添加含铝化合物A对α-氧化铝载体的影响

Effect of Aluminium Compound A on the Properties of α-Alumina Carrier

在制备α-氧化铝载体时加入含铝化合物A,会影响载体焙烧过程中氧化铝的转晶过程,改变晶体形貌,同时影响载体抗压强度、吸水率及孔结构等物性。采用颗粒强度测定仪、压汞仪、物理吸附仪、扫描电子显微镜等手段表征含铝化合物A的加入对载体物性的影响。用该载体制备银催化剂,并评价银催化剂的反应性能。实验结果表明,随含铝化合物A加入量的增大,载体吸水率及孔容逐渐降低,晶体形貌逐渐由"片状"向"片状与块状同时存在"继而向"块状"转变;当含铝化合物A粒度较大时,载体平均孔径较大,比表面较低。加入适量粒度较大的含铝化合物A对催化剂选择性改善较为明显。

In the synthesis of a-Alumina carrier, the addition of Aluminium compound A would affect the crystal transformation during the calcination, and change the crystal morphology, which influenced the compressive strength, water absorption and pore structure properties of the carrier. Many characterizations were used to investigate the effects of aluminium compound A on the carrier, such as strength analyzer, mercury penetration method, physical adsorption apparatus and scanning electron microscope. Silver catalysts were prepared with these carriers, and their catalytic performances were evaluated for the epoxidation of ethylene to ethylene oxide. The results show that with the addition of aluminium compound A, the water absorption and pore volume decreased, and the crystal morphology changed from ＂flake＂ to ＂flake and block mixed＂ and then to ＂block＂ gradually. Furthermore, the larger the size of the aluminium compound A was, the larger the average pore size and the lower the specific surface area. The selectivity of the silver catalyst was improved obviously with the addition of appropriate aluminium compound A.