| Mesoporous titania with rutile crystal framework was generated by chemical co-precipitation method using titanyl nitrate mixed with urea as precursors and triethylamine as structure–directing agent. The effect of crystalline seeds Sn on the crystal structure was investigated. The anatase mesoporous titania was generated directly by homogeneous precipitation method using titanium sulfate mixed with urea as precursor and octadecylamine as structure–directing agent. Samples with Ti/Ce molar ratios ranging from 1.0/0.0 to 0.0/1.0 were synthesized by co-precipitation method using ammonia water as precipitant. The XRD,TEM,HRTEM,FT-IR,UV-vis,XPS,XAFS and N2 adsorption-desorption isotherm techniques were used to characterize the products.The crystalline seeds SnO2 play an important role in the forming of rutile. BET surface area and pore volume are 252m2·g(1 and 0.34cm3·g(1, respectively, for the rutile mesoporous TiO2.The synthesized anatase TiO2 displayed a wormhole-like mesostructure lacking of long-range order with pore size of 4nm, BET surface area of 35m2·g(1 and pore volume of 0.1cm3·g(1. For the TiO2/CeO2 mixed oxides, it's interesting to notice that cubic fluorite CeO2 crystalline phases were got when Ti/Ce molar ratios were less than 0.8:1.0 and amorphous patterns were observed in the samples with Ti/Ce molar ratios higher than 1.0/1.0. However, pure TiO2 is anatase phase. Some Ti-rich mixed oxides are thermal stable and difficult to crystalline at temperature as high as 500℃. The TiO2/CeO2 mixed oxide powders are well-distributed and composed of rather uniform spherical nanoparticles with particle size about 10nm. Ti-rich nucleus and Ce-rich shell structure are obtained for the TiO2/CeO2 mixed oxides. The coordination number can be 4,5 or 6 for the Ti atom in the TiO2/CeO2 mixed oxides. |
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