In2O3-doped Pt/WO3/ZrO2 as a novel efficient catalyst for hydroisomerization of n-heptane Original Research Article

A series of Pt catalysts supported on In2O3-doped (In/Zr molar ratio = 0.01–0.04) WO3/ZrO2 (9–24 wt.% WO3) have been tested for the hydroisomerization of n-heptane at 473 K. Several techniques including X-ray diffraction, N2 adsorption, CO chemisorption and X-ray photoelectron spectroscopy were applied to characterize the physicochemical properties of the as-synthesized materials. The catalytic activity is strongly dependent on the surface WO3 loading and In/Zr ratio. The maximum activity was observed for the sample with a In/Zr molar ratio of 0.02, which gave 72% n-heptane conversion and 96% C7 isomer selectivity at 473 K, and can be kept constant over 80 h under reaction reactions. The incorporation of small amounts of In2O3 into Pt/WO3/ZrO2 increases the activity significantly (from 37% to 72%) and improves the isomerization selectivity moderately (from 90% to 96% at a conversion of 72%). The results of cumene cracking reveal that the remarkable activity and selectivity of the In2O3-promoted catalysts are caused by an enhancement in the number of Brønsted acid sites under reaction conditions and in the hydride transfer reaction rate of isomerized carbenium ions with hydride ions originating from hydrogen molecules.