磷酸盐改性对TS-1分子筛及其丙烯液相环氧化性能的影响

丙烯和过氧化氢在钛硅沸石TS-1上的液相环氧化反应是合成环氧丙烷HPPO新工艺的核心.首先比较了 3种酸性磷酸盐溶液(磷酸二氢铵、磷酸二氢钾和磷酸二氢钠)和两种碱性磷酸盐溶液(磷酸氢二钠和磷酸三钠)浸渍改性对TS-1沸石及其环氧化性能的影响,发现酸性磷酸盐溶液改性可以明显提高TS-1的过氧化氢转化率和环氧丙烷选择性,但...

Effect of Phosphates Modification on TS-1 Zeolite and its Catalytic Performance in Epoxidation of Propylene and Hydrogen Peroxide

Liquid-phase epoxidation of propylene and hydrogen peroxide over titanium silicalite-1 (TS-1) is the basis of the new HPPO technology for propylene oxide synthesis. A comparative study was conducted to gain insight into the effects of impregnation modification of acidic phosphate solutions (ammonium dihydrogen phosphate, monopotassium phosphate and monosodium phosphate) and alkaline phosphate solutions (sodium hydrogen phosphate and sodium phosphate) on TS-1 zeolite and its catalytic performance in the epoxidation. Results show that impregnation modification with the acidic phosphate solutions can notably increase both hydrogen peroxide conversion and selectivity of propylene oxide of TS-1, However, impregnation modification with the alkaline phosphate solutions can obviously deteriorate the catalytic performance of TS-1. Therefore, only the acidic phosphate modified TS-1 catalysts were focused in sample characterizations. Results indicate that the reason why the TS-1 catalysts modified with the acidic phosphates exhibit improved catalytic performances mainly lies in the interactions of phosphate anion species with tetra-coordinated titanium and hexa-coordinated species. Said interactions should be weak since it would be unbound by water rinse and the phosphate anion species would be washed away. Even so, the interactions seem enough to passivate the hexa-coordinated titanium species and to modify the local environment of the tetra-coordinated titanium active sites.