TPAOH-NH3·H2O溶液处理TS-1/SiO2对丙烯环氧化反应影响

将SiO₂负载的钛硅分子筛(TS-1/SiO₂)用四丙基氢氧化铵和氨水混合溶液处理并用于催化丙烯环氧化制环氧丙烷反应。结果表明,混合溶液处理的钛硅分子筛比用四丙基氢氧化铵或氨水单独处理的样品具有更好的催化性能。随着混合碱中氨水浓度从0.01 mol·L^-1增加到0.03 mol·L^-1,附着在分子筛表面的二氧化硅载体消失,可能被溶解并再结晶到分子筛表面。同时,在此溶解再结晶过程中,分子筛内部产生许多介孔,使其催化性能显著提升,而二氧化硅表面酸性位被消除。四丙基氢氧化铵和氨水协同作用产生大的介孔,有利于高分子量副产物扩散出催化剂粒子,导致催化剂稳定性明显提升而催化活性和选择性不受影响。

Effect TPAOH-NH3·H2O solution treatment on catalytic performance of TS-1/SiO2 for propylene epoxidation

Titanium silicate-1 (TS-1)/SiO₂ extrudates were post-treated with NH₃·H₂O and tetrapropyl ammonium hydroxide (TPAOH), studied in propylene epoxidation with hydrogen peroxide in fixed-bed reactor.The results demonstrated that the TS-1 treated with mixed bases showed better catalytic performance than that treated with NH₃·H₂O or TPAOH alone.When NH₃·H₂O concentration increasing from 0.01 mol·L^-1 to 0.03 mol·L^-1 in post treatment,particles of SiO₂ supports disappeared, which might be dissolved and recrystallized on TS-1 crystals.At the same time,TS-1 crystals also pass dissolution and recrystallization process with large number of mesopores formed inside.Catalytic properties of TS-1 greatly enhanced, while acid sites from SiO₂ surface depleted.Large pores created by synergetic effect of ammonia and TPAOH facilitated diffusion of high molecular weight by products resulting in appreciable improvement of catalyst stability while activity and selectivity not influenced.