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Item type:Publication, Access status: without files , Synthesis gas production by catalytic partial oxidation of natural gas using ceramic foam catalyst(2018-01-01); ; ; ; Catalytic partial oxidation (CPOX) of natural gas was investigated over granule and ceramic foam Rh/CeO2+ZrO2+MgO catalysts under high throughput (GHSV of 180,000–1,600,000 h−1) conditions at various pressures from 0.1 to 2.1 MPaA. The application of ceramic foam as the substrate of Rh/CeO2+ZrO2+MgO catalyst improved the stability of the catalytic performance. It was found that the catalyst deactivation occurred when Reynolds number for flow through the catalyst bed exceeded around 20 and flow in the void of the catalyst bed changed from laminar flow regime to transitional flow regime. This change of fluid flow causes the acceleration of the mass transfer of the reactants from the gas phase to the catalyst surface and a rapid increase of the exothermic surface reaction rates over the catalyst, leading to hot spot formation. Due to larger void and smaller strut diameter of the ceramic foam, the configuration of the foam catalyst can make linear velocity lower in the catalyst bed and maintain laminar flow regime up to higher GHSV conditions than the granule catalyst, resulting in higher stability of the foam catalyst by suppression of hot spot formation. Chemical species measurements in the ceramic foam catalysts by means of a capillary sampling method revealed that the consumption rates of CH4 and O2 over Rh/CeO2+ZrO2+MgO were much lower than those over Rh/MgO and mild exothermic oxidation reaction over Rh/CeO2+ZrO2+MgO proceeds in wide region of the catalyst bed. High resistance to oxidation of Rh surface over CeO2+ZrO2+MgO even in the presence of O2 during CPOX reaction is considered to change the rates of both complete combustion reaction and reforming reaction, and to increase a contribution of another way to produce syngas.Publicationtype: Journal Article6654 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Carbon formation in catalytic partial oxidation of methane on platinum : model studies on a polycrystalline Pt foilA polycrystalline Pt foil has been investigated as model catalyst in methane catalytic partial oxidation to synthesis gas. It is demonstrated that a substantial amount of carbonaceous deposits forms on the Pt foil upon reaction light-off blocking a large fraction of Pt surface atoms. By using in situ Raman spectroscopy and quantitative spectral analysis the evolution and spatial distribution of these carbonaceous compounds with reaction temperature and reaction time have been characterized. The chemical composition of the carbon material changes from highly reactive and strongly disordered directly after reaction light-off to highly ordered, oxidation and steam reforming resistant after several hours time on stream at 800 °C reaction temperature. Remarkably the carbon distribution at the Pt surface was found to be inhomogeneous and related to the nature of the microcrystals forming the polycrystalline foil in a yet unknown manner.Publicationtype: Journal Article8 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , In-situ investigation of gas phase radical chemistry in the catalytic partial oxidation of methane on Pt(2009-04-15); ; ; ; The catalytic partial oxidation of methane on platinum was studied in situ under atmospheric pressure and temperatures between 1000 and 1300 °C. By combining radical measurements using a molecular beam mass spectrometer and threshold ionization with GC, GC-MS and temperature profile measurements it was demonstrated that a homogeneous reaction pathway is opened at temperatures above 1100 °C, in parallel to heterogeneous reactions which start already at 600 °C. Before ignition of gas phase chemistry, only CO, H2, CO2 and H2O are formed at the catalyst surface. Upon ignition of gas chemistry, CH3-radicals, C2 coupling products and traces of C3 and C4 hydrocarbons are observed. Because the formation of CH3-radicals correlates with the formation of C2 products it can be concluded that C2 products are formed by coupling of methyl radicals in the gas phase followed by dehydrogenation reactions. This formation pathway was predicted by numerical simulations and this work presents an experimental confirmation under high temperature atmospheric pressure conditions.Publicationtype: Journal Article19