• Membrane Journal
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• v.22 no.6
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• pp.424-434
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• 2012

In this study, a ceramic membrane was prepared by CVD. Tube type alpha alumina support was used for substrate and added the Ga salt in intermediate layer. Synthesized method was counter diffusion CVD method at $650^{\circ}C$ with tetramethylorthosilane (TMOS). Gas permeation was measured at $600^{\circ}C$ using single-component $H_2$, $N_2$, $CO_2$ and $CH_4$. During the steam treatment, $H_2/N_2$ permselectivity of non-Ga silica membrane was decreased 926 to 829 at $600^{\circ}C$. On the other hand $H_2/N_2$ permselectivity of added Ga silica membrane was stable 910 to 904 at $600^{\circ}C$. These results show that the metal-doped membranes improved steam stability for gas separation.

• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.340-346
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• 2014

Continuous and dense ZIF-7 membranes were successfully synthesized on ${\alpha}-Al_2O_3$ porous substrate via two-step crystallization technique. ZIF-7 seeding layer was first deposited on porous ${\alpha}-Al_2O_3$ substrate by in-situ low temperature crystallization, and then ZIF-7 membrane layer can be grown through the secondary high-temperature crystallization. Two synthesis solutions with different concentration were used to prepare ZIF-7 seeding layer and membrane layer on porous ${\alpha}-Al_2O_3$ substrate, respectively. As a result, a continuous and defect-free ZIF-7 membrane layer can be prepared on porous ${\alpha}-Al_2O_3$ substrate, as confirmed by scanning electron microscope. XRD characterization shows that the resulting membrane layer is composed of pure ZIF-7 phase without any impurity. A single gas permeation test of $H_2$, $O_2$, $CH_4$ or $CO_2$ was conducted based on our prepared ZIF-7 membrane. The ZIF-7 membrane exhibited excellent H2 molecular sieving properties due to its suitable pore aperture and defect-free membrane layer.

• Membrane Journal
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• v.25 no.4
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• pp.343-351
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• 2015

In this study, we synthesis polyimide with high gas selectivity using 2,2-bis(3,4-carboxylphenyl) hexafluoropropane, 2,4,6-Trimethyl-1,3-phenylenediamine (DAM) and 4,4-Methylenedianiline (p-MDA), and then the asymmetric membrane was fabricated by non-solvent phase separation method. To confirm the property change of the membrane using different solvent, we measured and compared the viscosity of the polymer solution, cloud point and non-solvent phase separation coefficient. The morphology and gas separation property of membrane prepared by phase separation method was confirmed using Field Emission Scanning Electron Microsope and the single gas permeation measurement apparatus. The single gas ($CH_4$, $N_2$, $O_2$, $CO_2$) permeation property and selectivity value of the membrane prepared with NMP was higher than the membrane prepared with DMAc. We confirmed that the gas selectivity of the membrane increased and the permeation property decreased with increasing of the solvent evaporation time.

• Journal of Hydrogen and New Energy
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• v.24 no.1
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• pp.29-35
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• 2013

A dense mixed ionic and electronic conducting ceramic membrane is one of the most promising materials because it can be used for separation of oxygen from the mixture gas. The $ABO_3$ perovskite structure shows high chemical stability at high temperatures under reduction and oxidation atmospheres. $BaCo_{1-x-y}Fe_xZr_yO_{3-{\delta}}$ (BCFZ) was well-known material as high mechanical strength, low thermal conductivity and stability in the high valence state. Glycine Nitrate Process (GNP) is rapid and effective method for powder synthesis using glycine as a fuel and show higher product crystallinity compared to solid state reaction and citrate-EDTA method. BCFZ was fabricated by modified glycine nitrate process. In order to control the burn-up reaction, $NH_4NO_3$ was used as extra nitrate. According to X-Ray Diffraction (XRD) results, BCFZ was single phase regardless of Zr dopants from y=0.1 to 0.3 on B sites. The green compacts were sintered at $1200^{\circ}C$ for 2 hours. Oxygen permeability, methane partial oxidation rate and hydrogen production ability of the membranes were characterized by using Micro Gas Chromatography (Micro GC) under various condition. The high oxygen permeation flux of BCFZ 1-451 was about $1ml{\cdot}cm^{-2}s^{-1}$. Using the humidified Argon gas, BCFZ 1-433 produced hydrogen about $1ml{\cdot}cm^{-2}s^{-1}$.

• Membrane Journal
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• v.25 no.6
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• pp.488-495
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• 2015

Aminated polyphenylene oxide (APPO) based on polyphenylene oxide (PPO) was synthesized using trimethylamine and chloromethyl ethyl ether. Then, the electro-physical properties of APPO membranes which were prepared from the 8 wt% APPO solution dissolved in chloroform were characterized. Contact angle was $44.4^{\circ}$, swelling degree was 37.9%. The typical electrical properties of ion exchange capacity and ion conductivity were 2.3 meq/g, 0.027 S/cm, respectively. And the single gas permeation experiments were performed by using the time-lag method for $N_2$, $O_2$, $CH_4$, $CO_2$, $SO_2$. For the acid gases of $CO_2$ and $SO_2$, their permeability were measured 20.7 and 511.5 barrers, respectively. In the case of selectivity, $CO_2/CH_4$, $CO_2/N_2$ and $SO_2/CO_2$ were measured 39.8, 42.2, 24.7, respectively.

• Membrane Journal
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• v.28 no.5
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• pp.351-360
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• 2018

In this study, propylene/propane separation mechanism through NaY zeolite membrane was investigated. As permeation temperature increased, both propylene and propane permeances increased, saturated and decreased again, and a maximum selectivity was shown at around 50 to $60^{\circ}C$. Propane permeance in mixed gas experiment was much smaller than that in single gas experiment, and propylene/propane mixed gas selectivity was much larger than single gas permselectivity. As permeation time increased in transient permeation experiment, propylene permeance initially increased and saturated, while propane permeance decreased and saturated. All the experimental results announced that propylene/propane separation through NaY zeolite membrane was from preferentially adsorbed propylene molecules. The adsorbed propylene molecules efficiently prevented propane molecules from permeating through the membrane, and sufae diffused through the membrane. NaY zeolite capillary membrane prepared in the present study showed a high mixed gas selectivity of 12 and high propylene permeance of 497 GPU for a propylene/propane (89 : 11) mixture at $50^{\circ}C$ and 4 bar. Therefore, it was concluded that NaY zeolite membrane is one of promising membrane materials for propylene/propane separation due to the low cost and high separation performance.

• Journal of the Korean Society for Heat Treatment
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• v.15 no.2
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• pp.57-64
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• 2002

The 22%Cr-5%Ni-3%Mo duplex and 18%Cr-8%Ni austenitic stainless steels have been nitrogen permeated under the $1Kg/cm^2$ nitrogen gas atmosphere at the temperature range of $1050^{\circ}C{\sim}1150^{\circ}C$. The nitrogen-permeated duplex and austenitic stainless steels showed the gradual decrease in hardness with increasing depth below surface. The duplex stainless steel showed nitrogen pearlite at the outmost surface and austenite single phase in the center after nitrogen permeation treatment, while the obvious microstructural change was not observed for the nitrogen-permeated austenitic stainless steel. After solution annealing the nitrogen-permeated stainless steels(NPSA treatment) at $1200^{\circ}C$ for 10 hours, the hardness of the duplex and austenitic stainless steels was constant through the 2 mm thickness of the specimen, and the ${\alpha}+{\gamma}$ phase of duplex stainless steel changed to austenite single phase. Tensile strengths and elongations of the NPSA-treated duplex stainless steel remarkably increased compared to those of solution annealed (SA) duplex stainless steel due to the solution strengthening effect of nitrogen and the phase change from a mixture of ferrite and austenite to austenite single phase, while the NP-treated austenitic stainless steel displayed the lowest value in elongation due to inhomogeneous deformation by the hardness difference between surface and interior.

• Membrane Journal
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• v.30 no.6
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• pp.450-459
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• 2020

Membrane-based separations have the potential to reduce energy consumption and environmental impact associated with conventional processes. However, many researches have been done to develop new membrane materials with greater selectivity and permeability. Here, we report highly selective membranes by introducing bulky ethyl substituents into the polyimide. The ethyl group in the ortho position to the imide nitrogen interferes the chain packing and increases chain stiffness and the distance between the polymer chains. The polyimide membranes were synthesized from various aromatic dianhydrides and 4,4'-methylenebis(2,6-diethylaniline) (MDEA). The synthesized membranes with increased gas diffusion length due to bulky substituents showed improved propylene/propane (C3H6/C3H8) selectivity. Single gas permeation showed high C3H6/C3H8 selectivity of 14.5, and C3H6 permeability of 7.0 barrer was found in MDEA-polyimide. Mixed-gas permeation results also demonstrate that MDEA-polyimide can achieve high selectivity in mixed-gas environment. Furthermore, this approach could significantly increase the feasibility of economic propylene separation compared to conventional polymer materials.

• Membrane Journal
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• v.20 no.3
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• pp.249-258
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• 2010

In this study, we tried to observe the permeation on the single $O_2$, $CF_4$ and $SF_6$ gas using a PSF (polysulfone), PC (tetra-bromo polycarbonate) and PI (polyimide) hollow fiber membranes. We also observed the permselectivity on the $O_2/SF_6$ and $CF_4/SF_6$. According to the results of single gases permeation for different pressures, PSF membrane has the highest $O_2$ permeation of 37.5 GPU and PC membrane has the highest $SF_6$ permeation of 2.7 GPU and the highest $CF_4$ permeation of 2.5 GPU at 1.1 MPa. According to the results of single gases permeation for different temperatures, PSF membrane has the highest permeation of $O_2$ at $45^{\circ}C$ and PC membrane has the highest permeation of $SF_6$ and $CF_4$ at $25^{\circ}C$. From the result of $O_2/SF_6$ and $CF_4/SF_6$ permselectivity for different pressures and temperature, the highest permeation and the lowest permselectivity were observed in the PSF and PC membrane. On the contrary, the lowest permeation and the highest permselectivity was observed in the PI membrane.

• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.196-200
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• 2018

In this study, the intermediate layer in Pd-based hydrogen separation membrane was synthesized to minimize the surface roughness and defects using powder-type and sol-type metal oxides. The surface properties and gas permeation characteristics were analysed by SEM and $N_2$ gas permeation test. The coating layer composed of sol type metal oxides has smooth surface, especially the layer coated by $TiO_2$ sol has little pin holes, cracks and defects. The binary layer composed of powder type and sol type metal oxides has similar flux characteristics to a single sol type layer. The Pd-based composite membrane improved by the binary intermediate layer exhibited $0.32mol/m^2s$ of the hydrogen permeation flux with a selectivity ($H_2/N_2$) of ~10,890 at 672 K and a pressure difference of 1 bar.