Influence of preparative method on Al2O3-doped Pt/WO3-ZrO2 catalyst for n-heptane isomerization

Alumina-doped Pt/WO3/ZrO2 catalysts were prepared using either a constant or variable pH method. The obtained catalyst samples were characterized using N-2 adsorption, X-ray diffraction, ultraviolet-visible diffuse reflectance, CO chemisorption, X-ray photoelectron spectroscopy, Al-27 magic-angle spinning nuclear magnetic resonance, and infrared spectroscopy of adsorbed pyridine. Compared to the catalyst prepared using the variable pH method, the catalyst prepared using the constant pH method had a higher surface area and Pt dispersion. More Bronsted acid sites were generated in the presence of H-2 on the latter catalyst, and this was responsible for its higher catalytic activity in n-heptane hydroisomerization. When the reaction temperature was 200 degrees C and the weight hourly space velocity of n-heptane was 0.9 h(-1), the Pt/WO3/Al2O3-ZrO2 catalyst prepared using the constant pH method gave 70.0% conversion of n-heptane, which was significantly greater than the conversion obtained using the corresponding catalyst prepared using the variable pH method (43.5%). (C) 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.