Process for preparing acetic acid, methyl acetate, acetic anhydride or mixtures thereof

Claim 1

A process for preparing an acetic acid product selected from the group consisting of acetic acid, methyl acetate, acetic anhydride and mixtures thereof by conversion of a synthesis gas mainly consisting of hydrogen and carbon oxides, said process comprising the steps of: (i) introducing said synthesis gas into a first reactor at a pressure of 5-200 bar and a temperature of 150°-400° C., and converting said synthesis gas therein in the gas phase into methanol and dimethyl ether in the presence of a catalyst selected from the group consisting of a mixture of CuO-ZnO-Al 2 O 3 having a composition of about 60 atom % Cu, 25 atom % Zn and 15 atom % Al, and a zeolite so as to obtain a mol proportion 0.1:1 to 3:1 of carbon monoxide to methanol plus dimethyl ether, said mol proportion being defined by the expression CO/(CH 3 OH+2CH 3 OCH 3 ), and then (ii) carbonylating the mixture formed in step (i) by passing the effluent from the first reactor to a second reactor and converting methanol and dimethyl ether therein in a fluid phase to said acetic acid product at a pressure of 1-800 bar and a temperature of 100°-500° C. in the presence of a catalyst consisting of activated carbon impregnated with rhodium(III)chloride and methyl iodide and then (iii) recovering from effluent of said second reactor at least one product stream consisting of the acetic acid products.