Permeation Rates Of CO2 Research Articles

A novel PVI-PVA/PS composite membrane modified by metal ions for CO2 separation: Effect and mechanism

The membrane process is potentially more energy-efficient than conventional separation technologies in the separation of carbon dioxide (CO2) /nitrogen (N2) from flue gas. In this work, a series of PVI (Polyvinylimidazole)-PVA (Polyvinyl alcohol) /PS (Polysulfone) membranes were prepared by co-blending two polymers, PVI and PVA, as the separation layer of the fixed carrier composite membrane. The separation performance increased by the dual action of PVA and the imidazole group in the PVI. Furthermore, Mg2+-PVI-PVA/PS and Cu2+-PVI-PVA/PS composite membranes were developed by adding Mg2+ and Cu2+, and the separation performance was considerably improved by complexing metal ions with PVA and PVI. Especially, Mg2+-PVI-PVA/PS demonstrated superior separation performance, with a CO2 permeation rate of 12 GPU and a CO2/N2 separation factor of 183 at a pressure of 1 bar. What’s more, the mechanism study clarified that the prepared composite membrane mainly relies on the facilitated transfer mechanism to achieve the selective separation of CO2. The presence of water molecules significantly improved the CO2 permeability and separation selectivity, indicating that PVI-PVA and Mg2+ could promote the hydration reaction of CO2 and H2O, forming easily mobile HCO3- carriers.

PDMS-based artificial lung membranes with enhanced permeation to overcome the bottleneck in CO2/O2 selectivity

Artificial lung membranes are the heart for extracorporeal oxygenation. Hereinto, the nonporous PDMS-based membranes have excellent biocompatibility, and also isolation ability to both blood and harmful matters. Nevertheless, their CO2/O2 selectivity, in the conventional cases using pure-oxygen sweeping stream, is not enough to accomplish sufficient CO2 removal in balance with O2 addition. In this work, the oxygenation mode using oxygen-enriched stream, faithfully based on the permeation mechanism, is established to overcome this bottleneck. To neutralize the negative impacts caused by lowering oxygen content and its partial pressure, PDMS-based composite membranes with ultra-thin selective layer to enhance mass transfer have been fabricated successfully. The experiments manifest that the selective layer, on the basic condition that the composite structure is stable enough to make surface modification and realistic utilization, is decreased to 376 nm on the porous substrates. O2 and CO2 permeation rates through the ultimate membrane samples have been enhanced to 502 GPU and 4117 GPU, respectively. In this instance, the essential oxygenation could be sustained with O2 partial pressure less than 446 mmHg in the sweeping stream. The minimum membrane area for a common treatment case is 0.05 square meters. Once the membrane area is increased to 0.18 square meters, the sterile air after purification could be directly used for oxygenation. In comparison to the oxygenation devices being used currently, membrane area can be saved by about 90 %, which is highly significant to reduce the injuring influence on blood cells. All in all, the artificial lung membranes with ultra-thin PDMS coating layer have promising future in realistic utilization.

Residual Saturation Effects on CO2 Migration and Caprock Sealing: A Study of Permeability and Capillary Pressure Models

In CO2 geological storage, multiphase flow plays a vital role in the movement and distribution of CO2. However, due to the limitations of fluid buoyancy and capillary forces, CO2 encounters challenges in penetrating the caprock, and the potential for leakage remains a concern due to variations in injection conditions. The migration and distribution of CO2 in the process of CO2 geological storage in saline formations are determined by relative permeability and capillary pressure, which are key factors. Consequently, this study focuses on two essential models: relative permeability and capillary pressure models. A two-dimensional isothermal reservoir–caprock model was constructed, utilizing data from the Shenhua CCS demonstration project. The analysis indicates that the core parameters in the model are residual gas saturation and residual water saturation. Specifically, residual gas saturation governs the diffusion distance of CO2 within the reservoir–caprock system, while its combined effect with residual water saturation affects the permeation rate of CO2. Through the application of the Analytic Hierarchy Process (AHP) to analyze the impact of different models on caprock integrity, it was determined that when selecting caprock models and optimizing parameters, precedence should be given to models with lower residual saturation and caprocks that offer sufficient capillary pressure for optimal sealing effects. These research findings can serve as references for practical CO2 storage projects, providing guidance on activities such as adjusting water injection strategies and controlling gas injection pressures to optimize geological storage efficiency.

Enhancing CO2/(light gases) separation performance of Pebax-based mixed-matrix membranes by [BMIM][AC] ionic liquid

Incorporating the proper additive with an affinity towards target gases is considered a helpful strategy for simultaneously improving membrane permeability and selectivity. In this research, the superior features of polyetherblockamide polymer (Pebax1657), 1–Butyl3–methylimidazolium acetate ([BMIM][AC]) ionic liquid (IL), and aluminum oxide (Al2O3) nanoparticles were blended to produce efficient ternary mixed-matrix membranes for CO2 removal from light gases. The fabricated membranes structures have been evaluated by FTIR3ATR, FESEM, XRD, and DSC analyses. The permeation rates of unmixed CH4, N2, and CO2 gases through the resulting membranes were obtained at 25 °C and a feed pressure range of 4–10 bar. The gas permeability results showed that embedding Al2O3 nanoparticles as the loading up to 6 wt% increased the CO2/(light gases) separation performance. Besides, adding the IL into the polymer matrix boosted the membranes gas separation efficiencies caused by the increased CO2 solubility and their fractional free volume. The results also revealed that the resulting membrane containing 15 wt% of [BMIM][AC] IL and 6 wt% of Al2O3 nanoparticles, which has the best gas separation efficiency, is the optimum ternary mixed-matrix membrane. The comparison between the optimized membrane and the unloaded one efficiencies demonstrated that CO2/N2 and CO2/CH4 selectivities, along with the CO2 permeability, rose from 63.40, 19.93, and 115.39 Barrer for the unloaded membrane to 81.18, 25.14, and 166.42 Barrer for the optimum membrane (around 28 %, 26 %, and 44 % increments), at 10 bar and 25 °C, respectively.

Hyper-Cross-Linked Polymers with Sulfur-Based Functionalities for the Prevention of Aging Effects in PIM-1 Mixed Matrix Membranes

The instability of gas permeation rates over time in PIM-1-based membranes is one of the obstacles preventing the implementation of this technology on larger scales. The addition of porous materials to the PIM-1 matrix is a known process to reduce aging effects in PIM-1-based membranes. Many porous solids of various chemical natures have been tested, ranging from inorganic to inorganic–organic hybrids to completely organic materials. Here, we report on the synthesis of two hyper-cross-linked polymers (HCPs) based on the diphenyl sulfide monomer, synthesized in either dichloromethane at 35 °C or dichloroethane at 78 °C. Two mixed matrix membranes (MMMs) were obtained from the addition of 3 wt % of either filler to PIM-1. Both the CO2 permeation rates and the CO2/N2 selectivity were measured for the pure PIM-1 membrane and for the two MMMs over a period of 400 days. PIM-1 exhibits a classic aging behavior with an 85% drop in the CO2 permeation rate with respect to the initial value. For the two MMMs, a retention of 50% of the initial CO2 permeability was instead observed after more than 400 days of aging. Despite the low surface area and low pore volume of the fillers, we show that diphenyl sulfide-based HCPs can reduce the aging rate in PIM-1 membranes.

Gas Permeability and Mechanical Properties of Polyurethane-Based Membranes for Blood Oxygenators.

The production of medical devices follows strict guidelines where bio- and hemocompatibility, mechanical strength, and tear resistance are important features. Segmented polyurethanes (PUs) are an important class of polymers that fulfill many of these requirements, thus justifying the investigation of novel derivatives with enhanced properties, such as modulated carbon dioxide and oxygen permeability. In this work, three segmented polyurethane-based membranes, containing blocks of hard segments (HSs) dispersed in a matrix of soft segment (SS) blocks, were prepared by reacting a PU prepolymer (PUR) with tris(hydroxymethyl)aminomethane (TRIS), Congo red (CR) and methyl-β-cyclodextrin (MBCD), rendering PU/TRIS, PU/CR and PU/MBCD membranes. The pure (control) PU membrane exhibited the highest degree of phase segregation between HSs and SSs followed by PU/TRIS and PU/MBCD membranes, and the PU/CR membrane displayed the highest degree of mixing. Pure PU and PU/CR membranes exhibited the highest and lowest values of Young’s modulus, tangent moduli and ultimate tensile strength, respectively, suggesting that the introduction of CR increases molecular mobility, thus reducing stiffness. The CO2 permeability was highest for the PU/CR membrane, 347 Barrer, and lowest for the pure PU membrane, 278 Barrer, suggesting that a higher degree of mixing between HSs and SSs leads to higher CO2 permeation rates. The permeability of O2 was similar for all membranes, but ca. 10-fold lower than the CO2 permeability.

A novel poly (4-methyl-1-pentene)/polypropylene (PMP/PP) thin film composite (TFC) artificial lung membrane for enhanced gas transport and excellent hemo-compatibility.

Extracorporeal membrane oxygenation is a technique that provides short-term supports to the heart and lungs. It removes CO2 from the blood and provides enough oxygen, which is a huge help in the fight against COVID-19. As the key component, the artificial lung membranes have evolved in three generations including silicon, polypropylene and poly (4-methyl-1-pentene). Herein, we for the first time design and fabricate a novel poly (4-methyl-1-pentene)/polypropylene (PMP/PP) thin film composite (TFC) membrane with the anticoagulant coating composed of poly (sodium 4-styrenesulfonate) and cross-linked poly (vinyl alcohol). Poly (sodium 4-styrenesulfonate) provides sulfonic acid groups to inhibit the coagulant factors (FVIII and FXII), and cross-linked poly (vinyl alcohol) increase the stability of the anticoagulant coating and further improve the hydrophilicity via abundant hydroxyl groups to depress the protein adsorption. Long-term anticoagulant property was demonstrated by whole human blood for 28 days. Blood compatibility was evaluated by hemolysis rate, anticoagulation activity (APTT, TT and PT), complement activation, platelet activation and contact activation. Pure CO2, O2 and N2 permeation rates were determined to evaluate the mass transfer properties of PMP/PP TFC membranes. Gas permeation results revealed that gas permeation flux increased in the TFC membranes because of the decrease of crystallinity. Overall, the so prepared PMP/PP membrane shows good CO2/O2 selectivity and blood compatibility as novel TFC artificial lung membrane.

Simulation Model for Prediction of Gas Separation in Membrane Contactor Process.

The purpose of this study is to establish a practical simulation model based on mass balance, mass transport equations and equilibrium equation between gas and liquid phases across a porous membrane in membrane contactor process in order to predict the separation behavior by the gassing process of gas mixture in membrane contactor. The established simulation model was verified by comparison between the simulated values and real process values in the separation of CH4/CO2 mixture, showing an excellent agreement between them. The parameter R-value in the model, which is a kind of the permeability of permeant across porous membrane, has been determined by fitting a numerical solution of the model equation to the experimental data to obtain a practical value of the parameter. A parametric study on the gassing process of N2/CO2 mixture in membrane contactor was made with the help of the practical simulation model to investigate the effects of operation parameters on separation performance and to characterize the separation behavior of membrane contactor process. A series of simulations of the separation of N2/CO2 mixture in membrane contactor were conducted, and the optimization on the membrane process was discussed to maximize the separation performance in terms of N2 recovery percent in retentate and CO2 permeation rate. It was observed from the analysis of the result of the simulation that liquid flow rate has a negative effect on N2 recovery percent in retentate but a positive effect on the separation of CO2, while R-value affects the separation performance in the other way. It is confirmed in this study that the developed simulation can be used as a tool to optimize the parameters, i.e., feed gas pressure, liquid flow rate and R-value to maximize the separation performance.

CO2-permselective membrane reactor for steam reforming of methane

Steam reforming of methane (SRM) for hydrogen production with simultaneous CO2 removal in a CO2-permselective membrane reactor is studied experimentally and analyzed by a mathematical model. The membrane consists of a thick porous BYS (Bi1.5Y0.3Sm0.2O3-δ)-SDC (Sm0.2Ce0.8O2-δ) support layer and a thin, dense SDC-carbonate dual-phase layer (∼150 μm) for CO2 separation. Experimental results of CO2 permeation in the BYS-SDC membrane and SRM reactions in a fixed-bed reactor were conducted to obtain the CO2 permeation and SRM reaction rate parameters for the model. The model's reliability is confirmed by comparing the simulation results with atmospheric pressure experimental data for SRM in the BYS-SDC membrane reactor. Simulation results are presented to show the effects of permeation number (θ) and Damkohler number (Da) (which respectively represent membrane CO2 permeance and SRM reaction rate), feed pressure in the reaction side, and sweep side conditions on the performance of SRM in the membrane reactor. Overall, increasing θ results in an increase of H2 yield, retentate H2 concentration, CO2 recovery, and a decrease of retentate CO concentration, with such effects being enhanced at higher Da and feed pressure or vacuum in the sweep side. CO2 permeance affects CH4 conversion only at high feed pressures. At feed pressure of 5 atm and applying vacuum at the sweep side of the membrane reactor, the simulation results show that the membrane reactor can achieve over 99% CH4 conversion, H2 yield, and CO2 recovery and produce an essentially pure H2 stream with zero CO concentration at Da >10,000 and θ > 1.

Controlling molten carbonate distribution in dual-phase molten salt-ceramic membranes to increase carbon dioxide permeation rates

Dual-phase molten salt-ceramic membranes show high permselectivity for CO2 when molten carbonate is supported in a porous oxygen-ion and/or electron conductor. In this arrangement, the support likely contributes to permeation. Thus, if one is to understand and ultimately design membranes, it is also important to perform experiments with an inert support where permeation relies upon the molten carbonate properties alone. Here, a nominally inert material (Al2O3) was used in order to restrict permeation to molten carbonate. Model Al2O3 dual-phase membranes were fabricated using laser drilling to provide an order of magnitude difference in molten salt-gas interfacial area between feed and permeate sides. Molten carbonate thickness in the model membranes was also varied, independent of the molten salt-gas interfacial area. For all thicknesses studied, CO2 permeation rates showed a significant temperature dependence from 500 to 750 °C, suggesting an activated process was rate-limiting, likely a permeate-side molten salt-gas interfacial process, i.e. desorption of CO2. We applied these findings in asymmetric hollow-fibre supports, a geometry with inherent modularity and scalability, by developing a new carbonate infiltration method to control molten carbonate distribution within the hollow fibre. Compared to a conventionally prepared dual-phase hollow-fibre membrane with an uncontrolled distribution of carbonates, permeation rates were increased by up to 4 times when the molten salt was confined to the packed-pore network, i.e. without infiltrating the hollow-fibre micro-channels. X-ray micro-CT investigations supported the idea that the resulting increase in interfacial area for desorption of CO2 was the key structural difference contributing to increased permeation rates. For CO2 separation, where large volumes of gas must be processed, such increases in permeation rates will reduce the demand for membrane materials, although one must note the higher permeation rates achievable with oxygen-ion and/or electron conducting supports.

Measuring Membrane Permeation Rates through the Optical Visualization of a Single Pore.

Membranes are a critical technology for energy-efficient separation processes. The routine method of evaluating membrane performance is a permeation measurement. However, such measurements can be limited in terms of their utility: membrane microstructure is often poorly characterized; membranes or sealants leak; and conditions in the gas phase are poorly controlled and frequently far-removed from the conditions employed in the majority of real processes. Here, we demonstrate a new integrated approach to determine permeation rates, using two novel supported molten-salt membrane geometries. In both cases, the membranes comprise a solid support with laser-drilled pores, which are infiltrated with a highly CO2-selective molten carbonate salt. First, we fabricate an optically transparent single-crystal, single-pore model membrane by local laser drilling. By infiltrating the single pore with molten carbonate, monitoring the gas-liquid interface optically, and using image analysis on gas bubbles within the molten carbonate (because they change volume upon controlled changes in gas composition), we extract CO2 permeation rates with exceptional speed and precision. Additionally, in this arrangement, microstructural characterization is more straightforward and a sealant is not required, eliminating a major source of leakage. Furthermore, we demonstrate that the technique can be used to probe a previously unexplored driving force region, too low to access with conventional methods. Subsequently, we fabricate a leak-free tubular-supported molten-salt membrane with 1000 laser-drilled pores (infiltrated with molten carbonate) and employ a CO2-containing sweep gas to obtain permeation rates in a system that can be described with unprecedented precision. Together, the two approaches provide new ways to measure permeation rates with increased speed and at previously inaccesible conditions.

Improving CO2/CH4 separation efficiency of Pebax-1657 membrane by adding Al2O3 nanoparticles in its matrix

In this study, polymeric nanocomposite gas separation membranes were fabricated by incorporating different contents of aluminum oxide (Al2O3) (0, 2, 4, 6 and 8 wt %) into the matrix of poly (ether-block-amide) (Pebax). The resultant membranes properties were characterized by using FTIR, FESEM, XRD, and TGA. Permeation rates of pure CO2 and CH4 gases through the fabricated pristine and the nanoparticles-incorporated membranes were measured at different pressures (3, 6, 9, 12 and 15 bar) and a fixed temperature of 25 °C. The results revealed better separation efficiency (CO2 permeability and CO2/CH4 selectivity) of the nanocomposite membranes than the pristine membrane. For example, the CO2 permeability and ideal CO2/CH4 selectivity values for the neat membrane at the pressure of 3 bar were 123.46 Barrer and 21.21, respectively while those values for the membrane comprising 8 wt % of Al2O3 were 159.27 Barrer and 24.73.

Preparation of PEBAX-1074/modified ZIF-8 nanoparticles mixed matrix membranes for CO2 removal from natural gas

In this work, as synthesized and modified ZIF-8 nanoparticles were used as the filler particles for mixed matrix membranes (MMMs) preparation for natural gas CO2 removal. Characterization of the prepared MMMs using SEM, XRD and FTIR were performed provided essential insights to the MMMs structure and revealed no defect in the MMMs due to incorporation of the ZIF-8 nanoparticles within the polymer matrix. The nanoparticles were also loaded by ethylenediamine (ED) amine loaded and incorporated within the PEBAX1074 matrix up to 20 wt% without agglomeration. After modification of the nanoparticles with ED, the ZIF-8 nanoparticles loading in the MMMs were extended up to 30 wt% without any agglomeration. The MMMs CO2 and CH4 adsorption and permeation rate were evaluated at the room temperature and different transmembrane pressures. The unmodified ZIF-8 nanoparticles loaded MMMs adsorption capacities for CH4 and CO2 were found as 6.28, 27.07 cm3 STP/cm3, respectively, compared with those of the modified ZIF-8 nanoparticles loaded MMMs were found as 6.88 and 30.46 cm3 STP/cm3, respectively. CH4 and CO2 permeabilities through the unmodified ZIF-8 nanoparticles loaded MMMs were found as ~9.39 and 134 Barrer, respectively, while for the modified MMMs, CH4 and CO2 permeation were measured as ~14.2 and 344 Barrer, respectively. The results showed significant improvement in ideal and real CO2/CH4 selectivity (71% and 40%) at 30 wt% of the ZIF-8 loading.

Gas permeation through rubbery polymer nano-corrugated membranes

The purpose of this investigation is to fabricate PDMS membranes with reliable surface roughness in order to reduce the surface resistances and to study its impact on the permeation rate. The permeance of CO2 through PDMS membranes with rough surfaces at nanoscale is studied and compared with the one of membranes with flat surfaces. At very low thickness, rough membranes have a permeance greater than that of membranes with flat surfaces. The enhancement occurs in a regime where the gas transport is sorption desorption surface rate limited, and cannot be explained by the increase in surface area due to the corrugation. The analysis, introducing a phenomenological model in analogy with electrical flow, indicates that nano-corrugation reduces the surface resistance. To test the model, the permeance of N2 is also measured in the same experimental conditions and the influence of surface roughness on permeation rate of CO2, He, CH4 and N2 is studied. The comparison among the gases suggests that the Henry’s coefficient depends on the surface roughness and allows discussing the role of roughness on membrane selectivity.

Effect of a cyclic heating process on the CO 2 /N 2 separation performance and structure of a ceramic nanoporous membrane supporting the ionic liquid 1-methyl-3-octylimidazolium tricyanomethanide

This work presents an investigation of the CO2 and N2 mixed-gas permeation rates through a supported ionic liquid membrane (SILM) developed on a ceramic composite nanofiltration substrate with a separation layer pore size of 10 nm. The ionic liquid 1-methyl-3-octylimidazolium tricyanomethanide was used as supported liquid phase. The hybrid membrane was subjected to a cyclic heating process including isothermal steps of 180 °C, under inert gas flow. In this context, the effect of temperature (over the range of 25–180 °C) and feed composition on the permeation properties and CO2/N2 separation performance was studied prior to and after completion of each heating cycle. For all heating cycles, the highest CO2/N2 selectivity values (up to 50.4) were provided at ambient temperature unlike to CO2 permeance that was favored by elevation of temperature, reaching to 2.48 · 10−9 mol·m−2·s−1·Pa−1 at 180 °C. Thermal analysis by means of DSC and TGA investigations allowed to determine the physical state and thermal stability of the immobilized IL phase, thereby providing a better understanding of the determined gas permeation properties. Confinement into the nanopores of the developed SILM substantially affected the thermal behaviour and assisted decomposition of the ionic liquid phase upon heat treatment. UV/Vis spectroscopy indicated formation of functionalized by-products during prolonged periods of heating at 180 °C that could form stable chemical complexes with CO2 molecules, thus drastically affecting both CO2 solubility and diffusivity, and CO2/N2 separation efficiency.

Amino-functionalized surface modification of polyacrylonitrile hollow fiber-supported polydimethylsiloxane membranes

This study aimed to improve surface polarity of polydimethylsiloxane (PDMS) membranes and provide surface active sites which were easy to react with other chemicals. 3-Aminopropyltriethoxysilane (APTES) containing an amino group was introduced into a PDMS membrane by crosslinking to prepare polyacrylonitrile hollow fiber-supported PDMS membranes with an amino-functionalized surface. Fourier transform infrared and X-ray photoelectron spectroscopic analyses proved the existence of APTES and its amino group in the PDMS membrane. The concentration of N atoms on the PDMS membrane surface reached ∼6% when the mass ratio of APTES/PDMS oligomer in the PDMS coating solution was increased to 4/3. The water contact angle decreased from ∼114° to ∼87.5°, indicating the improved surface polarization of the PDMS membrane. The density and swelling degree of the PDMS membrane decreased and increased, respectively, with increasing APTES content in PDMS. This phenomenon increased CO2 permeability and decreased CO2/H2 selectivity, CO2/CH4 selectivity, and CO2/N2 selectivity. When the mass ratio of APTES/PDMS oligomer was increased from 0 to 4/3, the CO2 permeation rate of the hollow fiber-supported PDMS membranes initially decreased from ∼2370 GPU to ∼860 GPU and then increased to ∼2000 GPU due to the change in coating solution viscosity.

Improving CO2 permeability of ceramic hollow fibre-supported composite membranes by blending an ionic liquid in the Pebax/PEGDME selective layer

The ionic liquid [P66614][2-Op], with high CO2 capacity, was blended in the Pebax/PEGDME selective layer of the ceramic hollow fibre-supported composite membrane. CO2 permeation rate was improved by ~35% and high CO2/H2 selectivity was maintained.

Surface monofunctionalized polymethyl pentene hollow fiber membranes by plasma treatment and hemocompatibility modification for membrane oxygenators

The hemocompatibility of polymethyl pentene (PMP) hollow fiber membranes (HFMs) was improved through surface modification for membrane oxygenator applications. The modification was performed stepwise with the following: (1) oxygen plasma treatment, (2) functionalization of monosort hydroxyl groups through NaBH4 reduction, and (3) grafting 2-methacryloyloxyethyl phosphorylcholine (MPC) or heparin. SEM, ATR-FTIR, and XPS analyses were conducted to confirm successful grafting during the modification. The hemocompatibility of PMP HFMs was analyzed and compared through protein adsorption, platelet adhesion, and coagulation tests. Pure CO2 and O2 permeation rates, as well as in vitro gas exchange rates, were determined to evaluate the mass transfer properties of PMP HFMs. SEM results showed that different nanofibril topographies were introduced on the HFM surface. ATR-FTIR and XPS spectra indicated the presence of functionalization of monosort hydroxyl group and the grafting of MPC and heparin. Hemocompatibility evaluation results showed that the modified PMP HFMs presented optimal hemocompatibility compared with pristine HFMs. Gas permeation results revealed that gas permeation flux increased in the modified HFMs because of dense surface etching during the plasma treatment. The results of in vitro gas exchange rates showed that all modified PMP HFMs presented decreased gas exchange rates because of potential surface fluid wetting. The proposed strategy exhibits a potential for fabricating membrane oxygenators for biomedical applications to prevent coagulation formation and alter plasma-induced surface topology and composition.

High solvent resistance PTFPMS/PEI hollow fiber composite membrane for gas separation

Poly(fluoropropylmethylsiloxane) (PTFPMS), which had different properties with polydimethylsiloxane (PDMS) due to CF bond. The limitation for PTFPMS membrane to achieve industrial-scale applications was the forms of membrane modules. Thus, PTSPMS/polyetherimide (PEI) hollow fiber composite membranes have been prepared. Effects of PTFPMS concentration, coating method, selective layer thickness, operating pressure and temperature on the separation performance of the composite membranes have been investigated. PTFPMS can form a top dense layer on PEI substrate under a suitable concentration. The gas permeation rates decrease in the following order: CO2>C3H6>H2>O2>CH4>N2. Permeation rates of CO2 and C3H6 change significantly with the increase of operating pressure. Based on pure gas permeation rates, the selectivities range from 16.03 to 18.80 for CO2/N2 and 11.75–19.76 for C3H6/N2 under operating pressure ranging from 0.1 to 0.5MPa. Operating temperature has significant impact on permeation rates of CO2, CH4, O2, H2 and N2. PTFPMS/PEI hollow fiber composite membrane exhibits stable separation performance after immersed in i-octane and petroleum ether. The selectivity decreases ratio of PTFPMS/PEI hollow fiber composite membranes varies in the range of 1.56–10.70%, much lower than those of PDMS/PEI membranes of 8.02–21.34%.

Novel Tertiary Amino Containing Blinding Composite Membranes via Raft Polymerization and Their Preliminary CO2 Permeation Performance.

Facile synthesis of poly (N,N-dimethylaminoethyl methacrylate) (PDMAEMA) star polymers on the basis of the prepolymer chains, PDMAEMA as the macro chain transfer agent and divinyl benzene (DVB) as the cross-linking reagent by reversible addition-fragmentation chain transfer (RAFT) polymerization was described. The RAFT polymerizations of DMAEMA at 70 °C using four RAFT agents with different R and Z group were investigated. The RAFT agents used in these polymerizations were dibenzyl trithiocarbonate (DBTTC), s-1-dodecyl-s'-(α,α'-dimethyl-α-acetic acid) trithiocarbonate (MTTCD), s,s'-bis (2-hydroxyethyl-2'-dimethylacrylate) trithiocarbonate (BDATC) and s-(2-cyanoprop-2-yl)-s-dodecyltrithiocarbonate (CPTCD). The results indicated that the structure of the end-group of RAFT agents had significant effects on the ability to control polymerization. Compared with the above-mentioned RAFT agents, CPTCD provides better control over the molecular weight and molecular weight distribution. The polydispersity index (PDI) was determined to be within the scope of 1.26 to 1.36. The yields, molecular weight, and distribution of the star polymers can be tuned by changing the molar ratio of DVB/PDMAEMA-CPTCD. The chemical composition and structure of the linear and star polymers were characterized by GPC, FTIR, 1H NMR, XRD analysis. For the pure Chitosan membrane, a great improvement was observed for both CO2 permeation rate and ideal selectivity of the blending composite membrane upon increasing the content of SPDMAEMA-8. At a feed gas pressure of 37.5 cmHg and 30 °C, the blinding composite membrane (Cs: SPDMAEMA-8 = 4:4) has a CO2 permeation rate of 8.54 × 10−4 cm3 (STP) cm−2∙s−1∙cm∙Hg−1 and a N2 permeation rate of 6.76 × 10−5 cm3 (STP) cm−2∙s−1∙cm∙Hg−1, and an ideal CO2/N2 selectivity of 35.2.