Montmorillonite K30 Supported Tungstophosphoric Acid as an Efficient Catalyst for Condensation Reaction of Methyl N-phenylcarbamate for Generating Diurethane

Abstract

Methylene diphenyl-4,4 '-dicarbamate (MDC) was prepared via condensation reaction of methyl N-phenyl carbamate (MPC) and formaldehyde (HCHO) over montmorillonite K30 supported tungstophosphoric acid (TPA/K30) as an effective catalyst. A 26.2 wt.% TPA/K30 exhibited the highest product yield (75.5%) under a mild reaction temperature of 90 degrees C for 4 h at the molar ratio of MPC/HCHO = 4. Pyridine FTIR study indicates that Bronsted and Lewis acid sites in the TPA/K30 were found to be beneficial for achieving an excellent yield of MDC. Furthermore, the TPA/K30 could be reused at least four runs without significant loss in the original activity. [GRAPHICS]