Papers by Keyword: Macro Kinetics

Abstract: The synthesis of dimethyl carbonate (DMC) from urea and methanol includes two main reactions: one amino of urea is substituted by methoxy to produce the intermediate methyl carbamate (MC) which further converts to DMC via reaction with methanol again. In a stainless steel autoclave, the kinetics of these reactions was separately investigated without catalyst and with Zn-containing catalyst. Without catalyst, for the first reaction, the reaction kinetics can be described as first order with respect to the concentrations of methanol and methyl carbamate (MC), respectively. For the second reaction, the results exhibit characteristics of zero-order reaction. Over Zn-containing catalyst, the first reaction is neglected in the kinetics model since its rate is much faster than second reaction. After the optimization of reaction condition, 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 of DMC synthesis 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.

Abstract: It’s a gas-liquid-solid three-phase reaction system in the reactor for flue gas desulfurization using pyrolusite pulp. Based on the two-film mass transfer theory and shrine core model, the macro-kinetics of flue gas desulfurization using pyrolusite pulp in a double magnetic stirred reactor were investigated. The effects of diffusion in solid film, surface chemical reaction, diffusion in liquid phase and gas phase of the process, have been carried out to distinguish the control step of the process. It was observed that SO2 absorption efficiency increased with the decreasing of pyrolusite particle size and varied gently when the pyrolusite particle diameter decreased to 0.18mm. SO2 absorption efficiency increased not significantly along with the increase of temperature and the liquid phase stirring speed but increased significantly along with the increase of the gas phase stirring speed. Experiment results showed that under simulated industrial conditions, gas phase diffusion was the control step compared to other related factors, given that pyrolusite particle diameter was kept below 0.1mm.