Effect of 2-Butene Cis/Trans Isomers in the Metathesis of Ethylene and 2-Butene Over WO.sub.3/SiO.sub.2 Catalysts

Pure 2 % trans-2-butene and the mixture of 1 % cis- and 1 % trans-2-butene were used as feed to react with ethylene in metathesis reaction in order to produce propylene to study the effect of feed on WO.sub.3/SiO.sub.2 catalysts with various tungsten oxide loadings (5, 7, 9, and 11 wt%), which were prepared by incipient wetness impregnation. These catalysts were characterized by X-ray diffraction, nitrogen adsorption (BET), scanning electron microscopy, energy dispersive X-ray spectroscopy, ion-exchange titration, FT-Raman, ammonia temperature programmed desorption (NH.sub.3-TPD) and reactant-TPD. At high tungsten oxide loading, when the mixture of cis- and trans-2-butene was used as the reaction feed the conversion of 2-butene was lower than when pure trans-2-butene was used. However, the effect of cis-2-butene isomer on the conversion of 2-butene was less pronounced at low tungsten oxide loading. The dispersion of tungsten was a key factor to improve the activity of the tungsten catalysts when the mixture of cis- and trans-2-butene was used as a feed for metathesis reaction.