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Abstract: In this study, the hydrogen permeation behavior of a Pd93–Cu7 alloy membrane deposited on ceria-modified porous nickel support (PNS) was evaluated. PNS, which has an average pore size of 600 nm, was modified by alumina sol. Alumina sol was prepared using precursors that had a mean particle size of 300 nm. Alumina-modified PNS was further treated with ceria sol modification to produce a smoother surface morphology and narrow surface pores. A 7 μm thick Pd93–Cu7 alloy membrane was made on an alumina-modified PNS and a ceria-finished membrane was fabricated by magnetron sputtering followed by Cu-reflow at 700 °C for 2 h. SEM analysis showed that the membrane deposited on a ceria-finished PNS contained more clear grain boundaries than the membrane deposited on the alumina-modified PNS. The membrane was mounted in a stainless steel permeation cell with a gold-plated stainless steel O-ring. Permeation tests were then conducted using pure hydrogen and helium at temperatures ranging from 673 to 773 K and feed side pressures ranging from 100 to 400 kPa. These tests showed that the membrane had a hydrogen permeation flux of 2.8 × 10−1 mol m−2 s−1 with H2/He selectivity of >50,000 at a temperature of 773 K and pressure difference of 400 kPa. [Copyright &y& Elsevier]

Abstract: In this study, the effect of module configuration on the performance of Pd-based membrane devices was examined using a Pd-Au composite membrane deposited on a porous nickel support. Hydrogen permeation flux, recovery, and CO2 enrichment were experimentally examined using two different modules. The module configuration that had a narrower space between the surface of the membrane and cover plate provided a large linear flow velocity of the gas mixture, which allowed for a reduction in the concentration polarization. The CO2 enrichment capacity of the membrane module with a space distance of 0.4 mm was 4 times higher than the module with a space distance of 2.5 mm. In regards to the process design, the membrane with an effective area of 16.6 cm2 could enrich 40% of the CO2 at a flow rate of 2000 ml min−1 up to 87% with a hydrogen recovery ratio of >90% at 673 K and a total feed pressure of 1600 kPa. [Copyright &y& Elsevier]

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: Pd–Cu–Ni ternary alloy membranes were fabricated on a porous nickel support by sputtering followed by the Cu-reflow method. The weight composition of Pd:Cu:Ni was 88.9:7.4:3.7 and the thickness was 12μm. α–β phase transition tests were carried out using hydrogen gas in the temperature range from 373 to 623K using feed side pressures of 0.052 and 0.138MPa. There were neither peaks nor shoulders in the hydrogen flux across the entire temperature range, meaning that the α–β phase transition did not occur below the critical points of the Pd–H system, i.e. 565K, 1.97MPa. The durability of the membranes was demonstrated by performing temperature cycles from room temperature to 773K at a feed side pressure of 0.138MPa and this was attributed to the phase stability of the α-phase even at room temperature. [Copyright &y& Elsevier]

Abstract: Nickel filter was successfully fabricated by press process of micron-size nickel powder for particles separation from gasifier. Nickel powder having 2–10μm of particles size distribution was pressed in cylindrical metal mould under pressure of 45–330MPa to clarify the fabrication pressure effect on the pore properties of the filter and gas permeation flux. The pressed nickel filter was treated at 450°C for 10h to have thermal stability and mechanical strength. It was clarified that the fabrication pressure is very important to control the pore properties such as average pore diameter, porosity and total pore volume which have an effect on air permeation and pressure drop. The air permeation flux of nickel filter decreases with increasing fabrication pressure due to the decrease of total pore volume. The filtering test showed that they have separation efficiency over 99.9% on the particles which have size distribution of 20–450nm. [Copyright &y& Elsevier]

Abstract: Porous nickel support was successfully made by uniaxial pressing of nickel powder for gases separation or metal support of Pd and/or Pd-alloy dense membrane. Since the used nickel powder was prepared by pulsed wire evaporation (PWE) method, it has a good thermal stability. Furthermore, a broad particle size distribution from 20 to 5000nm cleared out the powder mixing step in the procedures of fabrication of porous nickel support. From the pore characterization and SEM analysis, it was clarified that the fabricated porous nickel support had so small uniform pore size of 33nm and very smooth surface so that it can be offered as new material for the substrate of palladium and/or palladium-based alloy membrane. As a result of single gas permeation test using H2 and N2, permeance was constant with increasing transmembrane pressure difference and the selectivity was around 3.7, which indicated that the gas permeation was contributed by Knudsen diffusion. Since it has thermal resistance up to 650°C, sputtering followed by cupper reflow could be applied to the formation of Pd–Cu–Ni ternary film on it. Furthermore, it showed the defect-free dense membrane characteristic. [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: 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]

Abstract: A metal catalyst-containing, 80 ml, micro-channel reactor (MCR) with a section dedicated to combustion reaction was investigated for the potential application of on-board methane steam reforming (MSR) to hydrogen production. The metal catalyst was introduced into the MCR as a shape of a thin plate that was diffusion-bonded with the other micro-channel plates. The combustion reaction was performed on the other side of the MCR for direct provision of the necessary heat for the endothermic MSR and for miniaturizing the system volume. In the MCR, both the methane conversion and the hydrogen production rate are extremely high compared with those of the equilibrium under atmospheric pressure. The required heat of reaction is successfully provided by the combustion of either hydrogen or the methane mixture on the other side of the MCR without the need for any heating cartridges. This novel micro-channel reformer is suitable for application as a compact fuel processor due to its production of hydrogen-rich syn-gas, small volume, simple catalyst loading and use of an active and easily stackable catalyst. [Copyright &y& Elsevier]