Cu-Zn-Zr/SBA-15介孔催化剂的制备及CO2加氢合成甲醇的催化性能

Direct Syntheses of Cu-Zn-Zr/SBA-15 Mesoporous Catalysts for CO_2 Hydrogenation to Methanol

以具有骨架结构的SBA-15介孔分子筛为载体,采用浸渍法合成了具有高比表面积、不同金属氧化物含量的Cu-Zn-Zr介孔催化剂CZZx/SBA-15(x=0.3,0.4,0.5,0.6).采用N2吸附-脱附(BET)、X射线衍射(XRD)、H2程序升温还原(H2-TPR)、CO2吸附(CO2-TPD)和透射电子显微镜(TEM)等手段对样品进行了表征.在固定床反应器上评价了其CO2加氢合成甲醇的催化性能.实验结果表明,CZZx/SBA-15催化剂具有介孔结构,负载的Cu O,Zn O和Zr O2能够很好地分散在表面,并且负载氧化物晶粒尺寸不同.催化剂的铜比表面积SCu与甲醇催化活性呈近似线性关系,其中CZZ0.4/SBA-15催化剂表现出最大甲醇选择性(54.32%),与CZZ相比,甲醇选择性增加24.85%.随着金属氧化物负载量的增大,催化剂比表面积和SCu明显减小,甲醇选择性与收率也相应减小,负载型CZZx/SBA-15催化剂表面结构对CO2加氢合成甲醇反应活性起关键作用.

A series of high surface areas and different mental oxide contents of Cu-Zn-Zr/SBA-15 mesoporous catalysts CZZx/SBA-15 （ x=0. 3, 0. 4, 0. 5, 0. 6 ） was directly synthesized by impregnation method. The catalysts were characterized by N2 adsorption-desorption （ BET ） , X-ray diffraction （ XRD ） , transmission electron microscopy（TEM）, H2 temperature-programmed reduction（H2-TPR）, CO2 temperature-programmed desorption（ CO2-TPD） and N2 O titration technique（ N2 O-RFC） . The catalytic activities of these catalysts were determined on the hydrogenation of CO2 to methanol in a fixed-bed reactor. The results showed that CZZx/SBA-15 catalysts possessed a highly ordered mesoporous structure, in which different grain size CuO, ZnO, ZrO2 species dispersed on the surface of SBA-15. A approximate linear relationship between the methanol synthesis activity and the total Cu0 surface area SCu was observed. CZZ0. 4/SBA-15 catalyst showed the largest methanol selectivity SCH3OH=54. 32%, which increased by 24. 85% as compared with CZZ catalyst. However, the methanol synthesis selectivity and yield decreased with the increasing of metal oxide content, which strongly suggested that the surface structure of the CZZx/SBA-15 catalysts played an important role in CO2 hydrogenation to methanol.