Improved Stabilization of Sulfated Zirconia by Molybdenum: Synergy of Metal Sites and Acid Sites in the n-Hexane Hydro-Isomerization

Hydrogen has a crucial role in preventing deactivation of sulfated zirconia (ZS). Hydro-isomerization of n-hexane is carried out with (ZS) doped with molybdenum mechanically mixed platinum supported by alumina. This catalyst presents an important improvement of the activity and stability compared to the non-doped one. At 443 K, doped and non-doped catalysts present, respectively, the activities 3 x 10(-8) and 2 x 10(-8) molL(-1) g(-1). By increasing temperature, while doped catalyst activity rises to 2.6 x 10(-7) molL(-1) g(-1), the activity of the non-doped one drops to 3.4 x 10(-9) molL(-1) g(-1). Characterization of solids by XRD shows the presence of ZrO2 tetragonal phase in all the solids. Raman spectroscopy confirms this finding. UV-Visible spectroscopy shows influence of calcination temperature on molybdenum geometry. At low temperature (673 K), specific surface area is developed (S-BET = 144 m(2) g(-1)) and the metal is in tetrahedral geometry as MoOx. Those sites enhance acidity and generate acid sites utilizing an atomic-scale spillover effect of H-2 on platinum particles.