Fixed Carrier Membranes Research Articles

Study on CO2 facilitated separation of mixed matrix membranes containing surface modified MWCNTs

ABSTRACTMixed matrix membranes (MMMs) for CO2‐facilitated separation were prepared by incorporating different surface‐modified multiwalled carbon nanotubes (MWCNTs) in a fixed carrier membrane material. Polymer containing amino groups, poly(vinylalcohol‐co‐vinylamine) (VA‐co‐VAm) was synthesized as polymeric matrix. MWCNTs as well as MWCNTs surface‐modified with OH and NH2 were applied as nanofillers. The physical property, chemical structure, and membrane morphology were characterized by FT‐IR, TG, XRD, DSC, CA, XPS, and SEM. The effects of content, functional group, temperature, and pressure on gas permselectivity were studied. Results show that the incorporation of nanofillers can effectively restrict the polymer chain packing and lead to low crystallinity. The MMMs exhibited higher CO2 permselectivity than the pure polymeric membrane. For all the MMMs, the CO2 permeance and selectivity increased with MWCNTs contents to a maximum and then decreased. MWCNT‐NH2 can be regarded as the most effective nanofiller. MMMs with 2.0 wt % MWCNT‐NH2 displayed the highest CO2 permeance of 132 GPU and CO2/N2 selectivity of 74. Both CO2 permeance and selectivity were decreased with feed gas pressure and temperature. The membrane exhibited good stability in the testing with the binary gas mixtures of CO2/N2 for 110 h under 0.54 MPa. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47848.

Preparation and characterization of inner-pressure hollow fiber composite membrane via two-way coating technique for CO2/CH4 separation

High-selectivity inner-pressure hollow fiber composite (HFC) membrane for CO2/CH4 separation was prepared through the Two-way coating (TWC) technique. The blends of poly(vinylamine) (PVAm)/polyvinyl alcohol (PVA) were coated onto porous hollow fiber polysulfone (PSF) ultrafiltration (UF) membrane with an effective membrane area of 0.4 m2. The effects of fabrication parameters on the permselectivity of the resultant HFC membrane were investigated and the optimum preparation conditions were obtained as follows: coating time for 30 min and air blowing time for 30 min after the coating. The prepared HFC membrane showed the typical characteristic of fixed carrier membrane with a high selectivity of CO2 and CH4: the separation factor of CO2/CH4 (40 vol% CO2 at 25 °C and 0.2 MPa) was 36.6 and the CO2 permeability was 56.3 GPU. Field emission scanning electron microscopy (FESEM) images indicated that the HFC membrane prepared by TWC technique had a uniform coating layer along the whole hollow fiber. Membrane permselectivity showed almost no difference between different membrane sections. The HFC membrane showed a good stability during the continuous testing process of 540 h. And the HFC membrane preserved at 30 °C and 40 % humidity exhibited a good durability with a basically unchanged separation factor after 30 days.

Adjusting carrier microenvironment in CO2 separation fixed carrier membrane

An ion-exchange material – Poly(diallyldimethylammonium carbonate) (PDDACA) containing mobile carbonate has been prepared and it has been blended in a fixed carrier membrane material – polyvinylamine (PVAm) containing abundant amine-group to adjust the carrier microenvironment of the fixed carrier membrane. It makes the mobile carrier cruise around the fixed carrier. On one hand, the CO2 can be transported continuously in the swing area of fixed carrier through the mobile carriers, the passivity of fixed carrier can be overcome and the utilization efficiency of fixed carrier can be enhanced. On the other hand, a loose and low crystalline system will be obtained by blending two polymers, the number of effective mobile carrier will be increased with mobile carriers unlocking from the crystalline area, and the loose and low crystalline system will provide a good environment for the movement of mobile carriers. These are conducive to enhance the performance of blend membrane in comparision with single polymer membrane. The CO2 permeance and CO2/N2 selectivity of PVAm-PDDACA membrane, which concurrently contains fixed amine carriers and movable carbonate carriers, can reach 909GPU and 102 at 0.11MPa, respectively. The performance of PVAm-PDDACA membrane is enhanced obviously in comparision with PVAm membrane and PDDACA membrane.

Cyclic tertiary amino group containing fixed carrier membranes for CO2 separation

Fixed carrier membranes containing amino groups show attractive performance in CO2 separation for clean energy supply and greenhouse gas reduction. However, the separation performance of fixed carrier membranes at high feed pressure is limited by the facilitated transport ability of membranes as well as the CO2-induced plasticization. In this work, the tertiary amino group containing fixed carrier membranes were prepared by interfacial polymerization (IP) with hexane-soluble trimesoyl chloride (TMC) and aqueous-soluble 1,4-bis (3-aminopropyl) piperazine (DAPP), N-aminoethylpiperazine (EAP) and 3,3′-diamino-N-methyldipropylamine (DNMDAm). The results show that the membrane prepared with TMC and DAPP exhibits the highest CO2 separation performance due to efficient CO2 facilitated transport and high plasticization resistance. Efficient facilitated transport of CO2 in the membrane is due to the high content of cyclic tertiary amino groups which possess high stoichiometric CO2 loading and high rate constant of amine-CO2 reaction. Moreover, high plasticization resistance of the membrane is attributed to the appropriate stiffness of polymer chains provided by IP. The membrane prepared with TMC and DAPP shows promising applications in high-pressure fuel gas purification.

Effects of Minor SO2 on the Transport Properties of Fixed Carrier Membranes for CO2 Capture

A key concern for application of fixed carrier membranes in CO2 capture is the effects of a trace amount of SO2 present in the flue gas. To eliminate this concern, the effects of SO2 in the feed gas on CO2/N2 permeance and selectivity of fixed carrier membranes were investigated by combining experimental and modeling study. The experimental results reveal that the separation performance of the membrane slightly decreases with increasing SO2 concentration in the feed gas due to the competitive sorption and competitive reaction caused by SO2. The decrease in separation performance is tolerable at even 5000 ppm of SO2 present in the feed gas. The facilitated transport model was modified by considering the competitive reaction to investigate the transport and interactions of CO2 and SO2. The modeling results suggest that the SO2 partial pressure at the membrane surface is much lower than that in the bulk feed gas due to the serious concentration polarization of SO2 under the mixed gas condition, and the decre...

Fabrication of high-performance facilitated transport membranes for CO2separation

At present, liquid membranes, ion-exchange membranes and fixed carrier membranes are the three popular facilitated transport membranes for CO2separation. We report a method to combine their advantages and overcome their deficiencies.

Investigation of gas permeation behavior in facilitated transport membranes: Relationship between gas permeance and partial pressure

In this work, a generalized expression for gas permeation, which takes account of the partial pressure, has been developed for both liquid membranes and fixed carrier membranes. The gas permeation behaviors with varying partial pressure were analyzed based on the generalized expression. Based on the expression for the permeance, the facilitated transport parameters of an immobilized liquid membrane and a fixed carrier membrane, including diffusion coefficient of uncomplexed solute and solute-carrier complex as well as reaction equilibrium constant, were calculated by fitting the experimental data of the permeance varying with the partial feed pressure. The calculated parameters agreed well with those in the literature. To check the present expression and the calculated parameters, the gas permeance of two kinds of immobilized liquid membranes and a fixed carried membrane were predicted under varying partial pressure. The predicted results were in satisfactory agreement with the experimental data. Moreover, the prediction for the effects of membrane thickness, carrier concentration and equilibrium constant on the relationship between gas permeance and partial pressure has been carried out.

Preparation of PMAM-B-PNVP and its Hydrolysate by RAFT Polymerization: Structure Characterization and its CO<sub>2</sub> Permeation Performance

Macromolecules chain transfer agents (MCTA) were synthesized through the reversible addition fragmentation chain transfer polymerization (RAFT) by using S-l-Dodecyl-S′-(α, α′-dimethyl-α-acetic acid) trithiocarbonate(MTTCD), S, S′-bis (2-hydroxyethyl-2′-dimethylacrylate) trihiocarbonate (BDATC), 2-cyanoprop-2-yl dithiobenzoate (CPDB) as the chain transfer agents, methacrylamide (MAM) as the first polymerization monomer. The results showed that the structures of the end-group of dithiocarbamates had significant effects on the activity of dithiocarbamates for the polymerization of PMAM. The derived block copolymer (PMAM-b-PNVP) was prepared by using the above mentioned polymer as macromolecular RAFT agent and NVP as the second polymerization monomer. N-vinyl-γ-sodium aminobutyrate-sodium methacrylate copolymer (VSA-MSA) containing -NH2 and -COOH as the CO2 facilitated carrier, a kind of new fixed carrier membrane material for CO2 separation, was synthesized by hydrolysis of the resulted PMAM-b-PNVP. The chemical composition and structure of PMAM-CTA, PMAM-b-PNVP, MSA-VSA were analyzed by FTIR, 1HNMR and DSC, the molecular weight and polydispersity index were analyzed by GPC. The Relative molecular mass of polymer was controllable. The polydispersity index (1.2~1.3) of the obtained polymer was narrow via using MTTCD and BDATC. The VSA-MSA/PS composite membranes were prepared. The CO2 and N2 permeation performance were tested at different pressure. The results showed that the resulted composited membrane had a CO2 permeation rate of 1.2×10-4 cm3 (STP) cm-2s-1cmHg-1 and a N2 permeation rate of 8.57×10-7 cm3 (STP) cm-2s-1cmHg-1 and an ideal CO2/ N2 selectivity of 140.02 at a feed gas pressure of 7.6 cmHg and 30 °C.

An Effective Method to Improve the Performance of Fixed Carrier Membrane via Incorporation of CO 2-selective Adsorptive Silica Nanoparticles

Fixed carrier membrane exhibits attractive CO 2 permeance and selectivity due to its transport mechanism of reaction selectivity (facilitated transport). However, its performance needs improvement to meet cost targets for CO 2 capture. This study attempts to develop membranes with multiple permselective mechanisms in order to enhance CO 2 separation performance of fixed carrier membrane. In this study, a novel membrane with multiple permselective mechanisms of solubility selectivity and reaction selectivity was developed by incorporating CO 2-selective adsorptive silica nanoparticles in situ into the tertiary amine containing polyamide membrane formed by interfacial polymerization (IP). Various techniques were employed to characterize the polyamide and polyamide-silica composite membranes. The TGA result shows that nanocomposite membranes exhibit superior thermal stability than pure polyamide membranes. In addition, gas permeation experiments show that both nanocomposite membranes have larger CO 2 permeance than pure polyamide membranes. The enhanced CO 2/N 2 separation performance for nanocomposite membranes is mainly due to the thin film thickness, and multiple permselective mechanisms of solubility selectivity and reaction selectivity.

Improvement of CO 2/N 2 separation characteristics of polyvinylamine by modifying with ethylenediamine

In this work, the idea of modifying the fixed carrier membrane for CO 2 separation by a cross-linking agent containing carriers to simultaneously improve the CO 2-induced plasticization resistance, the CO 2 permeance and the CO 2/N 2 selectivity of the membrane was suggested and confirmed. Polyvinylamine (PVAm), a polymer to prepare fixed carrier membrane for CO 2 separation, was synthesized by partial acidic hydrolysis of poly(N-vinylformamide) and further modified by using ethylenediamine (EDA). Elemental analysis, ATR-FTIR, XPS and XRD were employed to characterize the EDA modified PVAm. The result of ATR-FTIR and XPS showed that the EDA can effectively cross-link PVAm by the hydrogen bonds formed between amine groups of EDA and either amine or amide groups in PVAm. The composite membranes were developed by coating the PVAm–EDA mixed solutions with different mass ratio of EDA/PVAm ( m EDA/ m PVAm) on polysulfone (PS) ultrafiltration membrane. The effects of m EDA/ m PVAm in coating solution and wet coating thickness on the gas performance of the PVAm–EDA/PS composite membranes were investigated. The PVAm–EDA/PS membrane prepared by using coating solution with proper m EDA/ m PVAm (from 1 to 3) showed higher CO 2 permeance and much higher CO 2/N 2 selectivity as well as better CO 2-induced plasticization resistance than that of the PVAm/PS membrane. It is attributed to two factors: (1) the densification of polymer matrix by moderate hydrogen bond cross-linking; and (2) the increase of total carrier content in membrane. As CO 2-induced plasticization resistance improves, the selective layer thickness of the PVAm–EDA/PS membrane can be further reduced to obtain a higher CO 2 permeance and a proper CO 2/N 2 selectivity simultaneously. For CO 2/N 2 gas mixture (20/80 by volume), the PVAm–EDA/PS membrane prepared by using coating solution with m EDA/ m PVAm of 3 and 50 μm wet coating thickness displayed a CO 2 permeance of 607 GPU and CO 2/N 2 selectivity of 106 at CO 2 partial pressure of 0.02 MPa. The separation performance stability of the PVAm–EDA/PS membranes was investigated for 300 h and no deterioration in membrane permselectivity was observed. Moreover, the PVAm–EDA/PS membrane had no obvious degradation after exposure to H 2O-saturated SO 2 of 300,000 ppm h.

Effects of pressure and temperature on fixed-site carrier membrane for CO2 separation from natural gas

In this paper, the effect of testing temperature on the performance of fixed carrier membrane for CO2 separation were studied. The blend composite membranes were developed respectively with a blend of PEI-PVA (polyetheleneimine-polyvinyl alcohol) as separation layer and PS (polysulfone) ultrafiltration membranes as the substrates. The permselectivity of the membranes was measured with CO2/CH4 mixed gas. The effect of testing temperature on membrane separation performance was investigated. The results showed that both the permeances of CO2 and CH4 decreased with the increase of temperature, and the permeances decreased more quickly under low pressure than those under high pressure. At the feed pressure of 0.11 MPa, the CO2/ CH4 selectivity of PEI-PVA/PS blend composite membrane reduced along with temperature increment. Under the feed pressure of 0.21 MPa, as well as 1.11 MPa, the selectivity decreased with the increase of temperature.

Recent achievements in facilitated transport membranes for separation processes

Membrane separation processes have been extensively used for some important industrial separations, substituting traditional methods. However, some applications require the development of new membranes. In this work, we discuss recent progress achieved in this field, focusing on gas and liquid separation using facilitated transport membranes. The advantages of using a carrier species either in a liquid membrane or fixed in a polymer matrix to enhance both the flux and the selectivity of the transport are summarized. The most probable transport mechanisms in these membranes are presented and the improvements needed to spread this technology are also discussed. As examples, we discuss our very successful experiences in air fractioning, olefin/paraffin separation and sugar recovery using liquid and fixed carrier membranes.

Effects of Carrier Mobility on Carrier Saturation Phenomenon in Facilitated Transport Membranes

Permeation experiments of ethylene were performed to investigate the effect of carrier mobility on carrier saturation in a facilitated transport membrane. Poly(vinyl alcohol)-based membranes containing either Na+-ions or Ag+-ions were used to prepare mobile-carrier and fixed-carrier membranes. For the membranes containing 0.49 M Ag+-ions, the fluxes obtained from the mobile-carrier membrane were higher than those obtained from the fixed-carrier membrane. It was also observed that the fixed-carrier membrane was more susceptible to the carrier saturation than the mobile-carrier membrane. However, the effect of carrier mobility on permeation flux and carrier saturation was not noticed as the carrier concentration was increased.

Effect of heat cross-linking on carbon dioxide fixed-carrier membrane structure and performance

A new fixed-carrier composite membrane prepared with poly(N-vinyl-γ-sodium aminobutyrate) (PVSA) as the active layer and a polysulfone (PS) ultrafiltration membrane as the support was previously reported. In order to improve the permselectivity and stability, the PVSA/PS composite membrane was modified by using heat cross-linking. Cross-linked PVSA/PS composite membranes possess higher selectivity, a slightly lower CO 2 permeation rate and better stability than uncross-linked membranes. The cross-linking mechanism was studied by X-ray photoelectron spectroscopy. The effect of cross-linking time on the performance of the composite membrane was also investigated.

Pervaporative separation of organic mixtures using dinitrophenyl group-containing cellulose acetate membrane

This paper reports experimental results on pervaporation of benzene/cyclohexane mixtures and xylene isomer mixtures through a fixed-carrier membrane consisting of cellulose acetate (CA) as a base polymer and dinitrophenyl (DNP) group as a selective fixed-carrier. The result of the pervaporation of benzene/cyclohexane mixture using the unmodified CA membrane and the CA-DNP membrane showed that the DNP group was effective to increase the benzene selectivity. In the pervaporation of xylene isomer mixtures, the DNP group selectively facilitated the transport of xylene isomers through the membrane. The order of the preferentially permeating component was p-xylene > m-xylene > o-xylene.

Facilitated transport of CO 2 through ethylenediamine-fixed cation-exchange polysaccharide membranes

A new cation-exchange polysaccharide membrane containing a diamine complexing agent for CO 2 facilitated transport was developed. The facilitated transport of CO 2 through a ethylenediamine (EDA) fixed-cation exchange polysaccharide has been studied. In this study, polysaccharide from marine alga, SA was used as polymer matrix in order to prepare a new fixed-carrier membrane for CO 2 facilitated transport. The carrier was introduced in the membrane by soaking acidic cation-exchange membranes in EDA solutions. The EDA carrier exhibited a large facilitation effect in a cation-exchange polysaccharide membrane. The facilitation effect of CO 2 through the water-swollen SA membrane was small compared with the EDA-fixed SA. The effect of the carrier (EDA) content on the CO 2 facilitated transport of the EDA-fixed membranes prepared by varying EDA content in membranes was investigated. It was found that the CO 2 permeability of the EDA-fixed SA membranes increased with increasing carrier (EDA) content in the membrane.

Facilitated transport of cations (copper, silver, zinc) by solid dense membranes

For the removal of heavy metals, such as copper, zinc and silver from industrial effluents specific membranes have been developed containing carriers that are capable to transport these ions at a high rate by a facilitated transport mechanism. The carriers(crown ethers)are coupled to a polymer resulting in a fixed carrier membrane. We investigated the transport of silver, copper and zinc ions by sulfonated polisulfone and polyether ether ketone membranes modifies with crown-ether.

促進輸送膜による高選択的ガス分離の最近の展開

Recent developments in the facilitated transport membranes (FTMs) for gas separations with high selectivity are described focusing on CO2/N2, 02/N2 and olefin/paraffin separations. There are two types of FTM, i.e., mobile carrier membrane and fixed carrier membrane. For both types of membrane, the rate and equilibrium of the reaction between the carrier and the penetrant gas have decisive effects on the membrane performance. With respect to fixed carrier membranes for O2/N2 separation, a composite membrane with a very thin active layer of Co (II) -porphyrin complex of about 80nm thickness on a porous support exhibits promising O2 permeance and selectivity. Very efficient solid polymer electrolyte membranes containing silver salts have been developed for olefin/paraffin separations, and the threshold carrier concentration behavior has been elucidated from the coordination behavior of silver ion in the membrane. Finally, a novel type of “facilitated transport membrane” accompanied by permeation of a carrier solution, which overcomes the drawback of liquid membranes such as instability and low permeability, is shown to be very effective for CO2/N2 and C2H4/C2H6 separations.

Novel fixed‐carrier membranes for CO2 separation

AbstractA 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

Selective permeation of CO 2 through new facilitated transport membranes

A new membrane material containing facilitated transport groups for carbon dioxide has been synthesized through the hydrolysis of polyvinylpyrrolidone (PVP) obtained by radical polymerization. The composite membrane was prepared with the hydrolysate as the top layer and microporous membrane as the support. The permeation of pure CO 2 and CH 4 as well as a binary mixture of CO 2/CH 4 through the composite membrane was measured. The effects of feed gas pressure, heat treatment and support membranes on the composite membrane performance were studied. The results show that the composite membranes possess better CO 2 permeance and selectivity of CO 2 over CH 4 than that of other fixed carrier membranes reported in literature.