Facile CO2 Separation in Composite Membranes

CO₂ emission from anthropogenic sources has raised worldwide environmental concerns and hence proficient energy paradigm has tilted towards CO₂ capture. Membrane technology is one of the efficient technologies for CO₂ separation since it is environmentally friendly, inexpensive, and offers high surface areas. Various approaches are discussed to improve membrane performance focusing mainly on permeability and selectivity parameters. Different types of fillers are incorporated to reach the Robeson's upper bound curve. In this review, polymer‐inorganic nanocomposite membranes for the separation of CO₂, CH₄, and N₂ from various gas mixtures are comprehensively discussed. Metal organic frameworks (MOFs) and ionic liquid (ILs) mixed‐matrix membranes are also considered.     

高聚物/陶瓷复合膜的气体渗透及分离行为

以实验室制备成功的SR／Ceramic和PPESK／Ceramic复合膜为基础,对O2、N2、H2、CO、CO2、CH4等气体在高聚物／陶瓷复合膜上的渗透性能进行研究;在较宽的温度范围内考察了复合膜的使用效果,并获得各种气体的渗透活化能及其与气体临界温度的关系;渗透活化能随临界温度的增大而增低。同时,以空气分离体系为对象,考察了膜分离器的操作参数q和pr对膜分离系统过程行为的影响;实验结果和理论分析一致。     

Ceramic/Polyaniline Composite Porous Membranes

Ceramic/polyaniline composite porous membranes are successfully made by diffusing ammonium peroxydisulfate and aniline into inorganic membrane disks. The ceramic disks are fabricated by mixing CMC, water, kaolin and alumina followed by the processes of drying, milling, sieving, pressing at 4000 pounds, and firing. The pore size of the disk is approximately 1 m.When the concentration of the oxidant is 0.25 M and that of the monomer is 1 M, the incorporation of polyaniline into the ceramic disks levels off after about 40 hours. The maximum incorporation percentage is approximately 4.86 wt% (0.18 g of polymer/3.7 g of disk). Characterizations of the ceramic disk and its composites include N2-flow tests, solubility tests, BET, SEM, OM and acid diffusion studies. Nitrogen-flow tests indicate that the incorporated polyaniline is structurally unstable. However, after applying N2 gas of 23 psig for about 40 min, no further degradation is observed in these composite membranes even under 40 psig of N2 gas. BET shows that the surface area of the composite is greater than that of the ceramic disk. SEM reveals that polyaniline is grown on the surface of the pores of the ceramic disks. Time constants, corresponding to the time when the pH value reaches 36.8% of the initial value, are estimated from the results of acid diffusion studies. The magnitude of the time constant is in the following order: ceramic/Peani base > ceramic/Peani salt > ceramic/Pani base > ceramic/Pani salt > plain ceramic.     

Membranes for CO2 /CH4 and CO2/N2 Gas Separation

Membrane technology has emerged as a leading tool worldwide for effective CO₂ separation because of its well-known advantages, including high surface area, compact design, ease of maintenance, environmentally friendly nature, and cost-effectiveness. Polymeric and inorganic membranes are generally utilized for the separation of gas mixtures. The mixed-matrix membrane (MMM) utilizes the advantages of both polymeric and inorganic membranes to surpass the trade-off limits. The high permeability and selectivity of MMMs by incorporating different types of fillers exhibit the best performance for CO₂ separation from natural gas and other flue gases. The recent progress made in the field of MMMs having different types of fillers is emphasized. Specifically, CO₂/CH₄ and CO₂/N₂ separation from various types of MMMs are comprehensively reviewed that are closely relevant to natural gas purification and compositional flue gas treatment     

负载型TiO2复合陶瓷膜的制备与表征

采用料浆浇注法制备了硅藻土－莫来石（K－M）陶瓷支承体管，溶胶－凝胶法在其上制备了负载型TiO2复合膜，并采用ESEM、压汞法、IR和纯气体渗透性能测试装置对其进行了表征。结果表明：TiO2/K-M复合陶瓷膜成膜情况良好，孔径分布比较均匀；支承体和TiO2膜孔径分别集中分布在2．01μm和37nm左右；TiO2膜层与支承体存在键联和相互作用；TiO2膜层的气体渗透为努森扩散和粘性流共同控制。     

Various Techniques for Preparation of Thin‐Film Composite Mixed‐Matrix Membranes for CO2 Separation

The application of thin‐film composite mixed‐matrix membranes (TFC‐MMMs) for gas separation is widely considered as an efficient separation technology. The principal methods for the preparation of TFC‐MMMs are dip‐coating, phase inversion, and interfacial polymerization comprising different types of support layers. These methods influence the CO₂ permeation over the selective and support layers. A comprehensive review is provided for capturing new details of progress achieved in developing TFC‐MMMs with detailed performance of gas separation in the previous few years. Various preparation techniques of TFC‐MMMs and their effect on the gas separation performance of the prepared membranes are described.     

Ultrafiltration of W/CO2 Microemulsions in Ceramic Membranes

Abstract

Water‐in‐CO₂ (W/CO₂) reverse microemulsions stabilized with 1100 Da poly(ethylene glycol)‐poly(propylene glycol)‐poly(ethylene glycol) block copolymer were recovered using an ultrafiltration ceramic membrane in a custom high‐pressure cross‐flow separation unit. Viscosity‐corrected liquid CO₂ flux (298 K) through the membrane was investigated as a function of time and surfactant concentration to determine the cake layer mass transfer resistance. Rapid CO₂ flux decline was observed with increasing surfactant concentration, denoting cake layer buildup on the membrane surface. For instance, at 0.09 and 0.55 wt% surfactant, the ratio of cake resistance to membrane resistance was 0.4 and 3.8, respectively. Based on our previous work, the reverse‐micelles retain their aqueous core and are not altered during filtration. Ultimately, inorganic membrane separations can reduce energy consumption associated with compression/expansion cycles typically used in CO₂‐based processes.     

PDMS-PSF复合膜空分过程压力的影响

采用L-S相转化法制备了聚砜（PSF）非对称膜,在其表面涂覆硅橡胶（PDMS）制备PDMS-PSF复合膜,进行空分富氧实验。实验结果表明：在室温、操作压力为0．6MPa的测试条件下,富氧浓度最高可达40．4％,相应的渗透通量为0．43×10^-10（m^3／m^2·s·Pa）。同时系统考察了操作压力对复合膜的富氧分离性能的影响,对气体在PDMS—PSF复合膜中渗透行为的压力相关性进行了定性分析。     

Enhancing the CO2 Separation Performance of Matrimid 5218 Membranes for CO2/CH4 Binary Mixtures

The effect of CO₂‐philic additive polyethylene glycol (PEG) 200 in Matrimid 5218 on the separation performance of prepared membranes was evaluated in a binary gas mixture. Matrimid/PEG 200 flat‐sheet blended membranes with low PEG concentrations were prepared by the dense film‐casting method. Pure Matrimid and blended membranes were characterized by FTIR spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and permeation measurements. The addition of 4–5 % of PEG enhanced considerably the CO₂ permeability of the Matrimid matrix. The best formulation, Matrimid/PEG 200 (96/4), showed in comparison to pure Matrimid a more than threefold increase in CO₂ permeability and an increase in separation factor of about 40 %.     

咪唑鎓化聚醚砜CO2固定载体分离膜的初探

通过化学改性的方法以氯甲基辛基醚(CMOE)、1-甲基咪唑(MIm)和聚醚砜(PES)为材料制备了咪唑鎓化聚醚砜(Im PES),并以其为分离层,聚丙烯(PP)为支撑层制备了用于CO2分离的固定载体复合膜。考察了咪唑鎓化程度、聚合物浓度、操作温度和压力对Im PES/PP复合膜性能的影响。结果表明,咪唑鎓化程度(DIm)对复合膜的性能影响最大,随着咪唑鎓化程度的提高,特别是当DIm大于50%后,复合膜对CO2的分离性能有很大提高。当取代度DIm为64%、聚合物质量分数为20%、测试温度为30℃、压力为0.4MPa时,Im PES/PP复合膜的纯CO2渗透速率为23.92GPU,CO2/N2理想分离因子为65.34。     

PEBA/PSf Multilayer Composite Membranes for CO2 Separation: Influence of Dip Coating Parameters

Polyether block amide (PEBA) polymeric layers were prepared on polysulfone (PSf) supports via dip coating. The effects of the coating speed and the solution concentration on the membrane performance were studied. The membranes were characterized by scanning electron microscopy, Fourier transform infrared spectra, and gas permeation. The coating speed was adjusted in the range of 0.32–0.48 cm s⁻¹ at a solution concentration of 3 wt % to obtain suitable membranes so that the CO₂ permeance and the CO₂/N₂ selectivity increased by more than three and ten times, respectively, compared to other speed ranges. Statistical analysis also showed that the effect of the interaction between solution concentration and coating speed is more considerable than the separate effects of both factors.     

陶瓷支撑的有机复合膜及其在渗透汽化中的应用(英文)

Pervaporation(PV),as an environmental friendly and energy-saving separation technology,has been received increasing attention in recent years.This article reviews the preparation and application of macroporous ceramic-supported polymer composite pervaporation membranes.The separation materials of polymer/ceramic composite membranes presented here include hydrophobic polydimethylsiloxane(PDMS) and hydrophilic poly(vinyl alcohol)(PVA),chitosan(CS) and polyelectrolytes.The effects of ceramic support treatment,polymer solution properties,interfacial adhesion and incorporating or blending modification on the membrane structure and PV performance are discussed.Two in-situ characterization methods developed for polymer/ceramic composite membranes are also covered in the discussion.The applications of these composite membranes in pervaporation process are summarized as well,which contain the bio-fuels recovery,gasoline desulfuration and PV coupled proc-ess using PDMS/ceramic composite membrane,and dehydration of alcohols and esters using ceramic-supported PVA or PVA-CS composite membrane.Finally,a brief conclusion remark on polymer/ceramic composite mem-branes is given and possible future research is outlined.     

Separation of Zinc and Bismuth by Facilitated Transport through Activated Composite Membranes

Abstract

This paper reports the results on the further development of activated composite membranes (ACM) containing di‐2‐ethyhexyl‐dithiophosphoric acid (D2EHDTPA) as a carrier. The selectivity and transport properties of D2EHDTPA‐based ACMs towards different metal ions including bismuth and zinc appear to be interconnected with each other. It has been shown that unlike the liquid‐liquid extraction of bismuth, the use of D2EHDTPA‐ACM permits to recover and to concentrate bismuth from a highly saline medium without irreversible destruction of the carrier. The difference in the rates of bismuth and zinc transport through ACMs permits their separation since the former is concentrated in the stripping solution and the latter retains in the feed compartment of the membrane cell.     

离子液体支撑液膜分离CO2的研究进展

总结了离子液体支撑液膜分离CO2的研究进展,简要分析了气体在离子液体支撑液膜中的传质机理;介绍了离子液体支撑液膜的制备方法及影响离子液体支撑液膜稳定性的因素;指出了今后用于分离CO2的离子液体支撑液膜的发展方向。     

Sol-Gel法制备Al2O3-SiO2-TiO2-ZrO2复合陶瓷膜的研究

将Sol-Gel法应用于无机膜的制备,成功的研制出一种新型的膜面平整、膜厚均匀且无宏观缺陷的Al2O3-SiO2-TiO2-ZrO2复合陶瓷膜,复合膜含有γ-Al2O3、SiO2、TiO2、ZrO2和Al2SiO5等晶相,改变体系组成含量,晶相组成和含量随之变化,从而引起膜的显微结构的变化。利用XRD、SEM、AFM、EPMA等测试手段重点研究了膜的表面形貌和显微结构,并分析了添加剂、热处理方式等对膜的表面形貌和显微结构影响。     

PVAm–PIP/PS Composite Membrane with High Performance for CO2/N2 Separation

Polyvinylamine (PVAm) was modified using a cross‐linking agent containing carriers piperazine (PIP). Attenuated total reflectance fourier transform infrared, elemental analyzer, and X‐ray diffraction were used to characterize the PIP‐modified PVAm. The PVAm–PIP/polysulfone (PS) composite membrane was developed by coating PVAm–PIP mixed solutions with different mass ratios of PIP/PVAm (m_PIP/m_PVAm) on the PS ultrafiltration membrane. The effects of m_PIP/m_PVAm (from 0.715 to 2.860) in the coating solutions and wet coating thickness on the gas performance of the PVAm–PIP/PS composite membrane were investigated. The PVAm–PIP/PS composite membrane prepared showed higher performance than other membranes reported in the literature due to the large increase of the introducing carrier concentration and low crystallinity. Moreover, the separation performance stability of the PVAm–PIP/PS composite membrane was investigated and no deterioration in the membrane permselectivity was observed. Finally, the economic evaluation of the membrane with the highest performance prepared was carried out. © 2012 American Institute of Chemical Engineers AIChE J, 59: 215–228, 2013     

Fouling-resistant Composite Membranes for Separation of Oil-in-water Microemulsions

Fouling-resistant ceramic-supported polymer composite membranes were developed for removal of oil-in-water （O/W） mieroemulsions. The composite membranes were featured with an asymmetric three-layer structure, i.e., a porous ceramic membrane substrate, a polyvinylidene fluoride （PVDF） ultrafiltration sub-layer, and a polyamide/polyvinyl alcohol （PVA） composite thin top-layer. The PVDF polymer was east onto the tubular porous ceramic membranes with an immersion precipitation method, and the polyamide/PVA composite thin top-layer was fabricated with an inteffaeial polymerization method. The effects of the sub-layer composition and the recipe in the inteffaeial polymerization for fabricating the top-layer on the structure and performance of composite membranes were systematically investigated. The prepared composite membranes showed a good performance for treating the O/W microemulsions with a mean diameter of about 2.41μm. At the operating pressure of 0.4MPa, the hydraulic permeability remained steadily about 190L·m^-2·h^-1, the oil concentration in the permeate was less than 1.6mg·L^-1, and the oil rejection coefficient was always higher than 98.5% throughout the operation from the beginning.     

Novel Composite Membranes for Gas Separation: Preparation and Performance

High performance composite membranes based on molecular sieving silica (MSS) were synthesized using sols containing silicon co-polymers (methyltriethoxysilane and tetraethylorthosilicate). Alpha alumina supports were treated with hydrochloric acid prior to sol deposition. Permselectivity of CO2 over CH4 as high as 16.68 was achieved whilst permeability of CO2 up to 36.7 GPU (10–6 cm3 (STP) cm–2 · s–1 · cm Hg–1) was measured. The best membrane's permeability was finger printed during various stages of the synthesis process showing an increase in CO2/CH4 permselectivity by over 25 times from initial support condition (no membrane film) to the completion of pore structure tailoring. Transport measurement results indicate that the membrane pretreated with HCl has highest permselectivity and permeation rate. In particular, there is a definite cut-off pore size between 3.3 and 3.4 angstroms which is just below the kinetic diameters of Ar and CH4. This demonstrates that the mechanism for the separation in the prepared composite membrane is molecular sieving (activated diffusion), rather than Knudsen diffusion.     

TiC-TiB2复合陶瓷制备及性能研究

TiC-TiB2复合陶瓷因具有高硬度、高断裂韧性及优异的耐磨性,目前已成为工程陶瓷的研究热点。但是TiC-TiB2复合陶瓷的难以制备与难于致密,又使其应用受到极大限制。本文介绍了国内外TiC-TiB2复合陶瓷合成与制备方法、显微组织与力学性能等,特别提到了军械工程学院先进材料研究所采用超重力下燃烧合成技术,制备出大尺寸、高致密性的TiC-TiB2共晶复合陶瓷,从而为以后的更广泛应用提供了支持。