Vapor-phase epoxidation of propylene using H2/O2 mixture over gold catalysts supported on non-porous and mesoporous titania-silica: effect of preparation conditions and pretreatments prior to reaction
Vapor-phase epoxidation of propylene using H2/O2 mixture over gold catalysts supported on non-porous and mesoporous titania-silica: effect of preparation conditions and pretreatments prior to reaction
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DOI：
10.1016/j.apcata.2003.11.034
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发表时间：
2004-05
影响因子：
5.5
通讯作者：
C. Qi;M. Okumura;T. Akita;M. Haruta
中科院分区：
文献类型：
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作者：
C. Qi;M. Okumura;T. Akita;M. Haruta
以ti掺杂无孔二氧化硅为载体，采用沉积-沉淀法制备了用于环氧丙烷与o2和H2直接气相环氧化反应的纳米金催化剂。在室温下真空干燥的催化剂和在空气中573K煅烧的催化剂即使在低至323K的温度下也表现出形成PO的催化活性。煅烧后的催化剂在高温下比干燥后的催化剂更稳定，活性更强。悬浮液老化后的简单过滤使催化剂的活性和选择性更高，但稳定性不如完全洗涤固体前驱体。与Au/Ti-MCM催化剂相反，在氩气中预处理的Au催化剂的催化活性和H2efficiency明显高于在ti掺杂的无孔二氧化硅上沉积的Au催化剂。不同孔隙率的二氧化钛载体上的Au催化剂失活率相似，说明Au催化剂在数小时内的快速失活主要受表面性质的影响，而不是受载体的孔隙结构和扩散限制的影响。
Ti-doped nonporous silica was used as a support to prepare nanometer gold catalysts by the deposition–precipitation method for the direct vapor-phase epoxidation of propylene with O2and H2. Both the catalysts dried under vacuum at room temperature and the catalysts calcined at 573K in air exhibited catalytic activity to form PO even at a temperature as low as 323K. The calcined catalysts were more stable and more active at higher temperatures than the dried catalysts. Simple filtration after aging the suspension resulted in the catalysts more active and selective but less stable than the complete washing of the solid precursors. Pretreatment in argon appreciably increased the catalytic activity and H2efficiency over the Au catalysts deposited on Ti-doped nonporous silica, which was opposite to the case of Au/Ti-MCM catalysts. Similar deactivation rate of Au catalysts supported on a variety of titania–silica supports with different porosities suggests that quick deactivation of Au catalysts within hours is mainly affected by the surface properties rather than the pore structure and diffusion limitation of the supports.