银催化剂使用前后的微观变化

使用SEM、XPS和TPR-TPD等仪器表征了工业银催化剂反应前后的微观形态。在SEM中观察到反应后的催化剂表面银粒子，因烧结而导致催化剂表面的形态发生了很大变化．银粒子由于相互聚集而长大，在氧化铝表面大量暴露出来，改变了银与氧化铝之间原有的相互作用形态：XPS和TPR分析说明催化剂表面银主要以金属状态存在：TPD结果说明反应后的催化剂表面对氧的吸附性能发生了很大变化。研究表明：银催化剂活性和选择性的衰减主要是催化剂表面性质的变化所引起的。

Microscopic Feature of Silver Catalyst Pro-and-Aft Reaction

The microscopic feature of silver catalyst pro-and-aft reaction was investigated by use of the instruments SEM, XPS and TPR-TPD. It was found that the morphology on the surface of catalyst of silver particles after reaction by SEM was transformed much, which was caused by nodulizing. The silver particles became larger because of sintering, which exposed largely on the surface of Al2O3. The original interaction morphology between Ag and Al2O3 was altered. The analysis results by XPS and TPR indicated that Ag on the surface of catalyst existed as metal morphology. The absorbility of the surface of catalyst after reaction to oxygen was transformed a lot by TPD. The results show that the decrease of activity and selectivity of the catalyst is caused by the change of its surface properties.