The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Aldo Steinfeld - One of the best experts on this subject based on the ideXlab platform.
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solar syngas production from co2 and h2o in a two step Thermochemical Cycle via zn zno redox reactions thermodynamic Cycle analysis
International Journal of Hydrogen Energy, 2011Co-Authors: Peter G Loutzenhiser, Aldo SteinfeldAbstract:Abstract Solar syngas production from CO2 and H2O is considered in a two-step Thermochemical Cycle via Zn/ZnO redox reactions, encompassing: 1) the ZnO thermolysis to Zn and O2 using concentrated solar radiation as the source of process heat, and 2) Zn reacting with mixtures of H2O and CO2 yielding high-quality syngas (mainly H2 and CO) and ZnO; the ZnO is reCycled to the first, solar step, resulting in net reaction βCO2 + (1 − β)H2O → βCO + (1 − β)H2. Syngas is further processed to liquid hydrocarbon fuels via Fischer–Tropsch or other catalytic processes. Second-law thermodynamic analysis is applied to determine the Cycle efficiencies attainable with and without heat recuperation for varying molar fractions of CO2:H2O and solar reactor temperatures in the range 1900–2300 K. Considered is the energy penalty of using Ar dilution in the solar step below 2235 K for shifting the equilibrium to favor Zn production.
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co2 splitting in an aerosol flow reactor via the two step zn zno solar Thermochemical Cycle
Chemical Engineering Science, 2010Co-Authors: Peter G Loutzenhiser, Aldo Steinfeld, Elena M Galvez, Illias Hischier, Aron GrafAbstract:Abstract Using concentrated solar energy as the source of high-temperature process heat, a two-step CO 2 splitting Thermochemical Cycle based on Zn/ZnO redox reactions is applied to produce renewable fuels. The solar Thermochemical Cycle consists of (1) the solar endothermic dissociation of ZnO to Zn and O 2 ; (2) the non-solar exothermic reduction of CO 2 with Zn to CO and ZnO; the latter is reCycled to the 1st solar step. The second step of the Cycle is experimentally investigated in a hot-wall quartz aerosol flow reactor, designed for quenching of Zn(g), formation of Zn nanoparticles, and in - situ oxidation with CO 2 . The effects of varying the reactants stoichiometry, reaction temperatures, and inlet flow temperatures for radial and annular flows were investigated. Chemical conversions of Zn to ZnO of up to 88% were obtained for a residence time of 3 s. For all of the experiments, the reactions primarily occurred heterogeneously on the reaction zone surfaces, outside the aerosol jet flow.
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CO2 Splitting in a Hot-Wall Aerosol Reactor via the Two-Step Zn/ZnO Solar Thermochemical Cycle
ASME 2009 3rd International Conference on Energy Sustainability Volume 2, 2009Co-Authors: Peter G Loutzenhiser, Illias Hischier, M. Elena Gálvez, Anastasia Stamatiou, Aldo SteinfeldAbstract:Using concentrated solar energy as the source of high-temperature process heat, a two-step CO2 splitting Thermochemical Cycle based on Zn/ZnO redox reactions is applied to produce renewable carbon-neutral fuels. The solar Thermochemical Cycle consists of: 1) the solar endothermic dissociation of ZnO to Zn and O2 ; 2) the non-solar exothermic reduction of CO2 with Zn to CO and ZnO; the latter is the reCycled to the 1st solar step. The net reaction is CO2 = CO + 1/2 O2 , with products formed in different steps, thereby eliminating the need for their separation. A Second-Law thermodynamic analysis indicates a maximum solar-to-chemical energy conversion efficiency of 39% for a solar concentration ratio of 5000 suns. The technical feasibility of the first step of the Cycle has been demonstrated in a high-flux solar furnace with a 10 kW solar reactor prototype. The second step of the Cycle is experimentally investigated in a hot-wall quartz aerosol flow reactor, designed for in-situ quenching of Zn(g), formation of Zn nanoparticles, and oxidation with CO2 . The effect of varying the molar flow ratios of the reactants was investigated. Chemical conversions were determined by gas chromatography and X-ray diffraction. Chemical conversions of Zn to ZnO of up to 88% were obtained for a residence time of ∼ 3.05 s. For all of the experiments, the reactions primarily occurred outside the aerosol jet flow on the surfaces of the reaction zone.Copyright © 2009 by ASME
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kinetic analysis of the carbonation reactions for the capture of co2 from air via the ca oh 2 caco3 cao solar Thermochemical Cycle
Chemical Engineering Journal, 2007Co-Authors: V. Nikulshina, Maria Elena Galvez, Aldo SteinfeldAbstract:Abstract A thermogravimetric analysis of the carbonation of CaO and Ca(OH)2 with 500 ppm CO2 in air at 200–450 °C is performed as part of a three-step Thermochemical Cycle to capture CO2 from air using concentrating solar energy. The rate of CaO-carbonation is fitted to an unreacted core kinetic model that encompasses intrinsic chemical reaction followed by intra-particle diffusion. In contrast, the Ca(OH)2-carbonation is less hindered by diffusion while catalyzed by water formation, and its rate is fitted to a chemically-controlled kinetic model at the solid interface not covered by CaCO3. The rates of both carbonation reactions increase with temperature, peak at 400–450 °C, and decrease above 450 °C as a result of the thermodynamically favored reverse CaCO3-decomposition. Avrami's empirical rate law is applied to describe the CO2 uptake from the continuous air flow by CaO and Ca(OH)2, with and without added water. The addition of water vapor significantly enhances the reaction kinetics to the extent that, in the first 20 min, the reaction proceeds at a rate that is 22 and nine times faster than that observed for the dry carbonation of CaO and Ca(OH)2, respectively.
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Kinetic analysis of the carbonation reactions for the capture of CO2from air via the Ca(OH)2-CaCO3-CaO solar Thermochemical Cycle
Chemical Engineering Journal, 2007Co-Authors: V. Nikulshina, Maria Elena Galvez, Aldo SteinfeldAbstract:A thermogravimetric analysis of the carbonation of CaO and Ca(OH)2with 500 ppm CO2in air at 200-450 °C is performed as part of a three-step Thermochemical Cycle to capture CO2from air using concentrating solar energy. The rate of CaO-carbonation is fitted to an unreacted core kinetic model that encompasses intrinsic chemical reaction followed by intra-particle diffusion. In contrast, the Ca(OH)2-carbonation is less hindered by diffusion while catalyzed by water formation, and its rate is fitted to a chemically-controlled kinetic model at the solid interface not covered by CaCO3. The rates of both carbonation reactions increase with temperature, peak at 400-450 °C, and decrease above 450 °C as a result of the thermodynamically favored reverse CaCO3-decomposition. Avrami's empirical rate law is applied to describe the CO2uptake from the continuous air flow by CaO and Ca(OH)2, with and without added water. The addition of water vapor significantly enhances the reaction kinetics to the extent that, in the first 20 min, the reaction proceeds at a rate that is 22 and nine times faster than that observed for the dry carbonation of CaO and Ca(OH)2, respectively. © 2006 Elsevier B.V. All rights reserved.
Peter G Loutzenhiser - One of the best experts on this subject based on the ideXlab platform.
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solar electricity via an air brayton Cycle with an integrated two step Thermochemical Cycle for heat storage based on co 3 o 4 coo redox reactions iii solar Thermochemical reactor design and modeling
Solar Energy, 2017Co-Authors: Andrew J Schrader, Gianmarco De Dominicis, Garrett L Schieber, Peter G LoutzenhiserAbstract:Abstract A two-step solar Thermochemical Cycle based on Co3O4/CoO redox reactions integrated into an Air Brayton Cycle is considered for Thermochemical heat storage. The two-step Cycle encompasses (1) the thermal reduction of Co3O4 to CoO and O2 driven by concentrated solar irradiation and (2) the re-oxidation of CoO with O2 to Co3O4, releasing heat and completing the Cycle. An evacuated horizontal solar Thermochemical reactor is proposed with an inclined slope and quartz window for promoting direct irradiation of dense, granular Co3O4/CoO flows. Mechanical analysis of flat and spherical quartz window designs for a 5 kWth scale prototype was performed to ensure window stability. Detailed mass and heat transfer analysis for a 5 kWth scale prototype was performed coupling Monte Carlo ray tracing for radiative heat exchange to the energy balances for the bed and the reactor. A parametric study of the reactor design was performed with varying cavity depth, particle inlet temperature, and solar concentration ratio. The optimal solar reactor design maximized conversion of Co3O4 to CoO and particle outlet temperature while preventing particle overheating and achieved a Co3O4 to CoO conversion of 0.91, particle outlet temperature of 1385 K, maximum flow temperature of 1572 K, and absorption efficiency of 0.76.
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solar electricity via an air brayton Cycle with an integrated two step Thermochemical Cycle for heat storage based on co3o4 coo redox reactions ii kinetic analyses
Solar Energy, 2015Co-Authors: Alexander P Muroyama, Andrew J Schrader, Peter G LoutzenhiserAbstract:Abstract A two-step solar Thermochemical Cycle based on Co3O4/CoO redox reactions integrated into an Air Brayton Cycle is considered for Thermochemical heat storage. The two-step Cycle encompasses (1) the thermolysis of Co3O4 to CoO and O2 driven by concentrated solar irradiation and (2) the re-oxidation of CoO with O2 to Co3O4, releasing heat and completing the Cycle. The Cycle steps can be decoupled, allowing for Thermochemical heat storage and integration into an Air Brayton Cycle for continuous electricity production. Kinetic analyses to identify the rate limiting mechanisms and determine kinetic parameters for both the thermolysis of Co3O4 and the re-oxidation of CoO with O2 were performed using a combination of isothermal and non-isothermal thermogravimetry. The Co3O4 thermolysis between 1113 and 1213 K followed an Avrami–Erofeyev nucleation model with an Avrami constant of 1.968 and apparent activation energy of 247.21 kJ mol−1. The O2 partial pressure dependence between 0% and 20% O2–Ar was determined with a power rate law, resulting in a reaction order of 1.506. Ionic diffusion was the rate limiting step for CoO oxidation between 450 and 750 K with an apparent activation energy of 58.07 kJ mol−1 and no evident dependence on O2 concentration between 5% and 100% O2–Ar. Solid characterization was performed using scanning electron microscopy and X-ray powder diffraction.
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solar syngas production from co2 and h2o in a two step Thermochemical Cycle via zn zno redox reactions thermodynamic Cycle analysis
International Journal of Hydrogen Energy, 2011Co-Authors: Peter G Loutzenhiser, Aldo SteinfeldAbstract:Abstract Solar syngas production from CO2 and H2O is considered in a two-step Thermochemical Cycle via Zn/ZnO redox reactions, encompassing: 1) the ZnO thermolysis to Zn and O2 using concentrated solar radiation as the source of process heat, and 2) Zn reacting with mixtures of H2O and CO2 yielding high-quality syngas (mainly H2 and CO) and ZnO; the ZnO is reCycled to the first, solar step, resulting in net reaction βCO2 + (1 − β)H2O → βCO + (1 − β)H2. Syngas is further processed to liquid hydrocarbon fuels via Fischer–Tropsch or other catalytic processes. Second-law thermodynamic analysis is applied to determine the Cycle efficiencies attainable with and without heat recuperation for varying molar fractions of CO2:H2O and solar reactor temperatures in the range 1900–2300 K. Considered is the energy penalty of using Ar dilution in the solar step below 2235 K for shifting the equilibrium to favor Zn production.
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co2 splitting in an aerosol flow reactor via the two step zn zno solar Thermochemical Cycle
Chemical Engineering Science, 2010Co-Authors: Peter G Loutzenhiser, Aldo Steinfeld, Elena M Galvez, Illias Hischier, Aron GrafAbstract:Abstract Using concentrated solar energy as the source of high-temperature process heat, a two-step CO 2 splitting Thermochemical Cycle based on Zn/ZnO redox reactions is applied to produce renewable fuels. The solar Thermochemical Cycle consists of (1) the solar endothermic dissociation of ZnO to Zn and O 2 ; (2) the non-solar exothermic reduction of CO 2 with Zn to CO and ZnO; the latter is reCycled to the 1st solar step. The second step of the Cycle is experimentally investigated in a hot-wall quartz aerosol flow reactor, designed for quenching of Zn(g), formation of Zn nanoparticles, and in - situ oxidation with CO 2 . The effects of varying the reactants stoichiometry, reaction temperatures, and inlet flow temperatures for radial and annular flows were investigated. Chemical conversions of Zn to ZnO of up to 88% were obtained for a residence time of 3 s. For all of the experiments, the reactions primarily occurred heterogeneously on the reaction zone surfaces, outside the aerosol jet flow.
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CO2 Splitting in a Hot-Wall Aerosol Reactor via the Two-Step Zn/ZnO Solar Thermochemical Cycle
ASME 2009 3rd International Conference on Energy Sustainability Volume 2, 2009Co-Authors: Peter G Loutzenhiser, Illias Hischier, M. Elena Gálvez, Anastasia Stamatiou, Aldo SteinfeldAbstract:Using concentrated solar energy as the source of high-temperature process heat, a two-step CO2 splitting Thermochemical Cycle based on Zn/ZnO redox reactions is applied to produce renewable carbon-neutral fuels. The solar Thermochemical Cycle consists of: 1) the solar endothermic dissociation of ZnO to Zn and O2 ; 2) the non-solar exothermic reduction of CO2 with Zn to CO and ZnO; the latter is the reCycled to the 1st solar step. The net reaction is CO2 = CO + 1/2 O2 , with products formed in different steps, thereby eliminating the need for their separation. A Second-Law thermodynamic analysis indicates a maximum solar-to-chemical energy conversion efficiency of 39% for a solar concentration ratio of 5000 suns. The technical feasibility of the first step of the Cycle has been demonstrated in a high-flux solar furnace with a 10 kW solar reactor prototype. The second step of the Cycle is experimentally investigated in a hot-wall quartz aerosol flow reactor, designed for in-situ quenching of Zn(g), formation of Zn nanoparticles, and oxidation with CO2 . The effect of varying the molar flow ratios of the reactants was investigated. Chemical conversions were determined by gas chromatography and X-ray diffraction. Chemical conversions of Zn to ZnO of up to 88% were obtained for a residence time of ∼ 3.05 s. For all of the experiments, the reactions primarily occurred outside the aerosol jet flow on the surfaces of the reaction zone.Copyright © 2009 by ASME
P Tarquini - One of the best experts on this subject based on the ideXlab platform.
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energy and economic assessment of an industrial plant for the hydrogen production by water splitting through the sulfur iodine Thermochemical Cycle powered by concentrated solar energy
International Journal of Hydrogen Energy, 2012Co-Authors: Raffaele Liberatore, M Lanchi, Alberto Giaconia, P TarquiniAbstract:Abstract The faster and faster global growth of energy consumption generates serious problems on its supply and about the pollution that may result. Through the use of Thermochemical Cycles it is possible to use renewable energy to produce hydrogen from water, with the dual purpose of having an unlimited source of energy without producing greenhouse gases. This paper provides an energy assessment and a preliminary design of an industrial plant for the production of 100 tons/day of hydrogen by sulfur-iodine Thermochemical Cycle. Afterwards, an economic analysis is performed to assess the hydrogen production cost, with the assumption to power the process by solar energy. For this purpose, a double solar facility is sized: a parabolic trough plant, for the mean temperature duties, and a central receiver tower one for the higher temperature duties. The efficiency of the Thermochemical Cycle by itself is about 34%. If this value is associated with the electrical energy production, including the efficiency of the solar plants, the total heat-to-hydrogen efficiency of 21% is obtained, with a hydrogen production cost of about 8.3 €/kg.
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s i Thermochemical Cycle a thermodynamic analysis of the hi h2o i2 system and design of the hix decomposition section
International Journal of Hydrogen Energy, 2009Co-Authors: M Lanchi, Raffaele Liberatore, A Spadoni, A Ceroli, Luigi Marrelli, Marco Maschietti, P TarquiniAbstract:Abstract It is widely agreed that the most energy consuming part of the Sulphur–Iodine (S–I) Thermochemical Cycle for hydrogen production is represented by separation processes, especially for the HI decomposition section (HI x section). Therefore, the assessment of the real potential of the S–I Cycle requires an optimization of the separation sections and, hence, a deep knowledge of the thermodynamic behaviour of the systems to be separated. In this paper, a new thermodynamic model for the electrolyte system HI–H 2 O–I 2 is proposed and validated on vapour–liquid (V–L) equilibrium data at atmospheric pressure. The model provides a reliable description of the phase equilibria of the ternary system and is applied for the flow-sheeting of the HI x section at atmospheric pressure along with the energy assessment of the proposed scheme.
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decomposition of hydrogen iodide in the s i Thermochemical Cycle over ni catalyst systems
2007 AIChe Annual Meeting, 2009Co-Authors: P Favuzza, C Felici, M Lanchi, Raffaele Liberatore, C V Mazzocchia, A Spadoni, P Tarquini, A C TitoAbstract:The sulphur-iodine Thermochemical Cycle for hydrogen production has been investigated by ENEA (Agency of New Technologies, Energy and Environment, Italy) over the last 5 years, with a particular focus on chemical aspects. Regarding the hydrogen iodide decomposition, four γ-alumina-supported nickel catalysts were produced and characterized, and then tested in terms of catalytic activity and stability by means of a tubular quartz reactor. In particular, the relationship between catalytic activity and preparation procedure was investigated. From the experimental data acquired, it can be concluded that three of the four catalysts tested demonstrated high catalytic activity, since hydrogen iodide conversion was almost coincident with the theoretical equilibrium value. On the other hand, for all the catalysts, a gradual but considerable deactivation phenomenon was observed at 500 °C, while at a temperature higher than 650 °C the catalytic activity was recovered.
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experimental vapour liquid equilibrium data of hi h2o i2 mixtures for hydrogen production by sulphur iodine Thermochemical Cycle
International Journal of Hydrogen Energy, 2008Co-Authors: Raffaele Liberatore, M Lanchi, A Spadoni, A Ceroli, P TarquiniAbstract:Abstract The Sulphur–Iodine Thermochemical Cycle for hydrogen production has been investigated by ENEA in the framework of the Italian TEPSI Project whose main objective is the realization of an integrated loop plant at a laboratory scale. For the design of the separation–purification equipments, the study of vapour–liquid equilibrium characterization of the ternary HI–H2O–I2 system is considered a key factor. The aim of the present work is to provide new experimental isobaric vapour–liquid equilibrium data for this system by ebulliometry varying both temperature and solution composition. The temperature range has been extended up to about 144 °C, the iodine concentration range from 0.2%w/w to 90%w/w while HI weight fraction varies from 4%w/w to 67%w/w in the liquid phase. Most of the data obtained in this work are in good agreement with other experimental data retrieved from literature, which have been recorded in similar operative conditions but acquired by different procedures.
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hydrogen methanol production by sulfur iodine Thermochemical Cycle powered by combined solar fossil energy
International Journal of Hydrogen Energy, 2007Co-Authors: Alberto Giaconia, M Lanchi, Raffaele Liberatore, Roberto Grena, P TarquiniAbstract:Abstract Hydrogen production from water using the sulfur–iodine (S–I) Thermochemical Cycle, powered by combined solar and fossil heat sources, has been investigated. This combined energy supply was conceived in order to operate the chemical process continuously: a solar concentrator plant with a large-scale heat storage supplies thermal load for services at medium temperatures ( 550 ∘ C ) , while a fossil fuel furnace provides heat load at higher temperatures. Additionally, a methanol production plant fed with the carbon oxides generated from fossil fuel combustion was included. Since the sulfuric acid concentration/decomposition section is interfaced to both the fossil furnace and the solar plant, it was studied more exhaustively. Results obtained show that the major part of the total energy demand (ca. 70%) is renewable. An industrial scale plant with hydrogen capacity of ca. 26,000 tons/year coupled with a 267 MW th solar plant was considered, and the specific cost of the produced hydrogen and methanol determined.
Yanwei Zhang - One of the best experts on this subject based on the ideXlab platform.
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enhanced mechanism of the photo Thermochemical Cycle based on effective fe doping tio2 films and dft calculations
Applied Catalysis B-environmental, 2017Co-Authors: Chenyu Xu, Yanwei Zhang, Zhihua Wang, Jingche Chen, Xuhan Zhang, Junhu ZhouAbstract:Abstract To study the mechanism of the photo-Thermochemical Cycle (PTC), titanium dioxide (TiO2) and Fe-doped TiO2 films were produced using a sol-gel method and applied in the PTC for water splitting. A comparison of H2 production shows that Fe-doped TiO2 performed better than undoped TiO2. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) were used to assess the crystal structure and morphology of the films. UV–vis diffuse reflectance spectra (UV–vis DRS), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) analyses were also conducted to investigate the charge transfer and reaction mechanisms on the TiO2 surface. Density functional theory (DFT) calculations related to the anatase (101) surface of TiO2 and Fe-doped TiO2 were performed to verify and provide guidance for enhancing the PTC mechanism. As a result, several key factors of the mechanism have been clarified and a reaction mechanism has been proposed for the whole Cycle.
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carbon membrane performance on hydrogen separation in h2h2ohi gaseous mixture system in the sulfur iodine Thermochemical Cycle
International Journal of Hydrogen Energy, 2017Co-Authors: Shaojie Xu, Zhihua Wang, Yong He, Yanwei ZhangAbstract:Abstract Sulfur-iodine Thermochemical Cycle is considered as a promising route for hydrogen production without CO 2 emission. In this Cycle, the hydrogen iodide conversion rate plays an important role in the total thermal efficiency to some extent. To improve the efficiency of HI decomposition, the homemade carbon membranes supported by α-alumina porous tubes were well-designed in a specific way and evaluated aiming at removing H 2 from HI decomposition reaction side. Permeability, selectivity and stability of self-designed carbon membranes are investigated in some gaseous components in the present work. Firstly, single-component (H 2 /Ar) permeance was observed with differential pressure ranging from 0.05 to 0.2 Mpa. The result shows that differential pressure has little effect on H 2 and Ar permeance. Secondly, the hydrogen and argon permeance through carbon membrane is 3.1 × 10 −8 mol m −2 s −1 Pa −1 and 5.7 × 10 −10 mol m −2 s −1 Pa −1 respectively at 300 °C. The separation factor of H 2 and Ar is 54, which is greater than the theoretical value calculated by Knudsen diffusion equation. Thirdly, hydrogen permeability in the H 2 HI H 2 O gaseous mixture system owns nearly the same as that of the single-component (H 2 ) at 300–500 °C. Due to the large molecule diameter, most of HI are stopped by carbon membrane. However, H 2 O molecules could pass through the carbon membrane obviously. The permselectivity of H 2 /HI is over 310 at 500 °C. Last, after 10 h of stability tests, some slight damage are observed on the surface of carbon membrane according to the scanning electron micrograph (SEM). The structure change of carbon membrane gave rise to a little increase of H 2 permeance at 20–100 °C.
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catalytic performance and durability of ni ac for hi decomposition in sulfur iodine Thermochemical Cycle for hydrogen production
Energy Conversion and Management, 2016Co-Authors: Guangshi Fu, Yanwei Zhang, Yong He, Zhihua WangAbstract:Abstract This work reports the Ni content effect on the Ni/AC catalytic performance in the HI decomposition reaction of the sulfur–iodine (SI) Thermochemical Cycle for hydrogen production and the Ni/AC catalyst durability in a long-term test. Accordingly, five catalysts with the Ni content ranging from 5% to 15% were prepared by an incipient-wetness impregnation method. The activity of all catalysts was examined under the temperature range of 573–773 K. The catalytic performance evaluation suggests that Ni content plays a significant role in the Ni dispersion, Ni particle size, and eventually the catalytic activity in HI decomposition. 12% is the optimal Ni content for Ni/AC catalysts in HI decomposition which is balanced between poor dispersion of Ni particles and increasing active center. The results of 24 h durability test, which incorporated with BET and TEM investigations of the 12%Ni/AC catalyst before and after the reaction, indicate that establishing a better Ni particle dispersion pattern and improving the stability of Ni particles on the support should be considered in the future.
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effect of raw material sources on activated carbon catalytic activity for hi decomposition in the sulfur iodine Thermochemical Cycle for hydrogen production
International Journal of Hydrogen Energy, 2016Co-Authors: Guangshi Fu, Yanwei Zhang, Zhihua Wang, Zhenyu Huang, Junhu ZhouAbstract:Abstract In order to study the effect of raw material sources on the catalytic performance of activated carbon, five activated carbon samples generated by steam activation of various raw materials (wood, coal, shell, bamboo and coconut shell) were investigated for their catalytic performance in HI decomposition for the sulfur–iodine (SI) Thermochemical Cycle. Their catalytic activities were evaluated from 573 K to 823 K. XRD, BET, SEM, proximate and ultimate analyses were used to characterize the catalysts. The results showed the raw materials of activated carbon played an important role in the catalytic activity of the activated carbon sample in HI decomposition. AC-CS and AC-SHELL exhibited the highest activity, followed by AC-BAMBOO, AC-COAL and AC-WOOD. AC-CS had the highest carbon content and the lowest ash content of the activated carbon samples. The catalytic activity of the activated carbon samples increased in coordination with increasing fixed carbon content and decreasing ash content. A long-term evaluation of catalytic performance was performed with AC-CS to assess its stability during extended use as an HI decomposition catalyst.
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A novel photo-Thermochemical Cycle of water-splitting for hydrogen production based on TiO2−x/TiO2
International Journal of Hydrogen Energy, 2016Co-Authors: Yanwei Zhang, Zhihua Wang, Jingche Chen, Chenyu Xu, Kewei Zhou, Junhu ZhouAbstract:Abstract The traditional two-step Thermochemical Cycle of water-splitting that is based on metal-oxide redox pairs requires a high reaction temperature. In this study, we introduced a photochemical reaction into this Thermochemical Cycle and established a novel photo-Thermochemical Cycle. In this new Cycle, the process by which metal oxides are reduced through concentrated solar energy is replaced with a photochemical reaction while water is still dissociated via a Thermochemical reaction. Thus, photo-Thermochemical Cycles that combine these two reactions can be initiated at relatively low temperatures, unlike Thermochemical Cycles operated at extremely high temperatures. In this research, TiO2 was used as the catalyst, experiments were conducted to evaluate the feasibility of the proposed Cycle, and a preliminary mechanism was developed for this Cycle.
Zhihua Wang - One of the best experts on this subject based on the ideXlab platform.
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enhanced mechanism of the photo Thermochemical Cycle based on effective fe doping tio2 films and dft calculations
Applied Catalysis B-environmental, 2017Co-Authors: Chenyu Xu, Yanwei Zhang, Zhihua Wang, Jingche Chen, Xuhan Zhang, Junhu ZhouAbstract:Abstract To study the mechanism of the photo-Thermochemical Cycle (PTC), titanium dioxide (TiO2) and Fe-doped TiO2 films were produced using a sol-gel method and applied in the PTC for water splitting. A comparison of H2 production shows that Fe-doped TiO2 performed better than undoped TiO2. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) were used to assess the crystal structure and morphology of the films. UV–vis diffuse reflectance spectra (UV–vis DRS), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) analyses were also conducted to investigate the charge transfer and reaction mechanisms on the TiO2 surface. Density functional theory (DFT) calculations related to the anatase (101) surface of TiO2 and Fe-doped TiO2 were performed to verify and provide guidance for enhancing the PTC mechanism. As a result, several key factors of the mechanism have been clarified and a reaction mechanism has been proposed for the whole Cycle.
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carbon membrane performance on hydrogen separation in h2h2ohi gaseous mixture system in the sulfur iodine Thermochemical Cycle
International Journal of Hydrogen Energy, 2017Co-Authors: Shaojie Xu, Zhihua Wang, Yong He, Yanwei ZhangAbstract:Abstract Sulfur-iodine Thermochemical Cycle is considered as a promising route for hydrogen production without CO 2 emission. In this Cycle, the hydrogen iodide conversion rate plays an important role in the total thermal efficiency to some extent. To improve the efficiency of HI decomposition, the homemade carbon membranes supported by α-alumina porous tubes were well-designed in a specific way and evaluated aiming at removing H 2 from HI decomposition reaction side. Permeability, selectivity and stability of self-designed carbon membranes are investigated in some gaseous components in the present work. Firstly, single-component (H 2 /Ar) permeance was observed with differential pressure ranging from 0.05 to 0.2 Mpa. The result shows that differential pressure has little effect on H 2 and Ar permeance. Secondly, the hydrogen and argon permeance through carbon membrane is 3.1 × 10 −8 mol m −2 s −1 Pa −1 and 5.7 × 10 −10 mol m −2 s −1 Pa −1 respectively at 300 °C. The separation factor of H 2 and Ar is 54, which is greater than the theoretical value calculated by Knudsen diffusion equation. Thirdly, hydrogen permeability in the H 2 HI H 2 O gaseous mixture system owns nearly the same as that of the single-component (H 2 ) at 300–500 °C. Due to the large molecule diameter, most of HI are stopped by carbon membrane. However, H 2 O molecules could pass through the carbon membrane obviously. The permselectivity of H 2 /HI is over 310 at 500 °C. Last, after 10 h of stability tests, some slight damage are observed on the surface of carbon membrane according to the scanning electron micrograph (SEM). The structure change of carbon membrane gave rise to a little increase of H 2 permeance at 20–100 °C.
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catalytic performance and durability of ni ac for hi decomposition in sulfur iodine Thermochemical Cycle for hydrogen production
Energy Conversion and Management, 2016Co-Authors: Guangshi Fu, Yanwei Zhang, Yong He, Zhihua WangAbstract:Abstract This work reports the Ni content effect on the Ni/AC catalytic performance in the HI decomposition reaction of the sulfur–iodine (SI) Thermochemical Cycle for hydrogen production and the Ni/AC catalyst durability in a long-term test. Accordingly, five catalysts with the Ni content ranging from 5% to 15% were prepared by an incipient-wetness impregnation method. The activity of all catalysts was examined under the temperature range of 573–773 K. The catalytic performance evaluation suggests that Ni content plays a significant role in the Ni dispersion, Ni particle size, and eventually the catalytic activity in HI decomposition. 12% is the optimal Ni content for Ni/AC catalysts in HI decomposition which is balanced between poor dispersion of Ni particles and increasing active center. The results of 24 h durability test, which incorporated with BET and TEM investigations of the 12%Ni/AC catalyst before and after the reaction, indicate that establishing a better Ni particle dispersion pattern and improving the stability of Ni particles on the support should be considered in the future.
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effect of raw material sources on activated carbon catalytic activity for hi decomposition in the sulfur iodine Thermochemical Cycle for hydrogen production
International Journal of Hydrogen Energy, 2016Co-Authors: Guangshi Fu, Yanwei Zhang, Zhihua Wang, Zhenyu Huang, Junhu ZhouAbstract:Abstract In order to study the effect of raw material sources on the catalytic performance of activated carbon, five activated carbon samples generated by steam activation of various raw materials (wood, coal, shell, bamboo and coconut shell) were investigated for their catalytic performance in HI decomposition for the sulfur–iodine (SI) Thermochemical Cycle. Their catalytic activities were evaluated from 573 K to 823 K. XRD, BET, SEM, proximate and ultimate analyses were used to characterize the catalysts. The results showed the raw materials of activated carbon played an important role in the catalytic activity of the activated carbon sample in HI decomposition. AC-CS and AC-SHELL exhibited the highest activity, followed by AC-BAMBOO, AC-COAL and AC-WOOD. AC-CS had the highest carbon content and the lowest ash content of the activated carbon samples. The catalytic activity of the activated carbon samples increased in coordination with increasing fixed carbon content and decreasing ash content. A long-term evaluation of catalytic performance was performed with AC-CS to assess its stability during extended use as an HI decomposition catalyst.
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A novel photo-Thermochemical Cycle of water-splitting for hydrogen production based on TiO2−x/TiO2
International Journal of Hydrogen Energy, 2016Co-Authors: Yanwei Zhang, Zhihua Wang, Jingche Chen, Chenyu Xu, Kewei Zhou, Junhu ZhouAbstract:Abstract The traditional two-step Thermochemical Cycle of water-splitting that is based on metal-oxide redox pairs requires a high reaction temperature. In this study, we introduced a photochemical reaction into this Thermochemical Cycle and established a novel photo-Thermochemical Cycle. In this new Cycle, the process by which metal oxides are reduced through concentrated solar energy is replaced with a photochemical reaction while water is still dissociated via a Thermochemical reaction. Thus, photo-Thermochemical Cycles that combine these two reactions can be initiated at relatively low temperatures, unlike Thermochemical Cycles operated at extremely high temperatures. In this research, TiO2 was used as the catalyst, experiments were conducted to evaluate the feasibility of the proposed Cycle, and a preliminary mechanism was developed for this Cycle.
