Oxidative Dehydrogenation of Propane to Olefins Promoted by Zr Modified ZSM-5

Several ratios of highly active Zr modified ZSM-5 catalysts with good stability were prepared via the sol-gel method for oxidative dehydrogenation of propane (ODHP) to olefins (C2H4 + C3H6). The influence of ZSM-5 modification with Zr was studied, and the catalysts were thoroughly characterized with respect to structural morphology, crystallinity, specific surface area, ionic state, and surface acidity. The results showed that Zr modification of ZSM-5 leads to increased pore volume and crystallite size. The morphological and elemental analysis indicated irregularly nano-sized Zr/ZSM-5 catalysts, with a homogeneous dispersion of Zr particles and increased lattice oxygen. The incorporation of Zr to ZSM-5 moderated the surface acidity, caused an increase in the distribution of surface acid strength, and decreased the weak acid sites ratio, making it suitable for olefin selectivity. Zr/ZSM-5 (1:4) exhibited the best catalytic yield and long-time stability towards continuous propane conversion (59.48%), which was accompanied by 87.44% olefins selectivity and olefin yield of 52.23% due to the moderated acidic sites coupled with an increment in the lattice oxygen. Hence, this work offers insight into tuning the surface acidity of zeolites material that enhances superior mass transfer of reactants and products and has better stability and potential to be employed in ODHP applications. [GRAPHICS] .