Synthesis of dimethyl carbonate from urea and methanol using polyphosphoric acid as catalyst

Abstract

A new process was proposed for the synthesis of dimethyl carbonate (DMC) from urea and methanol in a batch operation. Polyphosphoric acid (PPA) was used as the catalyst and the absorbent for the ammonia, which was produced during the reaction. The effects of various operation conditions, such as reaction temperature, pressure, reaction time and the molar ratio of the reactants were investigated in the terms of DMC yield. The experimental results indicated that the optimal reaction conditions were the molar ratio of methanol/urea of 14, reaction time of 4 h, reaction temperature of 413 K, PPA/urea mass ratio of 1 and initial pressure of CO 2 of 0.8 MPa, respectively. The DMC yield of 67.4% was obtained in the optimal reaction conditions. The by-product, ammonia was also used as a starting material of a useful fertilizer in the proposed process.