稀土氧化物负载双组分催化剂用于直接合成碳酸二甲酯

利用稀土氧化物REO(RE=La,Ce,Y,Nd)为载体负载KCl和K2CO3制备了双组分固体碱催化剂,用于二氧化碳、甲醇及环氧丙烷一步直接合成碳酸二甲酯。研究了制备条件对催化活性的影响,并采用TG、XRD对催化剂进行了表征。结果表明,K2CO3负载质量分数17.6%为佳,KCl最佳负载量随载体的不同而不同,KCl-K2CO3/Y2O3催化剂中KCl的最佳负载量为17.6%,其他三种催化剂中KCl最佳负载量则为22.2%。载体对催化剂活性有较大的影响,KCl-K2CO3/Nd2O3催化活性最高;KCl-K2CO3/Y2O3在焙烧温度超过800℃时,其催化活性仍然随焙烧温度的升高而增加,高温焙烧使部分K+或者Cl-进入到Y2O3的晶格,生成KYO2或Y3O4Cl,以及YOx的结构,这些物种充当活性位使催化剂保持较高活性。

Direct Synthesis of Dimethyl Carbonate over Rare Earth Oxides Supported Catalysts

Solid base catalysts for direct synthesis of dimethyl carbonate(DMC) from carbon dioxide,methanol and propylene oxide were prepared by supporting KCl and K_2CO_3 onto the surface of La_2O_3,Y_2O_3,CeO_2 and Nd_2O_3,and characterized by TG and XRD techniques.The catalytic activity was efficiently influenced by the preparation conditions.An optimal loading amount of K_2CO_3 is 17.6%(mass),However,the optimal loading amount of KCl varied with supports,it is 17.6% for KCl-K_2CO_3/Y_2O_3 and 22.2% for other catalysts.Supports affects the activity of catalyst.The activity highest was KCl-K_2CO_3/ Nd_2O_3.The activity of KCl-K_2CO_3/Y_2O_3 increased with the increase of calcination temperature in the range of 800-900℃.Probably,the formation of KYO_2,Y_3O_4Cl or YOx species promoted the catalytic activities.