n-Butane isomerization on Pt/WO3-ZrO2: effect of the Pt incorporation

WO3-ZrO2 catalysts for n-butane isomerization were prepared by several diff erent procedures. The influence of a Pt promotor on catalyst activity and s electivity was investigated. Possible Pt-W interactions were particularly s tudied. It was found that Pt strongly interacted with the WO3-ZrO2 support, which impeded reducibility and decreased H-2 chemisorption capacity acid d ehydrogenation activity. At low Pt content hydrogenolytic activity and Ha c hemisorption were absent. The interaction depends on the distribution of WO 3 on the ZrO2 surface. The preparation conditions such as time of stabiliza tion of the WO3 precursor solution and the type of precursor used are very important for the catalytic activity. For Pt/WO3-ZrO2, there was no correla tion between H-2 chemisorption at room temperature, cyclohexane dehydrogena ting activity and the capacity to dehydrogenate n-C-4. This is due to the f act that the three measurements are performed at different temperatures, wi th quite different reaction rates and thermodynamic feasibilities. (C) 1999 Elsevier Science B.V. All rights reserved.