Role of methods and conditions of preparation of vanadium species supported on lamellar zeolite MCM-36 in their catalytic behaviour in oxidative dehydrogenation of propane

Abstract

In this work, we report successful preparation of hierarchical VOx-MCM-36 catalysts. Lamellar pillared zeolitic support (MCM-36) was prepared from layered precursor of MCM-22P zeolite by swelling and pillaring. Vanadium was introduced into MCM-36 support by different methods (including conventional impregnation and ion exchange) by means of different precursors and synthesis conditions. Textural properties of prepared catalysts were characterized by nitrogen adsorption-desorption isotherms, the concentration of vanadium was determined by X-ray fluorescence and vanadium complex speciation was investigated by diffuse reflectance UV-vis spectroscopy, hydrogen temperature programmed reduction (H2 -TPR), electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) spectroscopy. Effect of synthesis method and conditions on catalytic behaviour was tested in the oxidative dehydrogenation of propane at 540 °C. The vanadium is present in oxidation state IV, instead of usual oxidation state V, in the cases of the catalyst with low content of vanadium. The best selectivity to propene with 13 % of conversion (43.9 %) was obtained when the acid center was neutralized with potassium cations and the content of vanadium was 2 wt %.