Patent ID: 7737298

Claim:
A process for the production of acetic acid or a mixture of acetic acid and acetic anhydride in the liquid phase, comprising: (1) continuously feeding to a reaction zone (i) a feedstock compound selected from methyl acetate, dimethyl ether or a mixture thereof, (ii) methyl iodide, (iii) dissolved catalyst components, (iv) acetic acid, and (v) carbon monoxide, wherein the feedstock compound is converted to acetic anhydride at a temperature of about 100 to 300° C. and a total pressure of about 21 to 276 bar gauge to produce a liquid carbonylation product mixture comprising (i) a feedstock compound selected from methyl acetate, dimethyl ether or a mixture thereof, (ii) methyl iodide, (iii) dissolved catalyst components, (iv) acetic acid, (v) dissolved carbon monoxide and (vi) acetic anhydride product; (2) feeding liquid carbonylation product effluent from the reaction zone to an evaporation zone comprising at least one evaporation vessel wherein the total pressure is about 1 to 10 barg; (3) removing from the evaporation zone a vapor product effluent constituting about 30 to 90 weight percent of the liquid carbonylation product fed to the evaporation zone and comprising the feedstock compound; methyl iodide, acetic acid, and optionally acetic anhydride; and (4) removing from the evaporation zone a liquid product effluent constituting about 10 to 70 weight percent of the liquid reaction mixture fed to the evaporation zone and comprising acetic acid, optionally acetic anhydride and dissolved catalyst components; wherein methanol, water, or a mixture thereof is combined with liquid carbonylation product effluent (i) fed to the evaporation zone and/or (ii) within the evaporation zone and reacts exothermically with acetic anhydride to produce acetic acid or a mixture of acetic acid and methyl acetate and the heat of the methanol/acetic anhydride and/or water/acetic anhydride reaction increases the weight percent of vapor product removed from the evaporation zone.