有序介孔二氧化硅负载Zn和Zr多功能催化剂催化乙醇转化制丁二烯性能研究OA北大核心CSTPCD

Direct conversion of ethanol to butadiene is an effective strategy to reduce dependence on fossil resources and alleviate environmental problems.The development of novel catalysts can increase the production of butadiene.By adjusting the pore structure of mesoporous SiO2 materials,the rapid transfer of ethanol and important intermediates between the host and guest molecules can take place,and the adjustment of the acid-base properties and the synergistic effect of the active centers of catalysts can improve the catalytic performance of catalysts.A series of mesoporous SiO2 loaded Zn and Zr catalysts with different pore structures(ZnZr/SiO2,ZnZr/MCF,ZnZr/SBA-5 and ZnZr/KIT-6)were prepared by a wet impregnation method.The performances of catalysts for direct conversion of ethanol to butadiene were evaluated,and the synergistic effects of each active center of the catalysts and the influence of acid-base properties on the catalytic performance were revealed by various characterization techniques.The characterisation results show that the pore structure can effectively modulate the acid-base properties of the catalysts,and the mesostructured porous foam(MCF)can promote the interaction of Zn species with silanol to form strong Lewis acid sites.ZnZr/KIT-6 catalyst exhibits moderate acid properties because the interactions of Zr species with silanol on KIT-6 form moderate strength Lewis acid sites and KIT-6 inhibits the interaction of Zn species with silica hydroxyls to form strong acidic sites.In ZnZr/KIT-6 catalyst,Zn species mainly exist as ZnO,which is favourable for the dehydrogenation of ethanol to acetaldehyde.Compared to ZnZr/SBA-15 catalyst,ZnZr/KIT-6 catalyst has an increased amount of weak bases and a decreased amount of strong bases with a weaker base strength.Moderate acid and weak base properties are beneficial for the aldol condensation reaction in the direct conversion of ethanol to butadiene,so in the direct conversion of ethanol to butadiene reaction catalysed by ordered mesoporous SiO2 loaded Zn and Zr catalysts,ZnZr/KIT-6 catalyst shows the highest ethanol conversion rate and butadiene selectivity at a temperature of 350℃and a reaction space velocity of 1.23 h-1,which is 91.2%and 53.5%,respectively,and the butadiene space time yield is up to 0.35 g/(g·h).