JPH0568457B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a method for producing acetic anhydride by using methyl acetate as a raw material and reacting it with carbon monoxide through a catalytic reaction using rhodium as a main catalyst. Acetic anhydride is used in large quantities as a raw material for producing cellulose acetate, and is also useful as a raw material for pharmaceuticals, fragrances, dyes, and the like. BACKGROUND ART Acetic anhydride has conventionally been industrially produced by a method in which ketene obtained by thermal decomposition of acetic acid is reacted with acetic acid. On the other hand, as part of so-called C1 chemistry, active research is being conducted to produce acetic anhydride through the reaction of carbon monoxide with methyl acetate or dimethyl ether. In particular, the method using rhodium as the main catalyst (Japanese Unexamined Patent Publication No. 1983-30820) allows the reaction to proceed under milder conditions than other transition metal catalysts, but the reaction rate is insufficient for industrial use. However, since this is still insufficient, improvements have been made by using various reaction promoters in the rhodium catalyst system. In the carbonylation reaction that produces acetic anhydride from methyl acetate, many types of metals are effective promoters when added to a rhodium-iodine compound (typically methyl iodide) catalyst system to increase the activity of the catalyst. Are known. That is, in JP-A-50-52017, A, A, A,
Elements with a molecular weight of 5 or more from each group of B and B,
Group non-noble metals, lanthanide elements, and actinide elements are said to be effective, and lithium is mentioned as a particularly preferred metal. Also, the 1970s
-47922 also shows a method using salts of 14 types of metals, including lithium. Non-metallic compound promoters are also known, typically organophosphorus or organonitrogen compounds. Furthermore, a method is also known in which an organic phosphorus compound is added in combination with a metal compound such as chromium hexacarbonyl (Japanese Patent Laid-Open No. 115403/1983). In the production of acetic anhydride by the carbonylation method, methyl acetate or acetic anhydride itself acts as a solvent, so as in the prior art mentioned above, no solvent is often added. However, examples using solvents are also known. For example, in Japanese Patent Application Laid-Open No. 1983-47922, hydrocarbons, ethers,
Ketones, fatty acids are shown as inert solvents. In some cases, aliphatic carboxylic acids are more than just inert solvents. For example, JP-A No. 55-28980 discloses a cocatalyst consisting of a combination of picolinium salt or the like and an acid;
No. 99437, No. 56-99438, etc. also disclose examples in which the presence of an acid is essential. All of these examples require a compound containing nitrogen, phosphorus, or arsenic in addition to the carboxylic acid. Among the accelerators used in conventional technology, highly effective organic compounds such as organic phosphorus compounds and organic nitrogen compounds, and metal compounds such as chromium hexacarbonyl are expensive and have poor thermal and chemical stability. When used industrially, special measures are required to maintain the activity of the catalyst (see JP-A-55-51036). Purpose of the Invention Based on the prior art as mentioned above, the present invention provides a reaction method that does not require expensive and unstable organic compounds containing nitrogen group elements or special compounds such as chromium hexacarbonyl. The purpose of the present invention is to provide a production method that can accelerate the production of acetic anhydride from methyl acetate under mild conditions. Structure of the Invention The present invention provides a method for producing acetic anhydride by carbonylating methyl acetate with carbon monoxide in the presence of a rhodium catalyst and an iodine compound. This is a method for producing acetic anhydride characterized by carrying out the reaction in the presence of a rhodium catalyst. It is believed that the carbonylation of methyl acetate according to the method of the present invention is carried out through carbonylation of methyl iodide present in the reaction system. Specifically, the present invention provides a reaction process that includes the carbonylation reaction of methyl iodide and the conversion of acetyl iodide and methyl acetate to the desired acetic anhydride under substantially anhydrous conditions, such as the conversion of methyl acetate to anhydrous Suitable for the production of acetic acid and the production of a mixture of acetic anhydride and acetic acid from methyl acetate and methanol, greatly improved results can be obtained in terms of reaction rate and conversion rate of methyl acetate. Moreover, the selectivity of acetic anhydride is of course also good. The present invention differs from conventional rhodium-catalyzed reactions in that, in addition to the conventional rhodium-iodine system, an aluminum promoter is used in the reaction solution containing a carboxylic acid such as acetic acid, and a hydrogen-treated rhodium catalyst is used. This is the point of using it. This promoter-catalyst system does not require any organic nitrogen compounds, which were previously considered almost indispensable in improving this type of reaction, and on the contrary, better results can be obtained in the absence of organic phosphorus compounds. , is something that he is extremely good at. As noted above, many types of metals are known as promoters, including aluminum compounds. Aluminum iodide, aluminum oxide (JP-A-50-52017), aluminum chloride (JP-A-50-52017)
50-47922), aluminum isopropoxide (Japanese Patent Application Laid-Open No. 56-142234), and the like. However, it has never been known that these aluminum promoters exhibit special effects when used together with a hydrogen-treated rhodium catalyst to carry out a carbonylation reaction. In the present invention, the hydrotreated rhodium catalyst to be combined with the aluminum promoter is a catalyst that has been previously hydrotreated before being fed to the carbonylation reactor. Catalysts that have been hydrogenated in-situ with hydrogen coexisting with carbon oxides, as well as those that have been hydrogenated with nascent hydrogen forming in the catalyst liquid, such as when a promoter is added in the form of metallic aluminum. Any catalyst may be used. It is known that carbonylation of methyl acetate is carried out in the presence of hydrogen (Japanese Unexamined Patent Publication No. 51-65709,
55-28980, etc.), aluminum is not used, and the technology uses organic nitrogen compounds and organic phosphorus compounds. According to JP-A-50-52017, the accelerator can be used in the elemental state, e.g. as a finely ground or powdered metal, or as a compound, and examples are given of the use of chromium metal powder in combination with aluminum iodide or oxide. . In the present invention, when metal aluminum is used to prepare the catalyst liquid, in comparison with this known technology, carboxylic acid is not added to the reaction system in the prior art, and therefore the chromium metal powder is dissolved in the acid. It is thought that the metal acts as it is without any process. Similarly, aluminum oxide remains solid. On the other hand, in the present invention, since a catalyst liquid is prepared using metallic aluminum in a liquid to which a carboxylic acid is added, the aluminum is dissolved and the rhodium catalyst is hydrogen-treated by the hydrogen generated at that time. The accelerating effect in the present invention is exerted not so much in the carbonylation step of methyl iodide as in the step of obtaining an O-acetyl compound from the acetyl iodide produced by carbonylation under virtually anhydrous conditions. It is thought that there are. As mentioned above, in the rhodium-catalyzed carbonylation reaction to produce the corresponding O-acetyl compound from an O-methyl compound such as methyl acetate, the use of a carboxylic acid solvent, an aluminum promoter, and the reaction in the presence of hydrogen are individually known. It is a technology that However, the present invention is a new technology that achieves high activity that could not be expected based on what was known about the individual technical elements that constitute it. To give an example of the effect of the present invention, when aluminum iodide is added, the reaction does not proceed at all with a rhodium catalyst that has not been hydrogenated, but when hydrogen is added, the reaction is high (Example 53 and Examples 52 contrasts). Similarly, the effects of the present invention are demonstrated by comparison with comparative examples in which carboxylic acid is absent (Example 3, Example 55) and aluminum compound is absent (Example 2 and Example 44). (Rhodium Catalyst) Rhodium used as the main catalyst in the present invention can be introduced into the reaction system as a compound as exemplified below. Inorganic rhodium salts such as rhodium chloride, rhodium bromide, rhodium iodide, rhodium nitrate, rhodium carboxylate salts such as rhodium acetate, rhodium acetylacetonate, rhodium amine complex salts, rhodium trichlorotrispyridine, hydridocarbonyltris (triphenylphosph) organic rhodium complexes such as in) rhodium, chlorotris(triphenylphosphine) rhodium, chlorocarbonylbis(triphenylphosphine) rhodium, and cluster complexes such as dodecacarbonyltetrarhodium. The amount of rhodium used is not necessarily strictly limited, but the concentration in the reaction solution is usually 0.1 to 50 mmol/
and is preferably used in a range of 10 to 30 mmol/. (Iodine Compound) In the present invention, halogen compounds, particularly iodine compounds, commonly used in this field are used. As a representative example, alkyl iodides such as methyl iodide are most commonly used. Iodine can also be added in other forms such as hydrogen iodide. The amount of iodine used is not necessarily strictly limited, but the concentration in the reaction solution is usually 0.5 to 10 mol/, preferably 1 to 5 mol/. (Aluminum promoter) The aluminum promoter may be added as metal aluminum or in the form of an aluminum compound. Examples of aluminum compounds include formic acid, acetic acid, propionic acid, lauric acid,
aluminum salts of carboxylic acids such as stearic acid,
Aluminum alcoholates with alkoxy phases such as methoxy, ethoxy, isopropoxy, chlorine,
Aluminum halides containing halogen atoms such as bromine and iodine, aluminum acetylacetonate, aluminum nitrate, and the like are used. The shape of metal aluminum is solid, flaky,
It may be in any form such as pulverized or powdered, but powdery is particularly preferred for handling reasons. Also, alloys containing aluminum, such as nickel, cobalt,
An alloy of copper, iron, etc. and aluminum can also be used. The amount of aluminum to be used is 0.1 to 1000 times, preferably 1 to 100 times, particularly 5 to 50 times, in atomic ratio to the rhodium used. In order to exhibit a sufficient effect, the aluminum concentration in the reaction solution is usually 0.1 mol/or more, particularly 0.2 to 0.5 mol/. The present invention can be practiced in such a way that the catalyst and promoter systems are reused. At that time, the rhodium catalyst requires hydrogen treatment. (Hydrogen treatment) Hydrogen treatment of the rhodium catalyst can also be carried out using nascent hydrogen when metal aluminum is added and dissolved as described above, but in other cases, the solution containing the catalyst is treated with molecular hydrogen. This is accomplished by making contact. When hydrogen treatment is carried out simultaneously with the carbonylation reaction, the amount of hydrogen used is preferably within a concentration range of 1 to 30% of the mixed state with carbon monoxide. 30
% or more can be used, but this is not preferred because the amount of ethylidene diacetate and methane by-product increases significantly. In particular, it is preferable to add hydrogen in a concentration range of 5 to 20% from the viewpoint of carbonylation reaction rate and prevention of by-products. Prior to carbonylation, an independent hydrogen treatment may be performed, and in that case there are fewer restrictions on the selection of conditions. (Carboxylic acid) Another component that creates a reaction accelerating system in the present invention is a carboxylic acid. The most common is acetic acid, but aliphatic, alicyclic or aromatic carboxylic acids having 1 to 10 carbon atoms such as propionic acid and butyric acid can be used in some cases. Carboxylic acids such as acetic acid are usually added in that form to the reaction solution, but it may be added as long as it is converted into a carboxylic acid in the reaction system. As a typical example, when carbonylation is performed using a mixture of methyl acetate and methanol as a raw material to co-produce acetic anhydride and acetic acid,
There is no particular need to add it in the form of carboxylic acid.
The amount of carboxylic acid to be present in the reaction solution is usually 0.2 mol/or more, preferably 1 mol/or more,
Particularly preferred is 2 mol/or more. The amount of carboxylic acid may exceed half of the reaction solution, but if it increases unnecessarily, there are disadvantages such as lowering the raw material concentration, so it is usually kept within 80% of the reaction solution. (Starting material) The starting material to be carbonylated in the present invention is an O-
methyl compound and the product is the corresponding O-acetyl compound. A typical example is the production of acetic anhydride by carbonylation of methyl acetate. Dimethyl ether can also be converted to acetic anhydride by carbonylation. It can also be applied to the production of acetic acid by carbonylating methanol, but if only acetic acid is desired,
If the reaction is carried out in the presence of water in the reaction system, the reaction proceeds at a sufficiently high rate even without the use of the present invention.
However, when carbonylation is performed using a mixture of methyl acetate and methanol as a raw material to co-produce acetic anhydride and acetic acid, when obtaining a carbonylation product in a virtually anhydrous state, carbonylation of methanol The present invention is also useful for. It can also be applied to carbonylation reactions of carboxylic acid methyl esters, such as the production of propionic acid and acetic acid mixed anhydrides by carbonylation of methyl propionate (propionic anhydride and acetic anhydride are produced by disproportionation). (Reaction Conditions, Reaction Method) The reaction temperature and pressure when carrying out the present invention can be appropriately determined with reference to conventional techniques. The reaction temperature is usually 130-250℃, preferably
The temperature is 150 to 200°C, and the pressure of carbon monoxide is 1 to 100 Kg/cm 2 G, preferably 5 to 100 Kg/cm ² G during the reaction.
cm ² G, especially 20 to 80 Kg/cm ² G is used. The specific examples given below to illustrate the present invention are batch reactions carried out in autoclaves, and the pressures are expressed in charging pressures. However, it goes without saying that the present invention can be carried out in continuous reactions using techniques known in this field. It is also easy for those skilled in the art to separate and purify and obtain an acetyl compound from the reaction mixture obtained by the present invention. The remaining amount of methyl acetate and the amount of acetic anhydride produced in the post-reaction solution were determined by gas chromatography.
Furthermore, the conversion rate of methyl acetate and the yield of acetic anhydride were calculated using the following formula. The reaction rate was calculated based on the pressure decrease at the beginning of the reaction. Acetic anhydride yield (%) = Number of moles of acetic anhydride produced / Number of moles of methyl acetate charged x 100 Methyl acetate conversion rate (%) = Amount of methyl acetate charged - Amount of methyl acetate remaining in the solution after reaction / Charged methyl acetate Amount x 100 Example 1 Rhodium chloride trihydrate (RhCl _{3.3H 2} O) 0.163 was placed in a Hastelloy B autoclave with a content of 300 ml.
g, methyl iodide 14.2 g, aluminum powder 0.2
g, acetic acid, 10.2 g, and methyl acetate, 29.1 g, the internal air was replaced with carbon monoxide, and then the pressure was further increased to 40 kg/cm ² G with carbon monoxide.
The autoclave was then heated to 175°C. After the reaction started at 175°C and gas absorption was observed, the reaction was continued for 1 hour. After the reaction was completed, the reaction solution was taken out after cooling and releasing the residual pressure, and the reaction results were examined by gas chromatography analysis. Methyl acetate conversion rate 88.7%,
Acetic anhydride production amount: 348.3 mmol, reaction rate: 569.1 mol/
molRh・hour. Example 2 (Comparative Example) The same reaction as in Example 1 was carried out except that no aluminum powder was added. Although it was heated at 175°C for a long time, no gas absorption was observed, and analysis of the liquid after the reaction revealed that no acetic anhydride was produced at all. Example 3 (Comparative Example) The same reaction as in Example 1 was carried out except that acetic acid was not added and the amount of methyl acetate charged was 38.5 g. The reaction results were as follows. Methyl acetate conversion rate 51.4%,
Acetic anhydride production amount: 267.3 mmol, reaction rate: 431 mol/
molRh・hour. Example 4 The same reaction as in Example 1 was carried out except that 10.1 g of propionic acid was used instead of acetic acid. The conversion rate of methyl acetate was 88.6%, and production of 272.6 mmol of acetic anhydride and 69.0 mmol of propionic anhydride was observed. Reaction rate 527 mol/molRh・hr. Example 5 Rhodium chloride trihydrate 1.29 mg atomic Rh, methyl iodide 4.9 ml (approximately 12 g), methyl acetate 40 ml, acetic acid 24
Add 0.6g of aluminum powder to ml of mixture;
Carbon monoxide (preparation pressure 50Kg/cm ² G) under pressure 170
℃ and allowed to react at this temperature for 1 hour. reaction solution
When 75 ml was analyzed to check the reaction results, the amount of methyl acetate (input amount: 510.5 mmol) was 100.2 mmol. The yield of acetic anhydride based on the amount of methyl acetate charged was 80.4%. No acetyl iodide was found in the reaction solution. The reaction rate was 7.69 mol/hour. Examples 6-10 The same experiments as in Example 5 were carried out except that the amounts of methyl acetate (MA) and acetic acid were changed. The results are shown in Table 1. Note that Example 10 is a comparative example in which acetic acid was not added.

【table】

[Table] Example 11 The same experiment as in Example 5 was conducted except that 1.29 mg of dodecacarbonyltetrarhodium Rh ₄ (CO) ₁₂ atomic Rh was used as the rhodium catalyst and the amount of methyl iodide was doubled to 9.8 ml. The amount of acetic anhydride produced in 81ml of reaction solution is
459.4mmol, and other acetyl iodide
Found 5.5mmol. The reaction rate was 11.52 mol/hour, the conversion rate of methyl acetate was 91.3%, and the selectivity to acetic anhydride was 97.4% (yield 88.9%). Examples 12-17 Similar experiments were carried out by changing the amounts of methyl acetate (MA) and acetic acid for double the amount of methyl iodide. However, the rhodium catalyst used in Example 12 was Rh ₄ (CO) ₁₂ as in Example 11, and in the others it was RhCl ₃ .3H ₂ O (1.29 mg atomic Rh in each case). For comparison, Example 17 shows the case where acetic acid was not added.

[Table] Example 18 The same experiment as in Example 12 was conducted except that the amount of catalyst was reduced to 0.59 mg atomic Rh of Rh ₄ (CO) ₁₂ . reaction rate
The yield of acetic anhydride was 84.0% at 5.2 mol/h.
The reaction rate per rhodium catalyst is higher than in Example 12. Example 19 The same reaction as in Example 1 was carried out except that 0.115 g of Rh ₄ (CO) ₁₂ was used instead of RhCl ₃ .3H ₂ O. The results were as follows. Methyl acetate conversion rate 84.4%, acetic anhydride production amount 337.22 mmol, reaction rate 546 mol/
molRh・hour. Example 21 A mixture of methyl acetate and methanol (78 wt.% methyl acetate - methanol) as a raw material for carbonylation.
The same reaction as in Example 1 was carried out using 37.9 g of 22 wt.%), except that acetic acid was not added. However, the reaction time was 90 minutes. The reaction results were: methanol conversion rate 100%, methyl acetate conversion rate 61.1%, acetic anhydride production amount 267.0 mmol,
The amount of acetic anhydride produced was 244.4 mmol. Examples 22-26 Rhodium chloride trihydrate 1.29 mg atomic Rh, methyl iodide 4.9 ml (approximately 12 g), methyl acetate 32 ml, acetic acid 32
ml of the mixture, various amounts of aluminum powder were added and heated under pressure with carbon monoxide (feeding pressure 50Kg/cm ² G).
The mixture was heated to 170°C and reacted at this temperature for 1 hour.
The reaction results are shown in Table 3. This is clear from the results in Table 3. The reaction rate (mol/hr) determined from the amount of gas absorbed at the initial stage of the reaction increases even when 0.1 g of aluminum powder is added, but
If 0.4 to 0.6 g (approximately 0.2 to 0.3 mol/) is added, the reaction will be more rapid. Furthermore, a similar improvement effect can be achieved on the yield of acetic anhydride determined from the analytical values of the reaction solution. Examples 27 to 30 The influence of the amount of aluminum added was investigated in the same manner as in Table 3 when the amount of methyl iodide was doubled. Note that the conditions are the same as in Table 3 except as specified. The results are shown in Table 4. From the results in Table 4, the same effects as in Table 3 can be confirmed.

【table】

[Table] Examples 31 to 36 The effect of tributylphosphine, which has a reaction accelerating effect in the absence of aluminum addition, was investigated when it was also used in the present invention. 7.3g of tributylphosphine was added as Bu ₃ P ⁺ CH ₃・I ^- .
The conditions are the same as in Table 3 except as noted. The results are shown in Table 5. As is clear from Table 5, the promoting effect of the present invention is rather reduced.

[Table] Examples 37-39 Various aluminum alloys instead of aluminum
The reaction was carried out under the same conditions as in Example 32, except that 0.3 g (aluminum content in both cases was 50 wt.%) was used. The results are shown in Table 6.

[Table] Example 40 Rhodium chloride trihydrate (RhCl _{3.3H 2} O) 1.29 was added to a Hastelloy B autoclave with a capacity of 300 ml.
After charging 22 mmol of aluminum acetate, 4.9 ml of methyl iodide, 32 ml of methyl acetate, and 32 ml of acetic acid, replacing the air inside with carbon monoxide, pressurize with carbon monoxide until it reaches 40 kg/cm ² G. And then 5
Kg/cm ² of hydrogen was added to give a total of 45 Kg/cm ² G. Next, the mixture was heated to 170°C and reacted at this temperature for 1 hour. After the reaction was completed, the reaction mixture was cooled and the residual pressure was released, and then the reaction solution was taken out and subjected to gas chromatography analysis. The reaction results are shown in Table 7.

【table】

[Table] The following example is the same as Example 40 except for special notes, and the reaction results are summarized in Table 7. Example 41 (Comparative example) No hydrogen added. Example 42, Example 43 Hydrogen gas pressure is 1Kg/cm ² and 10Kg/cm ² respectively.
And so. Example 44 (Comparative example) No aluminum acetate was added. Example 45 The same mole of rhodium iodide was used as the rhodium compound, and the hydrogen pressure was 6 Kg/cm ² . Example 46 (Comparative Example) Same as Example 45 except that hydrogen was not added. Examples 47-51 Using rhodium iodide, the pressures of carbon monoxide and hydrogen were varied. Example 52 A 405 ml autoclave was charged with 0.93 mmol of rhodium chloride trihydrate, 22 mmol of aluminum iodide (AlI ₃ ), 4.5 ml of methyl iodide, 30 ml of methyl acetate, and 30 ml of acetic acid. 35 in carbon monoxide
Pressurize to Kg/cm ² G, add 5 Kg/cm ² of hydrogen,
The total weight was 40Kg/cm ² G. The reaction conditions were 170°C and 1 hour. Example 53 (Comparative Example) The same as Example 52 except that hydrogen was not added and only carbon monoxide was used at 40 kg/cm ² G. Example 54 Same as Example 52 except that 22 mmol of aluminum isopropoxide was used instead of aluminum iodide. Example 55 (Comparative example) Example except that 32 ml of acetic anhydride was used instead of 32 ml of acetic acid.
Same as 40. Example 56 A Hastelloy B autoclave with a capacity of 300 ml was charged with 1.29 mmol of rhodium iodide, 22 mmol of aluminum acetate, and 32 ml of acetic acid, and the air inside was replaced with carbon monoxide.
The pressure was increased to cm ² G, and 8 kg/cm ² of hydrogen was further added to give a total of 10 kg/cm ² G. The mixture was then heated to 130° C., and the rhodium catalyst was hydrogen-treated at this temperature for 1 hour. The autoclave was cooled and the gas analyzed, but no methane production was observed. The catalyst liquid after hydrogen treatment was homogeneous. After depressurizing the residual gas, hydrogen was removed by replacing the inside of the autoclave with carbon monoxide, and 32 ml of methyl acetate and 4.9 ml of methyl iodide were charged, and the autoclave was heated to 40 kg/cm ² G with carbon monoxide. The mixture was heated to 170° C. and reacted for 1 hour. The conversion rate of methyl acetate, the yield of acetic anhydride, and the reaction rate were all high, and ethylidene diacetate was not produced. A comparative example conducted under the same conditions except that a non-hydrogen-treated rhodium catalyst was used is Example 46.

Claims (1)

[Claims] 1. In a method for producing acetic anhydride by carbonylating methyl acetate with carbon monoxide in the presence of a rhodium catalyst and an iodine compound, in the presence of an aluminum promoter and a hydrogen-treated rhodium catalyst in a reaction solution containing acetic acid. A method for producing acetic anhydride, characterized by carrying out a reaction.