负载型ZrO2催化苯甲醛Meerwein-Ponndorf-Verley反应中的载体效应（英文）

采用浸渍法制备了Si-MCM-41和Al-MCM-41(Si/Al=50)介孔分子筛,SiO2,γ-Al2O3及MgO等负载的ZrO2催化剂,考察了其在以异丙醇为氢源苯甲醛Meerwein-Ponndorf-Verley(MPV)还原反应中的催化活性,并与纯ZrO2的催化活性进行对比.同时,采用X射线衍射、N2吸脱附法、X射线光电子能谱、紫外-可见漫反射光谱和吡啶原位吸附红外光谱等手段表征了催化剂.结果表明,ZrO2负载于Si-MCM-41,Al-MCM-41和SiO2后,催化活性明显提高,这归因于ZrO2与载体间存在强相互作用形成ZrOSi键,使催化剂表面ZrOH数量显著增多,Lewis酸中心强度增强,并出现Brnsted酸中心,三种催化剂的活性高低次序是5%ZrO2/Si-MCM-41>5%ZrO2/Al-MCM-41>5%ZrO2/SiO2.而5%ZrO2/Al2O3和5%ZrO2/MgO基本无催化活性,可归因为ZrO2与γ-Al2O3的弱相互作用使5%ZrO2/Al2O3的酸性与γ-Al2O3类似,ZrO2与MgO的强相互作用使5%ZrO2/MgO基本无酸性.

Support Effect in Meerwein-Ponndorf-Verley Reduction of Benzaldehyde over Supported Zirconia Catalysts

A series of zirconia catalysts supported on Si-MCM-41 and Al-doped MCM-41(Si/Al = 50) mesoporous molecular sieves,silica,γ-Al2O3,and MgO were prepared by the wet impregnation method.The catalytic activities of these materials in the Meerwein-Ponndorf-Verley reduction(MPV) of benzaldehyde with 2-propanol as reducing agent were investigated,and compared to that of hydrous zirconia.The materials were characterized by X-ray diffraction,nitrogen adsorption-desorption,X-ray photoelectron spectroscopy,UV-Vis diffuse reflectance spectroscopy,and Fourier transform infrared and thermal desorption of pyridine.Loading zirconia on Si-MCM-41,Al-MCM-41,and SiO2 gave improved catalytic activity.This is attributed to a strong interaction of zirconia with the support to form Si-O-Zr bonds,which gave a significant increase in the amount of exposed Zr-OH groups and stronger Lewis acidity as well as an appearance of Br?nsted acid sites.The activity of 5%ZrO2/Si-MCM-41 was the highest,followed by those of 5%ZrO2/Al-MCM-41 and 5%ZrO2/SiO2.However,5%ZrO2/Al2O3 and 5%ZrO2/MgO gave very low catalytic activities.This is ascribed to that the acidities of 5%ZrO2/Al2O3 and the γ-Al2O3 support were similar due to the weak interaction of zirconia with γ-Al2O3,and 5%ZrO2/MgO had no acidity because of the strong interaction between zirconia and MgO.