MgO Supported Sodium Silicate And Potassium Carbonate Catalyst Of Carbon Dioxide And Methanol Of Dimethyl Carbonate

Green chemicals are widely concerned by researchers because of their non-pollution to the environment.Dimethyl carbonate（DMC）as green chemicals has higher oxygen content,which could be used as gasoline additive to increase octane rating and improve combustion efficiency,reducing the environmental pollution caused by exhaust emissions.DMC can also substitute phosgene and dimethyl sulfate to act as carbonylation and methylation reagent.DMC can also directly synthesize protectant,food additives,antioxidant,surfactant,advanced resin,and environmentally friendly solvents,etc.In addition,propylene carbonate（PC）is also a kind of green chemicals,which is a kind of organic solvent with excellent performance,and is also a synthetic intermediate of fine chemicals.Thus,the synthesis of DMC has great practical and economic value.This article systematically studied the solid base catalysts for the synthesis of DMC by catalyzing CO₂ and methanol.The Na₂SiO₃ was loaded on different metal oxide with volumetric impregnation method to study its catalytic performance.It was found that the Na₂SiO₃ loaded on MgO has the best catalytic performance.A series of different load prepared with volumetric impregnation method of Na₂SiO₃/MgO style catalyst.The catalysts were characterized by XRD,BET,SEM,and TPD.When sodium silicate loading was 10%,the reaction temperature was 200℃,pressure was 2.0 MPa,the reaction time was 4 h,volume ratio of methanol and propylene oxide was 1.5:1,the speed was 250 r/min,and the reaction conditions of catalyst was 1 g.The results showed that the conversion of propylene oxide was 88.17%,the selectivity of dimethyl carbonate and propylene carbonate was was 45.22%and 24.21%,respectively.a series of Na₂SiO₃-K₂CO₃/MgO catalyst was prepared by adding K₂CO₃ and changing the amount of active components on the basis of Na₂Si O₃/MgO catalyst.The catalysts were characterized by XRD,BET,SEM,and TPD.The results showed that the catalyst performance was better when the K₂CO₃ loading was 17.5%.Through exploring the best condition of the reaction,we came to a conclusion as follows:in reaction temperature was 180℃,pressure was 2.0 MPa,the reaction time was 5 h,volume ratio of methanol and propylene oxide was 1.5:1,the speed was 250 r/min,the reaction conditions of catalyst was 1 g,Na₂SiO₃ 10%-17.5%K₂CO₃/MgO presented better catalytic properties.The epoxy propane conversion rate was 99.13%,the selectivity of dimethyl carbonate was 65.83%,the selectivity of propylene carbonate was 30.51%.