記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

CO2 reforming of methane was examined under direct irradiation of the catalytically activated metal foam absorber by solar-simulated, concentrated visible light in the small receiver- reactor system with a transparent window. Rh, Ru, or Ni was applied as the active metal on the aluminacoated or noncoated Ni-Cr-Al metal foam disk for the preparation of the absorber. Rh showed the best activity on the noncoated metal foam while Ru was the best on the alumina-coated one. The most active and stable RU Al2O3/Ni-Cr-Al-foam absorber yielded a maximum methane conversion of 73% at a GHSV of 8500 h(-1) and at ambient pressure, in which about 50% of the incident light energy reaching the absorber was stored as chemical enthalpy at a relatively low value of the average input-power density of radiation, rho = 180 kW m(-2) (the peak flux density of 274 kW m-2 at the center of the irradiated surface of the absorber). This catalytically activate metal foam absorber will be used in the receiver-reactor system for solar methane reforming at relatively low-energy fluxes of concentrated solar radiation.

DOI： 10.1021/ef0200525

Web of Science

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

CO2 reforming of methane was examined under direct irradiation of the catalytically activated metal foam absorber by solar-simulated, concentrated visible light in the small receiver- reactor system with a transparent window. Rh, Ru, or Ni was applied as the active metal on the aluminacoated or noncoated Ni-Cr-Al metal foam disk for the preparation of the absorber. Rh showed the best activity on the noncoated metal foam while Ru was the best on the alumina-coated one. The most active and stable RU Al2O3/Ni-Cr-Al-foam absorber yielded a maximum methane conversion of 73% at a GHSV of 8500 h(-1) and at ambient pressure, in which about 50% of the incident light energy reaching the absorber was stored as chemical enthalpy at a relatively low value of the average input-power density of radiation, rho = 180 kW m(-2) (the peak flux density of 274 kW m-2 at the center of the irradiated surface of the absorber). This catalytically activate metal foam absorber will be used in the receiver-reactor system for solar methane reforming at relatively low-energy fluxes of concentrated solar radiation.

DOI： 10.1021/ef0200525

Web of Science

researchmap

記述言語：英語   出版者・発行元：MARCEL DEKKER INC  

The cation-exchange capacities for the alkaline earth metals Ba, Mg, and Ca, and their immobilization in the interlayers of a novel swelling fluorine mica (Na-3-mica) with a high-layer-charge density were studied. The mica was fully exchanged or saturated with Ba, Mg, and Ca ions and the cation-exchange capacities were determined to be 246, 338, and 322 meq(100 g)(-1), respectively, on anhydrous basis of mica. The chemical analyses of the saturated micas indicated that about three exchangeable interlayer sodium ions per unit cell existed in the mica as a result of the total negative layer charge due to both Mg vacancies in octahedral sheets and Al substitution in tetrahedral Si sheets of the silicate. The Ba, Mg, and Ca leachabilities of the saturated micas were investigated in 0.5 M NaCl background solutions at room temperature and these were compared to the Sr leachability of the Sr-saturated mica. The degree of the cation immobilization in the interlayers increased in the order of Ca < Sr < Ba < Mg. This could be explained by the interlayer spacings and structures of the saturated micas.

DOI： 10.1081/SS-120016659

Web of Science

researchmap

記述言語：英語   出版者・発行元：MARCEL DEKKER INC  

The cation-exchange capacities for the alkaline earth metals Ba, Mg, and Ca, and their immobilization in the interlayers of a novel swelling fluorine mica (Na-3-mica) with a high-layer-charge density were studied. The mica was fully exchanged or saturated with Ba, Mg, and Ca ions and the cation-exchange capacities were determined to be 246, 338, and 322 meq(100 g)(-1), respectively, on anhydrous basis of mica. The chemical analyses of the saturated micas indicated that about three exchangeable interlayer sodium ions per unit cell existed in the mica as a result of the total negative layer charge due to both Mg vacancies in octahedral sheets and Al substitution in tetrahedral Si sheets of the silicate. The Ba, Mg, and Ca leachabilities of the saturated micas were investigated in 0.5 M NaCl background solutions at room temperature and these were compared to the Sr leachability of the Sr-saturated mica. The degree of the cation immobilization in the interlayers increased in the order of Ca < Sr < Ba < Mg. This could be explained by the interlayer spacings and structures of the saturated micas.

DOI： 10.1081/SS-120016659

Web of Science

researchmap

記述言語：英語   掲載種別：書評論文，書評，文献紹介等   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

This paper reviews the recent developments on thermochemical conversion of concentrated solar high temperature beat to chemical fuels. The conversion has the advantage of producing long term storable energy carriers from solar energy. This conversion also enables solar energy transportation from the sunbelt to remote population centers. The thermochemical pathway is characterized by a theoretical high efficiency. However, there are solar peculiarities in comparison to conventional thermochemical processes-high thermal flux density and frequent thermal transients because of the fluctuating insolation-, and conventional industrial thermochemical processes are generally not suitable for solar driven processes. Therefore, the adaptation to such peculiarities of solar thermochemical processes has been the important R&D task in this research field. Thermochemical water splitting, steam or CO2 gasification of coal, steam or CO2 reforming of methane, and hydrogenetive coupling of methane, are industrially important, endothermic processes to produce useful chemical fuels such as hydrogen, synthesis gas and C-2-hydrocarbons, which have been examined as solar thermochemical processes. The technical. developments and feasibilities to conduct these endothermic processes by utilizing concentrated solar radiation as the process heat are discussed here. My recent experimental results to improve the advanced solar thermochemical technologies are also given. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/S0360-1285(03)00059-5

Web of Science

researchmap

DOI： 10.1016/S0360-1285(03)00059-5

researchmap

記述言語：英語   出版者・発行元：CHEMICAL SOC JAPAN  

A series of layered perovskite-type tantalates with hydrated interlayer space, A(2)SrTa(2)O(7).nH(2)O (A=H, K, Rb), exhibited efficient photocatalytic activity for water splitting into H-2/O-2 mixture under UV irradiation without loading metal co-catalysts.

DOI： 10.1246/cl.2002.1158

Web of Science

researchmap

記述言語：英語   出版者・発行元：ROYAL SOC CHEMISTRY  

A significant effect of clay host was observed on the photocatalytic activity of TiO2; TiO2-pillared fluorine mica exhibited two orders of magnitude higher activity than TiO2 and TiO2-pillared montmorillonite for the photocatalytic degradation of gamma-HCH.

DOI： 10.1039/b206825g

Web of Science

researchmap

記述言語：英語   出版者・発行元：ROYAL SOC CHEMISTRY  

A significant effect of clay host was observed on the photocatalytic activity of TiO2; TiO2-pillared fluorine mica exhibited two orders of magnitude higher activity than TiO2 and TiO2-pillared montmorillonite for the photocatalytic degradation of gamma-HCH.

DOI： 10.1039/b206825g

Web of Science

researchmap

記述言語：英語   出版者・発行元：CHEMICAL SOC JAPAN  

A series of layered perovskite-type tantalates with hydrated interlayer space, A(2)SrTa(2)O(7).nH(2)O (A=H, K, Rb), exhibited efficient photocatalytic activity for water splitting into H-2/O-2 mixture under UV irradiation without loading metal co-catalysts.

DOI： 10.1246/cl.2002.1158

Web of Science

researchmap

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Solar CO2 gasification of coal was demonstrated under direct irradiation of the fluidized coal bed with the concentrated visible light from a solar furnace simulator in a small-scale quartz reactor. Pulverized Australian bituminous coal (the average particle size of 140 pm) was tested. The peak energy-flux density, FDpeak of the incident light beam was varied up to 1270 kW m(-2). The light-to-chemical (enthalpy) energy conversion via the solar gasification increased with increasing the energy-flux density of irradiation. The maximum energy conversion of 8% was obtained at the optimum gas velocity for fluidization of 0.96 N in min(-1).

DOI： 10.1021/ef020053x

Web of Science

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Solar CO2 gasification of coal was demonstrated under direct irradiation of the fluidized coal bed with the concentrated visible light from a solar furnace simulator in a small-scale quartz reactor. Pulverized Australian bituminous coal (the average particle size of 140 pm) was tested. The peak energy-flux density, FDpeak of the incident light beam was varied up to 1270 kW m(-2). The light-to-chemical (enthalpy) energy conversion via the solar gasification increased with increasing the energy-flux density of irradiation. The maximum energy conversion of 8% was obtained at the optimum gas velocity for fluidization of 0.96 N in min(-1).

DOI： 10.1021/ef020053x

Web of Science

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Catalytic activity and selectivity of Ni catalysts for solar CO2-reforming of methane were examined under direct irradiation of the catalyst by solar-simulated, concentrated Xe-arc lamp light, using a small-scaled transparent (quartz) packed-bed reactor. The Ni catalysts (17 wt %-Ni), supported with alpha-Al2O3, SiO2, ZrO2, and TiO2, were tested, and the Ni/alpha-Al2O3 showed the best activity and selectivity under the solar simulation, as well as under direct irradiation by infrared light. With the Ni/alpha-Al2O3 catalyst at the energy flux density of the incident light = 810 kW m(-2) and at the GHSV = 18700 h(-1), more than 90% of methane was chemically converted to syngas, in which 16% of the incident light energy wag stored as chemical enthalpy. The activity data were compared to those for the catalyst irradiated by infrared light or UV-cut Xe light at various reaction temperatures or incident energy flux densities. This comparison indicated that the solar-simulated reforming with the Ni/alpha-Al2O3 was scarcely enhanced by UV-photochemical effect and that the activity was mainly determined by the thermochemical effect or the catalyst-bed temperature.

DOI： 10.1021/ef000226n

Web of Science

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Catalytic activity and selectivity of Ni catalysts for solar CO2-reforming of methane were examined under direct irradiation of the catalyst by solar-simulated, concentrated Xe-arc lamp light, using a small-scaled transparent (quartz) packed-bed reactor. The Ni catalysts (17 wt %-Ni), supported with alpha-Al2O3, SiO2, ZrO2, and TiO2, were tested, and the Ni/alpha-Al2O3 showed the best activity and selectivity under the solar simulation, as well as under direct irradiation by infrared light. With the Ni/alpha-Al2O3 catalyst at the energy flux density of the incident light = 810 kW m(-2) and at the GHSV = 18700 h(-1), more than 90% of methane was chemically converted to syngas, in which 16% of the incident light energy wag stored as chemical enthalpy. The activity data were compared to those for the catalyst irradiated by infrared light or UV-cut Xe light at various reaction temperatures or incident energy flux densities. This comparison indicated that the solar-simulated reforming with the Ni/alpha-Al2O3 was scarcely enhanced by UV-photochemical effect and that the activity was mainly determined by the thermochemical effect or the catalyst-bed temperature.

DOI： 10.1021/ef000226n

Web of Science

researchmap

記述言語：英語  

Palladium-supported sepiolite clay has effectively catalyzed the Suzuki cross-coupling reaction of phenylboronic acid with aryl halide including less reactive electron-rich aryl bromides. © 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0040-4039(02)01132-2

Scopus

researchmap

DOI： 10.1081/SS-120003052

researchmap

記述言語：英語  

Selective photo-oxidation of benzene and cyclohexane were investigated by using TiO2 pillared clays (mica, montmorillonite and saponite). The characterization results indicated that all the TiO2 pillared clays contain TiO2 with similar structure, anatase-like small particles, in the different silicate layers of clays. The solvent effect on the photo-oxidation of benzene on TiO2 pillared clay was significant
both the activity and selectivity were increased by an addition of 10% water in acetonitrile solvent and they were further increased when the reaction was performed in an aqueous environment. In the latter condition, TiO2 pillared clays showed higher selectivity to oxygenates than TiO2 (Degussa P25). The product distribution among oxygenates also depends on the type of the clay host, indicating that the photocatalytic properties of TiO2 depend strongly on the type of clay host. For the cyclohexane photo-oxidation, TiO2 pillared clay showed much higher selectivity than TiO2, possibly because of the hydrophobic nature of pillared clay. © 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0926-860X(01)00863-8

Scopus

researchmap

DOI： 10.1016/S0038-092X(02)00112-3

researchmap

DOI： 10.1081/SS-120003052

researchmap

DOI： 10.1016/S0040-4039(02)02313-4

researchmap

DOI： 10.1016/S0038-092X(02)00112-3

researchmap

researchmap

DOI： 10.1016/S0926-860X(01)00863-8

researchmap

DOI： 10.1016/S0926-860X(01)00954-1

researchmap

記述言語：英語  

Ir/FSM-16 catalysts, prepared by the impregnation method, were investigated in the selective hydrogenation of linoleic acid (cis-9, cis-12 18:2). The results of various characterizations (X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 sorption and X-ray photoelectron spectra (XPS)) indicated that Ir/FSM-16 catalysts contain Ir particles located to a large extent within the FSM-16 channels. For the catalytic hydrogenation of linoleic acid, the Ir/FSM-16 catalyst with relatively higher Ir loading (20 wt.%) produced cis-monoenoic acids (cis 18:1), while dienoic isomers mostly with trans configuration were predominantly produced over Ir supported on non-porous SiO2. The cis/trans ratio of monoenoic acids for the former catalyst was four times larger than that for the latter catalysts. The observed stereoselectivity may be due to an inhibition of the geometric isomerization by the limited space between Ir particles and pore wall of FSM-16. © 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0926-860X(01)00954-1

Scopus

researchmap

DOI： 10.1016/S0040-4039(02)01132-2

researchmap

記述言語：英語   出版者・発行元：ROYAL SOC CHEMISTRY  

Direct 1,4-conjugate addition of naked aldehydes to vinylketones is catalysed effectively by N-methyl-3-aminopropylated FSM-16 mesoporous silica, which can be regarded as a novel heterogeneous catalysis for a practical C-C bond formation reaction.

DOI： 10.1039/b202488h

Web of Science

researchmap

記述言語：英語   出版者・発行元：ROYAL SOC CHEMISTRY  

Direct 1,4-conjugate addition of naked aldehydes to vinylketones is catalysed effectively by N-methyl-3-aminopropylated FSM-16 mesoporous silica, which can be regarded as a novel heterogeneous catalysis for a practical C-C bond formation reaction.

DOI： 10.1039/b202488h

Web of Science

researchmap

DOI： 10.1023/A:1013165014982

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Metal oxide-catalyzed CO2 gasification of coal was examined in a small-scale fluidized-bed reactor at 1073-1223 K and at atmospheric pressure, for the purpose of converting solar high-temperature heat to chemical fuels. The metal oxide powder of In2O3, ZnO, or Fe2O3 in the grain sizes of 4-9 mum was simply mixed with the ground bituminous coal (grain size < 300 mum) and the catalytic effects of the metal oxide on the Boudouard reaction (C-CO2 reaction) in the coal gasification were kinetically studied. The initial coal gasification rate followed the homogeneous or shrinking core model. Gasification activity followed the order of In2O3 > ZnO > Fe2O3 at high temperatures above 1123 K while the order changed to In2O3 > Fe2O3 > ZnO at lower temperatures. The comparison on the Arrhenius parameters for the catalytic and noncatalytic gasification suggests that the gas species of In2O(g) and Zn(g) are the intermediates to react with CO2 in the cases of the In2O3- and ZnO-catalyzed gasifications, respectively. High-temperature separation of used ZnO catalyst from the remaining coal ash by Zn evaporation was demonstrated at 1423 K.

DOI： 10.1021/ef0100404

Web of Science

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Metal oxide-catalyzed CO2 gasification of coal was examined in a small-scale fluidized-bed reactor at 1073-1223 K and at atmospheric pressure, for the purpose of converting solar high-temperature heat to chemical fuels. The metal oxide powder of In2O3, ZnO, or Fe2O3 in the grain sizes of 4-9 mum was simply mixed with the ground bituminous coal (grain size < 300 mum) and the catalytic effects of the metal oxide on the Boudouard reaction (C-CO2 reaction) in the coal gasification were kinetically studied. The initial coal gasification rate followed the homogeneous or shrinking core model. Gasification activity followed the order of In2O3 > ZnO > Fe2O3 at high temperatures above 1123 K while the order changed to In2O3 > Fe2O3 > ZnO at lower temperatures. The comparison on the Arrhenius parameters for the catalytic and noncatalytic gasification suggests that the gas species of In2O(g) and Zn(g) are the intermediates to react with CO2 in the cases of the In2O3- and ZnO-catalyzed gasifications, respectively. High-temperature separation of used ZnO catalyst from the remaining coal ash by Zn evaporation was demonstrated at 1423 K.

DOI： 10.1021/ef0100404

Web of Science

CiNii Article

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

A simple preparation process of Na-4-mica (ideal brittle mica composition of Na4Mg6Al4Si4O20F4. xH(2)O) from kaolinite yielded a nearly pure and very fine Na-4-mica with a crystallite size of about 0.2 um. Strontium-sodium ion exchange in the hydrated interlayers of the Na-4-mica was demonstrated with this fine mica. The forward ion exchange of Sr2+ --> 2Na(+) (Sr-ion adsorption) was determined after equilibration for 4 weeks, and the Sr exchange capacity reached a value of about 200 mequiv (100 g)(-1). The parabolic diffusion or modified Freundlich model described the forward exchange process well. Only a small reverse exchange 2Na(+) --> Sr2+ (Sr-ion desorption) occurred from the hydrated Sr2+-saturated sample in 4 weeks. The irreversible sodium-strontium ion-exchange isotherm was obtained at room temperature after 4 weeks of equilibration. This mica showed much higher selectivities for Sr and Ba than for Mg and Ca, as expected. This selective Sr-ion exchanger with a large ion-exchange capacity and extremely low Sr leachability is expected to be useful for Sr-90 removal followed by its immobilization at room temperature.

DOI： 10.1021/la001774w

Web of Science

CiNii Article

researchmap

DOI： 10.11362/jcssjnendokagaku1961.41.9

researchmap

記述言語：英語   出版者・発行元：KLUWER ACADEMIC PUBL  

The preparation of TiO2-pillared mica was carried out in a CH3COOH aqueous solution. Titanium ion species were obtained by an addition of Ti(C3H7O4 to an aqueous solution of CH3COOH and by subsequent aging of the solution for a prescribed time followed by intercalation of these ionic species into the interlayers of mica. Ti4+-intercalated mica was thus obtained by ion exchange. After the sample was calcined at 773 K in air, TiO2-pillared mica was produced. The pillaring of TiO2 in the interlayer of mica was confirmed by XPS. The surface area TiO2-pillared mica was about 100 times larger than that of mica alone. The basal spacings of the products heated above 523 K were in the range from 2.01 nm to 2.68 nm in the samples obtained under various conditions.

DOI： 10.1023/A:1009634506284

Web of Science

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Highly endothermic conversion of methane to C-2-hydrocarbons and hydrogen was catalytically demonstrated over the SnO2/Fe3O4/SiO2 at 1173 K under co-feeding of methane and steam. The main products were C2H4, C2H6, CO, CO2, and hydrogen. At a low W/F value (a high GHSV), methane was selectively converted to C-2-hydrocarbons and hydrogen, while at a high W/F value (a low GHSV), steam reforming of methane to produce CO and hydrogen became dominant. At the GHSV = 4000-12000 h(-1), 87-94% of C-2 selectivity with 4-6% of methane conversion was obtained at the C-2-formation rate = 4-8 mmol-C h(-1) g(-1)-cat. This process offers the efficient conversion of natural gas to C-2-hydrocarbon and hydrogen utilizing high-temperature heat such as concentrated solar radiation below 1173 K.

DOI： 10.1021/ef000200w

Web of Science

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Highly endothermic conversion of methane to C-2-hydrocarbons and hydrogen was catalytically demonstrated over the SnO2/Fe3O4/SiO2 at 1173 K under co-feeding of methane and steam. The main products were C2H4, C2H6, CO, CO2, and hydrogen. At a low W/F value (a high GHSV), methane was selectively converted to C-2-hydrocarbons and hydrogen, while at a high W/F value (a low GHSV), steam reforming of methane to produce CO and hydrogen became dominant. At the GHSV = 4000-12000 h(-1), 87-94% of C-2 selectivity with 4-6% of methane conversion was obtained at the C-2-formation rate = 4-8 mmol-C h(-1) g(-1)-cat. This process offers the efficient conversion of natural gas to C-2-hydrocarbon and hydrogen utilizing high-temperature heat such as concentrated solar radiation below 1173 K.

DOI： 10.1021/ef000200w

Web of Science

researchmap

DOI： 10.1021/ef000130t

researchmap

DOI： 10.1023/A:1013165014982

researchmap

DOI： 10.1021/la001774w

researchmap

記述言語：英語   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

Thermochemical methane reforming by a reactive redox system of WO, was demonstrated under direct irradiation of the metal oxide by a concentrated, solar-simulated Xe-lamp beam below 1173 K, for the purpose of converting solar high-temperature heat to chemical fuels. In the proposed cycling redox process, the metal oxide is expected to react with methane as an oxidant to produce syngas with a H-2/CO ratio of two, which is suitable for the production of methanol, and the reduced metal oxide which is oxidized back with steam in a separate step to generate hydrogen uncontaminated with carbon oxide. The ZrO2-supported WO3 gave about 45% of CO yield and 55% of H-2 yield with a H-2/CO ratio of about 2.4 in a temperature range of 1080-1160 K at a W/F ratio of 0.167 g min Ncm(-3) (W is the weight of WO3 phase and F is the flow rate of CHO. The activity data under the solar simulation were compared to those for the WO3/ZrO2 heated by irradiation of an infrared light. This comparison indicated that the CO selectivity was much improved to 76-85% in the solar-simulated methane reforming, probably by photochemical effect due to WO, phase. The main solid product of WO2 in the reduced WO3/ZrO2 was reoxidized to WO3 with steam to generate hydrogen below 1173 K. (C) 2001 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0038-092X(01)00058-5

Web of Science

CiNii Article

researchmap

記述言語：英語   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

Thermochemical methane reforming by a reactive redox system of WO, was demonstrated under direct irradiation of the metal oxide by a concentrated, solar-simulated Xe-lamp beam below 1173 K, for the purpose of converting solar high-temperature heat to chemical fuels. In the proposed cycling redox process, the metal oxide is expected to react with methane as an oxidant to produce syngas with a H-2/CO ratio of two, which is suitable for the production of methanol, and the reduced metal oxide which is oxidized back with steam in a separate step to generate hydrogen uncontaminated with carbon oxide. The ZrO2-supported WO3 gave about 45% of CO yield and 55% of H-2 yield with a H-2/CO ratio of about 2.4 in a temperature range of 1080-1160 K at a W/F ratio of 0.167 g min Ncm(-3) (W is the weight of WO3 phase and F is the flow rate of CHO. The activity data under the solar simulation were compared to those for the WO3/ZrO2 heated by irradiation of an infrared light. This comparison indicated that the CO selectivity was much improved to 76-85% in the solar-simulated methane reforming, probably by photochemical effect due to WO, phase. The main solid product of WO2 in the reduced WO3/ZrO2 was reoxidized to WO3 with steam to generate hydrogen below 1173 K. (C) 2001 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0038-092X(01)00058-5

Web of Science

CiNii Article

researchmap

DOI： 10.1016/S0038-092X(01)00058-5

researchmap

記述言語：英語   出版者・発行元：ROYAL SOC CHEMISTRY  

Na-2-mica of the ideal composition of Na2Mg6Al2Si6O20F4. xH(2)O was prepared from a mixture of NaF, magnesium nitrate, SiO2 and calcined kaolinite (the latter serving as a cost-effective aluminosilicate source) at 800 degreesC and was found to excel in Sr removal from solutions at room temperature. This mica was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Al-27 and Si-29 magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Fundamental studies of nNa(+) --> Mn+ (Mn+ = Sr2+, Ca2+, Li+, K+ and Cs+) equilibria revealed a high selectivity and large capacity for Sr2+ ion uptake. A relatively low-temperature heat treatment (200 degreesC) of the Sr-exchanged mica resulted in collapse of the hydrated interlayer spacings of the mica, which will be useful to immobilize strontium in the stable unhydrated phase. This selective Sr-ion exchanger is expected to be useful for Sr-90 removal and its immobilization.

DOI： 10.1039/b101186n

Web of Science

CiNii Article

researchmap

DOI： 10.1039/b101186n

researchmap

記述言語：英語   出版者・発行元：ROYAL SOC CHEMISTRY  

A simple and economical method for the synthesis of high-charge-density Na-4-mica (ideal chemical composition of Na4Mg6Al4Si4O20F4. xH(2)O) from kaolinite was investigated. Synthesis conditions were varied to control crystal size. This novel swelling Na-4-mica was synthesized from a mixture of kaolinite, magnesium nitrate (or ultrafine MgO) and NaF at 850 degreesC, and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size analysis by laser diffraction and Al-27 and Si-29 magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Decreasing the mass of NaF flux during the crystallization of Na-4-mica reduced the crystallite size from 2 to 0.2 mum. As the crystallite size decreased, the average particle size of the mica decreased from 5 to 2 mum. Al-27 MAS-NMR spectra showed that all or nearly all Al is in tetrahedral coordination whereas Si-29 MAS-NMR spectra showed that the nearest neighbour environment of Si is mainly in Si(3Al), as expected based on the Si:Al ratio.

DOI： 10.1039/b009418h

Web of Science

CiNii Article

researchmap

DOI： 10.1039/b009418h

researchmap

DOI： 10.1021/ef000130t

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Metal-oxide-catalyzed CO2 gasification of coal was demonstrated in small packed-bed and fluidized-bed reactors using a solar furnace simulator, for the purpose of converting solar high-temperature heat to chemical fuels. The catalytic activities of In2O3 and ZnO were investigated because used In2O3 or ZnO catalyst may be separated from remaining coal ash by In2O or Zn evaporation at high temperatures and at a reducing atmosphere. Bituminous coal with or without the metal-oxide catalyst in the quartz-tube reactor was directly irradiated by the concentrated Xe-lamp beam and CO2 was fed to the reactor at pCO(2) = 1.0. In the packed-bed reactor, In2O3 and ZnO much improved the chemical coal conversion by about 4-5 and 2-3 times at the catalyst loading of 17 wt %-In and 30 wt %-Zn in the coal-metal-oxide mixture, respectively, at temperatures around 1000-1400 K. In the fluidized-bed reactor at a small catalyst loading (8-10 wt %-metal in the coal-metal-oxide mixture) and at 1073-1163 K, In2O3 catalytically increased the coal-conversion rate by 3 times but ZnO scarcely showed the catalytic activity. This metal-catalyzed coal gasification process offers the efficient solar production of the syngas calorifically upgraded by solar energy.

DOI： 10.1021/ef000169y

Web of Science

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

Metal-oxide-catalyzed CO2 gasification of coal was demonstrated in small packed-bed and fluidized-bed reactors using a solar furnace simulator, for the purpose of converting solar high-temperature heat to chemical fuels. The catalytic activities of In2O3 and ZnO were investigated because used In2O3 or ZnO catalyst may be separated from remaining coal ash by In2O or Zn evaporation at high temperatures and at a reducing atmosphere. Bituminous coal with or without the metal-oxide catalyst in the quartz-tube reactor was directly irradiated by the concentrated Xe-lamp beam and CO2 was fed to the reactor at pCO(2) = 1.0. In the packed-bed reactor, In2O3 and ZnO much improved the chemical coal conversion by about 4-5 and 2-3 times at the catalyst loading of 17 wt %-In and 30 wt %-Zn in the coal-metal-oxide mixture, respectively, at temperatures around 1000-1400 K. In the fluidized-bed reactor at a small catalyst loading (8-10 wt %-metal in the coal-metal-oxide mixture) and at 1073-1163 K, In2O3 catalytically increased the coal-conversion rate by 3 times but ZnO scarcely showed the catalytic activity. This metal-catalyzed coal gasification process offers the efficient solar production of the syngas calorifically upgraded by solar energy.

DOI： 10.1021/ef000169y

Web of Science

CiNii Article

researchmap

記述言語：英語   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

The methane reforming process combined with metal oxide reduction was evaluated, for the purpose of converting solar high-temperature heat to chemicals below 1273 K. The metal oxide was endothermically reacted with methane, to produce CO, hydrogen and the component metal in the temperature range of 1173-1273 K. Of the metal oxide candidates, WO3 and V2O5 were found to be reactive and selective metal oxides for the purposes of methane reforming. The metallic tungsten produced by methane reforming could be used to split water and to generate hydrogen at a lower temperature of 1073 K. To improve the reactivities of WO3 for methane reforming and the subsequent splitting of water, supported tungsten oxides were examined in the temperature range of 1073-1273 K. The reactivities were much improved with the ZrO2-supported WO3, giving a methane conversion of 70% and a CO selectivity of 86%. Our findings indicate the possibility that the proposed two-step process using a WO3/W redox system may be a potentially new thermochemical path that produces useful energy carriers of processed metal, syngas and methanol for storing and transporting solar energy from the sun belt to remote population centers. (C) 2000 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0360-5442(99)00084-5

Web of Science

CiNii Article

researchmap

記述言語：英語   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

A number of metal-oxide redox systems were examined for a two-step thermochemical conversion of coal and water to CO and H-2 for the purpose of utilizing solar high-temperature heat below 900 degrees C: metal oxide+CHn (coal)-->metal+CO+n/2H(2), metal+H2O-->metal oxide+H-2. In2O3 and SnO2 were found to be the most reactive oxidants for coal under an N-2 gas stream below 900 degrees C. These reactive metal oxides were tested for the proposed two-step cyclic process in the pulse feeding mode of H2O, with a temperature swing and under an N-2 gas stream. The two-step cyclic process using the In2O3/coal mixture could be repeated with high coal conversions of about 80% in the temperature range of 600-900 degrees C by resupplying the consumed coal to the system. The repeated two-step process via the In2O3/In redox system resulted in efficient performance of the net reaction CHn (coal)+H2O-->CO+(n/2+1)H-2, while hydrogen was scarcely produced in the continuous feeding mode of H2O/N-2 over the In2O3/coal mixture, at a constant temperature of 900 degrees C. The separation of recovered In2O3 from the remaining coal ashes by In2O evaporation was also proposed, (C) 2000 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0360-5442(99)00067-5

Web of Science

CiNii Article

researchmap

researchmap

DOI： 10.1039/b000041h

researchmap

記述言語：英語   出版者・発行元：TAYLOR & FRANCIS INC  

The synthetic process of a high-charge-density sodium fluorophlogopite mica, Na-4-mica (with an ideal chemical composition of Na4Mg6Al4Si4O20F4. nH(2)O), using kaolinite as a raw material, has been investigated with respect to developing a simplified procedure and controlling crystal size. A fine and highly crystalline phase of the hydrated Na-4-mica, which is essential for practical applications, could be easily prepared from a mixture of kaolinite (or metakaolin) and magnesium nitrate using NaF flux at temperatures below 800 degrees C. An increased mass of NaF flux in the simplified process at 800 degrees C yielded somewhat larger and well-dispersed Na-4-mica crystals with hexagonal and plate-like shapes of 2-3 mu m in size. Cation-exchange equilibria was studied for alkaline earth metal ions of Sr, Ba, and Ca, as well as transition metal ions of Cu and Pb, at room temperature using the hydrated Na-4-mica synthesized by the simplified process. The order of selectivity for the alkaline earth metal ions was Ba2+ >> Sr2+ > Ca2+, and the cation-exchange capacities were 197, 83, and 77 mequiv (100 g)(-1), respectively.

DOI： 10.1081/SS-100100216

Web of Science

CiNii Article

researchmap

DOI： 10.1081/SS-100100216

researchmap

researchmap

DOI： 10.1016/S0360-5442(99)00084-5

researchmap

DOI： 10.1016/S0360-5442(99)00067-5

researchmap

DOI： 10.1021/ef990135u

researchmap

DOI： 10.1021/ef990135u

researchmap

DOI： 10.1039/b000041h

CiNii Article

researchmap

記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

Clay mineral sepiolite exhibited high selectivity for the catalytic conversion of diethylene glycol (DEG) into 1,4-dioxane. The selectivity for the 1,4-dioxane formation depended on weight hourly space velocity (WHSV) and the tunnel structure of sepiolite. When an excess DEG was supplied over the adsorption capacity of the tunnels in sepiolite, the selectivity for 1,4-dioxane formation from DEG decreased and by-products formation increased. These results indicate that cyclodehydration of DEG takes place in the internal space of the intracrystalline tunnels of sepiolite and by-products formation occurs on the outer surface of sepiolite. The Mg(II) ion along the tunnel wall of sepiolite acts as an active site for the cyclodehydration. (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S1381-1169(98)00290-8

Web of Science

CiNii Article

researchmap

記述言語：英語   出版者・発行元：E D P SCIENCES  

A two-step thermochemical process using a redox system of metal oxides for converting coal to CO and H-2 with H2O/CO2 was studied for the propose of utilizing solar high-temperature heat below 1173 K. In the first step, metal oxide was reacted with coal as an oxidant to produce CO and H-2: metal oxide + CHn(coal) --> metal + xCO + (l-x)CO2 + n/2H(2). The metal so formed was reoxidized with H2O or CO2 to generate H-2 or CO in the second step. A number of coal-metal oxide systems were thermodynamically examined and demonstrated at 1173 K. The coal-In2O3 and coal-SnO systems yielded 82 and 62%, respectively. With iron-based oxides, the In(III)-, Ni(II)- and Sn(II)-doped ferrites yielded 60-70% of coal conversions. In these coal-ferrite systems, magnetic separation of recovered ferrite from coal ashes can be expected. The proposed two-step process using In(III)-ferrite could be repeated with highly coal conversion of 60-90%. Our two-step process is superior to the conversions of coal and H2O/CO2 to H-2 and CO below 1173 K by the direct single-step reactions, CHn + H2O --> CO + (n/2+1)H-2 and CHn + CO2 --> 2CO + n/2H(2).

Web of Science

researchmap

記述言語：英語   出版者・発行元：E D P SCIENCES  

A high-temperature thermochemical process using a redox system of metal oxide is proposed for converting CH4 to CO, H-2, and C-2-hydrocarbons (C-2-HCs). Reactions were performed in a two-step redox cycle. In the first high-temperature and endothermic step, methane is reacted with metal oxide to produce C2-HCs and the reduced metal oxide:
2CH(4)+ metal oxide --> C2Hn + (4-n/2)H2O + reduced metal oxide
In the second step, H2O or CO2 is reacted with the reduced metal oxide to generate H-2 or CO at lower temperatures:
H2O + reduced metal oxide --> H-2 + metal oxide
CO2 + reduced metal oxide --> CO + metal oxide
The net reactions are 2CH(4) --> C2H(n) + (4-n/2)H-2, and 2CH(4) + (4-n/2)CO2 --> C2Hn + (4-n/2)(CO + H2O). A thermodynamic analysis showed that redox systems of Fe3O4/FeO, SnO2/SnO and WO3/WO2 are promising for the two-step process. The redox system of Fe3O4 was experimentally examined. Methane was selectively converted to C-2-HCs, H-2, and CO by the two-step process using the Sig-supported Fe3O4 (Fe3O4/SiO2) in the temperature range from 1123 to 1173 K. It was found that the high-temperature methane decomposition to bulk carbon was efficiently suppressed over Fe3O4/SiO2 This process offers the efficient endothermic net reaction for converting natural gas to C2H4, H-2, and CO with upgraded calorific values. utilizing concentrated solar radiation as the energy source of high-temperature process heat below 1173 K.

Web of Science

researchmap

researchmap

researchmap

researchmap

DOI： 10.1081/SS-100100772

researchmap

記述言語：英語  

Selective cation exchange for divalent transition metals of Cd, Ni, Co, Mn and Zn has been investigated with the high-charge-density sodium fluorophlogopite mica, Na-4-mica. The Na-4-mica was easily and economically prepared by the crystallization from a mixture of NaF, MgO and metakaolin, the latter serves as an inexpensive aluminosilicate source. Ion exchange isotherms for Cd2+, Ni2+, Co2+, Mn2+ and Zn2+ were obtained at room temperature and the thermodynamic functions of the ion exchange equilibria were calculated. The 2Na+ → M2+ exchange with the Na-4-mica showed the following selectivity: Zn2+ &gt
Ni2+ ≃Co2+ ≃Cd2+ &gt
Mn2+. The interlayer structure of the hydrated Na-4-mica with the open interlayer space in the range 12.1-13.9 Å was retained during the ion-exchange reaction, indicating the possibility of the reversible 2Na+ ⇆M2+ exchange. The basic selective cation exchange studies of the high-charge-density ion exchanger are of relevance in recovery of metals from waste solution, and waste water treatment and disposal.

DOI： 10.1039/a806758i

Scopus

researchmap

DOI： 10.1039/a900113a

CiNii Article

researchmap

DOI： 10.1039/a900113a

researchmap

記述言語：英語   出版者・発行元：TAYLOR & FRANCIS INC  

Selective cation exchange for Cu and Pb has been demonstrated with the high-charge-density sodium fluorophlogopite mica, Na-4-mica. The 2Na(+) --> M2+ exchange reaction (M = Cu or Pb) was investigated with Na-4-micas prepared by two different synthetic processes. One was easily and economically prepared by crystallization from a mixture of NaF, MgO, and metakaolin, the latter serves as an inexpensive aluminosilicate source. Another was prepared by solution-sol-gel processing. Ion-exchange isotherms for Cu2+ and Pb2+ were obtained at room temperature. The thermodynamic functions for the initial ion-exchange reactions were calculated because the isotherms were not completed. High selectivities for both copper and lead exchange were found on the highly crystallized Na-4-mica prepared from metakaolin. Their ion-exchange capacities were 225 and 257 milliequivalents per 100 g of dry clay for Cu2+ and Pb2+, respectively. This high level decontamination of copper and lead with the highly crystallized Na-4-mica from metakaolin will be a very important separation required for purification of drinking water as well as for wastewater treatment and disposal.

DOI： 10.1081/SS-100100772

Web of Science

CiNii Article

researchmap

記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

The crystal structure of lithium ion conductors, Li3Sc2(PO4)(3) and Li3-2x(Sc1-xMx)(2)(PO4)(3) (M = Ti, Zr) with x = 0.10, were refined by Rietveld analysis for neutron diffraction patterns in order to confirm the site location and site occupancy for Li ions. The Rietveld refinement confirmed that a high disorder was introduced to three kinds of Li sites in the high temperature superionic conduction phase of Li3Sc2(PO4)(3). The high temperature phase was stabilized at room temperature by substituting Ti4+ or Zr4+ for Sc3+ sites. The stabilized materials were also found to have similar high disorder over the Li sites. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0167-2738(98)00279-3

Web of Science

researchmap

記述言語：英語   出版者・発行元：KLUWER ACADEMIC PUBL  

The preparation of TiO2-pillared saponite was carried out in a CH3COOH aqueous solution. Titanium ion species to intercalate into the interlayer of saponite were obtained by an addition of Ti(C3H7O)(4) to an aqueous solution of CH3COOH and by subsequent aging of the solution for a prescribed time. Ti4+-intercalated saponite including organic materials was obtained by ion exchange. After the sample was calcined at 500 degrees C in air, TiO2-pillared saponite was obtained. The resulting TiO2-pillared saponite (Ti-Sapo) possessed surface areas in the range 300-400 m(2)/g and a sharp pore size distribution with the pore radius of 1.2 nm, The basal spacing of the product heated at temperature >250 degrees C was about 2.45 nm. The pillar height of TiO2 in the Ti-Sapo was estimated to be 1.5 nm.

Web of Science

researchmap

記述言語：英語   出版者・発行元：KLUWER ACADEMIC PUBL  

Sn-incorporated folded sheets mesoporous materials (Sn-FSM-16) with various contents of Sn were synthesized by using a mixture of water glass, SnCl4 and NaOH as starting materials. Hexadecyltrimethyl-ammonium chloride (surfactant) was used to intercalate into the layered silicate. The reaction process was followed by measurements of XRD patterns of intermediates. The Sn-FSM-16 was formed via the following mechanism: (1) layered silicates such as alpha-, beta- and delta-Na2Si2O5 were formed as intermediates by the calcination of the mixture of the starting materials; (2) the surfactant was intercalated into the layered silicates; (3) the surfactant-silicate complex with hexagonal structure was obtained as a precursor of Sn-FSM-16; (4) the precursor was calcined to decompose the surfactant in the interlayer and was changed to Sn-FSM-16. The structural aspect of Sn in Sn-FSM-16 was studied by XPS profiles of Sn 3d(5/2) and Si-2p, Si-29 MAS NMR and FTIR. The content of Sn in Sn-FSM increased with increasing concentrations of both Sn and NaOH in the starting materials. The surface area of Sn-FSM-16 decreased with an increase of Sn content in Sn-FSM (1160-620 m(2)/g).

Web of Science

researchmap

researchmap

DOI： 10.1007/s11746-998-0005-z

CiNii Article

researchmap

researchmap

researchmap

記述言語：英語   出版者・発行元：公益社団法人 日本磁気学会  

  The following reaction has been investigated over various metal oxides for the purpose of utilizing solar or nuclear heat as an energy source: (4+x) CH₄ + xH₂O → 2C₂H₄ + xCO + (3x+4)H₂. Oxides of Zn, Mn, Co, Ni, Mg, and Fe were used at 900 °C. The greatest activity for C₂H₄ formation was observed with Fe₃O₄ (magnetite). Substitution of Mn(II) for Fe(II) in magnetite slightly increased the activity for C₂H₄ formation. The surface-lattice oxygens of the wustite (FeO) phase formed by the reduction of MFe₂O₄ (M = Fe, Zn, Mn) with CH₄ are believed to be active in the oxidation of CH₄ to C₂H₄. If this oxidative coupling over MnFe₂O₄ is combined with the reverse water gas shift reaction, the highly endothermic reaction 13CH₄ + 9H₂O → 2C₂H₄ + 9CO + 31H₂ is realized below 900°C.

DOI： 10.3379/jmsjmag.22.S1_400

CiNii Article

researchmap

記述言語：英語   出版者・発行元：公益社団法人 日本磁気学会  

&nbsp;&nbsp;This paper proposes a new application of ferrites for a thermochemical reduction of CO₂ to CO with coal. Reactions are done in a two-step redox cycle:<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1) ferrite + CH_&tau; &rarr; reduced ferrite + xCO + (1-x)CO₂ + &tau;/2H₂<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2) reduced ferrite + (2-x)CO₂ &rarr; ferrite + (2-x)CO,<br>where CH_&tau; represents coal. A number of the systems of ferrites mixed with active carbon have been screened to find the most reactive ferrite for the first-step reaction. The Ni(II)-ferrite showed the greatest reactivity. Efficient net reaction CH_&tau; + CO₂ &rarr; 2CO + &tau;/2H₂ was demonstrated by the proposed two-step process using the mixture of Ni(II)-ferrite and australian bituminous coal in the temperature range of 800-900&deg;C. Our findings suggest that highly endothermic CO₂ reduction with coal will be conducted using concentrated solar radiation as the energy source below 900&deg;C.

DOI： 10.3379/jmsjmag.22.S1_403

CiNii Article

researchmap

記述言語：英語   出版者・発行元：公益社団法人 日本磁気学会  

&nbsp;&nbsp;Ultrafine ferrites, represented by x(MFe₂O₄)-y(Fe₃O₄)-z(Fe₂O₃), where x+y+z=1, were synthesized by the reduction (with dextrose) of the strongly alkaline Fe(III)-tartrate solutions containing M(II) ions (M(II) = Zn(II), Ni(II) and Cd(II)) at 100&deg;C. The particles with the average crystallite size ranging from 20 to 50 nm were obtained. The strongly alkaline solution of Fe(III)-tartrate yielded red-brown precipitates giving very broad peaks of the spinel type compound in the XRD pattern without any reduction processes at 100&deg;C. The Fe(II) ions formed by the reduction of the Fe(III) ions favor the formation of the ferrite particles. The M&ouml;ssbauer data showed that the vacancies, Fe(II) and Ni(II) ions were distributed in the octahedral sites, and Zn(II) and Cd(II) ions in the tetrahedral sites.

DOI： 10.3379/jmsjmag.22.S1_440

CiNii Article

researchmap

DOI： 10.1021/ef970236x

CiNii Article

researchmap

DOI： 10.1021/ef970236x

researchmap

記述言語：英語   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

Redox systems of iron-based oxides (ferrites) mixed with coal powder have been studied to determine the most reactive and selective working materials for thermochemical conversion of coal and water to CO and H-2. Reactions were performed in a two-step redox cycle in which the ferrites were reacted with coal powder at 900 degrees C to produce CO, H-2, and reduced ferrites (coal-gasification step); these were then reoxidized with water vapor to generate H-2 at 700 degrees C in a separate step (water-decomposition step). Magnetite and Mg(II)-, Mn(II)-, Ni(II)-, Zn(II)-, and In(III)-ferrites have been screened for reactivity and selectivity in the coal-gasification step. The In(III)-ferrite showed the greatest reactivity and selectivity for CO formation from coal at 900 degrees C. The CO-production rate in the coal-In(III)-ferrite reaction was 3.5 times as fast as that in the single-step direct coal-H2O reaction. The metallic phase of alpha-Fe and In, produced by the coal-In(III)-ferrite reaction, was reoxidized to the ferrite phase to generate I-I, in the water-decomposition step at 700 degrees C. The amount of H-2 evolved using In(III)-ferrite was 5 times larger than that using magnetite. The processes were repeated in the temperature range 700-900 degrees C, with the highly efficient net reaction CHtau(coal) + H2O --&gt; CO + (tau/2 + 1)H-2. (C) 1997 Elsevier Science Ltd.

DOI： 10.1016/S0360-5442(97)00041-8

Web of Science

CiNii Article

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

A high-temperature thermochemical process using a redox system of metal oxide is proposed for converting CH4 to C-2-hydrocarbons (C-2-HCs) and H-2. Reactions were performed in a two-step redox cycle. In the first high-temperature and endothermic step, methane is reacted with metal oxide to produce C-2-HCs and the reduced metal oxide. The reduced metal oxideis reoxidized with water to generate H-2 at a low temperature in the second step. A thermodynamic analysis showed that redox systems of Fe3O4/FeO, SnO2/SnO, and WO3/WO2 are promising for the two: step process. The redox system of Fe3O4 was experimentally examined. Highly selective conversion could be repeated with SiO2-supported Fe3O4 (Fe3O4/SiO2) to produce C-2-HCs (mainly C2H4) and H-2 alternately in the different steps at temperatures from 1123 to 1173 K; evolution of COx and deposition of bulk carbon were scarcely observed. Experimental studies using unsupported Fe3O4 showed that the formation of C-2-HCs in the first high-temperature step occurred favorably for the reduction from Fe3O4 to FeO in comparison to that from FeO to alpha-FeO. The two-step process using Fe3O4/SiO2 is superior to the production efficiencies of C-2-HCs and H-2 obtained by the direct single-step conversion of CH4; which offers the efficient conversion of natural gas utilizing high-temperature heat such as concentrated solar radiation.

DOI： 10.1021/ef9700691

Web of Science

researchmap

記述言語：英語   出版者・発行元：AMER CHEMICAL SOC  

A high-temperature thermochemical process using a redox system of metal oxide is proposed for converting CH4 to C-2-hydrocarbons (C-2-HCs) and H-2. Reactions were performed in a two-step redox cycle. In the first high-temperature and endothermic step, methane is reacted with metal oxide to produce C-2-HCs and the reduced metal oxide. The reduced metal oxideis reoxidized with water to generate H-2 at a low temperature in the second step. A thermodynamic analysis showed that redox systems of Fe3O4/FeO, SnO2/SnO, and WO3/WO2 are promising for the two: step process. The redox system of Fe3O4 was experimentally examined. Highly selective conversion could be repeated with SiO2-supported Fe3O4 (Fe3O4/SiO2) to produce C-2-HCs (mainly C2H4) and H-2 alternately in the different steps at temperatures from 1123 to 1173 K; evolution of COx and deposition of bulk carbon were scarcely observed. Experimental studies using unsupported Fe3O4 showed that the formation of C-2-HCs in the first high-temperature step occurred favorably for the reduction from Fe3O4 to FeO in comparison to that from FeO to alpha-FeO. The two-step process using Fe3O4/SiO2 is superior to the production efficiencies of C-2-HCs and H-2 obtained by the direct single-step conversion of CH4; which offers the efficient conversion of natural gas utilizing high-temperature heat such as concentrated solar radiation.

DOI： 10.1021/ef9700691

Web of Science

researchmap

DOI： 10.1016/S0360-5442(96)00097-7

CiNii Article

researchmap

DOI： 10.1016/S0360-5442(97)00021-2

researchmap

DOI： 10.1016/S0360-5442(97)00041-8

researchmap

DOI： 10.1016/S0360-5442(97)00021-2

researchmap

記述言語：英語   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

A number of redox systems composed of carbon and bivalent metal-ferrites, MFe(2)O(4)(M = bivalent metal ions), were studied to find the most reactive and selective working materials for a thermochemical water-decomposition cycle combined with CO production from a carbon compound. Magnetite and Mg(II)-, Mn(II)-, Co(II)-, Ni(II)-, and Zn(II)-ferrites mixed with carbon powder have been screened for reactivity and selectivity in the CO-production step (first step) and subsequent water-decomposition step (second step). The Ni(II)-ferrite showed the most reactivity and selectivity for CO formation from carbon in the first step at temperatures above 700 degrees C. The Ni(II)-ferrite could be completely reduced with carbon to the metallic phase of the Ni-Fe alloy and Ni in the first step although only a small portion of magnetite was reduced to wustite under similar conditions. The ferrites reduced in the first step were oxidized with water vapor to generate H-2 in the second step. The highest conversion of H2O to H-2 was obtained using the Ni(II)-ferrite. The total amount of evolved H-2 using Ni(II)-ferrite was 10 times larger than for the magnetite at 500 degrees C. The processes could be repeated using the phase transition between Ni(II)-ferrite and Ni-Fe alloy in the temperature range 700-800 degrees C, with the highly efficient net reaction H2O + C --&gt; H-2 + CO. Copyright (C) 1996 Elsevier Science Ltd.

DOI： 10.1016/0360-5442(96)00058-8

Web of Science

CiNii Article

researchmap

記述言語：日本語   出版者・発行元：日本粘土学会  

(1)球晶は前世紀の半ば頃に,その研究の萌芽をみて以来,一点を中心とする結晶外向成長の途上にある不安定な中問態の一型式とみなされた.生成環境相は濃厚系より希釈系に及び,結晶化度に幅があり(低いものは主に合成結晶,高いものは主に天然鉱物球晶),核形成よりみた系には,不均一に止らず均一系もある,全体を通じ,また部分を通じ,いくつかの共通性がある.これらを6.1に列挙した.(2)球晶の所定例について,上記の通性の中で重点を置き,球晶核とはなにかに視点を移し,成因に結びつけようとする報告がいくつかある.その骨子を紹介した(Morse and Donnay,Keller,Keith and Padden.(3)今世紀の中頃,結晶集合体に視点を置いた結晶化速度論の解析理論が出され(Avsami),これを受けて,高分子球晶の分野で,新しい解析理論と観察事実の整合が示され(Takayanagi),球晶の近代的研究の初期を迎えた.これらの概要を述べた.(4)希釈系の球晶の研究は,今日なお遅れている.将来の検討課題という意味で,結晶成長とコロイド系の様式の相剋の場という視点を書き添えて,この研究史観を終えた.

DOI： 10.11362/jcssjnendokagaku1961.35.188

CiNii Article

CiNii Books

researchmap

DOI： 10.1006/jcat.1996.0387

CiNii Article

researchmap

DOI： 10.1016/S0025-5408(96)00146-8

researchmap

DOI： 10.1016/0926-860X(96)00050-6

CiNii Article

researchmap

researchmap

記述言語：英語   出版者・発行元：The Magnetics Society of Japan  

Ultrafine Ni(II)-bearing ferrites (UNFs) with 14-100% Ni(II)-substitution of <i>x</i> in Ni_<i>x</i>Fe_3-<i>x</i>O₄ for Fe²⁺ in magnetite were synthesized by hydrolysis of Ni²⁺, Fe²⁺, and Fe³⁺ ions at 60°C,followed by aging of the co-precipitates at 60°C and eating to 300°C. The aged precipitates were the precursors of the UNFs, into which they were transformed by heating at 300°C The Ni(II)-substitution of the UNF was corroborated by a decrease in the lattice constant with an increase in the Ni(II) content of the product. The ferrite particles were nearly spherical and uniform. The average crystallite sizes ranged from 8 to 17 nm, which decreased with an increase in the Ni(II)ontent of the ferrite. In the average size range from 14 to 17 nm, the UNFs with various Ni (II)substitutions could be synthesized by changing the aging conditions. A transtion of the UNF (<i>x</i>= 1.0) from superparamagnetic to ferrimagnetic particles at room temperature occurred in the crystallite size range from 8 to 14 nm. The UNFs gave a room temperature saturation magnetization (<i>M</i>_s)much lower than the theoretical <i>M</i>_s.

DOI： 10.3379/jmsjmag.20.305

CiNii Article

CiNii Books

researchmap

DOI： 10.1016/0360-5442(96)00058-8

researchmap

DOI： 10.1111/j.1151-2916.1995.tb08491.x

CiNii Article

researchmap

DOI： 10.1016/0008-6223(95)00094-T

CiNii Article

researchmap

DOI： 10.1006/jssc.1995.1377

CiNii Article

researchmap

DOI： 10.1039/jm9950501413

researchmap

DOI： 10.1016/0025-5408(95)00077-1

CiNii Article

researchmap

DOI： 10.1016/0196-8904(95)00086-S

researchmap

記述言語：英語   出版者・発行元：Kluwer Academic Publishers  

Hydrogen-activated Ni(II)-bearing ferrite, Ni0.37 2+Fe0.49 2+Fe2.09 3+O4.00, showed a high rate of decomposition of carbon dioxide to carbon at 300°C. This is based on the redox process of the Ni(II)-bearing ferrite with the spinel type of crystal structure. The rates of both activation by hydrogen gas and oxidation in carbon dioxide gas were much improved in the Ni (II)-bearing ferrite. The rate of decomposition was 0.178 mol h-1 for the activated Ni(II)-bearing ferrite and 0.005 92 mol h-1 for the activated magnetite in the batch mode, being 30 times larger. The rate of carbon dioxide decomposition was 16 times higher in the flow system in comparison with that of the activated magnetite. © 1994 Chapman &amp
Hall.

DOI： 10.1007/BF00349965

Scopus

CiNii Article

researchmap

DOI： 10.1557/JMR.1994.0462

CiNii Article

researchmap

DOI： 10.1007/BF00354564

researchmap

DOI： 10.1007/BF00351423

researchmap

DOI： 10.1007/BF00400865

researchmap

DOI： 10.1007/BF01191956

researchmap

DOI： 10.1007/BF00400881

researchmap

DOI： 10.1007/BF00357836

CiNii Article

researchmap

記述言語：英語   出版者・発行元：ROYAL SOC CHEMISTRY  

Zn(II)-bearing ferrites with spinel-type structure have been synthesized in strongly alkaline solutions of iron(III) tartrate containing Zn(II) ions at 100-degrees-C. The Zn(II)-bearing ferrites contain few Fe(II) ions, but have a high cation vacancy content (high-vacancy-content Zn(II)-bearing ferrite). The ferrites are solid solutions represented by x(ZnFe2O4)-y(Fe3O4)-z(gamma-Fe2O3), where x + y + z = 1 (0.16 less-than-or-equal-to x less-than-or-equal-to 0.90, 0.01 less-than-or-equal-to y less-than-or-equal-to 0.02, 0.09 less-than-or-equal-to z less-than-or-equal-to 0.82). The cation vacancies are replaced with the Zn(II) ions in the reaction solution, and the replaced number increases with an increase in the concentration of the Zn(II) ions. The high-vacancy-content Zn(II)-bearing ferrites have an ultrafine particle size, &lt; 20 nm. The crystal growth of the ferrite particles is accelerated with the Zn(II) ions in the reaction solution.

DOI： 10.1039/jm9920200525

Web of Science

researchmap

DOI： 10.1111/j.1151-2916.1992.tb05574.x

researchmap

DOI： 10.1039/ft9928802771

CiNii Article

researchmap

researchmap

記述言語：英語  

The high-vacancy-content ferrites represented by x(MFe2O 4)·y(Fe3O4)·z(γ-Fe 2O3), where x+y+z=1 (z≳0.50), were obtained in the clear and strongly alkaline solutions of Fe(III) and M(II) tartrate [M(II)=Zn(II), Ni(II), and Cd(II)] or dextrose at 100°C. The vacancies were replaced with the bivalent metal ions in the reaction solutions, and the replaced number increased with an increase in the concentration of the bivalent metal ions. The ferrite particle size was dependent on the bivalent metal species and the content (x,y). The Fe(II) ions enhanced the crystal-growth rate. The particle size of the magnetites (x=0) increased from 100 to 800 Å with an increase in the Fe(II) ion content (y=0.10-0.35). The high-vacancy-content magnetite was transferred from superparamagnetic to ferrimagnetic particles as the size increased. The Zn(II), Ni(II), and Cd(II) ions did not enhance the growth rate so much as compared to the Fe(II) ions. The particle sizes were less than 200 Å, and most of the particles were superparamagnetic. The saturation magnetizations were lower than the theoretical values, and increased with an increase in the particle size, indicating the surface effect.

DOI： 10.1063/1.347838

Scopus

researchmap

researchmap

DOI： 10.1111/j.1151-2916.1990.tb07631.x

CiNii Article

researchmap

researchmap