Vapor-phase aldol condensation of formaldehyde with acetic acid on V 2O 5P 2O 5 catalysts

Abstract

V 2O 5P 2O 5 binary oxides with P V atomic ratios from 1.06 to 1.2 were found to be effective as catalysts for the aldol-type condensation of formaldehyde (HCHO) with acetic acid to form acrylic acid. As the source of HCHO, 37% formalin or trioxane was employed. In the case of trioxane, the yield of acrylic acid attained about 98 mol%, based on the charged HCHO with the acetic acid/HCHO molar ratio of 2.5. On the other hand, in the case of formalin, the yield attained about 75 mol%, and methyl acetate and methyl acrylate were also formed by the esterification of the acids with methanol present in the formalin. The main side-reaction is the decomposition of acetic acid to form acetone and CO 2. This side-reaction is greatly accelerated over acrylic acid formation by an elevation of the temperature. The rates of both reactions were found to be inhibited by water vapor. The reactions of HCHO with derivatives of acetic acid, such as methyl acetate and acetaldehyde, were also Studied.