Effect of metal-doped VPO catalysts for the aldol condensation of acetic acid and formaldehyde to acrylic acid.

Mo, W, Cr, La, and Ce additives were introduced into a VPO catalyst, and the resulting catalysts were investigated for the gas-phase aldol condensation reaction of formaldehyde and acetic acid. XRD, FT-IR, SEM, NH3-TPD, Py-IR, and BET were used to characterize the structure and properties of the catalysts. After the addition of the third component, the crystal structure changed to a certain extent; the surface acidity of the catalyst changed, and the conversion of acetic acid and the selectivity of acrylic acid also showed different degrees of influence. The acidity of the catalyst was the main factor affecting the catalytic performance. When La was added to the catalyst, the selectivity for acrylic acid was the highest, and the stability of the catalyst also improved. It is presumed that B acid is the main active site of this reaction, and a moderate amount of acid is favorable to facilitate the reaction.