directsynthesisofwsba15mesoporousmolecularsievesandtheircatalyticperformanceforepoxidationofcyclohexene

Abstract

Tungsten-containing mesoporous molecular sieves W-SBA-15 were synthesized under conventional hydrothermal conditions in strong acidic solution using Na2WO4 or H2WO4 as tungsten source and tetraethyl orthosilicate as silicon source. The molecular sieves were characterized by means of small angle XRD, N-2 adsorption, FT-IR, UV-Vis, SEM and XRF. When only P123 (EO20PO70EO20) was used as structure directing agent, the tungsten content in W-SBA-15 was half that in gel solution. While the mixture of P123 and cetyltrimethylammonium bromide was used as template, the tungsten in gel solution can be effectively incorporated into W-SBA-15. H2WO4 was more effective as tungsten source than Na2WO4. When the Si/W ratio was 40 in gel solution, the tungsten species in W-SBA-15 were highly dispersed. The W-SBA-15 materials had a high catalytic activity for epoxidation of cyclohexene