钛硅分子筛中铝杂质对其性能的影响

Effect of Aluminum Impurity on Performance of Titanium Silicalite

以四丙基溴化铵为模板剂 ,以硅溶胶为硅源 ,采用水热合成法制备了不同铝杂质含量的钛硅分子筛 ,并系统考察了铝杂质对钛硅分子筛性能的影响 .结果表明 ,原料中的铝杂质可促进钛硅分子筛晶化 ,但同时也引入了酸性中心 ;在丙烯环氧化反应中 ,铝杂质形成的酸性中心会催化环氧丙烷与溶剂的副反应 ;加入少量碱性添加物可抑制铝杂质的酸催化作用 ,提高环氧丙烷的选择性 。

Titanium silicalite TS-1 containing different amount of aluminum impurity was synthesized using tetrapropylammonium. bromide (TPABr) as the template and using colloidal silica as the silica source. The effect of aluminum impurity on the performance of titanium silicalite was systematically investigated. It was shown that a little amount of aluminum impurity can improve the crystallization of titanium silicalite, but some acid sites are introduced into the sample simultaneously. The acid sites originated from framework aluminum can catalyze the side reaction of propylene oxide (PO) with the solvent methanol in propylene epoxidation. If a small amount of base is added into the medium, the side reaction can be inhibited and the PO selectivity can increase significantly. But the excess base can deactivate the titanium silicalite TS-1 catalyst. The titanium silicalite catalyst exhibited excellent performance for propylene epoxidation both in the autoclave reactor and in the fixed-bed reactor. All of the criteria such as H2O2 conversion X(H2O2),H2O2 utilization efficiency U(H2O2) and PO selectivity S (PO) still kept above 90% when the time on stream in the fixed-bed reactor reached 200 h.