Preparation and thermal treatment of Pd/Ag composite membrane on a porous α-alumina tube by sequential electroless plating technique for H2 separation

Pd/Ag/α-Al2O3 composite membranes were prepared by sequential electroless plating technique. The prepared membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spec-troscopy, and inductively coupled plasma atomic emission spectroscopy techniques (ICP-AES). Effects of annealing time, Ag content, and air treatment on the hydrogen permeation flux and morphology of the alloys were investigated. The results of the investigation showed that the prepared type of tube had a good potential as substrate for membrane preparation. In addition, a uniform defect-free alloy was prepared by annealing at 550 ℃ in H2 atmosphere. The permeation results showed an increase in H2 permeation flux by increasing the Ag content and the annealing time. In addition, the air treatment of the prepared membranes at 400 ℃ for 1 h changed the morphology of the alloy and substantially enhanced the hydrogen flux.     

The enhancement of oxygen flux on Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) hollow fibers using silver surface modification

Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) hollow fibers were fabricated using a phase inversion/sintering method. As oxygen permeation of BSCF hollow fibers is controlled by the rate surface exchange kinetics, catalytic Ag particles were coated on both inner and outer surfaces using chemical deposition method, as verified by SEM and EDX. The Ag coated BSCF membranes showed up to 100% increase in oxygen permeation at 700 °C, and improvements lower than 10% were measured at 950 °C as compared with unmodified membranes. It was found that Ag catalyst surface loading was non-homogenous and concentrated on the perovskite grain boundaries. As a result, lighter Ag surface loading delivered improved oxygen flux while oxygen flux reached a maximum even though in the presence of excess catalyst loading. The catalytic activity of Ag was beneficial in enhancing surface reaction kinetics up to 850 °C attributed to the spillover effect. Above this temperature, the increase in oxygen permeation rate was marginally diminished due to the reduction of the spillover effect.     

Preparation and hydrogen permeation of SrCe0.95Y0.05O3−δ asymmetrical membranes

Asymmetrical thin membranes of SrCe_0.95Y_0.05O_3−δ (SCY) were prepared by a conventional and cost-effective dry pressing method. The substrate consisted of SCY, NiO and soluble starch (SS), and the top layer was the SCY. NiO was used as a pore former and soluble starch was used to control the shrinkage of the substrate to match that of the top layer. Crack-free asymmetrical thin membranes with thicknesses of about 50 μm and grain sizes of 5–10 μm were successfully pressed on to the substrates. Hydrogen permeation fluxes (J_H2) of these thin membranes were measured under different operating conditions. At 950 °C, J_H2 of the 50 μm SCY asymmetrical membrane towards a mixture of 80% H₂/He was as high as 7.6 × 10⁻⁸ mol/cm² s, which was about 7 times higher than that of the symmetrical membranes with a thickness of about 620 μm. The hydrogen permeation properties of SCY asymmetrical membranes were investigated and activation energies for hydrogen permeation fluxes were calculated. The slope of the relationship between the hydrogen permeation fluxes and the thickness of the membranes was −0.72, indicating that permeation in SCY asymmetric membranes was controlled by both bulk diffusion and surface reaction in the range investigated.     

Preparation and hydrogen permeation of BaCe0.95Nd0.05O3−δ membranes

A mixed proton–electron conducting perovskite made of BaCe_0.95Nd_0.05O_3−δ (BCN) was prepared by EDTA/citric acid complexing method. The precursor was characterized by differential scanning calorimetry (DSC), thermogravimetry (TG), and X-ray diffraction (XRD). In order to learn the perovskite formation process during the calcination, the intermediate, i.e. the sample calcined at 750 °C for 5 h, was investigated by scanning (STEM), energy-filtered (EFTEM), and high-resolution transmission electron microscopy (HRTEM) as well as electron energy-loss spectroscopy (EELS). The results revealed that the perovskite structure was formed via a solid-state reaction between barium–cerium mixed carbonate and cerium–neodymium mixed oxide particles. Dense mixed proton–electron conducting BCN membranes were made by pressing BCN powder followed by sintering. The microstructure of the sintered membranes was investigated by scanning electron microscopy (SEM). Hydrogen permeation through the BCN membrane was studied using a high-temperature permeator. The hydrogen permeation fluxes under wet conditions are higher than those under dry conditions, which is due to increased proton concentrations in the H⁺ hopping via OH groups. The hydrogen permeation increased with increasing hydrogen and steam concentrations in the feed. For a steam concentration of 15 vol.%, the hydrogen permeation flux reaches 0.026 ml/min cm².     

Fabrication and development of interfacial polymerized thin-film composite nanofiltration membrane using different surfactants in organic phase; study of morphology and performance

The effects of addition of cationic cetyltrimethylammonium bromide (CTAB), non-ionic (Triton X-100) and anionic sodium dodecyl sulfate (SDS) surfactants in organic phase for preparing the composite nanofiltration membranes were investigated. The interfacial polymerization technique was employed by applying trimesoyl chloride (TMC) and piperazine (PIP) as the reagents for the preparation of poly(piperazineamide) on a UF support. The obtained thin layer membranes were placed in oven for 2 min at 70 °C. Water permeation performance, salt rejection, membrane surface charge, chemical structure and membrane morphology including top surface and cross-section were investigated for characterization of the prepared membranes using IR-ATR, SEM, filtration and zeta potential measurement. The prepared membranes using SDS showed higher flux compared to the other membranes. SEM surface images demonstrate some defects and cracks on the thin layer surface of the membrane prepared with SDS. For membrane containing CTAB, the salt rejection increased in the order of Na₂SO₄ > NaCl > MgCl₂ with variation around 50–90%.     

The effect of heat treatment of PES and PVDF ultrafiltration membranes on morphology and performance for milk filtration

The flat sheet polyethersulfone (PES) and poly(vinylidene fluoride) (PVDF) membranes were prepared by immersion precipitation technique. The influence of hot air and water treatment on morphology and performance of membranes were investigated. The membranes were characterized by AFM, SEM, cross-flow filtration of milk and fouling analysis. The PES membrane turns to a denser structure with thick skin layer by air treatment at various temperatures during different times. This diminishes the pure water flux (PWF). However the milk permeation flux (MPF) was considerably improved at 100 °C air treatment for 20 min with no change in protein rejection. The smooth surface and slight decrease in surface pore size for air treated PES membrane at 100 °C compared to untreated membrane may cause this behavior for the membrane. The water treatment of PES membranes at 55 and 75 °C declines the PWF and MPF and increases the protein rejection. This is due to slight decrease in membrane surface pore size. The treatment of PES membrane with water at higher temperature results in a porous structure with superior performance. The fouling analysis of 20 min treated membrane indicates that the surface properties of 100 °C air treated and 95 °C water treated PES membranes are improved compared to untreated membrane. The SEM observation depicts that the morphology of air and water treated PVDF membranes was denser and smoother with increasing the heat treatment temperature. The 20 min air treated PVDF membranes at 100 °C and water treated at 95 °C exhibited the highest performance and antifouling properties.     

Electroless Pd and Ag deposition kinetics of the composite Pd and Pd/Ag membranes synthesized from agitated plating baths

The atomic absorption spectroscopy (AAS) has been successfully utilized for the measurement of the Pd and Ag ion concentrations in the plating baths and to elucidate the effects of temperature, initial metal ion and reducing agent concentrations and agitation on the electroless plating kinetics of Pd and Ag metals. The initial metal ion concentrations for Pd and Ag were varied over a range of 8.2–24.5 mM and 3.1–12.5 mM, respectively. The plating reactions were conducted in a constant temperature electroless plating bath over a temperature range of 20–60 °C and an initial hydrazine concentration range of 1.8–5.4 mM. It was found that the electroless plating of both Pd and Ag were strongly affected by the external mass transfer in the absence of bath agitation. The external mass transfer limitations for both Pd and Ag deposition have been minimized at or above an agitation rate of 400 rpm, resulting in a maximum conversion of the plating reaction at 60 °C and dramatically shortened plating times with the added advantage of uniform deposition morphology. The derivation of the differential rate laws and the estimation of the reaction orders and the activation energies for the electroless Pd and Ag kinetics were conducted via non-linear regression analysis based on the method of initial rates. For a constant-volume batch reactor, the integrated rate law was solved to calculate the conversion and the reactant concentrations as a function of plating time. The model fits were in good agreement with the experimental data. Furthermore, the bath agitation and the plating conditions used in the kinetics study were adopted for the synthesis of 16–20 μm thick composite Pd/Ag membranes (10–12 wt% Ag) and a pure-Pd membrane with a hydrogen selective dense Pd layer as thin as 4.7 μm. While hydrogen permeance of the Pd/Ag membranes A and B at 450 °C were 28 and 32 m³/m²-h-atm^0.5, the H₂ permeance for the 4.7 μm thick pure-Pd membrane at 400 °C was as high as 63 m³/m²-h-atm^0.5_. The long-term permeance testing of all the membranes synthesized from agitated plating baths resulted in a relatively slow leak growth due primarily to the improved morphology obtained via the bath agitation and modified plating conditions.     

Hydrogen permeation of thin,free-standing Pd/Ag23% membranes before and after heat treatment in air

Free-standing Pd/Ag23 wt% membranes with five different thicknesses ranging from ∼1.3 to ∼5.0 μm were prepared by magnetron sputtering. The hydrogen permeation was determined before and after a thermal treatment in air at 300 °C. For all membranes studied, the thermal treatment resulted in enhanced permeation, and for some membranes, the hydrogen flux more than doubled. A permeance of 1.7 × 10⁻² mol/m² s Pa^0.5 was observed for ∼1.3 μm thick membranes, which is one of the highest reported. Bulk diffusion was found to be the main rate-limiting step after thermal treatment in air. The permeability was quite similar for all membranes studied after this treatment, with a mean value of 2.1 × 10⁻⁸ ± 5 × 10⁻¹⁰ mol m/m² s Pa^0.5. Topography studies by atomic force microscopy showed that the samples thermally treated in air had higher surface roughness, larger surface area and larger surface grains than samples not heat-treated in air.     

Preparation of PFSA/PSf hollow fiber composite membranes with recovered PFSA for the pervaporation separation of EtOH/H2O

Perfluorosulfonic acid/Polysulfone(PFSA/PSf) hollow fiber composite membranes have been prepared by dip-coating method using PSf ultrafiltration (UF) membrane as substrate with recovered PFSA. The composite membranes were applied to the pervaporation separation of 95% ethanol (EtOH)/H₂O mixture. SEM images show that the thickness of the PFSA skin layer of the composite membranes is about 2 μm, much thinner than those of other PFSA composite membranes revealed in the literatures. Effects of annealing temperature, coating solution concentration and counter-ions of PFSA on the pervaporation performances of the composite membranes were investigated. The total flux decreases and separation factor increases with the increase of annealing temperature. The highest permeation flux of 3230 g m^?2 h^?1 and a separation factor of 5.4 is obtained for the composite membrane annealed at 80°C. The lowest permeation flux of 396 g m^?2 h^?1 and a separation factor of 27.7 is obtained for the composite membrane annealed at 160°C. The permeation performances of the PFSA/PSf composite membrane are evidently influenced by the counter-ions of PFSA. The flux sequence of the PFSA/PSf composite membranes with different counter-ions is H⁺>Li⁺>Ca²⁺>Mg²⁺>Na⁺>K⁺>Ba²⁺>Fe³⁺>Al³⁺, and the separation factor sequence is H⁺<Li⁺<Al³⁺<Na⁺<Mg²⁺<Ca²⁺<K⁺<Ba²⁺<Fe³⁺. The apparent activation energy ΔE _app values of the composite membranes with different counter-ions were calculated by Arrhenius law. The sequence of ΔE _app values for the membranes with monovalent counter-ions is Li⁺>Na⁺>K⁺. There are very little variations of ΔE _app values between the composite membranes with three divalent counter-ions (Mg²⁺, Ca²⁺ and Ba²⁺), and the ΔE _app values of the composite membranes with two trivalent counter-ions (Fe³⁺ and Al³⁺) are relatively high.     

Hydrogen permeability of 2.5 μm palladium–silver membranes deposited on ceramic supports

The permeability of hydrogen selective Pd-based membranes was tested in different experimental conditions. The membranes were obtained by depositing palladium–silver films onto ceramic porous supports, with film composition of about 20 wt% of silver and thicknesses of about 2.5 μm. Their permeance was measured at 400 °C at total trans-membrane pressures between 0.2 and 6 bar, using pure feeds of H₂ and N₂, as well as H₂/N₂ and H₂/CO mixtures; the temperature dependence of permeability was investigated using pure H₂ feeds at 300, 400 and 500 °C. The membranes exhibit a very attractive behavior, maintaining a virtually infinite selectivity throughout the testing, with permeance values among the highest values reported in literature for similar membranes. Permeation of pure hydrogen accurately follows Sieverts’ law and confirms the presence of a chemisorption–dissociation–diffusion mechanism, characterised by the transport of atomic hydrogen through the Pd–Ag layer as the limiting step. In the case of H₂/N₂ mixtures, the high membrane permeance originates also significant concentration polarization phenomena resulting in apparent deviations from Sieverts’ behavior; the presence of CO in the feed may reduce hydrogen permeability even by 75%, although this effect is shown to be fully reversible after a subsequent air treatment at 400 °C. The temperature dependence of the membrane permeability is of Arrhenius type, with an activation energy of about 17 kJ/mol, that is, close to what is reported for Pd–Ag membranes following Sieverts’ behavior.     

Pervaporation separation of water–acetic acid mixtures through poly(vinyl alcohol)-silicone based hybrid membranes

Hybrid membranes were prepared using poly(vinyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) via hydrolysis followed by condensation. The obtained membranes were characterized by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction and differential scanning calorimetry. The remarkable decrease in degree of swelling was observed with increasing TEOS content in membranes and is attributed to the formation of hydrogen and covalent bonds in the membrane matrix. The pervaporation performance of these membranes for the separation of water–acetic acid mixtures was investigated in terms of feed concentration and the content of TEOS used as crosslinking agent. The membrane containing 1:2 mass ratio of PVA and TEOS gave the highest separation selectivity of 1116 with a flux of 3.33 × 10⁻² kg/m² h at 30 °C for 10 mass% of water in the feed. Except for membrane M-1, the observed values of water flux are close to the values of total flux in the investigated composition range, signifying that the developed membranes are highly water selective. From the temperature dependence of diffusion and permeation values, the Arrhenius apparent activation parameters have been estimated. The resulting activation energy values, obtained for water permeation being lower than those of acetic acid permeation values, suggest that the membranes have higher separation efficiency. The activation energy values calculated for total permeation and water permeation are close to each other for all the membranes except membrane M-1, signifying that coupled-transport is minimal as due to higher selective nature of membranes. Further, the activation energy values for permeation of water and diffusion of water are almost equivalent, suggesting that both diffusion and permeation contribute almost equally to the pervaporation process. The negative heat of sorption values (ΔH_s) for water in all the membranes suggests the Langmuir's mode of sorption.     

The effects of fabrication and annealing on the structure and hydrogen permeation of Pd–Au binary alloy membranes

The addition of gold to palladium membranes produces many desirable effects for hydrogen purification, including improved tolerance of sulfur compounds, reduction in hydride phase formation, and, for certain compositions, improved hydrogen permeability. The focus of this work is to determine if sequential plating can be used to produce self-supported alloy membranes with equivalent properties to membranes produced by conventional metallurgical techniques such as cold-working.Sequential electroplating and electroless plating were used to produce freestanding planar Pd–Au membranes with Au contents ranging from 0 to 20 wt%, consisting of Au layers on both sides of a pure Pd core. Membranes were characterized by single-gas permeation measurements, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), and high temperature, controlled-atmosphere XRD (HTXRD). Sequentially plated foils tested without any prior annealing had significantly lower H₂ permeabilities than either measured or literature values for homogeneous foils of equivalent composition. This effect appears to be due to the formation of stable gold-enriched surface layers. Pretreatment of membranes to 1023 K created membranes with hydrogen permeabilities equivalent to literature values, despite the fact that trace amounts of surface gold remained detectable with XRD.     

Structure and Electron Spin Resonance of Annealed Sol-Gel Glasses Containing Ag

In this work, SiO₂ samples with silver, prepared using the sol-gel method, were analyzed after being thermally treated in air in the range of 100 to 800°C. The sol-gel starting solutions were prepared by mixing tetra-ethyl-orthosilicate (TEOS), water and ethanol. Samples with 4 different H₂O/TEOS molar ratios (3.3, 5, 7.5 and 11.7 respectively) and with different nominal Ag concentrations were prepared (1, 2 and 4%vol. of Ag). It was found that upon annealing, different silver spices were formed, such as Ag₂ ⁺, Ag⁺, Ag°, and metallic silver aggregates. The identification of these spices was carried out by means of X-ray diffraction, Electron Paramagnetic Resonance (EPR), optical emission and optical absorption. It was also found that the specific type of silver spices observed depends on the structure of the SiO₂ matrix and on the annealing temperatures. It was found that samples prepared from precursor solutions with a low H₂O/TEOS ratio have a more open structure, and therefore silver diffuses faster and forms agglomerates at lower temperatures. Samples prepared from solutions with larger H₂O/TEOS ratios have a more dense structure, which allows the formation of atomic or molecular spices in addition to silver particles. A systematic study of this system was carried out using EPR on samples prepared from solutions having different H₂O/TEOS molar ratios, various Ag concentrations and subjected to different thermal treatments.     

Morphological study of supported thin Pd and Pd–25Ag membranes upon hydrogen permeation

Morphological change of Pd and Pd–25Ag membranes supported by V–15Ni alloy upon hydrogen permeation was investigated in the temperature range 423–673 K. The supported Pd–25Ag membrane exhibited higher resistance to hydrogen-induced cracking and grain growth than the supported Pd membrane. Long-term permeation of Pd–25Ag/V–15Ni composite membrane was carried out at 573 and 673 K for 200 h. There was no strong metallic interdiffusion between the Pd–25Ag membrane and the V–15Ni support after the long-term permeation at 573 K but small amounts of oxide had formed on the surface of Pd–25Ag membrane. Whisker and fissure-oxide morphologies were dominant on the exit and entrance side of the Pd–25Ag/V–15Ni composite membrane, respectively, accompanied by severe metallic interdiffusion after the long-term permeation at 673 K. AES and FE-SEM results revealed that metallic interdiffusion and selective oxidation of vanadium were responsible for the deterioration of Pd–25Ag membrane at 673 K. Hydrogenation–dehydrogenation of Pd and Pd–25Ag membranes supported by stainless steel and V–15Ni alloy were in situ examined by an optical microscope. The formation of hydride was uniform in the Pd/V–15Ni sample but localized in the Pd–25Ag/V–15Ni sample, suggesting that the hydrogen transfer through interface was strongly dependent on the composition of Pd alloy membranes. As for the stainless steel supported samples, both Pd and Pd–25Ag membranes had fractured.     

Preparation of “pore-fill” type Pd–YSZ–γ-Al2O3 composite membrane supported on α-Al2O3 tube for hydrogen separation

Mesoporous YSZ–γ-Al₂O₃ membranes were coated on α-Al₂O₃ (Ø2 mm) tube by dipping the α-Al₂O₃ support tube into mixed sol consists of nano-size YSZ and bohemite particles followed by drying and calcination at 600 °C. Addition of bohemite in YSZ sol helped a good adhesion and uniform coating of the membrane film onto α-Al₂O₃ support. The quality of the mesoporous YSZ–γ-Al₂O₃ membranes was evaluated by the gas permeability experiments. The number of defects was minimized when the γ-Al₂O₃ content became more than 40%. Addition of γ-Al₂O₃ inhibited the crystal growth of YSZ, sintering shrinkage and distortion stress. Increase of calcination temperature and time results in the increase of pore size and N₂ permeance. A hydrogen perm-selective membrane was prepared by filling palladium into the nano-pores of YSZ–γ-Al₂O₃ layer by vacuum-assisted electroless plating. Crystal growth of palladium was observed by thermal annealing of the membrane at 600 °C for 40 h. The Pd–YSZ–γ-Al₂O₃ composite membrane revealed improved thermal stability allowing long-term operation at elevated temperature (>500 °C). This has been attributed to the improved fracture toughness of YSZ–γ-Al₂O₃ layer and matching of thermal expansion coefficient between palladium and YSZ. Although fracture of the membrane did not occur, decline of H₂ flux was observed when the membrane was exposed in 600 °C. This has been attributed to the agglomeration of palladium particles by crystal growth and dense packing into the pore networks of YSZ–γ-Al₂O₃ by elevation of temperature.     

Oxygen production at low temperature using dense perovskite hollow fiber membranes

A dense perovskite hollow fiber made of BaCo_xFe_yZr_zO_3−δ (BCFZ) was evaluated for the oxygen separation at low temperatures (400–500 °C). An oxygen permeation flux of 0.45 ml/min cm² was obtained at 500 °C, which is the first oxygen permeation data reported at such low temperature so far. A degradation of the oxygen permeation at 500 °C was observed, but the oxygen fluxes through the hollow fiber membrane can be regenerated by thermal treatment at 925 °C for 1 h in air. Energy-dispersive X-ray spectroscopy (EDXS) shows that a strong element segregation occurs in the membrane during operation at low temperature.     

Development of polyelectrolyte complexes of chitosan and phosphotungstic acid as pervaporation membranes for dehydration of isopropanol

Using a solution technique, chitosan-based polyelectrolyte complexes (PECs) were developed as pervaporation membranes by incorporating phosphotungstic acid (PTA). The resulting membranes were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Membranes were tested for their ability to separate water–isopropanol mixtures by pervaporation in the temperature range of 30–50 °C. The experimental results demonstrated that both flux and selectivity were increased simultaneously with increasing PTA content in the membrane. The permeation flux of pure chitosan membrane was increased dramatically from 4.13 to 11.70 × 10⁻² kg/m² h and correspondingly its separation factor was increased from 4490 to 11,241 and then decreased to 7490 at 30 °C for 10 mass% of water in the feed. The total flux and flux of water were found to be almost overlapping particularly for PECs membranes, suggesting that these could be used effectively to break the azeotropic point of water–isopropanol mixtures. From the temperature dependency of diffusion and permeation values, the Arrhenius activation parameters were estimated and discussed in the context of membranes efficiency. The pure chitosan and a small amount of PTA-incorporated PECs membranes exhibited positive heat of sorption while other PECs membranes exhibited negative heat of sorption, giving exothermic contribution.     

Further evidence for formation of xenon dihydride from neutral hydrogen atoms: a comparison of ESR and IR spectroscopic results

A comparative study of the decay of hydrogen atoms and formation of xenon dihydride upon annealing electron-irradiated xenon/hydrocarbon mixtures revealed a remarkable correlation between these two processes. The addition of an electron scavenger had a similar effect on the yield of trapped H atoms resulting from irradiation at 15 K and the formation of XeH₂ upon subsequent annealing. The results suggest that ≈70% of the initially trapped H atoms react at 40 K to yield XeH₂ under the experimental conditions. The contribution of hydrogen abstraction from alkane molecules is less important and the recovery of the parent alkane molecule due to H^·+R^· combination is negligible.     

Studies on Indian Ocean Manganese Nodules: XI. Physicochemical Characterization and Catalytic Activity of Silver Oxide Mixed Manganese Nodules

The promoting effect of Ag₂O on the physicochemical properties and catalytic activity of manganese nodules has been investigated. The surface area and surface oxygen increased with addition of Ag₂O, reaching a maximum at 1 mol% of Ag, and then decreased with further addition of Ag₂O. The catalytic activity of manganese nodules substantially increased with addition of Ag₂O over a wide range (0.25–25 mol% Ag). Addition of only 0.25 mol% of Ag to the nodule decreased the temperature of complete CO oxidation from 350°C to as low as 100°C. This enhanced activity was explained by the concerted action of Ag and Mn, where CO was preferentially adsorbed on Ag₂O and oxidized. The reduced Ag was then reoxidized rapidly by oxygen transferred from Mn. The promoting effect of Ag₂O on H₂O₂decomposition and ketonization of acetic acid, however, was less pronounced.     

Separation performance of polyimide composite membrane prepared by dip coating process

The effects of the preparation conditions in a dip coating process on polyimide composite membranes have been investigated. Polyimide precursor obtained from pyromellitic dianhidride (PMDA) and 4,4′-oxydianiline (ODA) was mixed with triethylamine and poly(amic acid)tri-ethylamine salt (PAA salt) was made. An asymmetric polyimide membrane (PI-2080) as a supporting membrane was dipped in a PAA salt (concentration 0–5 wt.%) methanol solution. The coating layers of PAA salt were converted to these of polyimide by annealing at 200°C for 3 h in an ordinary vacuum oven.The performance of the polyimide composite membrane was evaluated by gas permeation (N₂, O₂, CO₂, at 1 kg/cm²) and pervaporation (feed: a 95 vol.% ethanol aqueous solution at 30–60°C). The composite membranes prepared using a coating solution of 5 wt.% PAA salt showed the CO₂/N₂ selectivity of over 25 on gas permeation, and separation factor α (H₂O/EtOH) of over 800 with a total flux of 0.21 kg/m² h on pervaporation.