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通过浸渍法制备活性炭(AC)、全硅介孔分子筛MCM-41、硅胶(SiO2)、γ-Al2O3等四种载体负载的MgO催化剂,考察其在以异丙醇为氢源的苯乙酮Meerwein-Ponndorf-Verley(MPV)反应中的催化活性,并和纯MgO进行对比研究,同时对样品进行XRD、TEM、N2吸附-脱附、XPS及CO2-TPD等表征分析,研究载体效应对催化剂活性的影响.结果表明:纯MgO因其比表面积较小,表面暴露的碱中心数目较少,其活性较低.10%MgO/AC中MgO具有良好的分散性,且与AC载体不发生强相互作用,MgO以小晶粒形式存在于载体表面,致使催化剂表面的碱中心数目显著提高;另外,苯乙酮上苯环π电子与AC载体中石墨层π电子可能存在相互作用,致使催化剂活性中心附近的苯乙酮浓度增大;上述两方面原因使该催化剂具有良好的活性.而在10%MgO/MCM-41,10%MgO/SiO2,10%MgO/γ-Al2O3中,载体均与MgO发生强相互作用,使得其碱中心数目急剧下降,导致其催化活性不明显.
The activated carbon (AC), all-silico-mesoporous molecular sieve MCM-41, silica gel (SiO2) and γ-Al2O3 were used to prepare MgO catalysts supported by impregnation method. -Pontorforf-Verley (MPV) reaction, and compared with the pure MgO, while the samples were characterized by XRD, TEM, N2 adsorption-desorption, XPS and CO2-TPD analysis of the effect of the carrier on the catalytic activity The results show that pure MgO has low activity due to its small specific surface area and less alkali center exposed on the surface.The MgO has good dispersibility in 10% MgO / AC and does not interact strongly with AC support , MgO is present on the surface of the carrier in the form of small grains, resulting in a significant increase in the number of alkali centers on the surface of the catalyst. In addition, π electrons on the benzene ring of acetophenone may interact with the π electrons of the graphite layer in the AC carrier, In the vicinity of the acetophenone concentration increased; the above two reasons that the catalyst has good activity in 10% MgO / MCM-41,10% MgO / SiO2, 10% MgO / γ-Al2O3, the carrier and MgO A strong interaction occurs that causes a sharp drop in the number of its base centers, leading to its catalysis Not obvious.