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Wyświetlanie 1-10 z 11
Tytuł:
Catalytic performance of sucrose-derived CMK-3 in oxidative dehydrogenation of propane to propene
Autorzy:
Janus, Paula
Michorczyk, Piotr
Wach, Anna
Kuśtrowski, Piotr
Opis:
CMK-3 carbon replica was synthesized by carbonization of sucrose introduced to the pore system of a SBA- 15 hard template followed by dissolving $SiO_{2}$ with HF. The material with a stable hexagonal structure and an expanded surface area $(S_{BET}=1287m^{2}/g)$ was obtained. TG measurements showed that CMK-3 type mesoporous carbon started to be intensively oxidized by molecular $O_{2}$ above 723 K. This carbon sample was tested as a catalyst of dehydrogenation of propane to propene under oxidative ($O_{2}:C_{3}H_{8}$=0.25, 0.50 and 1.00) and non-oxidative (O 2 :C 3 H 8 = 0.00) conditions in the temperature range from 573 to 873 K. The propene yield increased with rise in the reaction temperature, however above 573 K the formation of side- products ($C_{2}H_{6}, C_{2}H_{4}, CH_{4}$ and $H_{2}$) was observed. Moreover, coke was deposited on the catalyst surface. A decrease in the mass of a catalyst bed after the catalytic runs suggested the participation of oxygen in burning of deposited and bulk coke. The surface composition of a spent catalyst was investigated by XPS and TPD analysis. The changes in the concentration of oxygen functional groups, caused by the catalytic reaction, were observed regardless of a reaction temperature and feed composition.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
First steps on the way to a modular concept for the preparation of carbon based catalysts
Autorzy:
Bron, Michael
Janus, Paula
Kuśtrowski, Piotr
Klepel, Olaf
Wach, Anna
Erler, Thomas
Walter, Reni
Opis:
The preparation of carbon based catalysts following a modular concept has been investigated. A template assisted route was applied to obtain catalysts exhibiting different fractions of graphitic species while retaining their mesoporosity. The carbon materials were characterized by means of low temperature nitrogen adsorption, powder X-ray diffraction, thermogravimetry, X-ray photoelectron spectroscopy, transmission electron microscopy, and Raman spectroscopy. The synthesized replicas were tested as catalysts in oxidative dehydrogenation of ethylbenzene and electrochemical oxygen reduction reaction. The role of the different carbon species, namely amorphous carbon, small graphitic crystallites, and large graphitic crystallites in the catalytic behavior was discussed.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Chemically activated poly(furfuryl alcohol)-derived CMK-3 carbon catalysts for the oxidative dehydrogenation of ethylbenzene
Autorzy:
Rodríguez-Reinoso, Francisco
Janus, Paula
Silvestre-Albero, Ana M.
Janus, Rafał
Jarczewski, Sebastian
Wach, Anna
Kuśtrowski, Piotr
Opis:
The surface of CMK-3 carbon, synthesized by the reversible replication of mesoporous silica (SBA-15) using poly(furfuryl alcohol) as a carbon precursor, was activated by wet oxidation with an aqueous solution of HNO3 or H2O2. The process was performed at 50 °C using solution containing different concentrations of the oxidizing agent. It was found that during the modification no significant changes in textural and structural properties of CMK-3 replica occurred. However, the treatment resulted in the formation of appreciable amounts of surface species containing oxygen. XPS and DRIFT spectroscopy allowed to identify and quantify the surface functional groups. Their stability was studied by TG-FTIR measurements. CO and CO2 were found as main gaseous products evolved during thermal decomposition under inert atmosphere. Finally, the modified samples were tested in the catalytic oxidative dehydrogenation of ethylbenzene to styrene at 350 °C in the presence of oxygen as an oxidizing agent (at O2/ethylbenzene molar ratio of 1.0 and 3.0). At the beginning of the catalytic run, the highest styrene yield and selectivity was achieved at the lower O2 content over the catalysts treated with nitric acid. Nevertheless, all studied catalysts underwent a gradual deactivation due to coke formation and changes in the distribution of surface moieties.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
A simplified route to the synthesis of CMK-3 replica based on precipitation polycondensation of furfuryl alcohol in SBA-15 pore system
Autorzy:
Janus, Paula
Kuśtrowski, Piotr
Wach, Anna
Jarczewski, Sebastian
Janus, Rafał
Silvestre-Albero, Ana M.
Rodríguez-Reinoso, Francisco
Opis:
A novel method of synthesis of mesoporous, polymer-derived CMK-3 carbon replica was proposed. Instead of a multi-stage, time-consuming and toxic solvent involving procedure, the direct, acid-catalyzed precipitation polycondensation of furfuryl alcohol to poly(furfuryl alcohol) (PFA), as the carbon precursor, in the pore system of SBA-15 silica was used. The optimal PFA/SBA-15 mass ratio resulting in the complete pore filling was found. The final carbon material was obtained by carbonization of the formed composite and subsequent removal of silica by treatment with HF. Low-temperature sorption of nitrogen, powder X-ray diffraction and transmission electron microscopy confirmed the formation of well-ordered, hexagonal carbon mesostructure. The produced CMK-3 exhibited the presence of oxygen-containing surface groups, recognized as mainly carbonyl and carboxyl species by X-ray photoelectron spectroscopy and temperature-programmed desorption. The presence ofthese groups caused the mesoporous carbon to be catalytically active in the oxidative dehydrogenation of ethylbenzene to styrene.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Wyświetlanie 1-10 z 11

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