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
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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
Zdrojový dokument:Scientific papers of the University of Pardubice. Series A, Faculty of Chemical Technology. 20/2014
ISSN:1211-5541
Abstrakt:
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 %.