Characterization and catalytic activity of Pt supported on Pt/ZrO2Al2O2-WO3 prepared by sol-gel

Abstract

The catalysts with 1.0 wt% amounts of Pt supported on ZrO2-Al2O3-W03 (ZrO2 70 wt%; Al2O3 17.5 wt%; ZrO2 12.5 wt%) prepared by sol-gel in the isomerization of n-heptane. The catalysts were characterized by N2 physisorption, XRD, TPR and FT-IR of adsorbed pyridine. The preparation of ZrAlW mixed oxides by sol-gel favored the high dispersion of WO3 and the stabilization of zirconia in the tetragonal phase. The Al2O3 incorporation avoided the formation of monoclinic WO3 bulk phase and increase surface area of the catalysts. Various oxidation states of WO3 species coexist on the surface of the catalysts after calcination. The improvement in the activity of Pt/ZrAlW catalysts is ascribed to a moderated acid strength and acidity, which can be correlated to the coexistence of W⁶⁺ and reduced-state WO_x species. Selectivity results showed that the catalyst produced 2MH, 3MH and the high octane 2,3DMP, 2,4DMP isomers.