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Two different catalysts, Ni-(ZrO2) and Ni-(La2O3)0.1-(ZrO2)0.9, were synthesized to use as catalysts in the autothermal reforming of methane. Ni-(ZrO2) catalyst without lanthanum prepared in this study has a good initial performance, but as the reactions keep progressing, the activities gradually decrease. In contrast, the activities of Ni-(La2O3)0.1-(ZrO2)0.9 catalyst have high thermal stability and coke resistance due to the presence of La. Both methane conversion and hydrogen yield of Ni-(La2O3)0.1-(ZrO2)0.9 in non-reduced form are better than reduced form and as good as commercial Ni-based catalyst (ICI 57-4). [ABSTRACT FROM AUTHOR]

Abstract: A diffusion-bonding procedure at a low temperature, i.e. 500°C, based on the high mobility of silver atoms was developed with a newly designed plate-and-frame type hydrogen purification membrane module consisting of a unit cell and a housing. Two membranes made of palladium and copper sputtered on polished porous nickel supports (PNS) followed by Cu-reflow at 750°C, respectively, were assembled in a unit cell to verify that the low temperature diffusion-bonding method could be applied to gas-tight membranes. Ring-shaped silver foils with a thickness of 50μm were placed between the membranes and the unit cell body made of nickel plate. A pair of membranes, a pair of silver foils and the unit cell body were compressed with a pair of covers and eight screws by a 17cm long torque wrench at 12Nm. The diffusion-bonded unit cell was welded in a module housing comprised of a feed port and a retentate port by a laser-operated welder. After the module was constructed, gas-tightness tests were carried out using helium and the measured helium leakage was 8×10−5 molm−2 s−1 at 0.7MPa, which is the same as the value detected before diffusion bonding with a Viton O-ring. The hydrogen permeation test and durability test consisting of three cycles of alternately changing the temperature and transmembrane pressure difference were carried out using a single gas, hydrogen, and it was found that the hydrogen permeation flux remained constant during the durability test and that the helium leakage did not increase after the durability test. [Copyright &y& Elsevier]

Abstract: In order to decrease its resistance we enlarged the pore size of a porous nickel support (PNS) by using nickel powder with a larger particle size. The gas permeation test showed that this increased the gas permeation flux compared with the previous support. To make up for the various disadvantages, such as the enlarged surface roughness and pore size, a polishing process was introduced with sandpaper, followed by wet polishing with alumina powder. The polishing treatment was very effective in leveling off the surface of the porous nickel support, but it almost completely plugged the pores. Those pores blocked by the polishing process could be regenerated during Cu-reflow at 973K by the upward diffusion of nickel and in this way a 12μm defect-free Pd–Cu–Ni ternary alloy film was formed on the polished porous nickel support. Furthermore, we were able to obtain a three times higher hydrogen permeability than that reported in previous studies, because of the decreased support resistance of the porous nickel support. [Copyright &y& Elsevier]

Abstract: This paper shows the effect of support resistance on the pressure exponent. Pd–Cu–Ni ternary alloy film is formed on the newly developed porous nickel support which has Knudsen diffusion. Permeation flux of hydrogen was measured at 673, 723 and 773K under two different permeation directions, i.e. support to film (SF mode) and film to support (FS mode). It was found that the permeation direction had an effect on the hydrogen permeation flux and the pressure exponent as well. For both of permeation directions, the interface pressure of Pd alloy film and porous nickel support was determined and it was affected by permeation direction. The obtained interface pressure was used to clarify the reason why the pressure exponent was deviated from the Sieverts’ law and it was found that the reason is the support resistance rather than surface reaction. [Copyright &y& Elsevier]

Abstract: This paper introduces and discusses the latest research on the use of H2 generated via the NaBH4 hydrolysis reaction for proton exchange membrane fuel cells (PEMFCs). To realize the NaBH4–PEMFC system, many hydrolysis catalysts such as Ru/anion-exchange resins, Pt/LiCoO2, Co powder/Ni foam, PtRu/LiCoO2 and Ru/carbon have been proposed. Through these efforts, the hydrolysis reaction conversion approached 100%. In addition, the average H2 generation rate based on most of the reports generally ranged from 0.1 to 2.8 H2 l min−1 g−1 (catalyst), which produced a level of PEMFC performance equivalent to 0.1–0.3 kW g−1 (catalyst). However, it was also reported that the H2 generation rate was 28 H2 l min−1 g−1 (catalyst) with the catalyst of Pt/carbon (acetylene black). Considering these reports and the advantageous features of NaBH4 hydrolysis, the NaBH4–PEMFC system seems to be technologically feasible and would constitute an alternative system of supplying H2 in fuel cells. However, some challenges remain, such as the deactivation of the catalyst, the treatment of the by-products, and the proper control of the reaction rate. In addition, if the price of NaBH4 were to be further reduced, this system could become the most powerful competitor in portable application fields of PEMFC. [Copyright &y& Elsevier]

Abstract: Pd–Cu–Ni alloy membrane was successfully deposited 4μm in thickness on porous nickel support by multitarget sputtering and Cu-reflow technique. The surface of porous nickel support needed not to be modified because it has very uniform and small pore distribution as 33nm. From the XRD and SEM analysis, it was clarified that the fabricated Pd–Cu–Ni ternary alloy film had Pd–Cu–Ni alloy character and no defects on the surface of thin membrane. The weight composition of Pd:Cu:Ni was 89:4.5:6.5 from EDS analysis. As a result of single gas permeation test using H2 and N2, hydrogen permeance increased with an increase of operating temperature and transmembrane pressure difference. Furthermore, hydrogen separation factor with single gas test was infinity indicating pinhole-free palladium-based alloy membrane. In additions, it was so stable that the morphology of the surface was not changed and there were no indications of metal interdiffusion during time-on-stream test for 10 days with the cycling of operating temperature and transmembrane pressure difference. [Copyright &y& Elsevier]

We prepared a disc-type Pd–Au alloy membrane, on which a Pt–ZrO 2 protection layer was deposited to protect the hydrogen membrane from H 2 S poisoning. The effect of the protection layer on the performance and morphology of the Pd–Au alloy membrane during H 2 S exposure was investigated. The hydrogen flux did not decrease significantly in the presence of the protection layer, which covered the surface of the membrane. When the membrane with the protection layer was exposed to a mixture of H 2 S, the hydrogen flux decreased to 35% of the original value, which is half of the decrease observed with the bare Pd–Au membrane. The hydrogen flux of the poisoned membrane was almost completely recovered after changing back to pure H 2 gas. Under harsh conditions, the membrane with the protection layer was found to retain the hydrogen flux and selectivity, while the selectivity of the bare membrane decreased to zero, indicating that it was disintegrated. This means that the Pt–ZrO 2 layer prevents direct contact between Pd and H 2 S, thus protecting the Pd membrane from poisoning. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a combined test of the WGS (water–gas shift) reactor and a Pd-based composite membrane was carried out for pre-combustion CO2 capture in a coal gasifier. The two series of WGS reactions, i.e., a high-temperature shift and a low-temperature shift, were performed under a gas composition of 60% CO and 40% H2 at 2100 kPa to imitate coal gasification. The CO2 enrichment and H2 recovery tests at 673 K and 2100 kPa with the high-pressure membrane module after the WGS reaction presented the enriched CO2 concentration and H2 recovery ratios of ∼92% and ∼96%, respectively. The long-term stability test showed that the CO2 concentration decreased to 78.2%, and CO was generated and reached to 8.8% in the retentate stream after 47 h because of reverse WGS and CO2 hydrogenation reaction on 316L stainless steel module. The stability test for ∼3137 h showed that these catalytic activities could be successfully prevented using steel with higher Cr and Ni contents, such as 310S. The WGS-membrane combination test using the outlet gas from a real coal gasifier was continued for ∼100 h and showed that the WGS catalysts and membrane module made of 310S would be stable under real conditions. [Copyright &y& Elsevier]

Abstract: In this study, we investigate the configuration of a Pd–Au composite membrane on a porous nickel support and membrane modules for withstanding the capture of CO2 from a coal gasifier for a long time. The hydrogen permeation flux, recovery and CO2 capture were experimentally evaluated using two different modules and two conditions. As in our study, the CO2 capturing and durability tests were performed with a 40% CO2/60% H2 feed gas mixture in stainless steel (SS) 316L and 310S membrane modules. As a result, it is achieved the durability tests for more than 1150, 1100 (SS 316L module) and 3150 h (SS 310S module) with pressure cycles from 100 to 2000 kPa at 673 K. The durability of the membranes and membrane modules was demonstrated under pressure cycles from 100 to 2000 kPa at 673 K and the SS 310S module was very stable after 3150 h. The durability test for more than 3000 h demonstrated that there was no significant intermetallic diffusion between the PNS and Pd–Au layer. The CO2 capturing test performed using a 40% CO2/60% H2 mixture confirmed that the CO2 capturing capacity of the membrane and membrane module was 2.0 L/min for a CO2 concentration in the retentate stream of 92.3% and that the hydrogen recovery ratio increased with increasing pressure and reached 93.4%. Furthermore, we suggest that the SS 310S module configuration, CO2 capturing test using Pd–Au/ZrO2/PNS membrane and membrane module is very suitable for application as an Integrated Gasification Combined Cycle (IGCC) system due to very simple numbering-up stackable module design was successful. [Copyright &y& Elsevier]

We investigated the thermal stability of exo-tetrahydrodicyclopentadiene(exo-THDCP, C10H16) in theabsence and presence of 1,2,3,4-tetrahydroquinoline (THQ), which actsas a hydrogen donor (H-donor). It was found that conversion of exo-THDCP was faster at the higher temperature. The increasein the rate of

Abstract: A mathematical model for the moving bed is developed to simulate the fuel and steam reactor in the TRCL (Three-Reactor Chemical-Looping) process. An ideal plug flow of the solid and gas is assumed in modeling the fuel and steam reactor in the TRCL process. The model considered the mass, heat balances, equilibrium, physical properties, such as the heat capacity and viscosity, and kinetics. From this model, the temperature, gas conversion and solid conversion profiles can be predicted for fuel and steam reactors. The oxygen carrier inventory (the mass of the oxygen carrier) in the fuel and steam reactor was calculated with variation of the solid inlet temperature, solid conversion, Fe2O3 content and steam feed rate. The temperature of the oxygen carrier to the reactor was the most sensitive parameter for determining the required inventory of the oxygen carrier. An increase in the solid inlet temperature was predicted to decrease the required inventory of the oxygen carrier. In the steam reactor, a solid inlet temperature increase over 1150 K will cause an increase in the inventory of the oxygen carrier due to the equilibrium conversion. An excessively low or high active material content will require a larger inventory of the oxygen carrier in the fuel reactor. In this study, approximately 20 wt.% of the Fe2O3 content was suitable for reducing the inventory of the oxygen carrier while achieving a solid conversion of 0.9 in the fuel reactor. [Copyright &y& Elsevier]

Abstract: The three-reactor chemical-looping process (TRCL) for the production of hydrogen from natural gas is quite attractive for both CO2 capture and hydrogen production. The TRCL process consists of a fuel reactor, a steam reactor and an air reactor. In the fuel reactor, natural gas is oxidized to CO2 and H2O by the lattice oxygen of the oxygen carrier. In the steam reactor, the steam is reduced to hydrogen through oxidation of the reduced oxygen carrier. In the air reactor, the oxygen carrier is fully oxidized by air. In this process, the oxygen carrier is recirculated among the three reactors, which avoids direct contact between fuel, steam and air. In this study, various candidate materials were proposed for the oxygen carrier and support, and a thermal analysis of the process was performed. The oxygen carrier for the process must have the ability to split water into hydrogen in its reduced state, which is a different chemical property from that of the chemical-looping combustion medium. The selection of the oxygen carrier and support require careful consideration of their physical and chemical properties. Fe2O3, WO3 and CeO2 were selected as oxygen carriers. Thermal analysis indicated an expected hydrogen production of 2.64 mol H2 per mol CH4 under thermoneutral process conditions. The results indicated that hydrogen production was affected mainly by the steam-conversion rate. The solid-circulation rate and temperature drop in the fuel reactor were calculated for the selected oxygen carriers with different metal oxide contents and solid-conversion rates. [Copyright &y& Elsevier]

Abstract: This paper describes a study of methane steam reforming using a novel catalytic nickel membrane for hydrogen production. The catalytic nickel membrane was made by the uniaxial-pressing and thermal treatment of nickel powder. Since the nickel powder had catalytic activity, it was unnecessary to deposit an additional reforming catalyst on the nickel filter. The methane conversion, reformate composition, and hydrogen production rate were investigated at very high gas hourly space velocities of 22,350–100,700h−1 with a steam to carbon ratio of 3.0. When a mixture of methane and water was introduced into the catalytic nickel filter, the experimental trends exceeded the theoretical equilibrium model, because of the difference in the permeation rates of the gases, even with residence times of only ∼0.036s. [Copyright &y& Elsevier]

Abstract: This paper proposes a novel two-step thermochemical cycle for hydrogen production from water using germanium oxide. The thermochemical cycle is herein referred to as KIER 4. KIER 4 consists of two reaction steps: the first is the decomposition of GeO2 to GeO at approximately 1400–1800°C, the second is hydrogen production by hydrolysis of GeO below 700°C. A 2nd-law analysis was performed on the KIER 4 cycle and a maximum exergy conversion efficiency was estimated at 34.6%. Thermodynamic analysis of GeO2 decomposition and hydrolysis of GeO confirmed the possibility of this cycle. To demonstrate the cycle, the thermal reduction of GeO2 was performed in a TGA with mass-spectroscopy. Results suggest GeO2 decomposition and oxygen gas evolution. To confirm the thermal decomposition of GeO2, the effluent from GeO2 decomposition was quenched, filtered and analyzed. SEM analysis revealed the formation of nano-sized particles. XRD analysis for the condensed-filtered particles showed the presence of Ge and GeO2 phases. The result can be explained by thermodynamic instability of GeO. It is believed that GeO gas disproportionates to ½Ge and ½GeO2 during quenching. 224ml hydrogen gas per gram of reduced GeO2 was produced from the hydrolysis reaction. [Copyright &y& Elsevier]

Abstract: This study examines the effect of hydrogen peroxide (H2O2) on the open-circuit voltage (OCV) of a proton exchange membrane fuel cell (PEMFC) and the reduction of H2O2 in the membrane using a ruthenium/carbon catalyst (Ru/C) at the anode. Each cathode and anode potential of the PEMFC in the presence of H2O2 is examined by constructing a half-cell using 1.0M H2SO4 solution as an electrolyte and Ag/AgCl as the reference electrode. H2O2 is added to the H2SO4 solution and the half-cell potential is measured at each H2O2 concentration. The cathode potential is affected by the H2O2 concentration while the anode potential remains stable. A Ru catalyst is used to reduce the level of H2O2 formation through O2 cross-over at the interface of a membrane and the anode. The Ru catalyst is known to produce less H2O2 through oxygen reduction at the anode of PEMFC than a Pt catalyst. A Ru/C layer is placed between the Nafion® 112 membrane and anode catalyst layer and the cell voltage under open-circuit condition is measured. A single cell is constructed to compare the OCV of the Pt/C only anode with that of the Ru/C-layered anode. The level of hydrogen cross-over and the OCV are determined after operation at a current density of 1Acm−2 for 10h and stabilization at open-circuit for 1h to obtain an equilibrium state in the cell. Although there is an increase in the OCV of the cell with the Ru/C layer at the anode, excessive addition of Ru/C has an adverse effect on cell performance. [Copyright &y& Elsevier]

Abstract: This study investigates the effect of the anode diffusion layer on the cell performance and stability of a direct borohydride fuel cell (DBFC). Carbon paper with various PTFE contents and thicknesses is used as the anode diffusion layer. In the case of the DBFC, both hydrogen evolution and liquid fuel diffusion have to be considered while selecting an anode diffusion layer. Among the various PTFE-containing diffusion layers, the non-contained diffusion layer yields the best performance. Adding PTFE to the diffusion layer leads to improved gas transport but is unsuitable in the DBFC. In addition, the thinnest (100μm) diffusion layer gives the best performance among the diffusion layers with various thicknesses. The decrease in the length of the diffusion path is beneficial for both the release of hydrogen gas and the diffusion of liquid fuel. In addition, it is found that the hydrogen evolution rate increases with increasing cell performance. Overall, adequate diffusion of liquid fuel is more important for the performance of a DBFC than the release of hydrogen gas. [Copyright &y& Elsevier]

Abstract: A Pt–Zr catalyst coated FeCrAlYmesh is introduced into the combustion outlet conduit of a newly designed microchannel reactor (MCR) as an igniter of hydrogen combustion to decrease the start-up time. The catalyst is coated using a wash-coating method. After installing the Pt–Zr/FeCrAlYmesh, the reactor is heated to its running temperature within 1min with hydrogen combustion. Two plate-type heat-exchangers are introduced at the combustion outlet and reforming outlet conduits of the microchannel reactor in order to recover the heat of the combustion gas and reformed gas, respectively. Using these heat-exchangers, methane steam reforming is carried out with hydrogen combustion and the reforming capacity and energy efficiency are enhanced by up to 3.4 and 1.7 times, respectively. A compact fuel processor and fuel-cell system using this reactor concept is expected to show considerable advancement. [Copyright &y& Elsevier]

Abstract: Nickel porous membrane was successfully made for hydrogen separation or metal support for Pd and/or Pd-alloy dense membrane. Ni porous membrane made by uniaxial pressing has so small and uniform pore size to be the support of dense membrane. We fabricated the Ni porous membrane with two kinds of Ni powder (average particle size of 0.15 and 5μm). It was clarified that the broad distribution of particle size is very important to the packing degree of membrane and selectivity of H2 and H2 permeation was contributed by Knudsen and surface diffusion from the results of permeation test under room temperature to 200°C. With various particle size as well as the increasing compressed pressure, we could obtain more compactness, thereby achieving the satisfactory selectivity of H2. [Copyright &y& Elsevier]

Abstract: Microchannel reactor offers opportunities for the development of compact fuel processor for PEMFCs. The design and experimental work concerning a microdevice for the methane steam reforming with hydrogen catalytic combustion is presented herein. We designed novel flow channel on reformer sheets and microholes on combustor sheet to inhibit the hot spot, which takes place in front of the reactor. Experimental results show that the Pt–Sn/Al2O3 coated microchannel combustor was active enough to initiate hydrogen combustion at room temperature and able to increase reactor temperature up to 800°C by hydrogen combustion uniformly. The performance of the microchannel reformer was investigated at various operating conditions. The developed micro fuel processor generates enough hydrogen for power output of 26W as fuel cell. [Copyright &y& Elsevier]