共查询到20条相似文献,搜索用时 31 毫秒
1.
A ternary diffusion model has been developed for the evaporation step of the phase inversion process. The model is applied to the analysis of mass transfer dynamics of the evaporation step for the methanol–acetone–cellulose acetate (CA) ternary casting system. The combined analysis of quantitatively computational results from the ternary evaporation model and qualitative dynamic results during the quench process has shown that the evaporation step is essentially necessary to prepare the defect‐free, ultrathin skinned asymmetric CA membrane for the separation of CO2/CH4. The skin layer of high CA concentration obtained by evaporation has an ability to suppress liquid–liquid phase separation. And the skin layer with high tensile strength can resist the interfacial tension caused by spinodal decomposition from the substructure. Although the CA concentration in the skin layer increases considerably because of the evaporation step and the following delay time during the quench process, the substructure can still induce the spinodal decomposition because the strong coagulant, methanol, can diffuse rapidly across the ultrathin skin layer. Hence the defect‐free, ultrathin‐skinned asymmetric membrane for gas separation can be prepared from methanol–acetone–CA casting system by evaporation step and the wet phase inversion. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1564–1571, 2002 相似文献
2.
Integrally skinned asymmetric flat sheet membranes were prepared from poly(2,6‐dimethyl 1,4‐phenylene oxide)(PPO) for CO2–CH4 separation. Various experiments were carried out to identify PPO membranes, which have good mechanical strength and gas separation abilities. Membrane strength and selectivity depend on the interplay of the rate of precipitation and the rate of crystallization of the PPO. The effects of major variables involved in the membrane formation and performance, including the concentration of the polymer, solvent, and additive, the casting thickness, the evaporation time before gelation, and the temperature of the polymer solution, were investigated. Factorial design experiments were carried out to identify the factor effects. The membrane performance was modelled and optimized to approach preset values for high CO2 permeance and a high CO2 : CH4 permeance ratio. Membranes were prepared based on the optimum conditions identified by the model. Essentially, defect‐free membranes were prepared at these conditions, which resulted in a pure gas permeance of 9.2 × 10−9 mol/m2 s Pa for CO2 and a permeance ratio of 19.2 for CO2 : CH4. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1601–1610, 1999 相似文献
3.
Fixed‐carrier composite hollow‐fiber membranes were prepared with polyvinylamine (PVAm) as the selective layer and a polysulfone ultrafiltration membrane as the substrate. The effects of the PVAm concentration in the coating solution, the number of coatings, and the crosslinking of glutaraldehyde and sulfuric acid on the CO2 permeation rate and CO2/CH4 selectivity of the composite membranes were investigated. As the PVAm concentration and the number of coatings increased, the CO2/CH4 selectivity increased, but the CO2 permeation rate decreased. The membranes crosslinked by glutaraldehyde or sulfuric acid possessed higher CO2/CH4 selectivities but lower CO2 permeation rates. For the pure feed gas, a composite hollow‐fiber membrane coated with a 2 wt % PVAm solution two times and then crosslinked with glutaraldehyde and an acid solution in sequence had a CO2 permeation rate of 3.99 × 10?6 cm3 cm?2 s?1 cmHg?1 and an ideal CO2/CH4 selectivity of 206 at a feed gas pressure of 96 cmHg and 298 K. The effect of time on the performance of the membranes was also investigated. The performance stability of the membranes was good during 6 days of testing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1885–1891, 2006 相似文献
4.
Permeability and selectivity of CO2, O2, N2, and CH4 were determined for the asymmetric membrane of aromatic polyimide derived from 2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 3,3′-diaminodiphenylsulfone (m-DDS) at 35°C and at pressure up to 76 cmHg. The average apparent skin layer thickness of all asymmetric membranes measured was 2.6 μm. The selectivities for (O2/N2) and (CO2/CH4) in the membranes were 11.5 at O2 permeance of 3.2 × 10−7 and 153 at CO2 of 6.3×10−7 [cm3(STP)/cm2 s cmHg], respectively, without the necessity of an additional coating process. The average gas selectivities of the asymmetric memberanes were much larger than those determined for the dense membrances. The effect of the microstructure of polyimide on the gas selectivity is discussed. © 1996 John Wiley & Sons, Inc. 相似文献
5.
《Polymer Composites》2017,38(1):32-39
Mixed matrix asymmetric membranes were prepared by the addition of silver nanoparticles to cellulose acetate/acetone/formamide casting solutions with ratios acetone/formamide varying from 1.44 to 2.77 to prepare ultrafiltration/nanofiltration membranes covering a wide range of hydraulic permeabilities. Binding of the silver nanoparticles to the polymer matrix is revealed through comparison of the FTIR spectra of the cellulose acetate and the Ag/cellulose acetate membranes. In the later, there is a decrease of the ratio between the bands intensities at 2,000–2,500 cm−1. Membrane surface charge of the mixed matrix membranes varies with the pore size and pH, and when compared with cellulose acetate membranes there is a decrease of the negative surface charge densities. The silver nanoparticles in all mixed matrix membranes results in an enhancement of the hydraulic permeabilities, ranging from 10.8 kg m−2 h−1 bar−1 to 67.1 kg m−2 h−1 bar−1. POLYM. COMPOS., 38:32–39, 2017. © 2015 Society of Plastics Engineers 相似文献
6.
A new membrane material having two kinds of CO2 carriers was obtained. Composite membranes were prepared with the material and support membranes. The facilitated transport of CO2 through these membranes was performed with pure CH4 and CO2 as well as CH4/CO2 mixtures containing 50 vol % CO2. The results show that the membranes possess better CO2 permeance than that of other fixed carrier membranes reported in the literature. In the measurements with pure gases, at 26°C, 0.013 atm of CO2 pressure, the membrane with polysulfone support displays a CO2 permeance of 7.93 × 10?4 cm3 /cm2 s cmHg and CO2/CH4 ideal selectivity of 212.1. In the measurements with mixed gases, at 26°C, 0.016 atm of CO2 partial pressure, the membrane displays a CO2 permeance of 1.69 × 10?4 cm3 /cm2 s cmHg and CO2/CH4 selectivity of 48.1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2222–2226, 2002 相似文献
7.
Integrally skinned asymmetric gas separation membranes of polyethersulfone (PES)/polyurethane (PU) blend were prepared using supercritical CO2 (SC-CO2) as a nonsolvent for the polymer solution. The membrane consisted of a dense and a porous layer, which were conjoined to separate CO2 from CH4. The FTIR, DSC, tensile and SEM tests were performed to study and characterize the membranes. The results revealed that an increase in SC-CO2 temperature causes an increment in permeance and a decrease in membrane selectivity. Furthermore, by raising the pressure, both permeance and selectivity increased. The modified membrane with SC-CO2 had much higher selectivity, about 5.5 times superior to the non-modified membrane. This higher selectivity performance compared to previous works was obtained by taking the advantages of both using partial miscible blend polymer due to the strong polar–polar interaction between PU PES and SC-CO2 to fabricate the membrane. The response surface methodology (RSM) was applied to find the relationships between several explanatory variables and CO2 and CH4 permeance and CO2/CH4 selectivity as responses. Finally, the results were validated with the experimental data, which the model results were in good agreement with the available experimental data. 相似文献
8.
Prachya Watasit Suparat Rukchonlatee Artit Ausavasukhi Chonlada Ritvirulh Tawan Sooknoi 《应用聚合物科学杂志》2021,138(42):51229
The CO2 and CH4 permeabilities of poly(ethylene-co-vinyl acetate) (EVA)/SiO2 composite membrane were investigated at atmospheric pressure. The membranes were fabricated by compression molding and characterized by Fourier transformed infrared spectroscopy, differential scanning calorimetry, a universal testing machine, and a contact angle analyzer. The effect of vinyl acetate content (18–33 wt%) was evaluated for both single-gas and mixed-gas permeation systems. A non-pressurized homemade-permeation cell was used for the single-gas permeation of CO2 and CH4, while a tubular membrane was utilized for a continuous separation of CO2/CH4 mixture. CO2 flux was readily increased (from 0.7 to 2.0 ml/m2.s) with vinyl acetate content (18–33 wt%). The enhanced CO2 permeability is attributed to the increase in polarity and also the decrease in crystallinity of the membrane. A satisfied gas separation selectivity (CO2/CH4) of 4.31 could be obtained from tubular membrane with 28 wt% VA content. The incorporation of SiO2 as a filler (0.5–2.0 wt%) especially increased the membrane polarity and hence the CO2 flux up to 6.0 ml/m2.s. However, the CH4 flux was not affected by VA and SiO2 contents. 相似文献
9.
High‐temperature CO2 selective membranes offer potential for use to separate flue gas and produce a warm, pure CO2 stream as a chemical feedstock. The coupling of separation of CO2 by a ceramic–carbonate dual‐phase membrane with dry reforming of CH4 to produce syngas is reported. CO2 permeation and the dry reforming reaction performance of the membrane reactor were experimentally studied with a CO2–N2 mixture as the feed and CH4 as the sweep gas passing through either an empty permeation chamber or one that was packed with a solid catalyst. CO2 permeation flux through the membrane matches the rate of dry reforming of methane using a 10% Ni/γ‐alumina catalyst at temperatures above 750°C. At 850°C under the reaction conditions, the membrane reactor gives a CO2 permeation flux of 0.17 mL min?1 cm?2, hydrogen production rate of 0.3 mL min?1 cm?2 with a H2 to CO formation ratio of about 1, and conversion of CO2 and CH4, respectively, of 88.5 and 8.1%. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2207–2218, 2013 相似文献
10.
In this study, the effects of 1-Ethyl-3-methylimidazolium tetrafluoroborate ionic liquid on CO2/CH4 separation performance of symmetric polysulfone membranes are investigated. Pure polysulfone membrane and ionic liquid-containing membranes are characterized. Field emission scanning electron microscopy (FE-SEM) is used to analyze surface morphology and thickness of the fabricated membranes. Energy dispersive spectroscopy (EDS) and elemental mapping, Fourier transform infrared (FTIR), thermal gravimetric (TGA), X-ray diffraction (XRD) and Tensile strength analyses are also conducted to characterize the prepared membranes. CO2/CH4 separation performance of the membranes are measured twice at 0.3 MPa and room temperature (25 °C). Permeability measurements confirm that increasing ionic liquid content in polymer-ionic liquid membranes leads to a growth in CO2 permeation and CO2/CH4 selectivity due to high affinity of the ionic liquid to carbon dioxide. CO2 permeation significantly increases from 4.3 Barrer (1 Barrer=10-10 cm3(STP)·cm·cm-2·s-1·cmHg-1, 1cmHg=1.333kPa) for the pure polymer membrane to 601.9 Barrer for the 30 wt% ionic liquid membrane. Also, selectivity of this membrane is improved from 8.2 to 25.8. mixed gas tests are implemented to investigate gases interaction. The results showed, the disruptive effect of CH4 molecules for CO2 permeation lead to selectivity decrement compare to pure gas test. The fabricated membranes with high ionic liquid content in this study are promising materials for industrial CO2/CH4 separation membranes. 相似文献
11.
Poly(N‐vinyl‐γ‐sodium aminobutyrate‐co‐sodium acrylate) (VSA–SA)/polysulfone (PS) composite membranes were prepared for the separation of CO2. VSA–SA contained secondary amines and carboxylate ions that could act as carriers for CO2. At 20°C and 1.06 atm of feed pressure, a VSA–SA/PS composite membrane displayed a pure CO2 permeation rate of 6.12 × 10?6 cm3(STP)/cm2 s cmHg and a CO2/CH4 ideal selectivity of 524.5. In experiments with a mixed gas of 50 vol % CO2 and 50 vol % CH4, at 20°C and 1.04 atm of feed pressure, the CO2 permeation rate was 9.2 × 10?6 cm3 (STP)/cm2 s cmHg, and the selectivity of CO2/CH4 was 46.8. Crosslinkages with metal ions were effective for increasing the selectivity. Both the selectivity of CO2 over CH4 and the CO2 permeation rate had a maximum against the carrier concentration. The high CO2 permeation rate originated from the facilitated transport mechanism, which was confirmed by Fourier transform infrared with attenuated total reflectance techniques. The performance of the membranes prepared in this work had good stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 275–282, 2006 相似文献
12.
Hybrid FSC membrane for CO2 removal from natural gas: Experimental,process simulation,and economic feasibility analysis
下载免费PDF全文
![点击此处可从《American Institute of Chemical Engineers》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xuezhong He May‐Britt Hägg Taek‐Joong Kim 《American Institute of Chemical Engineers》2014,60(12):4174-4184
The novel fixed‐site‐carrier (FSC) membranes were prepared by coating carbon nanotubes reinforced polyvinylamine/polyvinyl alcohol selective layer on top of ultrafiltration polysulfone support. Small pilot‐scale modules with membrane area of 110–330 cm2 were tested with high pressure permeation rig. The prepared hybrid FSC membranes show high CO2 permeance of 0.084–0.218 m3 (STP)/(m2 h bar) with CO2/CH4 selectivity of 17.9–34.7 at different feed pressures up to 40 bar for a 10% CO2 feed gas. Operating parameters of feed pressure, flow rate, and CO2 concentration were found to significantly influence membrane performance. HYSYS simulation integrated with ChemBrane and cost estimation was conducted to evaluate techno‐economic feasibility of a membrane process for natural gas (NG) sweetening. Simulation results indicated that the developed FSC membranes could be a promising candidate for CO2 removal from low CO2 concentration (10%) NGs with a low NG sweetening cost of 5.73E?3 $/Nm3 sweet NG produced. © 2014 American Institute of Chemical Engineers AIChE J 60: 4174–4184, 2014 相似文献
13.
Preparation of vinyl amine‐co‐vinyl alcohol/polysulfone composite membranes and their carbon dioxide facilitated transport properties
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A vinyl amine–vinyl alcohol copolymer (VAm–VOH) was synthesized through free‐radical polymerization, basic hydrolysis in methanol, acidic hydrolysis in water, and an anion‐exchange process. In the copolymer, the primary amino groups on the VAm segment acted as the carrier for CO2‐facilitated transport, and the vinyl alcohol segment was used to reduce the crystallinity and increase the gas permeance. VAm–VOH/polysulfone (PS) composite membranes for CO2 separation were prepared with the VAm–VOH copolymer as a selective layer and PS ultrafiltration membrane as a support. The membrane gas permselectivity was investigated with CO2, N2, and CH4 pure gases and their binary mixtures. The results show that the CO2 transport obeyed the facilitated transport mechanism, whereas N2 and CH4 followed the solution–diffusion mechanism. The increase in the VAm fraction in the copolymer resulted in a carrier content increase, a crystallinity increase, and intermolecular hydrogen‐bond formation. Because of these factors, the CO2 permeance and CO2/N2 selectivity had maxima with the VAm fraction. At an optimum applied pressure of 0.14 MPa and at an optimum VAm fraction of 54.8%, the highest CO2 permeance of 189.4 GPU [1 GPU = 1 × 10?6 cm3(STP) cm?2 s?1 cmHg?1] and a CO2/N2 selectivity of 58.9 were obtained for the CO2/N2 mixture. The heat treatment was used to improve the CO2/N2 selectivity. At an applied pressure of 0.8–0.92 MPa, the membrane heat‐treated under 100°C possessed a CO2 permeance of 82 GPU and a CO2/N2 selectivity of 60.4, whereas the non‐heat‐treated membrane exhibited a CO2 permeance of 111 GPU and a CO2/N2 selectivity of 45. After heat treatment, the CO2/N2 selectivity increased obviously, whereas the CO2 permeance decreased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40043. 相似文献
14.
The intermolecular interactions between methanol/water and Nafion™ membranes have been investigated using IR spectroscopy. The evolution of IR spectra of the Nafion™ membranes, immersed in various concentrations of methanol solution depends strongly on the methanol concentration. The O–H bending vibration modes at 1,636, 1,660 and 1,672 cm–1 associated with the hydrogen bonding of (H3O+…SO3–) as well as (CH3OH2+…SO3–), and at 1,702, 1,717 and 1,711–1,736 cm–1 associated with the hydrogen bonding of (CF2…H–O–CH3), (CF2…H–OH), (CF2…+H3O) and (CF2…H–OSO2–) were observed. The vibration mode of (CF2…H–O) was found to be appearing obviously at 3,821–3,900 cm–1 when the Nafion™ membrane was immersed in the methanol solution with concentration higher than 6 M. On the other hand, the wavenumber of the O–H stretching peak increases with an increase in the methanol concentration. Results of IR spectra revealed that the methanol molecules show better capability to penetrate into the hydrophobic domain of the Nafion™ membrane than water. The intermolecular interaction between the hydrophobic domains of Nafion™ and methanol molecules becomes more observable at a higher methanol concentration. 相似文献
15.
Cellulose hollow fiber membranes (CHFM) were prepared using a spinning solution containing N‐methylmorpholine‐N‐oxide as solvent and water as a nonsolvent additive. Water was also used as both the internal and external coagulant. It was demonstrated that the phase separation mechanism of this system was delayed demixing. The CHFM was revealed to be homogeneously dense structure after desiccation. The gas permeation properties of CO2, N2, CH4, and H2 through CHFM were investigated as a function of membrane water content and operation pressure. The water content of CHFM had crucial influence on gas permeation performance, and the permeation rates of all gases increased sharply with the increase of membrane water content. The permeation rate of CO2 increased with the increase of operation pressure, which has no significant effect on N2, H2, and CH4. At the end of this article a detailed comparison of gas permeation performance and mechanism between the CHFM and cellulose acetate flat membrane was given. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1873–1880, 2004 相似文献
16.
We have developed a new type of asymmetric membranes having a homogeneous hyperthin skin layer, which was used as a polyimide synthesized by 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2-bis(4-amino phenyl) hexafluoro-propane (BAAF). The skin layer thicknesses of the 6FDA-BAAF polyimide asymmetric membranes were 40–60 nm, and the porosity was 10-6% when a defect size was assumed as 5 nm. The permselectivity of 6FDA-BAAF polyimide asymmetric membranes after silicone coating had α of 40 for CO2/CH4 and a flux of 1.0 [Nm3/m2-h-atm] (=3.7 × 10−4 [cm3(STP)/cm2 s cmHg]) for CO2, α of 4.3 for O2/N2 and a flux of 2.0 × 10−1 [Nm3/m2/h/atm] (=7.1 × 10−5 [cm3(STP)/cm2s cmHg]) for O2. These values were constant for large-scale manufacturing. © 1996 John Wiley & Sons, Inc. 相似文献
17.
By using ethanol–water mixtures in a wide range of alcohol concentrations and temperatures, cellulose acetate membranes with a wide range of surface porosities can be obtained. Two different casting solution compositions were used, involving cellulose acetate, acetone, and aqueous magnesium perchlorate (composition I) or formamide (composition II). All reverse osmosis experiments were carried out at 250 psig using a 3500 ppm NaCl–H2O feed solution at laboratory temperature. The effective area of film surface was 12 cm2 in all cases. With composition I, with pure water gelation medium at 0°C, the resulting membrane gave a solute separation of 5% and product rate of 220 g/hr, whereas with 95% alcohol as gelation medium, the resulting membrane gave a solute separation of ~1% and product rate of 1240 g/hr under otherwise identical experimental conditions. With composition II membranes, the maximum product rate of 360 g/hr with the corresponding minimum solute separation of ~1% was obtained with 71.2% alcohol–water gelation medium at 0°C. Increase in the temperature of the gelation medium in the range 12° ?25°C tends to increase the average size of pores on the membrane surface. These results offer a basis for the development of cellulose acetate ultrafiltration membranes. 相似文献
18.
The normal and log-normal distributions are used to describe the pore size distribution of dry asymmetric cellulose acetate membranes for CO2/CH4 separations. Various optimization techniques are implemented to determine the distribution parameters R and σ as well as the constants A1, and A2, related to pore structure and surface transport. respectively. By using the Simplex method, a unique solution for the characterization parameters is easily obtained irrespective of the starting search point. The permeation data of helium was used to characterize the membranes and determine the flow parameters which can be used to predict the performance of those membranes in separating CO2/CH4 mixtures. 相似文献
19.
Siti Nadiah Mustafa Kamal Choe Peng Leo Abdul Latif Ahmad Mohd Usman Mohd Junaidi 《Polymer Engineering and Science》2014,54(9):2177-2186
Polydimethylsiloxane/polyethersulfone (PDMS/PES) asymmetric membranes are widely applied in gas separation. However, the effects of common cosolvent on these membranes remain unknown. In order to study the changes in membrane morphology and gas separation properties, asymmetric PDMS/PES membranes were prepared. The studied parameters were types of cosolvents, tetrahydrofuran (THF) concentration, evaporation time, and PDMS concentration. Membrane morphology was examined using scanning electron microscopy and gas separation was conducted using pure CO2, N2, CH4, and Hat 25°C. The addition of cosolvent into the polymer solution decreased the dope viscosity and delayed liquid–liquid demixing during phase inversion. Macrovoids formation was observed in substructure layer after adding THF and these macrovoids elongated with the reduction in THF content. There were microvoids formed on top of macrovoids and microvoids layer became thicker due to the increasing evaporation time of solvents before coagulation in nonsolvent. The PDMS coating on the PES membrane formed a dense skin layer and exhibited higher selectivity compared to the uncoated membrane. Membrane contained THF cosolvent with 60 s evaporation time and 3 wt% coated PDMS is the optimum membrane among other membranes in this work. The CO2/N2 selectivity was enhanced by 73.3% with CO2 permeance of 44.86 GPU. POLYM. ENG. SCI., 54:2177–2186, 2014. © 2013 Society of Plastics Engineers 相似文献
20.
Polyetherimide (PEI) was used as a polymeric additive for preparing an asymmetric polyethersulfone (PES) membrane for the separation of CO2 from CH4. In pure gas experiments, the higher skin layer thickness and the lower porosity of the sub layer for the membrane prepared from the polymer blend with the composition of 98:2 lead to an increase in CO2/CH4 selectivity and a decrease in the CO2 permeance in contrast with a pristine PES. For higher PEI contents, the higher fractional free volume of the membranes improves the gas permeance and reduces the CO2/CH4 selectivity. The incorporation of PEI in PES reduces the CO2 sorption in PES via decreasing the non-equilibrium free volume and imparts antiplasticization properties to the membrane. 相似文献