Synthesis and characterization of transition metal oxide-pillared materials with mesoporosity from layered silicate ilerite

摘要

Metal oxide (Ti, Fe, Zr)-pillared porous materials with various surface areas have been synthesized by the intercalation of metal organic between the layers of layered silicate ilerite. The surface areas of metal oxide-pillared ilerite materials depended significantly on pillaring time and the type and amount of pillaring metal oxide. The surface areas of Ti-, Fe- and Zr-ilerite materials were in the range of 152-338,150-290 and 147-245 m~2/g, respectively, depending on the pillaring condition. The results from X-ray diffraction and N_2 adsorption-desorption isotherms demonstrated that metal oxide-pillared ilerite materials possessed different pore structures from silica-pillared ilerite materials, due to the different nature of metal oxide and silica pillars. The gallery heights of Ti-, Fe- and Zr-ilerite materials were in the range of 3.55-4.05, 2.55-3.65 and 3.25-3.95 nm, respectively, which are 1-2 nm larger than that of silica-pillared ilerite materials. In addition, metal oxide-pillared ilerite materials exhibited the pore size distributions of mesoporosity. In the case of the metal oxide-pillared ilerite materials with homogeneous pore structures, the average pore diameters were in the range of about 2-5 nm, depending on the type of pillared metal oxide. Ti-ilerite materials exhibited relatively narrow range of pore size distribution. On the other hand, Fe-ilerite materials exhibited broad range of pore size distribution. The results from NH_3-TPD and IR measurements revealed that the metal oxide pillaring into the interlayers of ilerite produced acid sites and new hydroxyl groups. Zr-ilerite materials possessed a broad range of acid sites from weak to medium acidity, whereas Ti-ilerite and Fe-ilerite materials had only weak acid sites.