Condensation Reaction of Methyl N-Phenylcarbamate with Formaldehyde over Hβ Catalyst

The condensation reaction between methyl N-phenylcarbamate (MPC) and HCHO to form methylene diphenyl-4,4'-dicarbamate (MDC) over different solid acid catalyst was studied. The results showed that the catalysts with surface Lewis acid sites having higher acid strength favored MDC synthesis. Among the solid acid catalysts, H beta exhibited good catalytic activity for MPC condensation. Solvents also had an effect on the catalytic activity; protic solvents, methanol, or H2O, were detrimental, while dimethyl carbonate (DMC) was found to be the most appropriate reaction medium. The optimal reaction conditions consist of a reaction temperature of 160 degrees C, a reaction time of 3 h, n(DMC)/n(MPC)/n(HCHO)of 50:1:0.25 and 0.6 g/30 mL DMC catalyst amounts. Under these conditions, the MPC conversion is 37.2%, and the MDC yield (based on HCHO) is 76.4%. The H beta catalyst could be easily regenerated by calcination, and no significant loss in catalytic activity was observed after five repeat uses.