintaining a hydrogen partial pressure of 1.5 m/ad. Next, methyl acetate; 57 y/br,
+ 4 &/br, methi iodide 71
/ i 20 p/l+r, chromium hexacarbonyl; 0.44 &/I and rhodium trichloride trihydrate; was fed to the reactor, and the reaction Nl
About 1209/hr of the reaction mixture was continuously withdrawn for 1 s. Analysis of the effluent after 8 hours revealed the production of acetic anhydride and acetic acid, respectively.
7 g/llr -C,'N>-:'f(,.

Examples 2 to 5 and Comparative Examples 3 to 5 Simultaneous carbonylation reactions of methyl acetate-methanol mixtures were carried out by using the same reaction as in Example 1. , , n real 17
1ii Example 1 and Comparative Example 1, and Y and Comparative DI, l
2 Do threat 〆 J ri reaction ha hatch method te row lj ivy. reaction/h
l Its: is n℃-C combination I! The following Table 1 shows the relationship between the typical reaction conditions and the production of glacial acetic acid and acetic acid when the reaction was carried out for 15 hours.

In this case, 1 is used as a carbon oxide-containing gas.
Using acid 11S carbon gas, the partial pressure of carbon monoxide in the reaction system was reduced to 1'i by 3 hours of reaction.
1. Carbon monoxide was immediately produced one after another by combining with -1 sea urchin pressure amount 1z.

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Claims (1)

[Claims] 1 n) Rhodium or its gold I7g compound, b
) trisubstituted phosphine, C) chromium or zircon or a metal compound thereof, and +1) methyl acetate and methanol in the liquid phase in the presence of an iodine compound in a molar ratio of methyl acetate/methanol in the range of 115 to 3/1. A process for the simultaneous production of acetic anhydride and acetic acid, characterized in that the mixture is brought into contact with a generalized carbon-containing gas. 2. The method for producing J-blue according to claim 1, wherein the mixture of methyl acetate and methanol is a mixture of both. Claim 1, wherein the 4-3-carbon oxide-containing gas is a mixed gas of hydrogen and carbon monoxide containing 1 to 10% hydrogen! II'! Pickling method.