Ceramic Supported PDMS and PEGDA Composite Membranes for CO2 Separation

Composite membranes have attracted increasing attentions owing to their potential applications for CO2 separation. In this work, ceramic supported polydimethylsiloxane （PDMS） and poly （ethylene glycol） diacrylate （PEGDA） composite membranes were prepared. The microstructure and physicochemical properties of the compos- ite membranes were characterized. Preparation conditions were systematically optimized. The gas separation performance of the as-prepared membranes was studied by pure gas and binary gas permeation measurement of CO〉 N2 and H〉 Experiments showed that PDMS, as silicone rubber, exhibited larger permeance and lower separation factors. Conversely, PEGDA composite membrane presented smaller gas permeance but higher ideal selectivity for CO2/N2. Compared to the performance of those membranes using polymeric supports or freestanding membranes, the two kinds of ceramic supported composite membranes exhibited higher gas permeance and acceptable selectivity. Therefore, the ceramic supported composite membrane can be expected as a candidate for CO2 separation from light gases.     

Permeation properties of CO2and CH4in asymmetric polyethersulfone/polyesterurethane and polyethersulfone/polyetherurethane blend membranes

The transport performances of carbon dioxide and methane were studied in polyethersulfone,polyethersulfone/polyeterurethane (PES-ETPU) and polyethersulfone/polyestherurethane (PES-ESPU) blend membranes separately with different compositions.The variations in the structural characteristics of PES membrane after incorporation of ESPU and ETPU were investigated by different techniques.Additionally,the effect of pressure and composition on the permeance of CO2,CH4and ideal selectivity of CO2/CH4were checked on the membranes. The results revealed that the morphology of the blend membranes was affected by two opposite factors:thermo-dynamic enhancement and kinetic hindrance.The membranes with denser sponge layers were formed at lower ratio of PU/PES,while more porous structure with enlarged macrovoids membranes were observed at higher PU content.The results indicated that adding PU to PES membrane,caused permeance improvement of the gases with nearly no change and/or reduction in ideal selectivity of CO2/CH4.Moreover,PES-ETPU membranes showed higher permeability and less CO2/CH4selectivity in comparison with PES-ESPU samples. For PES-ESPU membrane containing 1.5% ESPU,CO2permeance at 10 bar was improved up to 20% with almost no change in CO2/CH4selectivity with respect to PES.Finally,response surface methodology was used to evaluate the effects of the operating parameters on the permeance and ideal selectivity.     

Effect of silver-nanoparticles generated in poly(vinyl alcohol)membranes on ethanol dehydration via pervaporation

Pervaporation is an important membrane separation method of chemical engineering. In this work,silver-nanoparticles-poly(vinyl alcohol) nanocomposite membranes(AgNPs-PVA) are produced for the sake of improving its potentials for pervaporation of ethanol–water mixture so that the usual opposite trend between membrane selectivity and permeation can be reduced. The nanocomposite membranes are fabricated from an aqueous solution of poly(vinyl alcohol) with silver nanoparticles via the in-situ generation technique in the absence of any reducing agent. Successful generation of the nano size silver is measured by the UV–vis spectrum showing a single peak at 419 nm due to the plasmonic effect of silver nanoparticles. Our nanocomposite AgNPs-PVA membranes are characterized using scanning electron microscope(SEM), Fourier-transform infrared(FT-IR) spectroscopy, X-ray diffraction and thermogravimetric analysis(TGA). The pervaporation tests of our new AgNPs-PVA membranes show good results since at a higher temperature and higher ethanol concentration in the feed, the prepared membranes are highly permeable for the water having stable selectivity values and therefore our membranes show better performance compared to that of the other PVA-based nanocomposite membranes.     

Strain-controlled graphdiyne membrane for CO2/CH4 separation: Firstprinciple and molecular dynamic simulation

Tensile strain of porous membrane materials can broaden their capacity in gas separation. In this work, using van der Waals corrected density functional theory(DFT) and molecular dynamics(MD) simulations, the performance and mechanism of CO_2/CH_4 separation through strain-oriented graphdiyne(GDY) monolayer were studied by applying lateral strain. It is demonstrated that the CO_2 permeance peaks at 1.29 × 10~6 gas permeation units(GPU) accompanied with CO_2/CH_4 selectivity of 5.27 × 10~3 under ultimate strain, both of which are far beyond the Robeson's limit. Furthermore, the GDY membrane exhibited a decreasing gas diffusion energy barrier and increasing permeance with the increase of applied tensile strain. CO_2 molecule tends to reoriented itself vertically to permeate the membrane. Finally, the CO_2 permeability decreases with the increase of the temperature from300 K to 500 K due to conserving of rotational freedom, suggesting an abnormal permeance of CO_2 in relation to temperature. Our theoretical results suggest that the stretchable GDY monolayer holds great promise to be an excellent candidate for CO_2/CH_4 separation, owing to its extremely high selectivity and permeability of CO_2.     

气体透过碳膜的非平衡动力学模拟研究

The permeation of various pure gas （H2, He, Ne, CH4 and At） through carbon membranes is investigated using a dual control volume grand canonical molecular dynamics method. A two-dimensional slit pore is employed instead of the one-dimensional pore. Compared with the experiments, simulation results show that the improvement of pore model is very necessary. The effects of membrane thickness, pore width and temperature on gas permeance and ideal separation factor are also discussed. Results show that gas permeates through membrane according to Knudsen diffusion in large pore, while Knudsen diffusion is accompanied by molecular sieving in small pore. Moreover, methane is easily adsorbed on the membrane surface due to strong attractive interactions of membrane and shows higher permeance than that of Knudsen flow. In addition, it is noted that when membrane thickness is thin enough the permeance of gas does not decrease with the increase of membrane thickness due to the strong adsorption until membrane resistance becomes dominant.     

Distinguished discriminatory separation of CO2 from its methane-containing gas mixture via PEBAX mixed matrix membrane

Highly selective separation of CO2 from its methane-containing binary gas mixture can be achieved by using Poly(ether-block-amide) (PEBAX) mixed matrix membranes (MMMs).According to FESEM and AFM analyses,silica-based nanoparticles were homogenously integrated within the polymer matrix,facilitating penetration of CO2 through the membrane while acting as barrier for methane gas.The membrane containing 4.6 wt％ fumed silica (FS) (PEBAX/4.6 wt％ FS) exhibits astonishing selectivity results where binary gas mixture of CO2/CH4 was used as feed gas.As detected by gas chromatography,in the permeate side,data showed a significant increase of CO2 permeance,while CH4 transport through the mixed matrix membrane was not detectable.Moreover,PEBAX/4.6 wt％ FS greatly exceeds the Robeson limit.According to data reported on CO2/CH4 gas pair separation in the literature,the results achieved in this work are beyond those data reported in the literature,particularly when PEBAX/4.6 wt％ FS membrane was utilized.     

碳分子筛填充硅橡胶膜用于渗透蒸发分离稀醋酸-水溶液

From the reference[1] it is known that the addition of silicalite-1 in silicone rubber membranes results in an increase of both flux and selectivity for alcohol in the separation of alcohol/water by pervaporation.In order to enhance performance of pervaporation toward the aqueous solution of acetic acid,incorporation of carbon molecular sieve(CMS)into a PDMS membrane was investigated. CMS is widely used in adsorption processes because of its high selectivity toward certain compounds[2]. It was assumed that the flux and selectivity of pure PDMS membrane could be enhanced owing to the preferential adsorption of CMS to organics.CMS content in the membrane and several important pervaporation operation parameters, including feed concentration of acetic acid, and feed temperature, were investigated.     

Gas separation using sol-gel derived microporous zirconia membranes with high hydrothermal stability☆

A microporous zirconia membrane with hydrogen permeance about 5 × 10?8 mol·m?2·s?1·Pa?1, H2/CO2 permselectivity of ca. 14, and excellent hydrothermal stability under steam pressure of 100 kPa was fabricated via polymeric sol–gel process. The effect of calcination temperature on single gas permeance of sol–gel derived zirconia membranes was investigated. Zirconia membranes calcined at 350 °C and 400 °C showed similar single gas permeance, with permselectivities of hydrogen towards other gases, such as oxygen, nitrogen, methane, and sulfur hexafluoride, around Knudsen values. A much lower CO2 permeance (3.7 × 10?9 mol·m?2·s?1·Pa?1) was observed due to the interaction between CO2 molecules and pore wall of membrane. Higher calcination tem-perature, 500 °C, led to the formation of mesoporous structure and, hence, the membrane lost its molecular siev-ing property towards hydrogen and carbon dioxide. The stability of zirconia membrane in the presence of hot steam was also investigated. Exposed to 100 kPa steam for 400 h, the membrane performance kept unchanged in comparison with freshly prepared one, with hydrogen and carbon dioxide permeances of 4.7 × 10?8 and~3 × 10?9 mol·m?2·s?1·Pa?1, respectively. Both H2 and CO2 permeances of the zirconia membrane de-creased with exposure time to 100 kPa steam. With a total exposure time of 1250 h, the membrane presented hydrogen permeance of 2.4 × 10?8 mol·m?2·s?1·Pa?1 and H2/CO2 permselectivity of 28, indicating that the membrane retains its microporous structure.     

苯酚体系支撑液膜不稳定性研究

The instability mechanisms of the supported liquid membrane using Celgard 2500 membranes as support and tributyl phosphate dissolved in kerosene as carrier for phenol transport was studied by electrochemical impedance spectroscopy. Emulsion formation is demonstrated to be one of the main causes for the instability of supported liquid membrane in the present system. The emulsion-facilitated conditions, such as higher membrane liquid concentration, faster stirring speed, lower salt concentration and higher HLB value, would accelerate the degradation of supported liquid membrane. Other mechanisms including solubility and os-motic pressure work together to increase the membrane liquid loss.     

CO2通过合成聚合物膜的促进传递

Two kinds of fixed carrier membrane materials containing secondary amine and carboxyl groups whichcan be used as carriers of CO2 were prepared. One was poly(N-vinyl-γ-sodium aminobutyrate)(PVSA), whichwas obtained through the hydrolysis of polyvinylpyrrolidone (PVP) synthesized with N-vinylpyrrolidone(NVP) byradical polymerization. The other was poly(N-vinyl-γ-sodium aminobutyrate-co-sodium acrylate)(VSA-SA), whichwas obtained through the hydrolysis of copolymer of N-vinylpyrrolidone and acrylamide(AAm) (NVP-AAm). Thecomposite membranes were developed with PVSA or VSA-SA as active layer and polysulfone (PS) as supportmembranes. The permeation rates of pure CO2 and CH4 gas as well as binary mixtures of CO2/CH4 throughthe composite membranes were measured. The results show that the composite membranes present better CO2permeation rates than other fixed carrier membranes do reported in literature. For example, at 26℃, 1330 Pa of CO2pressure, the PVSA/PS composite membrane displays a CO2 permeation rate of 5.95 × 10-7 cm3.cm-2.s-1.pa-1with CO2/CH4 ideal separation factor of 212.1. At 20℃, 6400Pa of CO2 pressure, the VSA-SA/PS compositemembrane displays a CO2 permeation rate of 4.24 × 10-8 cm3@cm-2.s-1.Pa-1 with CO2/CH4 ideal separationfactor of 429.7. The results with the gas mixtures are not as good as those obtained with pure gas because ofthe coupling effects between CO2 and CH4. The heat cross-linked membrane shows good separation factor due todensification of the polymer.     

Functionalized carbon nanotubes mixed matrix membranes of polymers of intrinsic microporosity for gas separation

ABSTRACT: The present work reports on the gas transport behavior of mixed matrix membranes (MMM) which were prepared from multi-walled carbon nanotubes (MWCNTs) and dispersed within polymers of intrinsic microporosity (PIM)-1 matrix. The MWCNTs were chemically functionalized with poly(ethylene glycol) (PEG) for a better dispersion in the polymer matrix. MMM-incorporating functionalized MWCNTs (f-MWCNTs) were fabricated by dip-coating method using microporous polyacrylonitrile membrane as a support and were characterized for gas separation performance. Gas permeation measurements show that MMM incorporated with pristine or functionalized MWCNTs exhibited improved gas separation performance compared to pure PIM-1. The f-MWCNTs MMM show better performance in terms of permeance and selectivity in comparison to pristine MWCNTs. The gas permeances of the derived MMM are increased to approximately 50% without sacrificing the selectivity at 2 wt.% of f-MWCNTs' loading. The PEG groups on the MWCNTs have strong interaction with CO2 which increases the solubility of polar gas and limit the solubility of nonpolar gas, which is advantageous for CO2/N2 selectivity. The addition of f-MWCNTs inside the polymer matrix also improved the long-term gas transport stability of MMM in comparison with PIM-1. The high permeance, selectivity, and long term stability of the fabricated MMM suggest that the reported approach can be utilized in practical gas separation technology.     

Facilitated transport by amine‐mediated poly(vinyl alcohol) membranes for CO2 removal from natural gas

The drive toward greater application of membrane has resulted in its rapid development in natural gas processing industry. In this work, amine‐mediated membranes were tailored for CO2 removal from CO2/CH4 stream. The effects of various parameters such as amine concentration, microporous support, feed pressure and composition were examined to study the permeation behavior of pure and mixed gases. Generally, CO2 transport through the DEA‐PVA membranes was higher than that of MEA‐PVA membranes for approximately 70%. The membrane containing 15 wt% DEA and 35 wt% MEA revealed higher permselectivity. CO2 permeance enhancement of amine‐PVA membranes in comparison with neat PVA membrane, confirmed that CO2‐amine reaction was the dominant transport mechanism. Additionally, with increasing feed pressure, CO2/CH4 permselectivity decreased due to carrier saturation. However, lower partial pressure of CO2 was in favor of reaction mechanism in pure and mixed gas tests. On the other hand, CH4 is not significantly affected by feed pressure confirming that solution‐diffusion is the governing transport mechanism. Additionally, PTFE support with higher wettability showed better performance (+8%) regardless of amine type, concentration and feed pressure. DEA‐PVA membrane has exhibited good stability during 2 weeks, unlike MEA‐impregnated membrane, which was probably due to carrier degradation over time. POLYM. ENG. SCI., 54:1268–1279, 2014. © 2013 Society of Plastics Engineers     

Interfacial polymerization of facilitated transport polyamide membrane prepared from PIP and IPC for gas separation applications

A facilitated transport polyamide (PA) membrane was developed for gas separation by interfacial polymerization reaction of piperazine (PIP) and isophthaloyl chloride (IPC) supported on polysulfone (PSF) membrane previously prepared by dry/wet phase inversion method. The properties of the prepared membranes were characterized by SEM, FT-IR, TGA, and XRD. SEM images showed that a defect-free PSF, and rough PA membranes were fabricated, while the FT-IR spectra confirmed the formation of PA layer on top of the PSF support. The separation performance of the thin film PA and PSF membranes was evaluated using four gasses (CO₂, CH₄, N₂, and O₂). Compared to the PSF membrane, the PA membrane demonstrated an increased selectivity of CO₂/CH₄ and CO₂/N₂ by 178%, 169%, respectively. This improvement was attributed to the presence of amine functional groups, which acted as a fixed carrier to facilitate the transport of CO₂ gas across the membrane. However, building the PA layer on top of PSF support reduced the membrane permeance of CO₂ from 2.41 to 2.12 GPU as a result of the increased mass transfer resistance. Furthermore, the effect of operating temperature and pressure on the separation performance of the membranes was investigated.     

Fabrication and characterization of PDMS coated PES membranes for separation of ethylene from nitrogen

Composite membranes were prepared for separation of ethylene from nitrogen using polyethersulfone (PES) as support and polydimethylsiloxane (PDMS-a grade of silicone rubber) as active layer at various concentrations. Permeance and ideal selectivity were measured for all membranes under the transmembrane pressure of 2 to 6 bars. Influences of affecting parameters on membrane performance (i.e. permeance and selectivity) were investigated. The studied parameters include: PES concentration in casting solution, solvent type, PDMS concentration in coating layer, support thickness, coating thickness and coagulation atmosphere. For all coated membranes, the ethylene permeance was higher compared to the nitrogen permeance except for 5% coated air coagulated membrane. This membrane was more permeable for N₂ in comparison with ethylene under the pressures higher than 2 bars. The nitrogen permeance exhibited a rather constant value. There was no significant change in nitrogen permeance with respect to the coating layer, whereas ethylene permeance was highly influenced by coating layer composition and support thickness. The governing mechanism for the separation is solution-diffusion of ethylene in PDMS layer (solution-diffusion model). The SEM study was carried out for investigation of membrane morphology. In a run ethylene was passed through the membrane after the passage of nitrogen. In the second run ethylene was passed through the membrane before nitrogen. The nitrogen selectivity was reduced in the later test. This is due to the ethylene high solubility in membrane matrix.     

CO2在水作载体的微孔膜内的促进传递

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超临界流体沉积制备[Emim][BF4]支撑型离子液体膜及其气体分离性能

为了进一步提高支撑型离子液体膜的制备效率及其CO2气体分离性能,将离子液体[Emim][BF4]以超临界流体沉积法负载到非对称的Al2O3支撑体内,制备了一系列支撑型离子液体膜,分别测定了CO2和N2两种纯气体在其中的渗透率,探究了制备参数(沉积时间、离子液体加入量和共溶剂加入量)对膜性能的影响规律.结果表明,基于[E...     

Water vapor and CO2 transport through amine-containing facilitated transport membranes

Amine-containing CO₂ facilitated transport membranes have great potential to be applied for hydrogen purification from synthesis gas. In some applications, the humidity of the retentate stream is required as well as the purity of hydrogen. The membranes are highly hydrophilic, and they exhibit not only high CO₂ permeance but also high water vapor permeance. In this work, the transport of water vapor and CO₂ through the membranes composed of an amine-containing selective layer and a microporous polysulfone substrate was investigated. From the experiments conducted, water vapor permeance appeared to be independent of the selective layer thickness, indicating that the substrate is the controlling factor of the mass transfer resistance to water vapor transport. Moreover, water vapor permeance appeared to reduce linearly with increasing the number of the substrate layers. But, CO₂ permeance and CO₂/H₂ selectivity did not change significantly as the number of the substrate layers increased. These results indicated that the CO₂ separation performance is governed by the selective layer as expected. In addition, the membranes synthesized from Lupamin^® containing 34% polyvinylamine and 66% salt (sodium formate) demonstrated better CO₂ separation performance than those from pure polyvinylamine, presumably due to better water retention capability of the salt than polyvinylamine.     

界面聚合制备含丙烯氧基团的复合膜用于CO2分离

含有醚氧基团的膜与CO₂分子具有较强的极性作用,可以实现对CO₂/N₂物系的高效分离.其中,含丙烯氧(PO)基团的聚合物链段自由体积较大且不易结晶,是一类具有发展潜力的溶解选择性膜材料.以均苯三甲酰氯为油相单体,含PO基团的多胺为水相单体,通过界面聚合,成功制备了含PO基团的复合膜.分别采用聚醚胺D400、D230及T403为多胺水相单体,考察了膜内PO基团数量和交联度对复合膜分离性能的影响.结果表明,采用D400所制的复合膜由于具有最高的PO基团含量及较低的交联度,因此具有最高的CO₂渗透速率和CO₂/N₂分离因子.之后,考察了单体浓度、酸吸收剂种类以及水相溶液pH对复合膜分离性能的影响.通过优化这些制膜条件,制备出了CO₂/N₂分离性能较好的复合膜.