Formation of Acrylaldehyde by Vapor-Phase Aldol Condensation I. Basic Oxide Catalysts

Vapor-phase aldol condensation of formaldehyde with acetaldehyde to form acrylaldehyde was studied with various oxides supported on silica gel using 35% formalin as the source of formaldehyde. The silica gel unsupported catalyst prepared from colloidal silica showed a relatively high activity and selectivity to form acrylaldehyde. The catalytic activity was markedly enhanced by the incorporation of a basic or amphoteric oxide into the silica gel, while it fell with the incorporation of an acidic oxide such as P2O5 or B2O3. The highest yields of acrylaldehyde were obtained with the Si–Mg, Si–Li, Si–Na, and Si–Zn oxide systems. Effects of reaction variables were also studied using a catalyst with an Si : Mg atomic ratio of 100 : 10.