Methanol carbonylation process with rhodium catalyst, an iodide salt and a metallic co-catalyst selected from transition metals, indium, strontium, barium, zinc, tin and heteropoly acids

摘要

A carbonylation process for making acetic acid uses a metallic co-catalyst composition effective as a rhodium stabilizer and rate promoter at molar ratios of metal/rhodium of from about 0.5 to 30. A preferred process includes: (a) reacting methanol with a carbon monoxide feedstock in a rhodium-based catalytic reaction mixture having: (i) a rhodium catalyst metal, (ii) methyl iodide maintained from about 1 to 20 weight percent, (iii) a lithium iodide co-catalyst, (iv) a metallic co-catalyst composition, (v) water maintained from 0.1 weight percent to less than 8 weight percent, (vi) methyl acetate maintained from about 0.5 to about 30 weight percent, and (vii) acetic acid; (b) flashing crude acetic acid from the reaction mixture; and (c) purifying the crude acetic acid. This process achieves stability and a STY greater than 10 mol/L/hr, with substantially less than a theoretically equivalent inorganic iodide content corresponding to the metallic co-catalyst and lithium iodide.

主权项

1. A continuous process for the production of acetic acid comprising:
(a) reacting a compound, selected from the group consisting of methanol and reactive derivatives thereof, with carbon monoxide to produce acetic acid in an aqueous reaction mixture, the reaction being carried out while maintaining a concentration of water in the reaction mixture of from 0.1 wt % up to about 8 wt %, the reaction also being carried out in the presence of a homogeneous rhodium-based catalyst system comprising:
(i) a rhodium catalyst metal;(ii) an iodide promoter;(iii) an inorganic iodide-providing co-catalyst at a molar ratio of inorganic iodide-providing co-catalyst:Rh of less than 76:1; and(iv) a metallic co-stabilizing or rate-promoting composition including a metal selected from the group consisting of transition metals, indium, strontium, barium, zinc, tin, HPA, and mixtures thereof; and (b) recovering acetic acid from the reaction mixture; wherein the inorganic iodide-providing co-catalyst and the metal of the metallic co-stabilizing or rate-promoting composition are present in a molar ratio of 15:1 to 0.6:1 and wherein further the reaction mixture contains less than 70% of a theoretical amount of inorganic iodide equivalent to the presence of both the metal of the metallic co-stabilizing or rate-promoting composition and the inorganic iodide-providing co-catalyst.