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

WO3-ZrO2 catalysts for n-butane isomerization were prepared by several different procedures. The influence of a Pt promotor on catalyst activity and selectivity was investigated. Possible Pt-W interactions were particularly studied. It was found that Pt strongly interacted with the WO3-ZrO2 support, which impeded reducibility and decreased H-2 chemisorption capacity acid dehydrogenation activity. At low Pt content hydrogenolytic activity and Ha chemisorption were absent. The interaction depends on the distribution of WO3 on the ZrO2 surface. The preparation conditions such as time of stabilization 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 correlation between H-2 chemisorption at room temperature, cyclohexane dehydrogenating activity and the capacity to dehydrogenate n-C-4. This is due to the fact that the three measurements are performed at different temperatures, with quite different reaction rates and thermodynamic feasibilities. (C) 1999 Elsevier Science B.V. All rights reserved.