The Experts below are selected from a list of 14055 Experts worldwide ranked by ideXlab platform
Olaf Deutschmann - One of the best experts on this subject based on the ideXlab platform.
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Natural Gas Steam Reforming over Rhodium/Alumina Catalysts: Experimental and Numerical Study of the Carbon Deposition from Ethylene and Carbon Monoxide
Industrial & Engineering Chemistry Research, 2014Co-Authors: Claudia Eßmann, Lubow Maier, Aijun Li, Steffen Tischer, Olaf DeutschmannAbstract:Natural gas steam reforming (SR) over technically used rhodium/alumina (Rh/Al2O3) honeycomb catalysts is studied experimentally at temperatures between 923 and 1073 K and steam-to-carbon ratios (S/C) of unity, with regard to coke deposition caused by the decomposition of the product species ethylene (C2H4) and carbon monoxide (CO). Furthermore, the process is modeled using Detailed Reaction Mechanisms, and numerical simulations are carried out to describe the coke formation on Rh/Al2O3 catalysts quantitatively. The amount of deposited carbon was detected and analyzed for varying feed mixtures of the products CO and C2H4 diluted in N2. During the decomposition of CO, the saturation of the amount of coke is monitored by feeding CO in high concentrations. No saturation occurs for the same amounts of coke resulting from the decomposition of C2H4. The coking rate caused by the decomposition of C2H4 is found to be ∼25 times higher than the coking rate caused by the decomposition of CO. The differences in coking...
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steam reforming of methane ethane propane butane and natural gas over a rhodium based catalyst
Catalysis Today, 2009Co-Authors: Benjamin T. Schädel, Matthias Duisberg, Olaf DeutschmannAbstract:Abstract Steam reforming of methane, ethane, propane, butane, and a sulfur-free natural gas is studied over a rhodium-based monolithic honeycomb catalyst. The product distribution is analyzed as function of temperature (250–900 °C) and steam-to-carbon ratio (2.2–4) for two honeycomb channel densities (600 and 900 cpsi) and an uncoated monolith by gas chromatography and mass spectroscopy. The reactive flow in the single monolith channel is modeled by a two-dimensional flow field description coupled with Detailed Reaction Mechanisms modeling surface and gas-phase kinetics. Ethane, propane, and butane are converted at much lower temperature than methane, also in natural gas mixtures. An impact of the presence of the higher hydrocarbons on methane conversion in steam reforming of natural gas is found. Steam reforming in the pure gas phase occurs only above 600 °C and the product spectrum differs from that of catalytic conversion.
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Steam reforming of natural gas on noble-metal based catalysts: Predictive modeling
Studies in Surface Science and Catalysis, 2007Co-Authors: Benjamin T. Schädel, Olaf DeutschmannAbstract:Steam reforming of natural gas over a noble-metal based catalyst is studied experimentally and numerically at varying reactor temperature and steam-to-carbon ratio. The catalytic monolith applied in the experiment is modeled by a two-dimensional flow field coupled with Detailed Reaction Mechanisms for both surface and gas-phase Reactions and taking the complexity of natural gas compositions into account. Steam reforming of methane, ethane, propane, and butane as single components as well as of a real gas mixture is studied to develop and evaluate a multi-step surface Reaction mechanism. The model developed can now be used to predict conversion and selectivity in steam reforming of natural gas of widely varying composition.
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natural gas conversion in monolithic catalysts interaction of chemical Reactions and transport phenomena
Studies in Surface Science and Catalysis, 2001Co-Authors: Olaf Deutschmann, Renate Schwiedemoch, Luba Maier, Daniel ChatterjeeAbstract:Abstract The interaction of transport and kinetics in catalytic monoliths used for natural gas conversion is studied experimentally and numerically. The paper focuses on a precise flow field agreement between experiment and model. Therefore, we use extruded monoliths with rectangular channel cross-section and a three-dimensional Navier-Stokes simulation including Detailed Reaction Mechanisms and a heat balance. Latter also accounts for heat conducting channel walls and external heat loss. If a washcoat is used, a set of one-dimensional Reaction-diffusion equations is additionally applied for modeling the transport and heterogeneous Reactions in the washcoat. Partial oxidation of methane to synthesis gas on rhodium coated monoliths has been studied as example.
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modeling the partial oxidation of methane in a short contact time reactor
Aiche Journal, 1998Co-Authors: Olaf Deutschmann, L D SchmidtAbstract:Partial oxidation of methane in monolithic catalysts at very short contact times offers a promising route to convert natural gas into syngas (H2 and CO), which can then be converted to higher alkanes or methanol. Detailed modeling is needed to understand their complex interaction of transport and kinetics in these systems and for their industrial application. In this work, the partial oxidation of methane in noble-metal (Rh and Pt)-coated monoliths was studied numerically as an example of short-contact-time reactor modeling. A tube wall catalytic reactor was simulated as a model for a single pore of the monolithic catalyst using a 2-D flow field description coupled with Detailed Reaction Mechanisms for surface and gas-phase chemistry. The catalytic surface coverages of adsorbed species are calculated vs. position. The reactor is characterized by competition between complete and partial oxidation of methane. At atmospheric pressure, CO2 and H2O are formed on the catalytic surface at the entrance of the catalytic reactor. At higher pressure, gas-phase chemistry becomes important, forming more complete oxidation products downstream and decreasing syngas selectivity by about 2% at 10 bar. Temperature (from 300 to ∼ 1,200 K), velocity, and transport coefficients change very rapidly at the catalyst entrance. The dependence of conversion and selectivity on reactor conditions was examined.
Benjamin T. Schädel - One of the best experts on this subject based on the ideXlab platform.
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steam reforming of methane ethane propane butane and natural gas over a rhodium based catalyst
Catalysis Today, 2009Co-Authors: Benjamin T. Schädel, Matthias Duisberg, Olaf DeutschmannAbstract:Abstract Steam reforming of methane, ethane, propane, butane, and a sulfur-free natural gas is studied over a rhodium-based monolithic honeycomb catalyst. The product distribution is analyzed as function of temperature (250–900 °C) and steam-to-carbon ratio (2.2–4) for two honeycomb channel densities (600 and 900 cpsi) and an uncoated monolith by gas chromatography and mass spectroscopy. The reactive flow in the single monolith channel is modeled by a two-dimensional flow field description coupled with Detailed Reaction Mechanisms modeling surface and gas-phase kinetics. Ethane, propane, and butane are converted at much lower temperature than methane, also in natural gas mixtures. An impact of the presence of the higher hydrocarbons on methane conversion in steam reforming of natural gas is found. Steam reforming in the pure gas phase occurs only above 600 °C and the product spectrum differs from that of catalytic conversion.
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Steam reforming of natural gas on noble-metal based catalysts: Predictive modeling
Studies in Surface Science and Catalysis, 2007Co-Authors: Benjamin T. Schädel, Olaf DeutschmannAbstract:Steam reforming of natural gas over a noble-metal based catalyst is studied experimentally and numerically at varying reactor temperature and steam-to-carbon ratio. The catalytic monolith applied in the experiment is modeled by a two-dimensional flow field coupled with Detailed Reaction Mechanisms for both surface and gas-phase Reactions and taking the complexity of natural gas compositions into account. Steam reforming of methane, ethane, propane, and butane as single components as well as of a real gas mixture is studied to develop and evaluate a multi-step surface Reaction mechanism. The model developed can now be used to predict conversion and selectivity in steam reforming of natural gas of widely varying composition.
Robert J. Kee - One of the best experts on this subject based on the ideXlab platform.
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Detailed Reaction Mechanisms for the Oxidative Coupling of Methane over La2O3/CeO2 Nanofiber Fabric Catalysts
ChemCatChem, 2017Co-Authors: Canan Karakaya, Bahman Zohour, Selim Senkan, Huayang Zhu, Robert J. KeeAbstract:This study develops and validates Detailed Reaction Mechanisms to represent oxidative coupling of methane (OCM) over a La2O3/CeO2 nanofabric catalyst. The Reaction mechanism includes 39 reversible gas-phase Reactions and 52 irreversible surface Reactions among 22 gas-phase species and 11 surface species. The paper uses model-based interpretation of spatially resolved concentration and temperature profiles as measured in a laboratory-scale packedbed reactor. The Reaction Mechanisms are validated for inlet feed compositions in the range 7< CH4/O2 < 11. The results are supported by a Reaction pathway analysis that provides insight about the relative contributions of gas-phase and surface Reactions to form the desired C2+ and the undesired COx products. The results provide new quantitative insights on the complex nature of the OCM chemistry, which can assist practical process and reactor development.
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polarization characteristics and chemistry in reversible tubular solid oxide cells operating on mixtures of h2 co h2o and co2
Journal of The Electrochemical Society, 2011Co-Authors: Connor J Moyer, Huayang Zhu, Neal P Sullivan, Robert J. KeeAbstract:This paper reports the results of combined experimental and modeling studies of reversible solid-oxide cells. The tubular cells are fabricated using a Ni-YSZ (yttria-stabilized zirconia) fuel-electrode support, a dense YSZ electrolyte membrane, and a strontium-doped lanthanum manganate-YSZ composite air electrode. Experiments are designed to systematically vary gas-phase species partial pressures and operating temperatures. The fuels are mixtures of H 2 , CO, H 2 O, CO 2 , and Ar. Performance is measured under anodic (fuel cell) and cathodic (electrolysis) polarization. The models consider reactive porous-media transport within the composite electrodes, thermal chemistry on Ni and YSZ surfaces, and charge-transfer chemistry. All chemistry is modeled with elementary reversible Reactions. Close coupling between experimental measurements and model-based interpretation provides a basis for establishing Reaction pathways and rates. In addition to advancing fundamental understanding, the resulting Detailed Reaction Mechanisms are valuable for incorporation into predictive models that can be used for design and optimization of fuel-cell and electrolysis systems.
Jeongyeol Choi - One of the best experts on this subject based on the ideXlab platform.
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analysis of oscillation behaviour in unsteady shock induced combustion with Detailed Reaction Mechanisms
KOSCO SYMPOSIUM 논문집, 2015Co-Authors: Pradeep P Kumar, Kuisoon Kim, Jeongyeol ChoiAbstract:Unsteady Shock-Induced Combustion has been studied for the past few decades since it is considered as one of the potential ways to reach supersonic flights. Experimental observations of Unsteady SIC were observed as early as 1960‘s. But Lehr was the first to report in detail the Mechanisms of Shock-Induced Combustion experimentally. Numerical Studies on SIC were helpful in explaining the insight into the oscillatory behaviour in the mid 90‘s to early 2000‘s. Detailed Reaction Mechanisms is required to prediction the SIC flowfield more in detail. However at that time, very few Reaction Mechanisms on hydrogen-oxidation were reported. In the last decade, various number of hydrogen Reaction Mechanisms were reported. In this study, an attempt has been made to analyze the effect of various Reaction Mechanisms in an unsteady mode of Shock-Induced Combustion.
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characteristics of Detailed hydrogen Reaction Mechanisms for shock induced combustion
KOSCO SYMPOSIUM 논문집, 2013Co-Authors: Pradeep P Kumar, Jeongyeol ChoiAbstract:Hydrogen is one of the best propellant available today, because of its high reactivity, high performance and a green propellant with very low molecular weight, and is widely used in Rockets and Scramjet engines. Detailed Reaction Mechanisms have been proposed in the past decades but direct comparison of these Mechanisms are very hard to find for combustion especially at high pressure conditions. In this study, we intended for a basic comparison study of the Detailed Hydrogen Mechanisms for Shock Induced Combustions.
G.-s. Liu - One of the best experts on this subject based on the ideXlab platform.
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Detailed Reaction Mechanisms for coal-nitrogen conversion in pulverized fuel flames
Proceedings of the Combustion Institute, 2002Co-Authors: S. Niksa, G.-s. LiuAbstract:The simulation strategy described in this paper provides an alternative to conventional computationalfluid dynamics (CFD) postprocessing to estimate exhaust NO x emissions. The method first analyzes a conventional CFD furnace simulation to specify temperature histories and mixing rates. Then the bulk flow patterns are represented with an equivalent network of idealized reactor elements. Detailed Reaction Mechanisms are then applied over the reactor network, including the most fully validated Reaction Mechanisms for coal devolatilization and char oxidation and complete elementary Reaction Mechanisms for chemistry in the gas phase and on soot. The analysis depicts all the important tendencies among the major intermediates and products from a selection of coals that spanned almost the entire rank spectrum under Reaction conditions that spanned the domain of stoichiometric ratio in pulverized fuel flames, albeit in a lab-scale furnace. The main practical benefit of the mechanistic complexity is that simulations based on Detailed Mechanisms require far fewer parameter adjustments than conventional CFD simulations whenever different fuels are considered.
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Incorporating Detailed Reaction Mechanisms into simulations of coal-nitrogen conversion in p.f. flames
Fuel, 2002Co-Authors: S. Niksa, G.-s. LiuAbstract:The simulation strategy described in this paper provides an alternative to conventional CFD post-processing to estimate exhaust NOX emissions. The method first analyzes a conventional CFD simulation to specify temperature histories and mixing rates. The bulk flow patterns are then represented with an equivalent network of idealized reactor elements. Detailed Reaction Mechanisms are then applied over the reactor network. The analysis was able to depict all the important tendencies among the major intermediates and products from a selection of coals that spanned almost the entire rank spectrum, under Reaction conditions that spanned the domain of stoichiometric ratio in p.f. flames. The main practical benefit of the mechanistic complexity is that simulations based on Detailed Mechanisms require far fewer parameter adjustments than conventional CFD simulations whenever different fuels are considered.