(735g) Tungsten Incorporated Ordered Mesoporous Silicates As Catalysts for Epoxidation of Olefins

Tungsten was incorporated into three dimensional ordered mesoporous silicates (KIT-6 and KIT-5) synthesized by hydrothermal methods. The resulting materials, W-KIT-6¹ and W-KIT-5, were found to have a narrow pore size distribution ranging from 6-9 nm. The surface area decreased from 927 to 625 m²/g and from 798 to 431 m²/g for KIT-6 and KIT-5, respectively with an increase in tungsten content. The synthesized materials show ethylene epoxidation activity to ethylene oxide (EO) at mild temperatures (<40 °C) and pressure (~50 bars) using H₂O₂ as oxidant and methanol as solvent. The EO productivity was highest for low loading of tungsten (Si/W = 100); at this loading, the tungsten is incorporated into the framework of the support and is present in the highly active WO₄ form. Epoxidation activity of tungsten based catalysts is found to be similar to Ag-based catalyst used in conventional process (0.7-4.4 g EO/h/g Ag). At higher metal loadings (or low Si/W ratios), catalytically inactive WO₃ species were observed (XRD and Raman studies). Recycle studies established catalyst durability.

1. Ramanathan, A.; Subramaniam, B.; Badloe, D.; etal. Direct incorporation of tungsten into ultra-large-pore three-dimensional mesoporous silicate framework: W-KIT-6. J Porous Mater, 2011.