助剂对Au/TS-1催化丙烯气相直接环氧化活性的影响

Direct Epoxidation of Propylene on Promoted Au/TS-1 Catalyst in Gas Phase

采用沉积-沉淀法制备了Au／TS-1催化剂，考察了碱金属和碱土金属助剂对Au／TS-1催化剂在H2与02同时存在条件下丙烯气相直接环氧化反应的影响。实验结果表明，添加助剂的Au／TS-1催化剂的活性均有所提高，且环氧丙烷（PO）的选择性保持在90％左右。当载体中n（Si）：n（Ti）=100时，Au／TS-1催化剂（Au质量分数为0．13％）上的PO生成速率为25g／（h·kg），而添加K的Au—K／TS—1催化剂（Au质量分数为0．08％，K质量分数为0．14％）上的PO生成速率为44g／（h·kg），活性提高了近80％。表征结果显示，加入碱金属使Au颗粒变小（粒径为1～2nm），分散更加均匀，从而提高了催化剂的丙烯环氧化活性；而加入碱土金属后，催化剂上的Au负载量增加，也使催化剂活性有所提高。

A series of Au/TS-1 catalysts promoted with alkali metal or alkaline earth metal were prepared by deposition-precipitation and used in direct epoxidation of propylene in co-presence of H2 and 02. Addition of alkali metal or alkaline earth metal obviously increased formation rate of propylene oxide（PO）. When mole ratio of Si to Ti in TS-1 molecular sieves was 100, PO formation rate on Au/TS-1 catalyst（Au mass fraction was 0. 13% ） was 25 g/（h · kg）, while a K promoted Au-K/TS-1 catalyst（Au mass fraction is 0. 08%, K mass fraction is 0. 14% ） gave a PO formation rate of 44 g/（h · kg） ,almost 80% more than that on the unpromoted. The enhancement attributed to smaller particle sizes of Au diameter （ 1 - 2 nm） in alkali metal nitrate modified catalysts, while improvement of alkaline earth metal nitrate modified catalysts is due to increasing of Au loading induced by addition of formers.