Digitální knihovnaUPCE
 

20 (2014) Scientific papers, Series A

Permanentní URI k tomuto záznamuhttps://hdl.handle.net/10195/75412

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20142

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Autor: search.filters.author.Drenchev, Nikola

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Nyní se zobrazuje 1 - 2 z 2
  • Náhled
    Článekpeer-reviewedpublishedOtevřený přístup
    Characterization of vanadium sites on vanadium-containing mesoporous silica catalysts and their catalytic behaviour in propane ODH
    (University of Pardubice, 2014) Drenchev, Nikola; Švadlák, Daniel; Setnička, Michal; Čičmanec, Pavel; Bulánek, Roman
    Parameters that affect the catalytic behaviour of vanadium-containing mesoporous silicas in oxidative dehydrogenation reaction of propane are mainly aggregation state of surface VOx species and reducibility of vanadium species. Type and conditions of synthesis have big impact on the nature of vanadium species and, therefore, influence significantly catalytic properties. Two vanadiumcontaining mesoporous silica catalysts were synthesized by different techniques (including direct synthesis from hydrogel containing vanadium precursor and wet impregnation of SBA-15 mesoporous silica by vanadyl acetylacetonate) and their physico-chemical and catalytic properties were studied and compared. Direct synthesis of vanadosilicate led to catalysts with non-uniform mesoporosity, but exhibiting better spreading of vanadium on the surface resulting in species with lower degree of polymerization compared to impregnated catalyst. It is reflected in higher iso-conversional selectivity of directly synthesized catalyst towards propene.
  • Náhled
    Článekpeer-reviewedpublishedOtevřený přístup
    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
    (University of Pardubice, 2014) Hidalgo-Carrillo, Jesus; Švadlák, Daniel; Bulánek, Roman; Čičmanec, Pavel; Setnička, Michal; Drenchev, Nikola; Eliášová, Pavla
    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 %.