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

The effect of a gas pretreatment atmosphere (pure N-2, pure H-2 and mixed H-2/N-2) 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 H-2 pretreatment showed the highest catalytic performances. As revealed by various characterization results from N-2 physisorption, XRD, XPS, TEM, SEM-EDX, UV-Vis, Raman, H-2-TPR, and NH3-TPD techniques, the WO2.83 phase occurring from the H-2 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 H-2-treated non-calcined WO3/SiO2 catalyst.