Membranes For Hydrogen Purification Research Articles

High performance composite hollow fiber membranes for CO2/H2 and CO2/N2 separation

The search for a clean energy source as well as the reduction of CO2 emissions to the atmosphere are important strategies to resolve the current energy shortage and global warming issues. We have demonstrated, for the first time, a Pebax/poly(dimethylsiloxane)/polyacrylonitrile (Pebax/PDMS/PAN) composite hollow fiber membrane not only can be used for flue gas treatment but also for hydrogen purification. The composite membranes display attractive gas separation performance with a CO2 permeance of 481.5 GPU, CO2/H2 and CO2/N2 selectivity of 8.1 and 42.0, respectively. Minimizing the solution intrusion using the PDMS gutter layer is the key to achieving the high gas permeance while the interaction between poly(ethylene oxide) (PEO) and CO2 accounts for the high selectivity. Effects of coating solution concentration and coating time on gas separation performance have been investigated and the results have been optimized. To the best of our knowledge, this is the first polymeric composite hollow fiber membrane for hydrogen purification. The attractive gas separation performance of the newly developed membranes may indicate good potential for industrial applications.

Nitrogen Adsorption, Dissociation, and Subsurface Diffusion on the Vanadium (110) Surface: A DFT Study for the Nitrogen-Selective Catalytic Membrane Application

Catalytic nitrogen (N2)-selective membrane technology with potential applications of indirect CO2 capture and ammonia synthesis is introduced. Metallic membranes made from Earth-abundant group V metals, i.e., vanadium (V), and alloys with ruthenium (Ru) are considered. Similar to a traditional palladium (Pd)-based hydrogen (H2)-selective membrane for hydrogen purification, N2 molecules preferentially adsorb on the catalytic membrane and dissociate into two nitrogen atoms. Atomic nitrogen subsequently diffuses through the crystal lattice by hopping through the interstitial crystal sites of the bulk metal, ultimately leading to atomic nitrogen on the permeate side of the membrane. This study is focused on the nitrogen interactions only at the membrane surface and the first subsurface layer. The adsorption energies of molecular as well as atomic nitrogen on the vanadium surface (V(110)) and Ru-alloyed V surface (VxRu100–x/V(110), where x is the atomic composition of vanadium in the alloy) are calculated usin...

Computational prediction of experimentally possible g-C3N3 monolayer as hydrogen purification membrane

Membrane technology has been used for hydrogen purification. In this work, two-dimensional g-C3N3 monolayer was proposed as an effective hydrogen separation membrane on basis of density functional theory computations. The structure of g-C3N3 monolayer was optimized first, and the computed phonon dispersion confirmed its stability and supported the experimental feasibility. The permeability of H2 and impurity gases, including CO, N2 and CH4, was investigated. Compared with H2, it is more difficult for the impurity gases to penetrate through g-C3N3 monolayer. The high selectivity of H2 vs. CO, N2, and CH4 ensures a superior capability to conventional carbon and silica membranes. With high H2 permeability and selectivity, g-C3N3 monolayer is a potential H2 purification membrane.

Al2O3 Disk Supported Si3N4 Hydrogen Purification Membrane for Low Temperature Polymer Electrolyte Membrane Fuel Cells.

Reformate gas, a commonly employed fuel for polymer electrolyte membrane fuel cells (PEMFCs), contains carbon monoxide, which poisons Pt-containing anodes in such devices. A novel, low-cost mesoporous Si3N4 selective gas separation material was tested as a hydrogen clean-up membrane to remove CO from simulated feed gas to single-cell PEMFC, employing Nafion as the polymer electrolyte membrane. Polarization and power density measurements and gas chromatography showed a clear effect of separating the CO from the gas mixture; the performance and durability of the fuel cell was thereby significantly improved.

Effects of low Ag additions on the hydrogen permeability of Pd–Cu–Ag hydrogen separation membranes

Pd–Cu alloys are of potential interest for use as hydrogen purification membranes, but have relatively low permeability compared to the commercially used alloys such as Pd–Ag. In this work, the effects of partial Ag substitution on the hydrogen diffusivity, solubility and the permeability of Pd–Cu membranes with a bcc structure have been investigated. With the addition of 2.3 and 3.9at% Ag to Pd–Cu, lattice expansions of 0.11% and 0.35% were observed. Structural analyses by in-situ XRD showed that the bcc structure of the 2.3at% Ag alloy is retained upon heating to 600°C, whereas an fcc phase forms in the 3.9at% Ag alloy resulting in a mixed (bcc+fcc) structure. Whilst the diffusion coefficients between 350 and 400°C for both Pd–Cu–Ag ternary samples were shown to be lower than their binary alloys (which had similar structures), higher solubility values were obtained. The lower diffusion coefficients of the ternary alloys are related to an increase in the diffusion activation barrier in the presence of Ag, and the higher solubility values may be attributed to the lattice expansion and high Ag–H chemical interaction. Hydrogen permeation measurements showed that an enhancement in the hydrogen solubility of the bcc phase Pd45.8Cu51.9Ag2.3, does not have a substantial effect on the permeability of the membrane. In contrast, for the Pd45.1Cu51Ag3.9 sample with a mixed (bcc+fcc) phase, higher hydrogen solubility can lead to a remarkable improvement in permeability. Hence, it is suggested that the hydrogen permeability in the bcc phase is mainly controlled by hydrogen diffusion, and the solubility enhancement can only significantly improve the hydrogen permeability when the fcc phase is present.

Physical aging, high temperature and water vapor permeation studies of UV-rearranged PIM-1 membranes for advanced hydrogen purification and production

Ultraviolet (UV)-rearranged PIM-1 membranes have been shown to exhibit superior gas separation performance for H2/CO2 separation. The long-term aging studies of up to 100 days were investigated and revealed that the UV-rearranged PIM-1 membranes are much more stable than the original PIM-1 membrane. By positron annihilation lifetime (PAL) analyses, a constant decrease of o-Ps lifetime during physical aging of all membranes was observed, while o-Ps intensity changed sparingly. Compared to pure gas tests, the UV-irradiated PIM-1 membrane shows considerably enhanced separation performance in mixed gas tests with and without CO under high temperatures. Although the UV-rearranged PIM-1 membranes reveal deteriorating gas separation performance under humid feed conditions due to the effect of water vapor induced plasticization, the overall gas separation performance still outperforms most literature data. The successful validation of the separation performance for the UV-rearranged PIM-1 membranes under similar industrial testing conditions may possibly suggest the great potential of this type of membrane for the purification and production of industrial hydrogen.

Novel intensified catalytic nano-structured nickel–zirconia supported palladium based membrane for high temperature hydrogen production from biomass generated syngas

This Paper is directed on the improvement of the hydrogen permeability of palladium based membranes and their mechanical, chemical and thermal properties by using sandwich type composition based on Nano-Structured supports which at the end of this work demonstrated positive results. It is a new line of research to improve the performance of palladium membranes for hydrogen production and purification. In this study, a novel supported hydrogen selective membrane module was developed which is mechanically, thermally and chemically stable in order to separate hydrogen from syngas. The performance of the sandwiched membrane was evaluated and compared with commercial membrane of the same composition and thickness using hydrogen–nitrogen mixtures followed by the utilization of a syngas. It was shown that the sandwiched membrane had better hydrogen fluxes, good mechanical properties and high chemical stability during 15 days of testing with no failures detected. It also showed a good thermal stability where stable hydrogen concentrations obtained at different temperatures.

Hydrogen solubility and permeability of V–W–Mo alloy membrane for hydrogen separation and purification

Abstract The alloying effects of molybdenum (Mo) into V–W alloy on the solubility of hydrogen, the resistance to hydrogen embrittlement and the hydrogen permeability are investigated in a fundamental manner. It is found that the addition of Mo into V–W alloy decreases the hydrogen solubility. As a result, the applicable hydrogen pressures at the DBTC (the ductile-to-brittle transition hydrogen concentration, which is about 0.2 (H/M) for vanadium alloys) increases. In fact, about 0.15 MPa (673 K) to 0.6 MPa (773 K) of hydrogen pressures can be applied to V–5 mol%W–5 mol%Mo alloy membrane while keeping the hydrogen concentration less than or equal to the DBTC, which is about twice of hydrogen pressure applicable to V–5 mol%W alloy. Thus, the addition of Mo into V–W alloy improves the resistance to hydrogen embrittlement. In addition, the alloying of Mo into V–W alloy also improves the hydrogen permeability. For instance, the hydrogen permeability of V–5 mol%W–5 mol%Mo alloy is about 4–5 times higher than that of Pd–25mass%Ag alloy at 673–773 K.

Design of Nb–W–Mo alloy membrane for hydrogen separation and purification

Abstract The alloying effects of tungsten and molybdenum on the hydrogen solubility of niobium are investigated quantitatively. It is found that the equilibrium hydrogen pressure at the hydrogen concentration of 0.2 (H/M), PDBTC, increases linearly with increasing the amount of tungsten or molybdenum in niobium. On the basis of these results, the PDBTC – composition diagram for Nb–W–Mo system has been proposed. Using this diagram, Nb–8 mol%W–8 mol%Mo alloy has been designed which is expected to resist against hydrogen embrittlement under at least 0.2 MPa of hydrogen pressure. Then, the hydrogen solubility and the permeability of the designed alloy have been investigated in a fundamental manner. It is shown that the dissolved hydrogen concentration in Nb–8 mol%W–8 mol%Mo alloy does not exceed the critical value of the ductile-to-brittle transition hydrogen concentration (DBTC, which is about 0.2 (H/M)) even in a 0.25 MPa of hydrogen pressure at 773 K. This alloy membrane exhibits excellent hydrogen permeability without showing any hydrogen embrittlement during hydrogen permeation under this pressure and temperature conditions.

Development of hydrogen-selective CAU-1 MOF membranes for hydrogen purification by ‘dual-metal-source’ approach

Hydrogen provides reliable, sustainable, environmental and climatic friendly energy to meet world's energy requirement and it also has high energy density. Hydrogen is relevant to all of the energy sectors-transportation, buildings, utilities and industry. In all of these sectors, hydrogen-rich gas streams are needed. Thus, hydrogen-selective membrane technology with superior performances is highly demanded for separation and purification of hydrogen gas mixtures. In this study, novel [Al4(OH)2(OCH3)4(H2N-BDC)3]·xH2O (CAU-1) MOF membranes with accessible pore size of 0.38 nm are evaluated for this goal of hydrogen purification. High-quality CAU-1 membranes have been successfully synthesized on α-Al2O3 hollow ceramic fibers (HCFs) by secondary growth assisted with the homogenously deposited CAU-1 nanocrystals with a size of 500 nm as seeds. The energy-dispersive X-ray spectroscopy study shows that the HCFs substrates play dual roles in the membrane preparation, namely aluminum source and as a support. The crystals in the membrane are intergrown together to form a continuous and crack-free layer with a thickness of 4 μm. The gas sorption ability of CAU-1 MOF materials is examined by gas adsorption measurement. The isosteric heats of adsorption with average values of 4.52 kJ/mol, 12.90 kJ/mol, 12.82 kJ/mol and 27.99 kJ/mol are observed for H2, N2, CH4, and CO2 respectively, indicating different interactions between CAU-1 framework and these gases. As-prepared HCF supported CAU-1 membranes are tested by single and binary gas permeation of H2/CO2, H2/N2 and H2/CH4 at different temperatures, feed pressures and testing time. The permeation results show preferential permeance of H2 over CO2, N2, and CH4 with high separation factors of 12.34, 10.33, and 10.42 for H2/CO2, H2/N2, H2/CH4, respectively. The temperature, pressure and test time dependent studies reveal that HCFs supported CAU-1 membranes possess high stability, resistance to cracking, temperature cycling, high reproducibility, these of which combined with high separation efficiency make this type of MOF membranes are promising for hydrogen recycling from industrial exhausts.

Synthesis, Annealing, and Performances of Pd–Au Asymmetric Composite Membranes for Hydrogen Purification

Composite asymmetric Pd–Au membranes were prepared on porous Inconel and Hastelloy tubular supports by electroless deposition and galvanic displacement techniques and tested both before and after Au deposition in pure H2 atmosphere. The final membranes with average Au bulk content up to 16.7 wt % were 9–15 μm thick and showed H2/He ideal selectivities in excess of 900 for the entire period of their characterization. The annealing of the as-prepared membranes was conducted through the coating and diffusion mechanism in He and H2 atmospheres at 500 °C. The annealing conditions were chosen after nonisothermal and isothermal HT-XRD studies were carried out on Pd–Au coupons prepared with the same techniques used for the membranes fabrication. After the formation of the Pd–Au layer, the membranes showed steady H2 flux and stable Au gradient on the membrane top layer. Comparisons between permeance for Pd–Au and pure Pd membranes indicated that the membranes with an average Au bulk content of 4.5 and 5.4 wt % had...

Porous silicene as a hydrogen purification membrane

We investigated theoretically the hydrogen permeability and selectivity of a porous silicene membrane via first-principles calculations. The subnanometer pores of the silicene membrane are designed as divacancy defects with octagonal and pentagonal rings (585-divacancy). The porous silicene exhibits high selectivity comparable with graphene-based membranes for hydrogen over various gas molecules (N2, CO, CO2, CH4, and H2O). The divacancy defects in silicene are chemically inert to the considered gas molecules. Our results suggest that the porous silicene membrane is expected to find great potential in gas separation and filtering applications.

Rapid prediction of hydrogen permeation through amorphous metal membranes: an efficient computational screening approach

Efficient purification of hydrogen from high temperature mixed gas streams using dense metal membranes can potentially play a critical role in the large-scale production of hydrogen from gasification of coal or biomaterials. We use first-principles calculations together with statistical methods to systematically predict hydrogen permeability through amorphous ternary Zr–Cu–T films (T = 17 elements) and other selected amorphous materials. These results greatly expand the range of amorphous materials that have been considered as hydrogen purification membranes. More importantly, we demonstrate that relatively simple descriptions of the site binding energies in these amorphous materials can account for the key observations from our detailed first-principles calculations. This outcome significantly reduces the computational effort required in future screening of materials in this application and also places bounds on the ultimate performance of these materials.

Highly permeable chemically modified PIM-1/Matrimid membranes for green hydrogen purification

Polymers of intrinsic microporosity, e.g. PIM-1, are attractive materials for gas separation and energy development, which is ascribed mainly to their superior permeability. The H2 and CO2 permeability of PIM-1 is about 1300–4000 Barrer and 3000–8000 Barrer, respectively. However, it has a relatively low H2/CO2 selectivity of 0.4–0.8. Different from the previous UV rearrangement approach, for the first time we report here a viable method to tune the intrinsic properties of PIM-1 blend membranes from being CO2-selective to H2-selective via blending with Matrimid and subsequent cross-linking the mixed matrix membrane with diamines at room temperature. The ideal H2/CO2 selectivity of the membrane after modification by 2 h triethylenetetramine (TETA) improved dramatically from 0.4–0.8 to 9.6, with a H2 permeability of 395 Barrer. The modified membranes also show exceptional separation performance, surpassing the present upper bound for H2/CO2, H2/N2, H2/CH4 and O2/N2 separations. Positron annihilation lifetime spectroscopy (PALS) and Field emission scanning electron microscopy (FESEM) revealed that the diamine cross-linking successfully alters the membrane morphology from a dense to a composite structure. The X-ray diffraction (XRD) analysis and sorption data confirmed that the modified membrane has a smaller d-spacing and a decrease in the diffusivity coefficient. Our results also affirmed that the spatial structure, rather than the pKa value, of the diamine is the prevailing factor which governs the reactivity of diamines towards the PIM-1/Matrimid membrane due to the low concentration of cross-linkable polyimides distributing randomly in the polymer matrix. The fundamentals and knowledge gained throughout this study may facilitate the development of polymeric membranes for green H2 enrichment processes.

Room-temperature synthesis of ZIF-90 nanocrystals and the derived nano-composite membranes for hydrogen separation

Nanocrystals of ZIF-90 have been synthesized at room temperature through a novel procedure and incorporated into PBI-based nano-composite membranes for hydrogen purification. The physical and chemical structures of the ZIF-90 nanoparticles have been examined via multiple advanced instrumental analyses including DLS, XRD, FESEM, NMR and FTIR. The nanocrystals show identical morphology, crystallinity and chemical structure but a significantly reduced particle size (around 100 nm) when compared with the ZIF-90 particles in previous studies. The derived ZIF-90–PBI nano-composite membranes exhibit homogeneous particle dispersion and fine particle–polymer adhesion, as well as excellent hydrogen purification performance at various testing conditions. The 45/55 (w/w) ZIF-90–PBI membrane with the highest ZIF-90 volume loading of up to 50.9 vol% possesses the best ideal H2–CO2 separation performance with a moderate H2 permeability of 24.5 Barrer and a high H2–CO2 selectivity of 25.0 in pure gas permeation tests at 35 °C. The membrane also shows promoted gas separation performance during mixed gas tests at 180 °C with an H2 permeability of 226.9 Barrer and an H2–CO2 separation factor of 13.3 that surpasses the latest Robeson upper bound for H2–CO2 separation. This work not only expands the field of nano-composite membrane fabrication, but also provides prospects for interdisciplinary research combining nano-science and chemical engineering for clean energy development.

팔라듐 합금 수소 분리막의 전처리에 관한 연구

A Pd-based hydrogen membranes for hydrogen purification and separation need high hydrogen perm-selectivity. The surface roughness of the support is important to coat the pinholes free and thin-film membrane over it. Also, The pinholes drastically decreased the hydrogen perm-selectivity of the Pd-based composite membrane. In order to remove the pinholes, we introduced various surface pre-treatment such as alumina powder packing, nickel electro-plating and micro-polishing pre-treatment. Especially, the micro-polishing pretreatment was very effective in roughness leveling off the surface of the porous nickel support, and it almost completely plugged the pores. Fine Ni particles filled surface pinholes with could form open structure at the interface of Pd alloy coating and Ni support by their diffusion to the membrane and resintering. In this study, a surface pore-free Pd-Cu-Ni ternary alloy membrane on a porous nickel substrate was successfully prepared by micro-polishing, high temperature sputtering and Cu-reflow process. And permeation and leak tests showed that the Pd-Cu-Ni ternary alloy hydrogen membrane achieved both high permeability of permation flux and infinite selectivity.

Sorption properties of hydrogen-selective PDMS/zeolite 4A mixed matrix membrane

The present study explores the fundamental science of estimating sorption of gases in membranes comprised of inorganic porous fillers within a polymer matrix with a novel semi-empirical correlation. The sorption properties of H2, C3H8, CO2 and CH4 were determined in polydimethylsiloxane (PDMS)/zeolite 4A mixed matrix membranes (MMMs) to assess the viability of these membranes for hydrogen purification and natural gas sweetening. Zeolite filling in MMMs results an increase in solubility over neat PDMS membrane. In addition, incorporation of zeolite 4A to PDMS membrane improved H2 permeation and H2/CH4 selectivity. The results confirmed that zeolite 4A can significantly improve the separation properties of poorly H2-selective PDMS membrane from 0.7 up to 11 and this overcomes the Robeson upper-bound limitation. This improvement was explained referring the Flory–Huggins interaction parameter within MMMs.

H2-D2 Exchange Kinetics in the Presence of H2S over Pd4S, Pd70Cu30, and Pd47Cu53 Surfaces

H2S retards H2 transport across Pd membranes used for H2 separation by forming a Pd4S scale that has both low H2 dissociation activity and low H-atom permeability. As hydrogen purification membranes, alloys such as Pd70Cu30 and Pd47Cu53 are attractive alternatives to pure Pd due to their resistance to formation of bulk sulfides. Nonetheless, exposure to H2S can decrease the permeability of Pd70Cu30 and Pd47Cu53 membranes, presumably by poisoning the catalytic activity of their surfaces for H2 dissociation. In this work, the effect of H2S on H2 dissociation on Pd4S, Pd70Cu30, and Pd47Cu53 surfaces is investigated by microkinetic analysis of H2-D2 exchange kinetics over Pd4S, Pd70Cu30, and Pd47Cu53 surfaces in the presence of varying concentrations of H2S at near-ambient H2+D2 pressure. We show that the rate of H2-D2 exchange over all three surfaces is significantly suppressed when H2S is added to H2/D2/Ar reactant mixtures and that the suppression of H2-D2 exchange increases with increasing H2S concentrati...

Graphdiyne as Hydrogen Purification Membrane

The permselectivity of H2/O2, H2/N2, H2/CO, and H2/CH4 mixtures passing a graphdiyne membrane is studied by molecular dynamics simulations. At pressure range of 0.047–4.5 GPa, H2 can pass the graphdiyen membrane quickly, while all the O2, N2, CO, and CH4 molecules are blocked. At pressure of 47 kPa, the hydrogen flow is 7 mol/m2s. With increase of pressure, the hydrogen flow goes up, and reaches maximum of 6×105 mol/m2s at 1.5 GPa. Compared to other known membranes, graphdiyne can be used for means of hydrogen purification with the best balance of high selectivity and high permeance.

Hydrogen separation and purification using crosslinkable PDMS/zeolite A nanoparticles mixed matrix membranes

The transport properties of gases in polydimethylsiloxane (PDMS)/zeolite A mixed matrix membranes (MMMs) were determined based on pure gas permeation experiments. MMMs were prepared by incorporating zeolite 4A nanoparticles into a PDMS matrix using a new procedure. The permeation rates of C3H8, CH4, CO2, and H2 were evaluated through a dense homogeneous pure PDMS membrane and PDMS/4A MMMs to assess the viability of these membranes for natural gas sweetening and hydrogen purification. SEM investigations showed good adhesion of the polymer to the zeolite in MMMs. Permeation performance of the membranes was also investigated using a laboratory-scale gas separation apparatus and effects of feed pressure, zeolite loading and pore size of zeolite on the gas separation performance of the MMMs were evaluated. The MMMs exhibited both higher selectivity of H2/CH4 and H2 permeability as compared with the neat PDMS membrane, suggesting that these membranes are very promising for gas separations such as H2/CH4 separation.