Effect of pretreatment atmosphere of WO(x)/SiO(2) 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 WO(3)/SiO(2) 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 NH(3)-TPD techniques, the WO(2.83) 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 W(5+) species were obtained on the H(2)-treated non-calcined WO(3)/SiO(2) catalyst.