Macro kinetics for synthesis of dimethyl carbonate from urea and methanol on Zn-containing catalyst

In a stainless steel autoclave,the synthesis kinetics of dimethyl carbonate(DMC) from urea and methanol was separately investigated without catalyst and with Zn-containing catalyst.Without catalyst,for the first reaction of DMC synthesis(the reaction of urea with methanol to methyl carbamate(MC)),the reaction kinetics can be described as the first order with respect to the concentrations of both methanol and urea.For the second reaction of DMC synthesis(the reaction of MC with methanol to DMC),the results exhibit characteristics of zero-order reaction.For Zn-containing catalyst,the first reaction is neglected in the kinetics model since its rate is much faster than the second reaction.The macro-kinetic parameters of the second reaction are obtained by fitting the experimental data to a pseudo-homogenous model,in which a side reaction in forming process of DMC is incorporated since it decreases the yield of DMC drastically at high temperature.The activation energy of the reaction from MC to DMC is 104 kJ/mol while that of the side reaction of DMC is 135 kJ/mol.The highest yield of DMC is 23%.