Catalysis Today, Vol.36, No.3, 243-254, 1997
Synthesis of Methyl-Methacrylate by Vapor-Phase Condensation of Formaldehyde with Propionate Derivatives
The gas phase condensation of formaldehyde with propionic acid, propionic anhydride, and methyl propionate was studied over a series of V-Si-P catalysts of varying atomic ratios. Propionic anhydride gave the maximum yield of methacrylic acid (56%, based on formaldehyde fed to the reactor) at 300 degrees C, 2 atm, 290 cc g(-1) h(-1) and a stoichiometric anhydride/formaldehyde ratio of 2:1. This yield was obtained for the optimum V-Si-P catalyst, which had an atomic ratio of 1:10:2.8. This is the highest yield reported to date for the heterogeneous catalytic condensation of propionic anhydride with formaldehyde. A parameter called the q-ratio has been defined to correlate condensation yields to catalyst acid-base properties. Higher q-ratios (0