Studying On The Two-step Synthesis Of Methyl N-phneyl Carbamate From Methanol, Urea And Aniline

Methyl N-phneyl Carbamate (MPC) is an important chemical synthetic isocyanate intermediate. Synthesized by the multi-isocyanate polyurethane PU products, with high strength, resistance to denaturation, stability, high wear strength, high tear strength, low thermal conductivity, low temperature toughness and excellent chemical stability performance, widely used in plastic, rubber, fiber, paint, areas of exclusion mixture has a very high value. Take the urea as raw material synthesis Methyl carbamate (MC), and then the MC with aniline (AN) synthesis MPC is one route which has the prospect clean process.This article focuses on the synthesis route of methyl carbamate. First, Experiments have been carried out at different molar ratio of urea to methanol, temperatures, pressures, coupling agent quantities, and mass of the catalyst, reaction time so as to acquire their effects on the synthesis reaction and to find the optimal reaction condition. The results show that optimal reaction conditions are as follows:molar ratio of urea to methanol=1:9, reaction temperature 150℃,reaction pressure 1.3Mpa, mass fraction of the catalyst=0.25%, mass fraction of coupling agent quantities=40%, reaction time 2h. MC yield of up to 57.00% was obtained under the optimal conditions. Second, this article has also studied the reactions of synthesis MPC. In the presence of Pb(OCH3)2 catalyst, synthesis of methyl N-phenyl carbamate(MPC) from aniline and methyl carbamate was discussed. The effects of methanol dosage, reaction temperature, reaction time, catalyst dosage and the molar ratios of aniline to methyl carbamate on the reaction were studied, and the reaction mechanism over lead methylate catalyst was proposed. The results show that optimal reaction conditions are as follows:m(methanol)/m(MC)=2, reaction temperature 150℃, reaction time 5h, catalyst dosage(the ratio of entire raw materials) 0.35%, m(MC)/m(AN)=2.Under the optimum reaction conditions, the yield of MPC reached 97.5% and selectivity of MPC is 97.86%.