Synthesis of Methyl N-Phenyl Carbamate from Aniline and Dimethyl Carbonate over Supported Zirconia Catalyst

The novel supported zirconia catalysts for the synthesis of methyl N-phenyl carbamate (MPC) from aniline and dimethyl carbonate (DMC) are investigated. The unknown byproduct is determined as N,N-dimethylaniline (DMA) by GC-MS. The basic thermodynamics data of the main reaction and side reactions are calculated using Bensonʹs bond addition method. The results show that the synthesis of N-methylaniline (NMA) and DMA are the main competitive reactions to MPC synthesis. It is found that the best support for supported zirconia catalyst is SiO2 and that the best loading amount is 1%. The optimal reaction conditions over ZrO2/SiO2 are as follows: reaction temperature, 443.15 K; reaction time, 7 h; n(DMC)/n(aniline) = 20; catalyst/aniline = 25 wt %; the conversion of aniline is 98.6%; and the yield of MPC is 79.8%. The results of characterization for the fresh catalyst and the deactivated catalyst show that the decrease of the specific surface area is the reason for deactivation.