- Mechanistic Insights into Catalytic Ethanol Steam Reforming Using Isotope-Labeled Reactants
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The low-temperature ethanol steam reforming (ESR) reaction mechanism over a supported Rh/Pt catalyst has been investigated using isotope-labeled EtOH and H2O. Through strategic isotope labeling, all nonhydrogen atoms were distinct from one another, and allowed an unprecedented level of understanding of the dominant reaction pathways. All combinations of isotope- and non-isotope-labeled atoms were detected in the products, thus there are multiple pathways involved in H2, CO, CO2, CH4, C2H4, and C2H6product formation. Both the recombination of C species on the surface of the catalyst and preservation of the C?C bond within ethanol are responsible for C2product formation. Ethylene is not detected until conversion drops below 100 % at t=1.25 h. Also, quantitatively, 57 % of the observed ethylene is formed directly through ethanol dehydration. Finally there is clear evidence to show that oxygen in the SiO2-ZrO2support constitutes 10 % of the CO formed during the reaction.
- Crowley, Stephen,Castaldi, Marco J.
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supporting information
p. 10650 - 10655
(2016/09/03)
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- Cross-metathesis of propane and methane: A catalytic reaction of C-C bond cleavage of a higher alkane by methane
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Methane, a building block for basic chemicals through its incorporation into alkanes: when a methane/propane mixture is passed over a tantalum hydride catalyst at 250°C, propane is transformed into two ethane molecules through the incorporation of one methane unit. This reaction corresponds to a cross-metathesis of propane and methane (see scheme; Alk = alkyl).
- Soulivong, Daravong,Coperet, Christophe,Thivolle-Cazat, Jean,Basset, Jean-Marie,Maunders, Barry M.,Pardy, Richard B. A.,Sunley, Glenn J.
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p. 5366 - 5369
(2007/10/03)
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- The effect of propane activation over Ga-modified H-ZS M-5 catalysts
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In sity 13C MAS NMR was used to investigate the influence of total and partial pressure of propane on the initial stages of its conversion over a Ga/H-MFI catalyst. (2-13C) Propane was the labelled reactant.Different pressures were achieved by varying the amounts of propane and of nitrogen as diluent in the cell.The nature of primary and secondary labelled reaction products depends on total pressure.High total and partial pressures of propane enhance bimolecular primary formation of n-butane and isobutane via a BREST (Bifunctional Reaction Step) mechanism.Low total pressure leads to methane and polymeric fragments as primary products.A reaction pathway including the formation of a polymeric hydrocarbon-chain intermediate is proposed to account for secondary isobutane formation at low pressure.The influence of pressure on reaction equilibria and kinetics and on adsorption and exchange processes is discussed.
- Ivanova, Irina I.,Blom, Niels,Hamid, Sharifah B. Abdul,Derouane, Eric G.
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p. 454 - 458
(2007/10/02)
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- Cracking of (5-(13)C)-n-Nonane with Quartz Wool, Silica-Alumina and Type Y Zeolite
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The cracking mechanism of (5-(13)C)-n-nonane has been studied over quartz wool, silica-alumina and a type Y zeolite.The products observed at a reaction temperature of 510 deg C over quartz wool agree reasonably well with the currently accepted mechanism of free radical cracking.Reaction with silica-alumina at 500 deg C and zeolite at 230 deg C results in a (13)C labelled product distribution which agrees with neither a thermal cracking mechanism nor the currently accepted mechanism of β-scission of carbonium ion intermediates.Rather, the data suggest that the product distribution is a result of the temperature-dependent random description and cracking of a complex polymeric precursor.
- Weeks, Thomas J.,Ladd, Irwin R.,Bolton, Anthony P.
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