Solid base catalysts(xK/KCC-1)with different K theoretical loading(x,x is the molar ratio of K to Si,x=0.3,0.5,0.7,0.9,1.1)were synthesized by equi-volumetic impregnation method using dendrite fibrous silica(KCC-1)prepared from hydrothermal synthesis as support and potassium acetate as precursor,and characterized by XRD,FTIR,BET,CO2-TPD and SEM.xK/KCC-1 samples were then evaluated for their catalytic performance on the synthesis of methyl ethyl carbonate(EMC)via transesterification of dimethyl carbonate(DMC)and ethanol.The results indicated that xK/KCC-1 had two types of basic sites,the weak basic sites provided by K2SiO3 and the medium strong basic sites provided by K2CO3.With the increase in K theoretical loading,the weak basic sites gradually decreased,while the medium strong basic sites gradually increased,thus enhancing the reaction activity of transesterification.xK/KCC-1 with K theoretical loading ≤0.9 still maintained the dendritic fiber structure of KCC-1,allowing reactant molecules to diffuse well to the active sites.0.9K/KCC-1 exhibited the highest catalytic activity.Under the optimal reaction conditions of reaction temperature 80 ℃,reaction time 5 h,molar ratio of ethanol to DMC(4.494 g)4∶1,and 0.9K/KCC-1 dosage 5％of DMC mass,the conversion rate of DMC was 91.0％,and the EMC selectivity was 95.5％.Furthermore,0.9K/KCC-1 showed good cyclic stability,with a DMC conversion of 86.7％and an EMC selectivity of 95.2％after 5 recycles.
维普
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