Direct utilization of carbon dioxide in chemical synthesis: Vinyl acetate via methane carboxylation

The use of CO(2) as a reactant for chemical synthesis generally is limited by the unfavorable equilibrium that results from the large, negative free energy of formation of CO(2). Here, we report the direct catalytic synthesis of vinyl acetate from an equimolar gaseous mixture of CO(2) + CH(4) + C(2)H(2) at 1 atm and temperatures between 200 and 400 degrees C. We are not aware of any previous reports of this reaction, which appears to proceed in two steps: (1) acetic acid is formed by the reaction of CO(2) and CH(4); (2) acetic acid then reacts with acetylene to form vinyl acetate. The formation of acetic acid from CO(2) and CH(4) is very unfavorable thermodynamically. However, the reaction of acetic acid with acetylene shifts the overall equilibrium to the right. Although 5% Pt/Al(2)O(3) catalyzes the formation of vinyl acetate from the mixture of CO(2) + CH(4) + C(2)H(2), the most effective catalyst system is an admixture of 5% Pt/Al(2)O(3), Which has been shown to catalyze the direct formation of acetic acid from CH(4) + CO(2), and Zn acetate/carbon, which is known to catalyze the formation of vinyl acetate from acetic acid and acetylene. (c) 2007 Elsevier B.V. All rights reserved.