Catalysis effect and conversion process of transition metal chlorides in the synthesis of diethyl carbonate from ethyl carbamate and ethanol

Abstract

The catalysis effect of transition metal chlorides (TMC) for the synthesis of diethyl carbonate (DEC) from ethyl carbamate and ethanol was investigated in a batch reactor. Their activities were arranged as follows: MnCl2 > CoCl2 > ZnCl2 > CdCl2 > NiCl2, the corresponding yields of DEC were 11, 6.5, 3.7, 2.8, and 2.4 % at 190 °C in 12 h. The highest decomposition temperatures of their diammine complexes were sorted as follows: Ni(NH3)2Cl2 > Mn(NH3)2Cl2 > Co(NH3)2Cl2 > Cd(NH3)2Cl2 > Zn(NH3)2Cl2. These results indicated that the activity of TMC was not entirely determined by its ammonia capture ability, which is characterized by the decomposition temperature of diammine complex. On the other hand, the diammine TMC still showed activity for the synthesis of DEC. Their activities were a little lower than those of the corresponding TMC but the sequence was the same to that of TMC. In the reaction process, TMC was found to be coordinated with byproduct ammonia yielded in situ to form ammine complex, in which the number of ammonia molecule would change with the reaction conditions. These results indicated that the catalysis ability of TMC was the crucial influence factor for DEC yield and the reaction coupling ability of it was also benefit for DEC synthesis.