尖晶石载金属型费托合成催化材料的空气氛重氧化XPS分析与加氢活性

Oxidation in Exposure to Air of Spinel-Supported Fischer-Tropsch Catalyst-An X-Ray Photoelectron Spectroscopy Study

还原后的金属催化剂可因检修、再生、操作失误等原因而发生空气氛重氧化。关于金属催化材料新鲜还原态的X射线光电子能谱文献很多,而关于金属催化材料还原后发生空气氛重氧化的XPS文献则很少。使用三种不同合成路线制备了铝酸锌尖晶石型载钴催化剂,在还原后执行了室温下的空气氛重氧化,并开展了钴、锌、铝、氧元素的XPS分析及CO加氢活性考察。合成路线对催化材料的体相结构组成以及表面物相均能够产生相当的影响。XPS和X射线衍射技术的联用有助于催化材料的筛选。

The surface re-oxidation of the spinel-supported metallic type Fischer-Tropschcatalysts,synthesized by co-precipitation,sol-gel and dip-molding techniques and reduced in H_2/He at 550℃,was characterized with Xray diffraction and X-ray photoelectron spectroscopy（ XPS）. The impact of the synthesis methods on the surface reoxidation,CO-hydrogenation,phase-structures and contents of the catalysts,before and after exposure to air,was investigated for catalyst screening. The results show that the preparation methods significantly affected the catalytic activity and surface oxidation of Co^0. To be specific,depending on the synthesis routes,ZnO and Al_2O_3 phases coexist to a varying degree in the Co^0/ZnAl_2O_4; and the Co^0-grain surfaces,exposed to air,rapidly oxidized into Co（OH）_2 at room temperature. The Co^0/ZnAl_2O_4 synthesized by co-precipitation displays the highest temperature-dependent catalytic activity because of the highest density of Zn Al_2O_4 in the bulk and on the surfaces.