ChemInform Abstract: Vapor‐Phase Aldol Condensation of Formaldehyde with Propionic Acid on Vanadium Pentoxide‐Phosphorus Pentoxide.

Abstract

Abstract Vanadium pentoxide—phosphorus pentoxide binary oxides with a P:V atomic ratio of 1.06–1.2 were found to be effective as catalysts for the aldol condensation of formaldehyde with propionic acid to form methacrylic acid. As the source of formaldehyde, trioxane and 37% formalin were employed. In the case of trioxane, the chief product was methacrylic acid at low conversion, while the formation of carbon dioxide and propylene increased markedly with an increase in the conversion. The yield of methacrylic acid attained about 39 mol%, based on the charged formaldehyde, with a propionic acid: formaldehyde molar ratio of 2. On the other hand, in the case of the reaction with formalin, the rate was markedly slower than in the reaction with trioxane and, as a result, a higher reaction temperature was required to achieve an appreciable conversion. Methyl propionate and methyl methacrylate were obtained by the esterification of the acids with methanol present in the formalin, besides methacrylic acid, carbon dioxide and propylene. The yield of methacrylic acid attained about 27 mol%. The reactions of formaldehyde with derivatives of propionic acid, such as methyl propionate and propionaldehyde, were also studied.