CO为还原剂同时还原SO_2和NO的SnO_2-TiO_2固溶体催化剂 Ⅱ.催化剂的物理化学性质

SnO_2-TiO_2 Solid Solution Catalyst for Simultaneous Reduction of SO_2 and NO by CO Ⅱ. Physicochemical Properties of the Catalyst

用XRD ,XPS ,CO TPR ,NH3 TPD ,SO2 TPD和IR等方法表征了SnO2 TiO2 固溶体催化剂的物理化学性质 .不同配比的SnO2 和TiO2 均可形成均一的具有金红石结构的连续固溶体 ,其晶粒度比单纯的SnO2 或TiO2 的晶粒度小 .SnO2 TiO2固溶体的比表面积随SnO2 含量的增大呈火山形变化 ,说明在SnO2 TiO2 固溶体中SnO2 可阻止TiO2 由锐钛矿型变为金红石型过程中比表面积的减小 ,而TiO2 则提供了维持大表面的结构框架 .SnO2 倾向于在固溶体表面偏析 ,固溶体的表面氧含量高于单纯SnO2 的表面氧含量而低于单纯TiO2 的表面氧含量 .SnO2 ,TiO2 和SnO2 TiO2 表面含有能被CO还原的吸附氧和晶格氧 ,被还原的SnO2 ,TiO2 和SnO2 TiO2 的表面晶格氧的数量仅占所有晶格氧的 0 0 0 1% ,说明CO只使部分晶格氧还原并生成氧阴离子空穴 .TiO2 表面没有酸性 ,SnO2 和SnO2 TiO2 呈微弱酸性 .经CO还原的SnO2 TiO2 上存在大量的强碱中心 ,说明SnO2 和TiO2 之间发生了协同作用 .SnO2 TiO2 固溶体的这些物化性质均十分有利于SO2 +NO

The physicochemical properties of the SnO 2-TiO 2 solid solution catalyst have studied by XRD, XPS, CO-TPD, HN 3-TPD, SO 2-TPD and IR spectroscopy. Different ratios of SnO 2 to TiO 2 can form continuous solid solution which has rutile crystal structure. The particle size of the solid solution is smaller than that of pure TiO 2 or pure SnO 2. The change of the surface area of the SnO 2-TiO 2 solid solution with the SnO 2 or TiO 2 content is a volcano shape curve. The function of SnO 2 in the solid solution is to prevent its surface area from decreasing during the phase change of TiO 2 from anatase to rutile, and the function of TiO 2 is to form a structure frame to ensure large surface area. SnO 2 tends to enrich on the surface of the solid solution. The content of oxygen on the solid solution surface is higher than that on the pure SnO 2 surface but lower than that on the pure TiO 2 surface. The adsorbed oxygen on the surface of SnO 2, TiO 2 or SnO 2-TiO 2 and crystal lattice oxygen on the surface of them can be reduced by CO, but only about 0.001% of the crystal lattice oxygen can be reduced to form oxygen anion vacancy. TiO 2 increases the amount of the surface crystal lattice oxygen. The surface of TiO 2 is non-acidic, the surface of SnO 2 and SnO 2-TiO 2 is weakly acidic. The SnO 2-TiO 2 solid solution reduced by CO has a large number of strong basic centers as a result of the synergism between TiO 2 and SnO 2. These chemical properties of the SnO 2-TiO 2 solid solution are all favorable for the SO 2+CO, NO+CO and SO 2+NO+CO redox reactions.