• Tunnel and Underground Space
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• v.31 no.1
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• pp.41-51
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• 2021

The hydraulic fracturing developed to improve permeability of tight reservoir is one of key stimulation technologies for developing unconventional resources such as shale gas and deep geothermal energy. The experimental study was conducted to improve disadvantage of hydraulic fracturing which has simple fracture pattern and poor fracturing efficiency. The fracturing experiments was conducted for tight rock using various fracturing fluids, water, N2, and CO2 and the created fracture pattern and fracturing efficiency was analyzed depending on fracturing fluids. The borehole pressure increased rapidly and then made fractures for hydraulic fracturing with constant injection rate, however, gas fracturing shows slowly increased pressure and less fracture pressure. The 3D tomography technic was used to generate images of induced fracture using hydraulic and gas fracturing. The stimulated reservoir volume (SRV) was estimated increment of 5.71% (water), 12.72% (N2), and 43.82% (CO2) respectively compared to initial pore volume. In addition, permeability measurement was carried out before and after fracturing experiments and the enhanced permeability by gas fracturing showed higher than hydraulic fracturing. The fracture conductivity was measured by increasing confining stress to consider newly creating fracture and closing induced fracture right after fracturing. When the confining stress was increased from 2MPa to 10MPa, the initial permeability was decreased by 89% (N2) and 50% (CO2) respectively. This study shows that the gas fracturing makes more permeability enhancement and less reduction of induced fracture conductivity than hydraulic fracturing.

• Membrane Journal
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• v.24 no.6
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• pp.423-430
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• 2014

PTMSP/LDH composite membranes were prepared by adding 0, 1, 3, and 5 wt% LDH contents to PTMSP. The gas permeability and selectivity for $H_2$, $N_2$, $CH_4$, $C_3H_8$, $n-C_4H_{10}$ were investigated as a function of LDH content. As LDH content of PTMSP/LDH composite membranes increased to 5 wt%, the gas permeability for $H_2$ and $N_2$ gradually decreased, while $n-C_4H_{10}$ permeability rapidly increased. The gas permeability for $CH_4$ and $C_3H_8$ was found to decrease for the membranes with LDH content range of 0~3 wt%, however increase in the range of 3~5 wt%. As LDH content of PTMSP/LDH composite membranes increased to 5 wt%, the selectivity of membranes gradually increased for $H_2$, $N_2$, $CH_4$, $C_3H_8$, $n-C_4H_{10}$ over $H_2$, $N_2$. However the selectivity for $C_3H_8$ and $n-C_4H_{10}$ over $CH_4$ increased in the range of LDH content 0~3 wt% but decreased in the range of 3~5 wt%. The $CH_4$ and $n-C_4H_{10}$ selectivity over $H_2$ and $N_2$ increased as $CH_4$ and $n-C_4H_{10}$ permeability increased. The $n-C_4H_{10}$ selectivity over $CH_4$ increased with increasing $n-C_4H_{10}$ permeability up to 182,000 barrer and decreased above 182,000 barrer of $n-C_4H_{10}$ permeability. The $C_3H_8$ selectivity over $H_2$ and $N_2$ was found to decrease as the $C_3H_8$ permeability increased from 46,000 to 50,000 barrer, but to increase with increasing permeability from 50,000 to 52,300 barrer and decrease again with increasing permeability from 52,300 to 60,000 barrer. The $C_3H_8$ selectivity over $CH_4$ was found to decrease with increasing $C_3H_8$ permeability up to 52,300 barrer but increase above 52,300 barrer.

• Membrane Journal
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• v.2 no.2
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• pp.135-143
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• 1992

Separation of $N_2-SO_2$ mixed gas by polymer membranes, SEPA-97(CA), TFC, and FT-30 membrane, was investigated by varying pressure and temperature. The permeability coefficients and the separation factors of mixed gases were measured, and the influence of various factors on the gas permeability characteristics and separation performance were investigated. The range of pressure was 0.1~1.0 MPa, and that of temperature was 283~303 K. The experimental results showed that the permeability coefficients and the separation factors were increased with an increase in pressure, but they were deereased with increasing temperature. Among the examined membranes, FT-30 possessed the best gas-separating characteristics.

• Elastomers and Composites
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• v.33 no.1
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• pp.37-43
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• 1998

The permeation of gas through polymer membrane at temperatures above its glass transition, generally occurs by a solution-diffusion mechanism. This mechanism is performed by the affinity difference between polymeric materials and gas molecules, and various technologies, such as copolymerization, impregnation and so on, have been researched to improve the affinity of polymeric material for the gases. In this study, permeability and selectivity for some gases were obtained from steady-state rates of gas permeation through silicone rubber membrane which is prepared by supercritical fluid extraction method. The permeability was measured by the volumetric method proposed by Barrer. Permeability was increased generally with temperature and permeation pressure. Silicone rubber membrane shows a higher permeability to $CO_2$ than to $O_2$, $N_2$. This results probably reflect the relatively high solubility of CO_2 in silicone rubber membrane, which is due to the affinity of $CO_2$ molecules. Since separation powers of $CO_2/N_2$, $CO_2/O_2$ were more than 200, and 100, respectively, it is able to separate $CO_2$ from the air, and the optimum temperature and pres-sure was 328.15 K, 60 cmHg respectively. In future, it is possible that the silicone rubber membrane can be used for separation or concentration of $CO_2$ through experiment for mixed gas separation.

• Membrane Journal
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• v.27 no.2
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• pp.147-153
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• 2017

In this study, we investigated permeation properties of single gas ($N_2$, $O_2$, $CO_2$) through membranes composed of poly(ethylene oxide) (PEO) and poly(ethylene-co-vinyl acetate) (EVA) blend. The prepared membranes showed no new absorbance peaks, which indicate the physical blending of PEO and EVA by FT-IR analysis. SEM observation showed that the crystalline phase of PEO decreased with increasing EVA content in the PEO/EVA mixed matrix. DSC analysis showed that the crystallinity of the PEO/EVA blend membrane decreased with increasing EVA content. Gas permeation experiment was performed with various feed pressure (4~8 bar). The permeability increased in the following order: $N_2$ < $O_2$ < $CO_2$. The permeability of $CO_2$ in PEO/EVA blend membranes were increased with increasing feed pressure, However, the permeability of $N_2$ and $O_2$ were independent of feed pressure. On the other hand, the permeability of all the gases in PEO/EVA blend membranes increased with increasing amorphous EVA content in semi-crystalline PEO. In particular, the blend membrane with 40 wt% EVA showed $CO_2$ permeability of 64 Barrer and $CO_2/N_2$ ideal selectivity of 61.5. The high $CO_2$ permeability and $CO_2/N_2$ ideal selectivity are attributed to strong affinity between the polar ether groups of PEO or the polar ester groups of EVA and polar $CO_2$.

• Membrane Journal
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• v.32 no.5
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• pp.325-335
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• 2022

In this study, zeolitic imidazolate framework-9 (ZIF-9) was synthesized and Pebax/ZIF-9 mixed membranes were prepared by varying the content in poly(ether-b-amide)-1657 (Pebax-1657), and then a single gas (N₂, CO₂) was permeated to investigate the gas permeation characteristics of the mixed membrane. As the ZIF-9 content incorporated into the pure Pebax membrane increased, the N₂ permeability gradually decreased, and the CO₂ permeability increased up to the Pebax/ZIF-9 3 wt% mixed membrane, and then decreased at the content thereafter. And among the mixed membranes, the Pebax/ZIF-9 3 wt% mixed membrane showed the highest selectivity of 69.3 by selectively accepting CO₂ as the gate-opening phenomenon occurred for the polar gas, CO₂. In addition, both the CO₂ permeability and the CO₂/N₂ selectivity increased, resulting in the closest Robeson upper-bound.

• Membrane Journal
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• v.27 no.4
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• pp.319-327
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• 2017

Chitosan/Pebax composite membranes were prepared with 1 : 1, 1 : 2, 1 : 10, 1 : 30 mass ratio of pebax and chitosan. Gas permeation test were carried out under pressure $6kgf/cm^2$, 35, $45^{\circ}C$ and $65^{\circ}C$ at different temperatures. The gas permeability and selectivity ($CO_2/N_2$) of $N_2$ and $CO_2$ for the Chitosan/Pebax composite membranes were investigated. As the amount of Pebax added to chitosan was increased the gas permeability of both $N_2$ and $CO_2$ increased. The selectivity ($CO_2/N_2$) was 6.9~44.3 in the Chitosan/Pebax composite membranes. With the increase of contents of Pebax and the decrease of temperature, the selectivity ($CO_2/N_2$) increased.

• Membrane Journal
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• v.28 no.2
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• pp.105-112
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• 2018

In this study, PTMSP-GO composite membranes were prepared by the addition of GO (graphene oxide) into PTMSP [poly (1-trimethylsilyl-1-propyne)] having high gas permeability, to study of gaseous membrane using GO. Gas permeation properties for $N_2$, $CH_4$, $CO_2$ were investigated by increasing the amount of GO in the PTMSP. PTMSP-GO composite membranes had higher gas permeability in the order of $N_2$ < $CH_4$ < $CO_2$. The gas permeation tendency of $N_2$, $CH_4$, and $CO_2$ increased as the content of GO increased from 0 to 10 wt%, but the gas permeability decreased as increased from 10 to 30 wt%. In the range of low GO contents, the gas permeability decreased due to the decrease of diffusivity because GO acts as a barrier in the composite membrane, and the gas permeability increased due to the void at the interface above the content range. And $CO_2$ has an affinity with -COOH of GO, the selectivity ($CO_2/N_2$) and the selectivity ($CO_2/CH_4$) gradually increase with increasing GO content. And the selectivity($CO_2/N_2$) showed the highest selectivity at 10.6 for PTMSP-GO 10 wt% and the selectivity ($CO_2/CH_4$) showed the highest selectivity at 3.4 for PTMSP-GO 20 wt%. However, above a certain amount of GO, selectivity ($CO_2/N_2$) and selectivity ($CO_2/CH_4$) decreased because the coagulation phenomenon between GO was increased and the solubility effect of $CO_2$ decreased. The PTMSP-GO 20 wt% composite membrane exhibited enhanced gas permeation characteristics with increased $CO_2$ permeability and selectivity ($CO_2/CH_4$) over PTMSP membrane.

• Membrane Journal
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• v.28 no.4
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• pp.233-242
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• 2018

To study gas membrane using GO (graphene oxide), the PEBAX [poly(ether-block-amide)]-GO polymer composite membrane was prepared by adding GO to PEBAX. Through this composite membrane, gas permeation characteristics for $H_2$, $N_2$, $CH_4$, and $CO_2$ were studied. As a result of the gas permeation test, the permeability of $N_2$, $CH_4$, and $CO_2$ to PEBAX-GO composite membranes gradually decreased as the GO content increased. On the other hand, the gas permeability of $H_2$ increased with the increase of GO content, and it was 21.43 barrer at the GO content of 30 wt%, which was about 5 times higher than that of PEBAX membrane. This is because the GO was easier to operate with a fast and selective gas transport channel for $H_2$ than other gases. The increased selectivity ($H_2/N_2$) and selectivity ($H_2/CH_4$) were influenced by the diffusion selectivity by the permeate gas size. The increased selectivity ($CO_2/N_2$) and selectivity ($CO_2/CH_4$) were more influenced by the solubility selectivity due to the affinity of $CO_2$ and GO for -COOH.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.413-420
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• 2015

PTMSP-ZIF composite membranes were prepared by the addition of zeolitic imidazolate framework (ZIF-8) into poly (1-trimethylsilyl-1-propyne) (PTMSP) having high gas permeability to improve trade-off relationship of the polymer membrane. PTMSP-ZIF composite membranes were prepared with different amounts of ZIF-8; 0, 5, 10, 20, 30 and 40 wt%. Gas permeation properties for $H_2$, $N_2$, $CO_2$, and $CH_4$ were investigated by increasing the amount of ZIF-8 in the PTMSP. The gas permeability of PTMSP-ZIF composite membranes within 5~30 wt% of ZIF-8 contents increased as ZIF-8 contents went up and decreased thereafter. The gas permeability for $CO_2$ showed the maximum value of 76080 barrer at 30 wt% of ZIF-8 content and PTMSP-ZIF composite membrane containing 20 wt% of ZIF-8 content had the highest selectivity ($CO_2/N_2$) with the value of 8.2. The selectivity ($H_2/N_2$) and selectivity ($CO_2/CH_4$) were almost the same as PTMSP in the range 10~40 wt% of the ZIF-8. Overall, PTMSP-ZIF composite membranes resulted in maintained selectivity and increased permeability compared to those of PTMSP membranes.