氧化硅改性α-氧化铝载体对银催化剂结构与性能的影响

 通过硅溶胶浸渍方法，对已制成的α-氧化铝载体进行了表面改性，在孔表面上沉积了氧化硅改性层。孔结构测定表明，少量沉积没有明显改变载体的孔结构，所以对反应物和产物的物质传输不会产生明显的影响。改性载体负载银催化剂的氧吸附测试和催化性能评价结果表明，改性对单负载银催化剂上活性组分银的分散状况影响不大，但对催化性能产生明显的影响，催化活性明显降低，最高降幅达63%，选择性略有提高（提高0.5～3.4%）。分析表明，改性引起载体与银之间相互作用发生变化，这是催化性能发生明显变化的主要原因。该改性方法简单易行，且可以排除孔结构差异对催化剂性能的影响，可用于对比不同载体材料对负载型银催化剂性能的影响，具有一定的普遍意义。

EFFECTS OF α-Al2O3 SUPPORT MODIFIED BY SiO2 ON STRUCTURE AND PERFORMANCE OF SILVER CATALYST

By impregnating prepared silver catalyst supports with silica sol, amorphous silica layer was deposited over the pore surface of the supports and modified supports were prepared. Supports and catalysts were characterized with Mercury Porosimeter, TEM , XRD and Pulse Oxygen Adsorption measurement. Catalytic performances were evaluated by ethylene epoxidation reaction in micro-reactor. Experimental results indicated that modification had little infliences on both the pore structure of modified supports and the silver dispersion of the non-promoted catalysts, but the catalytic properties of silver catalysts varied obviously. The activitity of catalysts declined significantly (by 63% at most) and the selectivity increased slightly(0.5～3.4%). This modification method is simple while it can eliminate the effects of pore structure on catalytical performances and can be used to compare the effects of varieties of support materials on catalytical properties of silver catalyst.