【摘要】 用沉积 沉淀法制备了Au/TiO2 系列催化剂 ,并用XRD ,TG DTA ,BET ,TEM和IR等技术对催化剂的物相、组成和表面结构进行了表征 ,利用微反对催化剂在丙烯环氧化反应中的活性进行了评价 .结果表明 ,Au/TiO2 催化剂的比表面积在 10 0m2 /g以上 ,Au粒子以纳米级超细颗粒均匀分散在锐钛矿型TiO2 的表面 .催化剂表面的活性相是Lewis酸位Tin + 与Au粒子 ,Au可以吸附氢与氧并将其转化为过氧化物 .在 5 0～ 15 0℃温度范围内 ,丙烯的转化率为 0 5 6 %～ 1 16 %,环氧丙烷的选择性在 87%以上 .原料气中H2 或O2 的含量增大时 ,丙烯的转化率随之升高 .在催化剂中引入碱金属或碱土金属的硝酸盐作为助剂 ,可以不同程度地提高催化剂的活性 .更多还原

【Abstract】 The support TiO 2 was prepared by hydrolyzing Ti(OC 4H 9) 4 and the supported Au/TiO 2 catalyst was prepared by deposition-precipitation method. After Au was supported on Ti(OH) 4, the nitrate promoter was added into the catalyst precursor by impregnation method. The surface composition, phase, structure, particle size and specific surface area of the catalyst were studied using XRD, TG-DTA, BET, TEM and IR techniques. After calcined at 300 ℃ for 3 h, part of TiO 2 in the catalyst has crystallized into anatase state while Au is in micro-crystal state. The specific surface area of TiO 2 support and Au/TiO 2 catalyst is over 100 m 2/g. Au is not in oxidized state but in metal state, dispersed homogeneously on the catalyst surface as nano-sized particles. On the surface of Au/TiO 2 catalyst, Ti n+ is Lewis acid site, bonded mutually and formed Ti-O-Ti bridge bonds. The catalytic activity of Au/TiO 2 catalyst was tested in a micro-reactor through direct epoxidation of propylene with O 2 and H 2. Under the conditions of atmosphere pressure and 50～150 ℃, the conversion of propylene is 0.56%～1.12% and the selectivity for propylene oxide is over 87%. The increase of H 2 or O 2 in the feed can lead to enhance of C 3H 6 conversion. In the Au/TiO 2 catalyst, both Au and Ti n+ are active phase. In the reaction, Au particles adsorb O 2 and H 2, and transform them into peroxide species, which oxygenize propylene into propylene oxide. Addition of alkali metal or alkaline earth metal nitrates can increase the propylene conversion and propylene oxide yield while the change of propylene oxide selectivity is not obviously.更多还原