Acidic Property and Catalytic Activity of Tungsten Oxide

Abstract

Abstract A maximum activity of tungsten oxide for the isomerization of 1-butene was observed when the catalyst was evacuated at 600 °C, the ratio of cis-2-butene to trans-2-butene being 1.4. The activity was lost by the addition of NH3, but not affected by the addition of CO2 or H2O. The oxidation states of tungsten oxide treated with hydrogen at 550 and 650 °C were WO2.89 and WO2, respectively. The activity of WO2.89 for the double bond isomerization of 1-butene was almost the same as that of WO3 but the activity of WO2 for the double bond and skeletal isomerization of 1-butene and the dehydration of isopropanol was higher than that of WO3 or WO2.89· The coisomerization of cis-2-butene-d0/d8 revealed that the double bond isomerization of butenes proceeds by an intermolecular hydrogen transfer mechanism. When cis-2-butene-d8 was introduced to the catalyst on which cis-2-butene-d0 had been preadsorbed, the reactant and the product containing much of H were obtained, no d0-species being observed. It was concluded that the active sites for the isomerization of butenes are protons of polymerized butene formed by the adsorption on Lewis acid sites of tungsten oxide surface and the isomerization takes place via carbenium ion intermediates.