Effect of pretreatment atmosphere of WOx/SiO2 catalysts on metathesis of ethylene and 2-butene to propylene

Abstract

The effect of a gas pretreatment atmosphere (pure N₂, pure H₂ and mixed H₂/N₂) on the metathesis reaction between ethylene and 2-butene to propylene over calcined and non-calcined WO₃/SiO₂ catalysts was investigated. The non-calcined catalysts exhibited higher activity than the calcined catalysts under different gas pretreatment atmospheres. The non-calcined catalyst with the use of pure H₂ pretreatment showed the highest catalytic performances. As revealed by various characterization results from N₂ physisorption, XRD, XPS, TEM, SEM-EDX, UV-Vis, Raman, H₂-TPR, and NH₃-TPD techniques, the WO_2.83 phase occurring from the H₂ pretreatment of the non-calcined catalyst played an important role on the high activity of the catalyst. In addition, better tungsten dispersion, higher isolated surface tetrahedral tungsten oxide species, and W⁵⁺ species were obtained on the H₂-treated non-calcined WO₃/SiO₂ catalyst.