丁二烯在Ba,Cs,Cl促进的Ag/α-Al_2O_3催化剂上的环氧化反应及稳定性研究

Epoxidation of Butadiene and Stability over Ba,Cs and Cl-promoted Silver Catalysts

在Ba、Cs、C l促进的Ag/α-A l2O3催化剂上,考察了丁二烯的环氧化反应,获得较高的丁二烯转化率和乙烯基环氧乙烷选择性.在未添加卤代烃致稳剂条件下,催化剂短期稳定性超过140 h.并对反应前后的催化剂进行了XRD、TEM、XPS等晶相和表面分析.XRD结果表明催化剂经短期稳定性试验后,银的平均粒径变化不大,但TEM分析表明在银催化剂的局部有银颗粒的板结;而XPS结果表明催化剂表面C l有流失,Cs有富集.Cs-Ag的相互作用有可能促进吸附于Cs-A l活性位的氧物种插入吸附于Ag上的丁二烯.

The epoxidation of butadiene over Ba, Cs and Cl-promoted Ag/α-Al2O3 catalyst has been studied, and a high butadiene conversion and selectivity of vinyloxirane could be obtained. The stability test of catalyst indicates that the operation time can exceed 140h without adding hydrocarbon halide. The catalyst structure changed during the long-term reaction has been characterized by using XRD, TEM and XPS techniques. Average silver size of reac-ted catalyst has not changed apparently compared with fresh catalyst by XRD, but partly assembled silver grain was observed by TEM. Cs enrichment and Cl loss of catalyst surface in some extent were found from XPS after reaction.The effects of Cs on Ag are possible to promote an insert of oxygen species adsorbed on Cs-Al sites to butadiene adsorbed on Ag.