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Yasukazu Saito - One of the best experts on this subject based on the ideXlab platform.
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Efficient hydrogen generation from organic chemical hydrides by using catalytic reactor on the basis of Superheated Liquid-film concept
Chemical Engineering Science, 2008Co-Authors: Yasukazu Saito, Shinya Hodoshima, Atsushi Shono, Kiyoshi Aramaki, Morihiro Saito, Jun Kuwano, Katsuto OtakeAbstract:Abstract Under boiling and refluxing conditions for catalytic dehydrogenation of organic chemical hydrides (decalin, methylcyclohexane and others) in a batch-wise reactor, either suspended states with excess amounts of substrate or sand-bath states with its scarce amounts were found to be inferior generally to the so-called “Liquid-film states” with adequate amount ratios of substrate to catalyst, where the catalyst-layer temperatures were Superheated or raised higher than the boiling point, and, consequently, reactivities became more favorable at higher heating temperatures in contrast to the boiling suspended states. Equilibrium shifts due to reactive distillation were well demonstrated under boiling and refluxing conditions in naphthene dehydrogenation. Moreover, desorption of hydrogen from the active sites to the bubble space was enhanced in the Superheated Liquid-film states, with large translational entropy endowed. Provided the extents of equilibrium deviation were large enough (Prigogine's approach), thermodynamic couplings among irreversible processes would be realized between heat transfer and mass transfer as an example of the extended De Donder's equation. Restriction of chemical equilibrium could be removed under temperature gradient conditions, as the consequence that its Gibbs energy change became more negative than that under iso-temperature conditions. Within the framework of irreversible thermodynamics, the decreased retardation constant K in the Superheated Liquid-film states was interpreted in terms of a vector-level coupling between temperature gradient and desorption. Moreover, vigorous bubble formation would give additional favor to the reaction rates owing to enlarged repeating frequencies of sequential non-microreversible processes in dehydrogenation catalysis. Organic chemical hydrides are attractive from the viewpoints of safe, economical, exergy-saving and large hydrogen contents for hydrogen storage and distribution. Their main defects have been pointed out hitherto that the endothermic reaction temperatures are too high. In this paper, a new concept on Superheated Liquid-film catalysis is explored for dehydrogenation temperatures to decrease, which would result in not only saving exergy for external heating but also avoiding catalyst deactivation due to carbon deposit.
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Chemical recuperation of low-quality waste heats by catalytic dehydrogenation of organic chemical hydrides and its exergy analysis
Energy & Fuels, 2008Co-Authors: Shinya Hodoshima, Atsushi Shono, Yasukazu SaitoAbstract:Any technological breakthrough on storage, transportation, and distribution of hydrogen is urgently required to popularize hydrogen energy systems. In the present paper, organic chemical hydrides with appropriate characteristics (e.g., high storage capacities, facile reversibility, and being safe and cost-competitive), consisting of reversible catalysis pairs such as methylcyclohexane dehydrogenation/toluene hydrogenation and decalin dehydrogenation/naphthalene hydrogenation, have been proposed as the suitable materials for carrying hydrogen. Efficient hydrogen generation from organic chemical hydrides at moderate heating temperatures lower than 300 °C, being low enough to avoid serious coke formation over catalyst surface, was accomplished only by using carbon-supported nanosize platinum catalysts in Superheated Liquid-film states. Desorption of products from catalytic active sites was enhanced with the temperature gradient formed in the Superheated Liquid-film state, so that both high catalytic conversi...
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efficient hydrogen supply from tetralin with Superheated Liquid film type catalysis for operating fuel cells
Applied Catalysis A-general, 2005Co-Authors: Shinya Hodoshima, Hiroaki Nagata, Yasukazu SaitoAbstract:Abstract A catalytic reaction pair, consisting of tetralin dehydrogenation/naphthalene hydrogenation, has newly been proposed as a storage medium of hydrogen for operating polymer-electrolyte fuel cells. The hydrogen storage capacity of tetralin (3.0 wt.%, 28.2 kg-H2/m3) is lower than that of decalin (7.3 wt.%, 64.8 kg-H2/m3), with the decalin dehydrogenation/naphthalene hydrogenation pair operated. Nevertheless, the rates of tetralin dehydrogenation and naphthalene hydrogenation to tetralin are much faster than the rates of the latter reaction pair. With respect to hydrogen storage for static or domestic use with space advantages, tetralin would be superior to decalin due to the ability of supplying hydrogen easily. Very high reaction rates and conversions of hydrogen evolution from tetralin were accomplished stationarily with “Superheated Liquid-film-type catalysis” by heating at 210–240 °C, in contrast to the poor results obtained with ordinary suspended catalysis. In particular, a carbon-supported nano-size platinum catalyst in the Superheated Liquid-film state exhibited efficient tetralin conversion as high as 95% within 25 min contact at 240 °C under distillation conditions. At the same temperature range, the dehydrogenation rates for decalin that had been obtained were ca. 3.9–6.3 times slower than those for tetralin, suggesting the excellent characteristics of tetralin as a hydrogen storage medium. In addition, carbon-supported nickel–ruthenium composite catalysts were found to give dehydrogenation activities at 240 °C comparable with those of the platinum catalyst at 210 °C.
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hydrogen storage by decalin naphthalene pair and hydrogen supply to fuel cells by use of Superheated Liquid film type catalysis
Applied Catalysis A-general, 2005Co-Authors: Shinya Hodoshima, Atsushi Shono, Shigeki Takaiwa, Kazumi Satoh, Yasukazu SaitoAbstract:Abstract A catalytic reaction pair of decalin dehydrogenation/naphthalene hydrogenation has been proposed as a storage medium for fuel-cell hydrogen in mobile modes. The hydrogen capacities with decalin (7.3 wt.%, 64.8 kg-H 2 m 3 ) are higher than the target values of the Department of Energy, USA (6.5 wt.%, 62.0 kg-H 2 m 3 ). Platinum–rhenium composite catalysts supported on granular activated carbon in “Superheated Liquid-film” states gave excellent reactivities for decalin dehydrogenation, where the conversion of almost 100% from decalin to naphthalene was attained within 1 h by heating at 280 °C in a batch-wise reactor. “Superheated Liquid-film” conditions were also realized in a continuous-type reactor at the same temperature (280 °C). With the goal of maintaining rapid evolution of hydrogen stationarily, a rather wide range of decalin feed rates was allowable with use of platinum particles supported on activated carbon cloth. Decalin should be evaluated as an organic chemical hydride not only because of its storage densities but also because of its potential power densities for fuel-cell vehicles.
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characteristics of decalin dehydrogenation catalysis in the Superheated Liquid film state for mobile storage of hydrogen
Journal of Chemical Engineering of Japan, 2004Co-Authors: Shinya Hodoshima, Yasukazu SaitoAbstract:Efficient hydrogen evolution from decalin by heating at 210°C and cooling at 5°C was attempted in a batch-wise reactor by the use of “Superheated Liquid-film-type catalysis”. When the carbon-supported metal catalyst 0.75 g was immersed with decalin 3.0 ml under a reactive distillation conditions, a Liquid-film state was realized and the catalytic conversion of decalin was remarkably enhanced in contrast to the ordinary suspended state (e.g., 0.75 g/10 ml). Active sites in the Liquid-film state were Superheated, being higher in temperatures than the boiling point of the substrate solution, which gave the catalytic abilities of both high reaction rates and accelerated desorption of the reaction products from the catalyst surface, as evident from the Langmuir-type analysis. In addition, scarcity of substrate in the Liquid-film state improved the utilization efficiency of heat by allotting it more to the endothermic reaction rather than to inevitable evaporation. According to our repetitive reaction test with the same catalyst, reproducible activities were confirmed well. The adoption of Superheated Liquid-film-type catalysis for decalin dehydrogenation would make the reaction couple with naphthalene hydrogenation useful for mobile storage of hydrogen.
Shinya Hodoshima - One of the best experts on this subject based on the ideXlab platform.
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Efficient hydrogen generation from organic chemical hydrides by using catalytic reactor on the basis of Superheated Liquid-film concept
Chemical Engineering Science, 2008Co-Authors: Yasukazu Saito, Shinya Hodoshima, Atsushi Shono, Kiyoshi Aramaki, Morihiro Saito, Jun Kuwano, Katsuto OtakeAbstract:Abstract Under boiling and refluxing conditions for catalytic dehydrogenation of organic chemical hydrides (decalin, methylcyclohexane and others) in a batch-wise reactor, either suspended states with excess amounts of substrate or sand-bath states with its scarce amounts were found to be inferior generally to the so-called “Liquid-film states” with adequate amount ratios of substrate to catalyst, where the catalyst-layer temperatures were Superheated or raised higher than the boiling point, and, consequently, reactivities became more favorable at higher heating temperatures in contrast to the boiling suspended states. Equilibrium shifts due to reactive distillation were well demonstrated under boiling and refluxing conditions in naphthene dehydrogenation. Moreover, desorption of hydrogen from the active sites to the bubble space was enhanced in the Superheated Liquid-film states, with large translational entropy endowed. Provided the extents of equilibrium deviation were large enough (Prigogine's approach), thermodynamic couplings among irreversible processes would be realized between heat transfer and mass transfer as an example of the extended De Donder's equation. Restriction of chemical equilibrium could be removed under temperature gradient conditions, as the consequence that its Gibbs energy change became more negative than that under iso-temperature conditions. Within the framework of irreversible thermodynamics, the decreased retardation constant K in the Superheated Liquid-film states was interpreted in terms of a vector-level coupling between temperature gradient and desorption. Moreover, vigorous bubble formation would give additional favor to the reaction rates owing to enlarged repeating frequencies of sequential non-microreversible processes in dehydrogenation catalysis. Organic chemical hydrides are attractive from the viewpoints of safe, economical, exergy-saving and large hydrogen contents for hydrogen storage and distribution. Their main defects have been pointed out hitherto that the endothermic reaction temperatures are too high. In this paper, a new concept on Superheated Liquid-film catalysis is explored for dehydrogenation temperatures to decrease, which would result in not only saving exergy for external heating but also avoiding catalyst deactivation due to carbon deposit.
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Chemical recuperation of low-quality waste heats by catalytic dehydrogenation of organic chemical hydrides and its exergy analysis
Energy & Fuels, 2008Co-Authors: Shinya Hodoshima, Atsushi Shono, Yasukazu SaitoAbstract:Any technological breakthrough on storage, transportation, and distribution of hydrogen is urgently required to popularize hydrogen energy systems. In the present paper, organic chemical hydrides with appropriate characteristics (e.g., high storage capacities, facile reversibility, and being safe and cost-competitive), consisting of reversible catalysis pairs such as methylcyclohexane dehydrogenation/toluene hydrogenation and decalin dehydrogenation/naphthalene hydrogenation, have been proposed as the suitable materials for carrying hydrogen. Efficient hydrogen generation from organic chemical hydrides at moderate heating temperatures lower than 300 °C, being low enough to avoid serious coke formation over catalyst surface, was accomplished only by using carbon-supported nanosize platinum catalysts in Superheated Liquid-film states. Desorption of products from catalytic active sites was enhanced with the temperature gradient formed in the Superheated Liquid-film state, so that both high catalytic conversi...
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efficient hydrogen supply from tetralin with Superheated Liquid film type catalysis for operating fuel cells
Applied Catalysis A-general, 2005Co-Authors: Shinya Hodoshima, Hiroaki Nagata, Yasukazu SaitoAbstract:Abstract A catalytic reaction pair, consisting of tetralin dehydrogenation/naphthalene hydrogenation, has newly been proposed as a storage medium of hydrogen for operating polymer-electrolyte fuel cells. The hydrogen storage capacity of tetralin (3.0 wt.%, 28.2 kg-H2/m3) is lower than that of decalin (7.3 wt.%, 64.8 kg-H2/m3), with the decalin dehydrogenation/naphthalene hydrogenation pair operated. Nevertheless, the rates of tetralin dehydrogenation and naphthalene hydrogenation to tetralin are much faster than the rates of the latter reaction pair. With respect to hydrogen storage for static or domestic use with space advantages, tetralin would be superior to decalin due to the ability of supplying hydrogen easily. Very high reaction rates and conversions of hydrogen evolution from tetralin were accomplished stationarily with “Superheated Liquid-film-type catalysis” by heating at 210–240 °C, in contrast to the poor results obtained with ordinary suspended catalysis. In particular, a carbon-supported nano-size platinum catalyst in the Superheated Liquid-film state exhibited efficient tetralin conversion as high as 95% within 25 min contact at 240 °C under distillation conditions. At the same temperature range, the dehydrogenation rates for decalin that had been obtained were ca. 3.9–6.3 times slower than those for tetralin, suggesting the excellent characteristics of tetralin as a hydrogen storage medium. In addition, carbon-supported nickel–ruthenium composite catalysts were found to give dehydrogenation activities at 240 °C comparable with those of the platinum catalyst at 210 °C.
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hydrogen storage by decalin naphthalene pair and hydrogen supply to fuel cells by use of Superheated Liquid film type catalysis
Applied Catalysis A-general, 2005Co-Authors: Shinya Hodoshima, Atsushi Shono, Shigeki Takaiwa, Kazumi Satoh, Yasukazu SaitoAbstract:Abstract A catalytic reaction pair of decalin dehydrogenation/naphthalene hydrogenation has been proposed as a storage medium for fuel-cell hydrogen in mobile modes. The hydrogen capacities with decalin (7.3 wt.%, 64.8 kg-H 2 m 3 ) are higher than the target values of the Department of Energy, USA (6.5 wt.%, 62.0 kg-H 2 m 3 ). Platinum–rhenium composite catalysts supported on granular activated carbon in “Superheated Liquid-film” states gave excellent reactivities for decalin dehydrogenation, where the conversion of almost 100% from decalin to naphthalene was attained within 1 h by heating at 280 °C in a batch-wise reactor. “Superheated Liquid-film” conditions were also realized in a continuous-type reactor at the same temperature (280 °C). With the goal of maintaining rapid evolution of hydrogen stationarily, a rather wide range of decalin feed rates was allowable with use of platinum particles supported on activated carbon cloth. Decalin should be evaluated as an organic chemical hydride not only because of its storage densities but also because of its potential power densities for fuel-cell vehicles.
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characteristics of decalin dehydrogenation catalysis in the Superheated Liquid film state for mobile storage of hydrogen
Journal of Chemical Engineering of Japan, 2004Co-Authors: Shinya Hodoshima, Yasukazu SaitoAbstract:Efficient hydrogen evolution from decalin by heating at 210°C and cooling at 5°C was attempted in a batch-wise reactor by the use of “Superheated Liquid-film-type catalysis”. When the carbon-supported metal catalyst 0.75 g was immersed with decalin 3.0 ml under a reactive distillation conditions, a Liquid-film state was realized and the catalytic conversion of decalin was remarkably enhanced in contrast to the ordinary suspended state (e.g., 0.75 g/10 ml). Active sites in the Liquid-film state were Superheated, being higher in temperatures than the boiling point of the substrate solution, which gave the catalytic abilities of both high reaction rates and accelerated desorption of the reaction products from the catalyst surface, as evident from the Langmuir-type analysis. In addition, scarcity of substrate in the Liquid-film state improved the utilization efficiency of heat by allotting it more to the endothermic reaction rather than to inevitable evaporation. According to our repetitive reaction test with the same catalyst, reproducible activities were confirmed well. The adoption of Superheated Liquid-film-type catalysis for decalin dehydrogenation would make the reaction couple with naphthalene hydrogenation useful for mobile storage of hydrogen.
N. Burgio - One of the best experts on this subject based on the ideXlab platform.
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on the critical energy required for homogeneous nucleation in bubble chambers employed in dark matter searches
European Physical Journal C, 2019Co-Authors: Giacomo Bruno, N. Burgio, Massimo Corcione, L. Cretara, M. Frullini, W. Fulgione, L. Manara, Alessandro Quintino, A. SantagataAbstract:Two equations for the calculation of the critical energy required for homogeneous nucleation in a Superheated Liquid, and the related critical radius of the nucleated vapour bubble, are obtained, the former by the direct application of the first law of thermodynamics, the latter by considering that the bubble formation implies the overcoming of a barrier of the free enthalpy potential. Compared with the currently used relationships, the present equations, still allowing for reversible processes only, lead to thermodynamic energy thresholds of the bubble chambers employed in dark matter searches that are closer to the experimental values.
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moscab a geyser concept bubble chamber to be used in a dark matter search
European Physical Journal C, 2017Co-Authors: A Antonicci, N. Burgio, M Ardid, R Bertoni, G Bruno, Gianfranco Caruso, Daniele Cattaneo, F Chignoli, M Clemenza, Massimo CorcioneAbstract:The MOSCAB experiment (Materia OSCura A Bolle) uses the “geyser technique”, a variant of the Superheated Liquid technique of extreme simplicity. Operating principles of the new dark matter detector and technical solutions of the device are reported in detail. First results obtained in a series of test runs taken in laboratory demonstrate that we have successfully built and tested a geyser-concept bubble chamber that can be used in particle physics, especially in dark matter searches, and that we are ready to move underground for extensive data taking.
M Luque D De Castro - One of the best experts on this subject based on the ideXlab platform.
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static dynamic sequential Superheated Liquid extraction of phenols and fatty acids from alperujo
Analytical and Bioanalytical Chemistry, 2008Co-Authors: J A Perezserradilla, R Japonlujan, M Luque D De CastroAbstract:Superheated Liquids of different polarity have been used for sequential extraction of fatty acids and phenols from alperujo. Multivariate methodology has been used to optimise the static-dynamic extraction. Forty-two minutes are required to complete extraction (20 mg/kg of fatty acids and up to 2,200 mg/kg of hydroxytyrosol in the raw material used). The efficacy of the extraction has been demonstrated and compared with that of conventional methods (Folch and stirring-based methods for fatty acids and phenols, respectively), which needed 4.5 and 24 h for the extraction of fatty acids and phenols, respectively. The non-polar and polar extracts were injected into GC-MS and HPLC-MS-MS equipment, respectively, for individual separation-quantification of the target compounds. The simplicity of the experimental setup and the low costs of the raw material make the proposed method advisable when extraction of both fractions is required.
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ultrasound assisted dynamic extraction of valuable compounds from aromatic plants and flowers as compared with steam distillation and Superheated Liquid extraction
Talanta, 2008Co-Authors: Jannat M Roldangutierrez, Jose Ruizjimenez, M Luque D De CastroAbstract:A method for the extraction of valuable compounds from plants and flowers (viz. laurel, rosemary, thyme, oregano and tuberose) is proposed. The dynamic approach allows go-and-backward circulation of the extractant (ethanol) through the solid sample subjected to the action of an ultrasound probe (thus reducing sample amount and avoiding overpressure). A multivariate optimisation study and application of the optimum values of the variables to kinetics studies show that 10 min is sufficient to obtain extraction efficiencies that greatly surpass those provided by steam distillation for essential oils or Superheated Liquid extraction for these oils and other valuable compounds, with lower costs and higher quality of the extract. The extraction time of the proposed method is 176-165 min shorter than steam distillation and 31-20 min shorter than Superheated Liquid extraction, depending on the target compound.
Eckhard Weidner - One of the best experts on this subject based on the ideXlab platform.
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investigation of Superheated Liquid carbon dioxide jets for cutting applications
Journal of Supercritical Fluids, 2018Co-Authors: Lena Engelmeier, Stefan Pollak, Eckhard WeidnerAbstract:Abstract Water jet cutting is of increasing interest in manufacturing technology. By using carbon dioxide (CO2) instead of water, a dry processing becomes possible. To realize cutting results comparable to water, Liquid and coherent CO2-jets with high specific energy have to be formed. However, CO2 does not exist as a Liquid in thermodynamic equilibrium at atmospheric pressure. During the expansion through a nozzle from a Liquid state to atmospheric pressure the saturation curve is crossed and a spray consisting of a gaseous and solid phase is generated. We show that with sufficiently low injection temperatures the phase change is delayed and Liquid jets emanate from the nozzle even at atmospheric pressure. These jets disintegrate closer to the nozzle than water jets at same pressure and nozzle conditions. The shorter jet length results in lower kerf depths. But the kerf width is smaller with CO2 and a more precise cutting is possible.
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Superheated Liquid carbon dioxide jets: setting up and phenomena
Experiments in Fluids, 2017Co-Authors: Lena Engelmeier, Stefan Pollak, Franz Peters, Eckhard WeidnerAbstract:We present an experimental investigation on Liquid, Superheated carbon dioxide jets. Our main goal is to identify the setting up requirements for generating coherent jets because these raise expectations on applications in the cleaning and cutting industry. The study leads us through a number of phenomena, which are described, categorized and explained. The experiments are based on compressed (350 MPa) and cooled carbon dioxide, which expands through a cylindrical nozzle into the atmosphere. The nozzle provokes hydraulic flip by a sharp-edge inlet leading to separation and constriction. Upstream-temperature and pressure are varied and the jet’s structure and phase state are monitored by a high-speed camera. We observe coherent, Liquid jets far from equilibrium, which demands the solid or gaseous state. Therefore, these jets are Superheated. Carbon dioxide jets, like water jets, below certain nozzle diameters are subject to fluid dynamic instabilities resulting in breakup. Above certain diameters flashing jet breakup appears, which is associated with nucleation.
