制备方法对Al_(2)O_(3)-CeO_(2)物化性质及CO_(2)加氢制甲醇催化性能的影响

Effect of Preparation Methods on Physicochemical Properties of Al_(2)O_(3)-CeO_(2) and Its Catalytic Performance of CO_(2) Hydrogenation to Methanol

复合氧化物界面性质与CO_(2)加氢制甲醇反应的催化性能有着重要的关系。本文对比考察了物理共混法、浸渍法、传统共沉淀法和微流控连续共沉淀法对Al_(2)O_(3)-CeO_(2)复合氧化物界面性质和催化性能的影响。浸渍作用尽管使Al_(2)O_(3)/CeO_(2)界面产生了一定的结构性质调变,但贫瘠的氧空位缺陷导致催化反应效率低。共沉淀样品中固溶结构的存在增强了Al_(2)O_(3)/CeO_(2)界面的相互作用,增大了电子结合能,形成的大量氧空位缺陷有利于CO_(2)活化转化。而微流控连续共沉淀法合成样品因具有更小的晶粒尺寸、均匀的复合相结构和丰富的氧空位缺陷,表现出更为优异的催化性能。在原料气配比为V(H_(2))∶V(CO_(2))∶V(N_(2))=72∶24∶4,反应温度为320℃,反应压力为3 MPa,体积空速为9000 mL·g^(-1)·h^(-1)的条件下,Al2O3-CeO_(2)复合氧化物的CO_(2)转化率、甲醇选择性及甲醇时空产率分别达到15.3%,86.4%和0.076 g·mL^(-1)·h^(-1)。

The interfacial properties of the composite oxides have a significant relationship with the catalytic performance of CO_(2)hydrogenation to methanol.Accordingly,the effects of various preparation methods including physical blending,impregnation,traditional co-precipitation and microfluidic continuous co-precipitation on the interfacial property and catalytic performance of Al_(2)O_(3)-CeO_(2)composite oxides were investigated.Although the impregnation effect can moderately tune the interface properties of Al_(2)O_(3)/CeO_(2),the insufficient oxygen vacancy defects resulted in inferior catalytic performance.The solid solution structure of co-precipitation sample enhanced the interfacial interaction of Al_(2)O_(3)/CeO_(2)and the binding energy of the electron,forming sufficient oxygen vacancy defects to activate CO_(2).The sample prepared by the microfluidic continuous co-precipitation has the excellent catalytic performance due to its smaller grain size,uniform composite structure and sufficient oxygen vacancy defects.Under the conditions of V(H_(2))∶V(CO_(2))∶V(N_(2))=72∶24∶4,reaction temperature 320℃,reaction pressure 3 MPa and space velocity 9000 mL·g^(-1)·h^(-1),the CO2 conversion,methanol selectivity and methanol space-time yield of the Al_(2)O_(3)-CeO_(2)composite oxide can reach 15.3%,86.4%,and 0.076 g·mL^(-1)·h^(-1),respectively.