Design, synthesis and catalytic performance of vanadium-incorporated mesoporous silica KIT-6 catalysts for the oxidative dehydrogenation of propane to propylene

Abstract

A series of vanadium-incorporated mesoporous materials V-KIT-6 with different vanadium contents were synthesized by combining a direct hydrothermal method with a pH adjusting method and applied as catalysts for the oxidative dehydrogenation of propane. The structures of the catalysts were characterized by various techniques including N₂ adsorption–desorption, XRD, TEM, SEM, UV-vis DRS, H₂-TPR and Raman spectroscopy. The results reveal that the pH value plays a key role in the structure of the catalysts and the incorporated content of vanadium in the synthesis process of V-KIT-6 materials. The framework-incorporation of various contents of vanadium under mild acidic conditions (pH = 5) preserves the well-defined 3D interconnected mesoporous features of KIT-6 and promotes the dispersion of vanadium oxide species. The V-KIT-6 catalysts show much higher catalytic selectivity and productivity to propylene in the oxidative dehydrogenation of propane than the corresponding supported vanadium catalyst. The highest selectivity sum of C₂H₄ + C₃H₆ (70.2%) is obtained over the 5V-KIT-6 catalyst; meanwhile, a high space-time yield (STY_C3H6) of 3.91 kg_propylene kg_cat⁻¹ h⁻¹ is obtained. The superior catalytic performance of the V-KIT-6 catalysts in the oxidative dehydrogenation of propane can be ascribed to the high concentration of highly dispersed active sites as well as the favorable property of mass transfer and accessibility of the active sites to the reactant molecules in the 3D interconnected mesopores.