固相浸渍法制备NiO/CeO2催化剂及其在CO氧化反应中的应用

Preparation of NiO/CeO_2 Catalysts by Solid State Impregnation and Their Application in CO Oxidation

采用固相浸渍法制备了一系列NiO/CeO2催化剂,并通过与常规湿浸渍法比较,考察了制备方法对催化剂和CO氧化反应性能的影响.同时结合X射线衍射(XRD),N2吸附-脱附(BET),透射电镜(TEM),氢气-程序升温还原(H2-TPR),拉曼(Raman)光谱,X射线光电子能谱(XPS)等手段对催化剂的结构和表面物种分散状态进行了表征.CO氧化活性测试结果表明,当镍负载量相同时,固相浸渍法制备的催化剂相比于湿浸渍法表现出更好的催化性能.TEM、XPS、H2-TPR结果表明,固相浸渍法更有利于加强镍铈间的相互作用和得到高分散的镍物种,从而促进镍物种的还原.Raman结果表明固相浸渍法相比于湿浸渍法能产生更多氧空位,这有利于氧气在催化剂表面的活化,使得CO氧化反应更容易进行.

NiO/CeO2 catalysts with different NiO Ioadings were prepared by a novel solid state impregnation method. The physical and chemical properties of these catalysts were compared with those of catalysts prepared by traditional wet impregnation method. The catalysts were tested for low temperature catalytic CO oxidation and characterized by X-ray diffraction （XRD）, N2 physical adsorption, transmission electron microscopy （TEM）, H2 temperature-programmed reduction （H2-TPR）, Raman spectrum, and X-ray photoelectron spectroscopy （XPS）. CO oxidation results showed that nickel-ceria catalysts were good candidates for low temperature CO oxidation, with complete oxidation achieved at temperatures below 200 ~C. The activity of the catalysts increased with nickel loading, and those prepared using the solid state impregnation method displayed higher activities than those prepared by wet impregnation method at the same nickel loading. TEM, XPS, and H2-TPR results showed that solid state impregnation increased the dispersion of the nickel species on the surface of catalysts and strengthened the interactions between nickel and cerium, which benefited the reduction of nickel species. Raman results showed that the concentration of oxygen vacancies in the catalysts could be increased using the solid state impregnation method, likely because of more doped nickel ions in the ceria lattice, which promote the activation of oxygen molecules to facilitate the CO oxidation.