Study On Experiment And Industrialization Of Propylene Carbonate Form Urea And 1,2-propanediol

Propylene carbonate is an excellent organic chemical product,which has been widely used in organic synthesis,solvent,decarbonization,extraction,also is an intermediate of synthetic engineering plastics polycarbonate.This paper is based on the project of 40,000 tons/year urea two-step dimethyl carbonate in Hengyuan Chemical Industry,in which I study on the industrialized technology for the synthesis of propylene carbonate from urea and 1,2-propanediol and catalytic reaction.First,reaction thermodynamics was studied.Activated zinc carbonate catalyst was prepared and investigated in laboratory apparatus,and the optimal reaction conditions were obtained.The catalysts were characterized by XRD.Industrialization of the reaction technology was investigated and the economic evaluation was performed.Thermodynamic studies show that this reaction is endothermic,spontaneous and entropy increasing,with the reaction Gibbs free energy of-22.24kJ·mol-1,the reaction enthalpy is 36 kJ·mol-1,and the reaction entropy of 195.35J·mol-1·K-1 at 298.15K.In the temperature range of 273.15K?473.15K,the reaction Gibbs free energy decreases with the increase of temperature,and the equilibrium constant increases with the increase of temperature.Increasing temperature can accelerate the reaction rate and increase the equilibrium conversion.The optimum reaction conditions are as follow:reaction time of 2h,the mass ratio of catalyst to reactants of 1:100,the molar ratio of 1,2-propanediol to urea of 1:2,reaction temperature of 170?.Under these conditions,the yield of propylene carbonate is 94.7%.The XRD characterization of the catalyst shows that zinc carbonate hydroxide and zinc oxide are two crystalline forms in the catalyst,and zinc oxide is the main active component.The synergistic effect of basic zinc carbonate and zinc oxide promotes the improvement of catalytic activity.The experimental results were used to instruct the industrialization,in which propylene carbonate was successfully produced with the urea conversion of 99.98%and propylene carbonate of 69.364%in the product.The results of the test run are as follows:annual net cash flow increase is 11.69 million yuan;annual cash payments to employees are 8.24 million yuan.It shows that it has social benefits.