Green Process Development Of Dimethyl Carbonate

There exist disadvantages of high yield of propylene glycol as by-product, highenergy consumption in the process of dimethyl carbonate produced by propylene oxide,carbon dioxide and methanol. For this, indirect alcoholysis method using urea andpropylene glycol as raw material was introduced in order to improve the defects.Systematic studies of the new process were carried out.Influence factors the reaction was studied. Feasible production process conditionas flowed: reaction temperature was160℃, reaction time was two hours, mole ratioof propylene oxide and urea was4, catalyst content was2%in total. In this condition,propylene carbonate yield rate was more than77.19%.The reaction between urea and propylene oxide was studied by small scaleexperiment. The experiment results showed that the reaction was a second reaction andthe reaction kinetic equation was:r_A=1.5888exp（-562.602/T）CACBThere exist features of low equilibrium conversion and decalescence in thereaction. Section-heated-three-phase-plug-flow reactor was introduced to producepropylene carbonate based on enlarged-experiment.There exist features of slow reaction rate, low equilibrium conversion, azeotropybetween methyl and dimethyl carbonate. With traditional process conditions influenceof liquid-holdup on reaction was studied. The Results showed that DMC content canreach26.55%within the overflow dam height11centimeters. The residence timeincreased from valve tower8.6min to liquid-sprayed tower41.44min. Reflux ratiowas depressed from2to0.2. Energy consumption cost was reduced332.1yuan per tonproducts. Pilots using large liquid holdup liquid-sprayed tray instead of float-valve trayin ester-exchange reaction were carried out. With reflux ratio0.2and overflow damheight11centimeters, feed ratio and tower bottom temperature was studied. Feasibleprocess conditions were feed ratio5.6:1,tower bottom temperature90℃. Based on the small scale experiment and pilots, new reaction-distillation production process of dimethyl carbonate using the Section-heated-three-phase-plug-flow reactor and liquid-sprayed tower was advanced.