JP2000086572A - Production of acetic anhydride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple method for producing acetic anhydride under a extremely mild condition by reacting acetic acid with oxygen in the presence of a solid catalyst. SOLUTION: Acetic acid is reacted with oxygen (molecular oxygen, such as the pure oxygen, air, a diluted product obtained by diluting them with a gas inert to the reaction) in the presence of a solid catalyst (preferably the solid catalyst containing palladium) preferably in a vapor phase at 80-300 deg.C, preferably 120-250 deg.C reaction temperature under a normal pressure to 1.0 MPa pressure, preferably the normal pressure to 0.5 MPa pressure, at 200-20,000 hr-1 gas space velocity when the reaction is carried out by a flow-through type vapor phase catalytic reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing acetic anhydride from acetic acid. Acetic anhydride is a useful compound used in the production of cellulose acetate and in the production of intermediates for pharmaceuticals, pesticides and herbicides.

[0002]

2. Description of the Related Art The following method is known as a method for producing acetic anhydride. (A) A method of oxidizing acetaldehyde in liquid phase oxygen (US Pat. No. 2,225,486, US Pat.
No. 5,140,041, German Patent No. 867689, etc.). (B) A method of reacting ketene with acetic acid (DE 1076090). (C) A method of carbonylating dimethyl ether and / or methyl acetate with carbon monoxide (JP-A-51-115403, JP-A-55-28980, JP-A-56-10132, etc.). However, the method (a) has a drawback of poor selectivity because it produces by-produced acetic acid in addition to acetic anhydride, and has the disadvantage that explosive peracetic acid accumulates in the system depending on the reaction conditions. In the method (b), acetone or acetic acid is added in the amount of 650-7.
In order to obtain ketene by pyrolysis under a remarkably high temperature condition of 50 ° C., a heat-resistant reactor and a high-temperature heat source are required, which is not preferable. The method (c) has a drawback that a corrosion-resistant and pressure-resistant reactor material is required because the carbonylation reaction is performed under high pressure conditions of several tens of atmospheres together with the halogen compound.

When acetic anhydride is used as an acetylating agent, a dehydrating agent, etc., acetic acid is generally obtained as a by-product.
The above-mentioned methods (a) and (c) for producing acetic anhydride from a raw material other than acetic acid have the disadvantage that they cannot be recycled unless a separate reaction operation is carried out to convert to acetaldehyde or methyl acetate. I was

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing acetic anhydride which avoids the above-mentioned problems in the prior art and is efficient.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to avoid the above-mentioned problems and establish an efficient production method. As a result, acetic acid was converted to oxygen in the presence of a solid catalyst. It has been found that oxidative reaction produces acetic anhydride, which has led to the present invention. That is, the present invention is a method for producing acetic anhydride, which comprises reacting acetic acid with oxygen in the presence of a solid catalyst.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The reaction for producing acetic anhydride according to the present invention is represented by the following formula. 3CH ₃ COOH + 2O ₂ → (CH ₃ CO) ₂ O + 2CO ₂ + 3H ₂ O The acetic acid used in the present invention is not particularly limited in its production method, and acetic acid produced by a conventionally known method may be used. it can. When acetic anhydride is used as an acetylating agent, a dehydrating agent, or the like, acetic acid produced as a by-product may be used. The acetic acid used in the present invention may be used for the reaction with acetic acid alone, but may be used diluted with an appropriate solvent. There are no particular restrictions on the feed rate of acetic acid or the dilution ratio in the case of solvent dilution, and a suitable value is selected depending on the reaction type and reaction conditions. Examples of the solvent include ketone compounds, ether compounds, ester compounds, aliphatic hydrocarbons, aromatic hydrocarbons and the like.

The origin and concentration of oxygen used in the present invention are not particularly limited as long as it is molecular oxygen. For example, pure oxygen gas, air, or those obtained by diluting these gases with a gas component inert to the reaction can be used. The supply rate of oxygen gas and the dilution ratio in the case of inert gas dilution are not particularly limited, and a suitable value is selected depending on the reaction type and reaction conditions. Examples of the inert gas include nitrogen, argon, helium, carbon dioxide and the like. As the solid catalyst used in the present invention, a conventionally known solid catalyst having an activity in an oxygen oxidation reaction can be used.
A catalyst containing palladium is preferable as a catalyst component capable of effectively performing an oxidation reaction at a low reaction temperature of 0 ° C. or lower.

[0008] The palladium catalyst used in the present invention only needs to contain a palladium element, and there is no particular limitation on the starting material and production method. Examples of starting materials include oxides, hydroxides, halides, nitrates, acetates and various complex compounds of the element palladium. As a method for producing the catalyst, a conventionally known method for producing a solid catalyst such as a kneading method, a coprecipitation method, or a supporting method can be used. Particularly, from the viewpoint of effectively utilizing the palladium component, a production method by carrying is preferred. The catalyst carrier used in the supporting method is not particularly limited as long as it is used for producing a normal supported catalyst, and examples thereof include activated carbon, silica, alumina, diatomaceous earth and the like. The palladium content in the palladium catalyst used in the present invention is not particularly limited, but may be 0.1 to 20.
wt%, preferably in the range of 0.3-5 wt% is effective.

The palladium catalyst used in the present invention may be calcined, if necessary, during the catalyst production process or before the reaction.
It is desirable to perform a reduction treatment or the like. The calcination treatment is not particularly limited, and is generally performed by leaving it still or flowing in a calcination furnace under an air or inert gas atmosphere.
The treatment is preferably performed in a temperature range of ° C. For the reduction treatment, a conventional palladium reduction method can be adopted, and a reduction treatment with hydrazine, a reduction treatment with an aqueous alkaline formalin solution, a reduction treatment with hydrogen gas or the like is effective in a temperature range from room temperature to 500 ° C.

The shape of the solid catalyst used in the present invention is not particularly limited, and it can be used in the form of powder, coarse particles, tableted pellets, extruded pellets and the like. The method of using the solid catalyst used in the present invention is not particularly limited as long as it is a normal reaction method using a solid catalyst, and a fixed bed,
It can be used for the reaction in the state of a fluidized bed or a suspension bed. There is no particular limitation on the reaction format used in the present invention, flow type,
Any type of batch type can be used, but in the reaction of the present invention, water may be generated together with acetic anhydride, and acetic acid may be by-produced by the reaction between the two compounds. It is preferable to use a flow-type reaction system as a method of minimizing the reaction, and particularly preferable is a gas-phase contact type flow system. After the reaction, it is desirable to quickly separate acetic anhydride and water generated in order to avoid by-product of acetic acid due to the reaction between the two compounds, and the separation can be performed by a conventionally known method.

The reaction conditions used in the present invention are as follows: the reaction temperature is 80 to 300 ° C., preferably 120 to 250 ° C.
A range of ° C is appropriate. The reaction pressure is from normal pressure to 1.0 MPa,
Preferably, the pressure is in the range of normal pressure to 0.5 MPa. When the reaction is carried out by a flow-type gas phase contact reaction, the gas hourly space velocity is 20.
The range of 0 to 20000 hr ^-1 is appropriate.

[0012]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The following values were calculated for each example using the following equation. Acetic acid conversion rate = [supply acetic acid-unreacted acetic acid] / supply acetic acid x 10
0 (%) Yield of acetic anhydride = 3 x acetic anhydride (mol) / acetic acid supplied (mo
l) x 100 (%) Acetic anhydride selectivity = yield / conversion x 100 (%)

EXAMPLE 1 Palladium acetate was impregnated and supported on aluminum oxide (trade name: Neo Bead GB-13, manufactured by Mizusawa Chemical Co., Ltd.) from an acetone solution, and mixed with hydrogen / nitrogen mixed gas (composition ratio: 1/3).
A 1 wt% palladium-supported aluminum oxide catalyst was prepared by reducing at 0 ° C. for 3 hours. This catalyst was charged into a glass reactor, and while air was externally heated to 170 ° C under normal pressure, 1.37 L / hr of air (STP conversion) and acetic acid (Wako Pure Chemicals special grade reagent, purity> 99.7%) were passed through a vaporizer. It was supplied to the catalyst layer. The reaction was carried out for about 3 hours, and the product liquid collected by an ice water trap attached to the outlet of the reactor was analyzed by a GC device. The results are shown in Table 1. After the temperature distribution of the catalyst layer was stabilized, the generated gas collected at the outlet of the ice water trap for about 15 minutes was analyzed by a GC device. The results are shown in Table 2.

Example 2 A catalytic activity test was carried out in the same manner as in Example 1 except that the 1 wt% palladium-supported aluminum oxide catalyst prepared in Example 1 was used and the external heating temperature of the reactor was set at 175 ° C. The results are shown in Tables 1 and 2.

Example 3 1w was obtained in the same manner as in Example 1 except that aluminum oxide (trade name: ACBM-1, manufactured by Catalyst Chemicals, Inc.) was used as a catalyst carrier.
An aluminum oxide catalyst supported on t% palladium was prepared. Using this, a catalytic activity test was conducted in the same manner as in Example 1 except that the external heating temperature of the reactor was 165 ° C. The results are shown in Tables 1 and 2.

Example 4 A catalytic activity test was carried out in the same manner as in Example 1 except that the 1 wt% palladium-supported aluminum oxide catalyst prepared in Example 3 was used and the external heating temperature of the reactor was 170 ° C. The results are shown in Tables 1 and 2.

Example 5 A catalytic activity test was carried out in the same manner as in Example 1 except that the 1% by weight palladium-supported aluminum oxide catalyst prepared in Example 3 was used and the external heating temperature of the reactor was 175 ° C. The results are shown in Tables 1 and 2.

[0018]

TABLE 1 Example 1 2 3 4 5 catalyst weight (g) 4.2 4.2 3.3 3.3 3.3 acetic acid feed rate (g / h) 4.6 4.6 4.1 4.1 4.1 heating temperature (℃) 170 175 165 170 175 catalyst layer temperature ( ° C) 177 189 to 207 173 187 187 to 191 Acetic acid conversion (%) 5.5 14.0 11.9 15.8 16.6 Acetic anhydride selectivity (%) 87.9 62.0 53.6 78.6 77.6 Acetic anhydride yield (%) 4.8 8.7 6.4 12.4 12.9 Note: Catalyst layer Temperature = reaction temperature

[0019]

TABLE 2 Example 1 2 3 4 5 O ₂ consumption rate (mmol / h) 6.5 13 6.2 12 13 CO 2 production rate (mmol / h) 5.3 14 5.4 10 10 CO production rate (mmol / h) 0.0 0.1 0.0 0.0 0.0 CH ₄ generation rate (mmol / h) 0.0 0.1 0.0 0.0 0.0 O ₂ consumption rate / CO ₂ generation rate ratio 1.2 0.93 1.1 1.2 1.3

[0020]

According to the present invention, acetic anhydride can be produced by a simple method by reacting acetic acid and oxygen under extremely mild conditions without requiring high-temperature and high-pressure reaction conditions.

Claims (3)

[Claims] 1. A method for producing acetic anhydride, comprising reacting acetic acid with oxygen in the presence of a solid catalyst. 2. A reaction temperature of 80 to 300 ° C. in a gas phase.
The method according to claim 1, wherein the reaction is carried out. 3. The method according to claim 1, wherein a solid catalyst containing palladium is used.