CAJ | 학술논문

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Zr-O-Si 键,使催化剂表面Zr-OH数量显著增多,Lewis酸中心强度增强,并出现Br(o)nsted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.
채용침지법제비료Si-MCM-41화Al-MCM-41 (Si/Al=50)개공분자사,SiO2,γ-Al2O3급MgO등부재적ZrO2최화제,고찰료기재이이병순위경원분갑철Meerwein-Ponndorf-Verley(MPV)환원반응중적최화활성,병여순ZrO2적최화활성진행대비.동시,채용X사선연사、N2흡탈부법、X사선광전자능보、자외-가견만반사광보화필정원위흡부홍외광보등수단표정료최화제.결과표명,ZrO2부재우Si-MCM-41,Al-MCM-41화SiO2후,최화활성명현제고,저귀인우ZrO2여재체간존재강상호작용형성Zr-O-Si 건,사최화제표면Zr-OH수량현저증다,Lewis산중심강도증강,병출현Br(o)nsted산중심,삼충최화제적활성고저차서시5％ZrO2/Si-MCM-41＞ 5％ZrO2/Al-MCM-41＞ 5％ZrO2/SiO2.이5％ZrO2/Al2O3화5％ZrO2/MgO기본무최화활성,가귀인위ZrO2여γ-Al2O3적약상호작용사5％ZrO2/Al2O3적산성여γ-Al2O3유사,ZrO2여MgO적강상호작용사5％ZrO2/MgO기본무산성.
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 zireonia.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(o)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％ZrO2MgO had no acidity because of the strong interaction between zirconia and MgO.