The Experts below are selected from a list of 18420 Experts worldwide ranked by ideXlab platform
Ahmed F Ghoniem - One of the best experts on this subject based on the ideXlab platform.
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using potassium catalytic gasification to improve the performance of solid oxide direct carbon fuel cells experimental characterization and Elementary Reaction modeling
Journal of Power Sources, 2014Co-Authors: Yixiang Shi, Hongjian Wang, Ningsheng Cai, Ahmed F GhoniemAbstract:Abstract The performance of a solid oxide electrolyte direct carbon fuel cell (SO-DCFC) is limited by the slow carbon gasification kinetics at the typical operating temperatures of cell: 650–850 °C. To overcome such limitation, potassium salt is used as a catalyst to speed up the dry carbon gasification Reactions, increasing the power density by five-fold at 700–850 °C. The cell performance is shown to be sensitive to the bed temperature, emphasizing the role of gasification rates and that of CO production. Given the finite bed size, the cell performance is time-dependent as the amount of CO available changes. A reduced Elementary Reaction mechanism for potassium-catalyzed carbon gasification was proposed using kinetic data obtained from the experimental measurements. A comprehensive model including the catalytic gasification Reactions and CO electrochemistry is used to examine the impact of the catalytic carbon gasification process on the device performance. The power density is maximum around 50% of the OCV, where carbon utilization is also near maximum. Results show that bed height and porosity impact the power density; a thicker bed maintains the power almost constant for longer times while lower porosity delivers higher power density in the early stages.
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Experimental characterization and Elementary Reaction modeling of solid oxide electrolyte direct carbon fuel cell
Journal of Power Sources, 2013Co-Authors: Xiankai Yu, Jeffrey Hanna, Hongjian Wang, Bartlomiej Andrzej Glowacki, R I Tomov, Chen Li, Ahmed F GhoniemAbstract:Abstract A detailed mechanistic model for solid oxide electrolyte direct carbon fuel cell (SO-DCFC) is developed while considering the thermo-chemical and electrochemical Elementary Reactions in both the carbon bed and the SOFC, as well as the meso-scale transport processes within the carbon bed and the SOFC electrode porous structures. The model is validated using data from a fixed bed carbon gasification experiment and the SO-DCFC performance testing experiments carried out using different carrier gases and at various temperatures. The analyzes of the experimental and modeling results indicate the strong influence of the carrier gas on the cell performance. The coupling between carbon gasification and electrochemical oxidation on the SO-DCFC performance that results in an unusual transition zone in the cell polarization curve was predicted by the model, and analyzed in detail at the Elementary Reaction level. We conclude that the carbon bed physical properties such as the bed height, char conversion ratio and fuel utilization, as well as the temperature significantly limit the performance of the SO-DCFC.
Chen Li - One of the best experts on this subject based on the ideXlab platform.
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Experimental characterization and Elementary Reaction modeling of solid oxide electrolyte direct carbon fuel cell
Journal of Power Sources, 2013Co-Authors: Xiankai Yu, Jeffrey Hanna, Hongjian Wang, Bartlomiej Andrzej Glowacki, R I Tomov, Chen Li, Ahmed F GhoniemAbstract:Abstract A detailed mechanistic model for solid oxide electrolyte direct carbon fuel cell (SO-DCFC) is developed while considering the thermo-chemical and electrochemical Elementary Reactions in both the carbon bed and the SOFC, as well as the meso-scale transport processes within the carbon bed and the SOFC electrode porous structures. The model is validated using data from a fixed bed carbon gasification experiment and the SO-DCFC performance testing experiments carried out using different carrier gases and at various temperatures. The analyzes of the experimental and modeling results indicate the strong influence of the carrier gas on the cell performance. The coupling between carbon gasification and electrochemical oxidation on the SO-DCFC performance that results in an unusual transition zone in the cell polarization curve was predicted by the model, and analyzed in detail at the Elementary Reaction level. We conclude that the carbon bed physical properties such as the bed height, char conversion ratio and fuel utilization, as well as the temperature significantly limit the performance of the SO-DCFC.
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experimental characterization and mechanistic modeling of carbon monoxide fueled solid oxide fuel cell
Journal of Power Sources, 2011Co-Authors: Chen LiAbstract:Abstract The paper presents an Elementary Reaction based solid oxide fuel cell (SOFC) model coupled with anodic Elementary heterogeneous Reactions and electrochemical charge transfer Reactions for CO/CO2 fuel based on an anode supported button cell. The model is calibrated and validated using experimental data obtained for various CO/CO2 fuel compositions at 750, 800 and 850 °C. The comparison shows that the modeling results agree well with the experimental data. The effects of operating conditions on the cell performance and the detailed species concentration distribution are predicted. Then, the carbon deposition on the SOFC anode with CO/CO2 fuel is experimentally measured and simulated using the Elementary Reaction model. The results indicate that lower temperature and lower operation voltage are helpful to reduce the possibilities of carbon deposition on Ni particle surfaces.
Anu Koivula - One of the best experts on this subject based on the ideXlab platform.
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single molecule imaging analysis of Elementary Reaction steps of trichoderma reesei cellobiohydrolase i cel7a hydrolyzing crystalline cellulose iα and iiii
Journal of Biological Chemistry, 2014Co-Authors: Yusuke Shibafuji, Akihiko Nakamura, Takayuki Uchihashi, Naohisa Sugimoto, Shingo Fukuda, Hiroki Watanabe, Masahiro Samejima, Toshio Ando, Hiroyuki Noji, Anu KoivulaAbstract:Abstract Trichoderma reesei cellobiohydrolase I (TrCel7A) is a molecular motor that directly hydrolyzes crystalline celluloses into water-soluble cellobioses. It has recently drawn attention as a tool that could be used to convert cellulosic materials into biofuel. However, detailed mechanisms of action, including Elementary Reaction steps such as binding, processive hydrolysis, and dissociation, have not been thoroughly explored owing to the inherent challenges associated with monitoring Reactions occurring at the solid/liquid interface. The crystalline cellulose Iα and IIII were previously reported as substrates with different crystalline forms and different susceptibilities to hydrolysis by TrCel7A. In this study, we observed that different susceptibilities of cellulose Iα and IIII are highly dependent on enzyme concentration, and at nanomolar enzyme concentration, TrCel7A shows similar rates of hydrolysis against cellulose Iα and IIII. Using single-molecule fluorescence microscopy and high-speed atomic force microscopy, we also determined kinetic constants of the Elementary Reaction steps for TrCel7A against cellulose Iα and IIII. These measurements were performed at picomolar enzyme concentration in which density of TrCel7A on crystalline cellulose was very low. Under this condition, TrCel7A displayed similar binding and dissociation rate constants for cellulose Iα and IIII, and similar fractions of productive binding on cellulose Iα and IIII. Furthermore, once productively bound, TrCel7A processively hydrolyzes and moves along cellulose Iα and IIII with similar translational rates. With structural models of cellulose Iα and IIII, we propose that different susceptibilities at high TrCel7A concentration arise from surface properties of substrate, including ratio of hydrophobic surface and number of available lanes.
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single molecule imaging analysis of Elementary Reaction steps of trichoderma reesei cellobiohydrolase i cel7a hydrolyzing crystalline cellulose iα and iiii
Journal of Biological Chemistry, 2014Co-Authors: Yusuke Shibafuji, Akihiko Nakamura, Takayuki Uchihashi, Naohisa Sugimoto, Shingo Fukuda, Hiroki Watanabe, Masahiro Samejima, Toshio Ando, Hiroyuki Noji, Anu KoivulaAbstract:Trichoderma reesei cellobiohydrolase I (TrCel7A) is a molecular motor that directly hydrolyzes crystalline celluloses into water-soluble cellobioses. It has recently drawn attention as a tool that could be used to convert cellulosic materials into biofuel. However, detailed mechanisms of action, including Elementary Reaction steps such as binding, processive hydrolysis, and dissociation, have not been thoroughly explored because of the inherent challenges associated with monitoring Reactions occurring at the solid/liquid interface. The crystalline cellulose Iα and IIII were previously reported as substrates with different crystalline forms and different susceptibilities to hydrolysis by TrCel7A. In this study, we observed that different susceptibilities of cellulose Iα and IIII are highly dependent on enzyme concentration, and at nanomolar enzyme concentration, TrCel7A shows similar rates of hydrolysis against cellulose Iα and IIII. Using single-molecule fluorescence microscopy and high speed atomic force microscopy, we also determined kinetic constants of the Elementary Reaction steps for TrCel7A against cellulose Iα and IIII. These measurements were performed at picomolar enzyme concentration in which density of TrCel7A on crystalline cellulose was very low. Under this condition, TrCel7A displayed similar binding and dissociation rate constants for cellulose Iα and IIII and similar fractions of productive binding on cellulose Iα and IIII. Furthermore, once productively bound, TrCel7A processively hydrolyzes and moves along cellulose Iα and IIII with similar translational rates. With structural models of cellulose Iα and IIII, we propose that different susceptibilities at high TrCel7A concentration arise from surface properties of substrate, including ratio of hydrophobic surface and number of available lanes.
Koyo Norinaga - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Study on Elementary Reaction Steps in Thermal Decomposition Processes of Syringol-Type Monolignol Compounds
The Journal of Physical Chemistry A, 2018Co-Authors: Yuki Furutani, Yuki Dohara, Shinji Kudo, Jun-ichiro Hayashi, Koyo NorinagaAbstract:This paper theoretically investigated a large number of Reaction pathways and kinetics to describe the vapor-phase pyrolytic behavior of several syringol-type monolignol compounds that are derived from the primary pyrolysis of lignin: 1-(4-hydroxy-3,5-dimethoxyphenyl)prop-2-en-1-one (HDPP), sinapyl alcohol, 3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)propan-1-one (HHDPP), 1-(4-hydroxy-3,5-dimethoxyphenyl)propane-1,3-diol (HDPPD), and syringol. The possible pyrolytic pathways involving unimolecular decomposition, addition, and abstraction Reactions were investigated by comparing the energy barriers calculated at the B3LYP/6-311++G(d,p) level. In the proposed pathways, all syringol-type monolignols containing a side chain undergo its cleavage to form syringol through the formation of syringaldehyde or 4-vinylsyringol. Syringol is then converted into two products: (a) pyrogallol via the homolysis of the O–CH3 bond and hydrogenation or (b) guaiacol via addition of an H atom with a carbon bearing methoxyl group...
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Theoretical Study on Elementary Reaction Steps in Thermal Decomposition Processes of Syringol-Type Monolignol Compounds
2017Co-Authors: Yuki Furutani, Yuki Dohara, Shinji Kudo, Jun-ichiro Hayashi, Koyo NorinagaAbstract:This paper theoretically investigated a large number of Reaction pathways and kinetics to describe the vapor-phase pyrolytic behavior of several syringol-type monolignol compounds that are derived from the primary pyrolysis of lignin: 1-(4-hydroxy-3,5-dimethoxyphenyl)prop-2-en-1-one (HDPP), sinapyl alcohol, 3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)propan-1-one (HHDPP), 1-(4-hydroxy-3,5-dimethoxyphenyl)propane-1,3-diol (HDPPD), and syringol. The possible pyrolytic pathways involving unimolecular decomposition, addition, and abstraction Reactions were investigated by comparing the energy barriers calculated at the B3LYP/6-311++G(d,p) level. In the proposed pathways, all syringol-type monolignols containing a side chain undergo its cleavage to form syringol through the formation of syringaldehyde or 4-vinylsyringol. Syringol is then converted into two products: (a) pyrogallol via the homolysis of the O–CH3 bond and hydrogenation or (b) guaiacol via addition of an H atom with a carbon bearing methoxyl group in syrignol and the subsequent demethoxylation. The pyrolytic pathways of pyrogallol are classified into two processes: (a) the concerted dehydrogenation of the two hydroxyl H atoms and the unimolecular decomposition to produce acetylene (C2H2), ethynol (C2HOH), and CO or (b) the displacement of an OH with H to produce catechol and resorcinol. Additionally, HDPP undergoes O–CH3 bond cleavage to form but-1-en-3-yne. The high-pressure limit rate constants for all the proposed Elementary Reaction steps were evaluated on the basis of transition state theory
Yixiang Shi - One of the best experts on this subject based on the ideXlab platform.
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Elementary Reaction Modeling and Experimental Characterization on Methane Partial Oxidation within a Catalyst-Enhanced Porous Media Combustor
2016Co-Authors: Yuqing Wang, Yixiang Shi, Hongyu Zeng, Aayan Banerjee, Olaf Deutschmann, Ningsheng CaiAbstract:In this study, the fuel-rich combustion of methane in a two-layer porous media burner consisting of dense alumina pellets of different diameters was investigated experimentally and numerically. For a fixed inlet gas velocity of 0.15 m/s, methane-rich flames were stabilized near the interface of two layers for equivalence ratios from 1.4 to 1.6. It was found that 40% of the methane was converted to syngas at the equivalence ratio of 1.6 using a reforming efficiency based on low heating values. To further increase the hydrogen yield and make the burner more suitable for applications in fuel cells, a portion of the downstream layer was coated with 0.08 wt % Ni catalyst. The reforming efficiency of methane to hydrogen increased from 18.2% to 23.9% after the catalytic enhancement. A combined homogeneous and heterogeneous Elementary Reaction mechanism was developed for methane partial oxidation in the porous media burner with catalytic enhancement. A one-dimensional model was explored by coupling the combined mechanism with heat-transport and mass-transport processes within the burner. The modeled temperature profiles and gas compositions showed good agreement with the experimental results. The model is demonstrated to be a useful tool for understanding the Reaction processes within the burner and for burner design optimization. The nickel catalyst mainly promoted the water–gas shift Reaction, and the heterogeneous Reactions were dominant in the region where the catalyst was loaded. The burner design was optimized by studying the effects of the pellet diameter, layer length, and catalyst loading on the reforming efficiencies
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Elementary Reaction modeling of methane catalytic combustor effects of hysteresis in pd based catalyst activity
Combustion Science and Technology, 2015Co-Authors: Xiaoyu Zheng, Yixiang Shi, Xi Wang, Ningsheng CaiAbstract:An Elementary Reaction model of methane oxidation over γ-Al2O3–supported palladium is developed by considering the phenomena of bulk reduction, hysteresis of catalyst activity, and negative activation during the re-oxidation. Validation of this model into a practical reactor with reverse flow operation is contained. Simulation results show residence time and full cycle time to be the predominating factors of temperature and reduction state distribution, respectively. Hysteresis of catalyst activity causes a vibrating pattern of outlet conversion, which is considered to go against industrial application.
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using potassium catalytic gasification to improve the performance of solid oxide direct carbon fuel cells experimental characterization and Elementary Reaction modeling
Journal of Power Sources, 2014Co-Authors: Yixiang Shi, Hongjian Wang, Ningsheng Cai, Ahmed F GhoniemAbstract:Abstract The performance of a solid oxide electrolyte direct carbon fuel cell (SO-DCFC) is limited by the slow carbon gasification kinetics at the typical operating temperatures of cell: 650–850 °C. To overcome such limitation, potassium salt is used as a catalyst to speed up the dry carbon gasification Reactions, increasing the power density by five-fold at 700–850 °C. The cell performance is shown to be sensitive to the bed temperature, emphasizing the role of gasification rates and that of CO production. Given the finite bed size, the cell performance is time-dependent as the amount of CO available changes. A reduced Elementary Reaction mechanism for potassium-catalyzed carbon gasification was proposed using kinetic data obtained from the experimental measurements. A comprehensive model including the catalytic gasification Reactions and CO electrochemistry is used to examine the impact of the catalytic carbon gasification process on the device performance. The power density is maximum around 50% of the OCV, where carbon utilization is also near maximum. Results show that bed height and porosity impact the power density; a thicker bed maintains the power almost constant for longer times while lower porosity delivers higher power density in the early stages.
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Elementary Reaction kinetic model of an anode supported solid oxide fuel cell fueled with syngas
Journal of Power Sources, 2010Co-Authors: Yixiang Shi, Ningsheng CaiAbstract:Abstract In this paper, a detailed one-dimension transient Elementary Reaction kinetic model of an anode-supported solid oxide fuel cell (SOFC) operating with syngas based on button cell geometry is developed. The model, which incorporates anodic Elementary heterogeneous Reactions, electrochemical kinetics, electrodes microstructure and complex transport phenomena (momentum, mass and charge transport) in positive electrode|electrolyte|negative electrode (PEN), is validated with experimental performance for various syngas compositions at 750, 800 and 850 °C. The comparisons show that the simulation results agree reasonably well with the experimental data. Then the model is applied to analyze the effects of temperature and operation voltage on polarizations in each component of PEN, electronic current density in both electrodes and species concentrations distributions in anode. The numerical results of carbon deposition simulation indicate that higher temperature and lower operation voltage are helpful to reduce the possibility of carbon deposition on Ni surfaces by Bouduard Reactions. Furthermore, a sensitivity analysis of cell performance on syngas composition is performed for the typical syngas from entrained-flow coal gasifier and natural methane thermochemical reforming processes. The cell performance increases with the increasing of effective compositions (e.g. H2 and CO) in syngas and the large N2 content introduced by using air as oxidant leads to significant deterioration of performance.