Hoechst and US1 (now Quantum) developed, independently of one another, a supported palladium acetate catalyst. The metal and salt catalysts contain alkali acetates and other components (e. g., Cd, Au, Pt, Rh) which serve to increase activity and selec- tivity. During the course of the reaction, the catalyst changes, especially in its alkali acetate content. The alkali acetates migrate from the catalyst under the reaction conditions and must be constantly renewed