Effect of Pressure on Catalyst Activity and Carbon Deposition During CO2 Reforming of Methane over Noble-Metal Catalysts
01 Jan 2002-pp 269-283
TL;DR: In this article, the reforming of methane with CO2 was studied over 1wt% Rh/alumina, Pt/ZrO2, and Ce-promoted catalysts at 800°C and pressures of 1, 8, and 14 bar.
Abstract: The reforming of methane with CO2 was studied over 1wt% Rh/alumina, Pt/ZrO2, and Ce-promoted Pt/ZrO2 catalysts at 800°C and pressures of 1, 8, and 14 bar. It was found that high pressure resulted in greater carbon formation, lower methane and CO2 conversions, as well as a lower H2/CO ratio. Temperature-programmed oxidation (TPO), of the catalysts after reaction, shows several CO2 peaks for the Ce-promoted catalyst, indicating several sources or types of carbon and/or several locations on the catalyst are involved with carbon deposition. The change in the temperature and intensity of the TPO peaks with pressure indicates that more stable carbon is deposited at high pressure. Thermodynamic calculations for the endothermic reaction of CH4 with CO2, CH4 decomposition, and CO disproportionation were also performed. The results of these calculations are consistent with CO disproportionation being a larger contributor to carbon deposition at high pressure.
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TL;DR: In situ DRIFT analysis evidenced that the reaction proceeds over these catalysts through an initial pathway in which both methane and carbon dioxide initially dissociate over the metal along with a bifunctional pathways in which methane dissociates over the active metal and carbon carbon dioxide activated over the basic support surface via a formate intermediate.
Abstract: A synergistic approach was made to develop a highly stable and carbon resistant catalyst system based on cobalt and nickel supported over modified mesoporous silica for the dry reforming of methane (DRM). Modified mesoporous silica is prepared by a hydrothermal method, and the total Co & Ni composition is taken at around 5% by using the deposition-precipitation technique. CO2 reforming with methane was performed at 400-800 °C under atmospheric pressure as well as at a pressure of 1 MPa, keeping the CH4/CO2 ratio equal to unity. The catalyst assembly before and after the reaction was thoroughly characterized by a wide range of analytical techniques including N2 physisorption, XRD, TPR, TPO, TPH, XPS, SEM, TEM, elemental mapping, TG-DTG. The physicochemical characterization results confirmed the homogeneous distribution of nanosized metal particles into the hexagonal framework of modified silica, which plays a vital role towards a stronger metal support interaction that renders carbon deposition upon the active metal surface as well as avoids metal sintering at higher temperatures. At the same time, the coexistence of nanosized Co and Ni into the mesopores produced a synergy which provides better stability without any deactivation at high pressure reaction conditions. In situ DRIFT analysis evidenced that the reaction proceeds over these catalysts through an initial pathway in which both methane and carbon dioxide initially dissociate over the metal along with a bifunctional pathway in which methane dissociates over the active metal and carbon dioxide activated over the basic support surface via a formate intermediate. Density Functional Theory (DFT) calculations were also performed and further support the proposed mechanism from DRIFT studies.
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TL;DR: In this paper, high surface area molybdenum and tungsten carbide materials, synthesised by the temperature programming reduction of the relevant metal oxide with methane/hydrogen, are highly efficient catalysts for the conversion of methane to synthesis gas, via the steam reforming, dry reforming, or partial oxidation processes.
360 citations
TL;DR: A review of the literature on the catalysis of CO 2 /CH 4 reforming shows that Group VIII metals, when distributed in reduced form on suitable supports, are effective catalysts for this reaction as discussed by the authors.
307 citations
TL;DR: In this article, the state-of-the-art of the technologies with emphasis on new developments in equipment design, especially relating to the tubular reformer furnace and to the burner for the autothermal or secondary reformer.
219 citations
TL;DR: In this paper, the reducibility of the support and the catalytic activity of supported Pt on a series of catalysts supported on ceria-zirconia mixed oxides were investigated.
217 citations
TL;DR: In this article, the reforming of CH4 with CO2 over supported Rh catalysts has been studied over a range of temperatures (550-1000 K) and the role of the metal oxides used as the support and the physical mixture may be ascribed to the promotion in dissociation of CO2 on the surface of Rh, since the CH4 + CO2 reaction is first order in the pressure of CO 2.
Abstract: The reforming of CH4 with CO2 over supported Rh catalysts has been studied over a range of temperatures (550–1000 K). A significant effect of the support on the catalytic activity was observed, where the order was Rh/Al2O3>Rh/TiO2>Rh/SiO2. The catalytic activity of Rh/SiO2 was promoted markedly by physical mixing of Rh/SiO2 with metal oxides such as Al2O3, TiO2, and MgO, indicating a synergetic effect. The role of the metal oxides used as the support and the physical mixture may be ascribed to the promotion in dissociation of CO2 on the surface of Rh, since the CH4 + CO2 reaction is first order in the pressure of CO2, suggesting that CO2 dissociation is the rate-determining step. The possible model of the synergetic effect was proposed.
179 citations