Metathesis of ethylene and cis-2-butene under the catalysis of magnesium–tungsten oxide catalysts

Abstract

The effect of MgO on the WOx-catalyzed metathesis reaction of cis-2-butene and ethylene was studied using a series of magnesium-tungsten oxide catalysts for the first time. First, five experiments with different catalyst bed configurations in a fixed-bed tubular microreactor were carried out first. The results showed that MgO hardly affects the metathesis of ethylene and 2-butene, but will influence the cross-metathesis of 2-butene and 1-butene through affecting the isomerization between them. Next, six kinds of bimetallic magnesium–tungsten oxide catalysts were prepared by four incipient wetness impregnation methods to test whether there is a synergistic effect between MgO and WO3. The catalysts were characterized by XRD, UV-Raman, NH3-TPD, N2 adsorption–desorption and Py-IR. The results showed that MgO is not suitable to be used as the support for its excellent isomerization activity. The isomerization on the catalyst surface should be caused by basic sites on MgO. However, the addition of MgO to the bimetallic catalysts can increase the Lewis acid sites, which is useful to improve the metathesis activity. We hope these results will help future studies in the clarification of the complex mechanism of metathesis catalyzed by WO3/SiO2 and MgO, and in the development of new metathesis catalysts with higher activity.