α-Al_(2)O_(3)载体形貌及物性对银催化剂性能的影响

Effect of morphology and physical properties ofα-alumina on performance of silver catalyst

以水合Al_(2)O_(3)和α-Al_(2)O_(3)粉为原料制备银催化剂载体,对载体形貌、比表面积及孔结构等进行表征;采用过量浸渍法制备银催化剂,并对其性能进行评价。表征结果显示,采用纯水合Al_(2)O_(3)制备的载体A0呈交叉片状结晶;在载体原料中添加部分α-Al_(2)O_(3)粉,可导致载体结晶取向发生变化、结晶呈块状,载体中大孔比例增加,但吸水率和比表面积呈降低趋势。实验结果表明,由块状载体A1所制备的催化剂比片状载体A0所制备的催化剂反应温度高;采用α-Al_(2)O_(3)粉Ⅲ和Ⅳ为原料制得的载体A11,吸水率、比表面积与A0相近,堆密度比A0载体提高约17.6%;由A11载体制备的催化剂相比AO载体制备的催化剂反应温度降低8℃,同时环氧乙烷选择性提高0.26百分点。

Theα-Al_(2)O_(3) carriers were prepared from hydrated Al_(2)O_(3) andα-Al_(2)O_(3) powders.The silver catalysts were prepared by impregnation method and evaluated by the micro-reactor.The morphology,specific surface area and pore structure of the carriers were characterized.The results indicate that carrier A0 prepared with hydrated Al_(2)O_(3) tends to form flake crystal,while theα-Al_(2)O_(3) powder contributes to the formation of block crystal in the final carriers.The proportion of macropores increases,the water absorption and specific surface area decrease.The reaction temperature of the catalyst prepared from carrier A1 is higher than that the catalyst prepared from carrier A0.Carrier A11 prepared byα-Al_(2)O_(3)ⅢandⅣshows a block crystals uniformly,and the bulk density of A11 is 17.6%higher than that of A0.The reaction temperature reduces by 8℃and ethylene oxide selectivity increases by 0.26 percentage point on the catalyst prepared from A11 comparing with that catalyst prepared from A0.