The Research On The Synthesis Of Glycerol Carbonate From CO₂and Glycerol

CO2is the main greenhouse gas, and the rich resources of C1, the whole world has been calling for reducing emissions of CO2, and rational utilization of CO2.The lack of petrochemical energy makes the rapid development of biodiesel industry, and bring a lot of by-product glycerol, combined with the traditional procreative glycerol, lead to glycerol market is too saturated. Convert CO2and glycerol into glycerol carbonate is a reasonable use of resources, and the effective ways to decrease the cost of biodiesel production. Due to the limited on the thermodynamics of the reaction, need to add epoxy propane as coupling agent. On this basis, this paper aims to establish a effective synthesis methods of glycerol carbonate from CO2and glycerol. By homogeneous catalyst to explore the reaction mechanism of the synthesis of glycerol carbonate, and the affecting factors of reaction for synthesis of GC. Then the synthesis reaction was catalyzed by solid catalysts, and the catalytic performance of the solid catalysts, the reaction conditions were investigated in detail. The specific research content is as follows:(1) By comparing the catalytic performance of the different alkali metal (ammonium salts), KI showed the highest catalytic activity on the reaction for the synthesis of GC from CO2, glycerol and epoxy propane. The optimal reaction conditions for the synthesis of GC were as follows:reaction temperature393K, reaction time90min, pressure of CO25.0MPa, molar ratio of epoxy propane(PO) to glycerol3:1, and weight percentage of catalyst3.0%. Under this condition, the conversion of glycerol is64.8%, the conversion of PO is62.0%, the yield and selectivity of GC were60.7%and93.7%respectively.(2)According to the result of KI catalytic for the synthesis of GC, the reaction mechanism of the synthesis reaction has been speculated:the reaction is a coupling reaction, performed by two steps. First, reaction to generate the propylene carbonate from CO2and propylene oxide, Second, propylene carbonate and glycerol ester exchange reaction generated GC and propylene glycol.(3)KI as active component, solid catalysts KI/γ-Al2O3was prepared using impregnation method, research the catalytic performance and stability of the catalyst for synthesis of GC.KI was loaded0.15mmol.g-1on KI/γ-Al2O3, after repeated use4times, was still a high catalytic activity by experimental research. Under the optimal conditions:reaction temperature403K, reaction time120min, pressure of CO25.0MPa, molar ratio of epoxy propane(PO) to glycerol3:1, and weight percentage of catalyst2.0%. Under this condition, the conversion of glycerol is58.5%, the conversion of PO is63.1%, the yield and selectivity of GC were54.4%and93.3%respectively.(4)In order to improve the performance and stability of the solid catalyst, the composite catalyst KI/Al2O3-MgO was prepared by adding MgO into γ-Al2O3, and the catalytic and stability of the solid catalyst on the reaction for the synthesis of GC were examined. When γ-Al2O3was add MgO as0.1times the quality of γ-Al2O3, the KI/Al2O3-MgO catalyst has the good catalytic stability, after repeated use4times, the yield of GC just fell only2.8%. Under the optimal conditions:reaction temperature433K, reaction time90min, pressure of CO25.0MPa, molar ratio of epoxy propane(PO) to glycerol3:1, and weight percentage of catalyst2.0%. The conversion of glycerol is64.0%, the conversion of PO is65.4%, the yield and selectivity of GC were57.3%and89.5%respectively.