Formation of acrolein by the reaction of formaldehyde with ethanol

A mixture of formalin and ethanol was passed at 240 to 320°C over various metal oxides supported on silica gel and metal phosphates using nitrogen as the carrier gas. The main products were acrolein, acetaldehyde, methanol, and carbon dioxide. The highest yields of acrolein were obtained with the nickel phosphate and silica-supported tungsten, zinc, nickel, and magnesium oxides. The yield of acrolein, on ethanol basis, reached 40 to 52 mol-% with a formaldehyde-to-ethanol molar ratio of 2. The effects of the reaction variables on acrolein formation were studied using a nickel phosphate catalyst with a phosphorus-to-nickel atomic ratio of2/3. It was proposed that acrolein is formed by the aldol condensation of formaldehyde with acetaldehyde which is formed in the reaction of hydrogen transfer from ethanol to formaldehyde.