TiO_2-SiO_2复合氧化物的理化性质及其对柴油加氢精制性能的影响

Physicochemical properties of TiO_2-SiO_2 composite oxide and their effects on diesel hydrorefining performance

采用溶胶凝胶法结合CO2超临界流体干燥技术制备了不同Ti/Si原子比的TiO2SiO2复合氧化物(TSn),考察了Ti/Si原子比、焙烧温度对复合氧化物比表面积、孔结构、酸性及原子结合状态的影响,通过重油催化裂化柴油加氢精制反应考察了以TS1、TS4为载体的催化剂脱硫性能的差异.结果表明,TiO2经SiO2复合改性后,热稳定性和晶态稳定性大幅度提高;TiO2SiO2复合氧化物的酸性及原子间的相互作用与Ti/Si原子比有直接的关系;载体的晶态组成及酸性和催化剂的酸性对催化剂的加氢脱硫性能有显著影响,复合氧化物中锐态型TiO2的存在强化了载体与金属组分之间的相互作用,提高了催化剂的加氢脱硫活性,不同类型的酸性中心对柴油中不同类型的硫化物具有不同的脱除能力,Brnsted酸中心较多的催化剂对结构简单的硫化物脱除能力强,Lewis酸中心较多的催化剂对结构复杂的硫化物有较好的脱除效果.

A series of TiO2-SiO2 composite oxides, with different Ti/Si atomic ratios, were obtained by using the sol-gel method combined with the CO2 supercritical fluid drying （SCFD） method. The effects of the Ti/Si atomic ratio and calcination temperature on the properties of TiO2-SiO2 composite oxides, including specific surface area, pore structure, acidity and atomic coordination, were studied. The hydrodesulfurization （HDS） property of catalysts supported on TS-1 and TS-4 was investigated by using the residual fluid catalytic cracking （RFCC） diesel oil as feedstock. The experimental results showed that the pore structure stability and crystalline state stability of TiO2 modified by SiO2 increased dramatically. The acidity and interaction between the atoms of the TiO2-SiO2 varied with Ti/Si atomic ratio. The crystalline state and acidity of supports influenced the HDS property of catalysts. The presence of anatase TiO2 in the TiO2-SiO2, strengthened the interaction of the supports and active metals, and enhanced the HDS activity of the catalysts. The different acidic sites of catalysts showed different HDS properties to different type of sulfur compounds. The catalysts with a larger number of BrSnsted acidic sites showed better HDS performance for the simple structure sulfur compounds. On the contrary, the catalysts with a larger number of Lewis acidic sites showed better HDS performance for the complicated structure sulfur compounds.