Global Kinetics And Simulation Of The Fixed-bed Reactor For Dimethyl Carbonate Synthesis

Dimethyl carbonate?DMC?and methylal?DMM?are important green fuel additives.The oxidative carbonylation and selective oxidation of methanol are two green and high economic value-added routes for sythesis of DMC and DMM.While the low single pass conversion of methanol in the sythesis of DMC makes a great deal of unreacted raw materials to recycle,and results in high energy consumption.To solve this problem,we created a serial coupling process by combining the two routes of methanol oxidative carbonylation and selective oxidation to improve the methanol single pass conversion.Based on the coupling process in a fixed-bed reactor,we studied the global kinetics of DMC and DMM synthesis from methanol over PdCl₂-CuCl₂-KOAc/AC and V₂O₅/TiO₂catalyst,respectively.Mathematical simulation was performed on commercial scale reactor.We measured the reaction data of DMC synthesis from methanol over PdCl2-CuCl2-KOAc/AC catalyst.A kinetic model of power functions type was established,which was presented by the form of partial pressures of CO,O₂ and methanol.Based on the experiment results,the parameters of the kinetic model were determined with Matlab software.The residual error distribution and the statistic test showed that the model was highly reliable.The kinetic equations werer_DMC=3.27×10⁵exp?-4.63×10⁴/RT?P_CH3OH^0.1835P_CO^0.0404P_O2^0.9997 mol/?g.h?r_CO2=4.51×10⁵exp?-4.60×10⁴/RT?P_CO^1.2707P_O2^0.0084 mol/?g.h?A pseudo-homogenous two-dimensional model of the reactor was established for DMC synthesis from methanol and the simulation of the commercial scale reactor was studied.The simulation results indicated the presence of large radial temperature difference and concentration difference.The quantitative relationship between space velocity,feed composition,inlet temperature,operating pressure and temperature of the medium out of the tube and temperature distributions,methanol conversion,CO conversion,selectivity profile of DMC to CO were studied.The optimum operating condition was determined as follows:the molar ratio of CH₃OH/CO/O₂ was 0.20/0.27/0.53,the space velocity was 7500h^-1,the inlet temperature was 433.15 K,the boiling water temperature was 453.15 K,and the operating pressure was 0.30 MPa.We measured the reaction data of DMM synthesis from methanol over V₂O₅/TiO₂catalyst.A kinetic model of power functions type was established,which was presented by the form of partial pressures of O₂ and methanol.The kinetics parameters were determined with simplex method and Runge-Kutta method by Matlab software,The residual error distribution and the statistic test showed that the simulation model was highly reliable.The kinetic equation was r_DMM=1.40×10^-3exp?-1.14×10⁴/?RT??P_CH3OH^1.3041P_O2^-2.0000 mol/?g.h?.Based on the results of the kinetic studies,the serial coupling process was analyzed and calculated for DMC and DMM synthesis in a fixed-bed reactor orderly-packed with PdCl₂-CuCl₂-KOAc/AC and V₂O₅/TiO₂ catalyst.The simulation results were in consistent with the experiment results,which confirmed that the simulation model was highly reliable.In conclusion,the serial coupling process greatly improved the methanol single pass conversion and reduced energy consumption.