TH64667B - Method for producing acetate acid - Google Patents

Abstract

DC60 (19/03/56) This method produces acetic acid by continuously reacting methanol with carbon monoxide in the presence of a rhodium catalyst, iodide salt, methyl iodide, methyl acetate, and water; thus, acetic acid is produced at a rate of 11 mol/L.hr. or more while maintaining the acetaldehyde content of the reaction mixture at 500 ppm or less. The reaction is carried out at a carbon monoxide partial pressure in the gas phase of the reactor of 1.05 MPa or more and/or at a methyl acetate content of 2% by weight or more in the reaction mixture to maintain the acetaldehyde production rate at 1/1500 or less of the acetic acid production rate. This method can reduce by-products without reducing the reaction rate of acetic acid even at low water content. And with low hydrogen partial pressure in the reaction system, a method is used to produce acetic acid by continuously reacting methanol with carbon monoxide in the presence of a rhodium catalyst, iodine salt, methyl iodine, methyl acetate, and water; thus producing acetic acid at a production rate of 11 mol/L.cm. or more while maintaining the acetaldehyde content of the reaction mixture at 500 ppm or less. The reaction is carried out at a carbon monoxide partial pressure in the gas phase of the reactor of 1.05 MPa or more and/or at a methyl acetate content of 2% by weight or more in the reaction mixture to maintain the acetaldehyde production rate at 1/1500 or less of the acetic acid production rate. This method can reduce by-products without reducing the reaction rate of acetic acid even at low water content and low hydrogen partial pressure in the reaction system.

Claims (9)

1. A method for producing acetic acid, consisting of the following steps: continuous reaction of methanol with carbon monoxide under catalytic conditions using rhodium, iodide salts, methyl iodide, methyl acetate, and water; thus producing acetic acid at a production rate of 11 mol/L.cm. or more while maintaining the acetaldehyde content of the reaction mixture at 500 ppm or less, with the reaction carried out at a carbon monoxide partial pressure in the gas phase of the reactor of 1.05 MPa or more and/or at a methyl acetate content of the reaction mixture of 2% by weight or more to maintain the acetaldehyde production rate at 1/1500 or less of the acetic acid production rate of that method. 2. The method under claim 1, in which the reaction is carried out at a partial hydrogen pressure in the gas phase of the reactor of 100 kilopascals or less. 3. The method under claim 1, in which the reaction is carried out at a partial hydrogen pressure in the gas phase of the reactor of 70 kilopascals or less. 4. The method under claim 1, in which the reaction is carried out at a partial hydrogen pressure in the gas phase of the reactor of 70 kilopascals or less and the amount of methyl acetate of the reaction mixture of 3.1 percent by weight or more. 5. Any of the methods under claims 1 through 4, in which the reaction is carried out with a water content of 3 percent by weight or less in the reaction mixture. 6. Any of the methods under claims 1 through 5, in which acetic acid is produced at a production rate of 15 mol/L.hr. or more. 7. Any of the methods under claims 1 through 6, in which the rate of acetaldehyde production is maintained to 1/2500 or less of the rate of acetic acid production. 8. Any of the methods under claims 1 through 7, which also include a purification process comprising the following steps: separation of the reaction mixture into acetic acid and process mixtures containing residual components and recovery of the acetic acid; separation and removal of carbonyl impurities from the process mixture; and recycling of the residual process mixture to a reactor. 9. Any of the methods under claims 1 through 4, which also include a purification procedure comprising the following steps: (A) Separation of the reaction mixture into volatile and non-volatile components by distillation, in which the volatile component consists of acetic acid, water, methyl acetate, and methyl iodine, and the non-volatile component consists of a rhodium catalyst and iodine salt; (B) Separation of the volatile component into high-boiling and low-boiling components by distillation, in which the high-boiling component consists of acetic acid, and the low-boiling component consists of water, methyl acetate, and methyl iodine; (C) Recycling of the non-volatile component to a reactor; (D) Separation and removal of carbonyl impurities from the low-boiling component obtained in step (B) to obtain the remaining component; (E) Recycling of the remaining components obtained in step (D) to the reactor; (F) Separation of acetic acid from the high-boiling components obtained in step (B) by distillation; and (G) Pretreatment of the acetic acid obtained in step (F) with a silver or mercury exchanged cation exchange resin as per claim 9, in which steps (B), (D), and (F) are performed using three or fewer distillation columns.