Gas permeability and permselectivity of plasma‐treated polypropylene membranes

The effects of NH₃‐plasma and N₂‐plasma treatment on rubbery polypropylene (PP) membrane upon permeation behavior for CO₂, O₂, and N₂ were investigated from their permeability measurements. The NH₃‐plasma and N₂‐plasma treatment on PP membranes could increase both the permeability coefficient for CO₂ and the ideal separation factor for CO₂ relative to N₂. For O₂ transport, both the permeability coefficient for O₂ and the ideal separation factor for O₂ relative to N₂ also increased. NH₃‐plasma and N₂‐plasma treatment on PP membranes possibly brings about an augmentation of permeability for CO₂ and permselectivity of CO₂ relative to N₂ simultaneously, but unfortunately the plasma‐treated PP membrane does not reach the level of CO₂ separation membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Structure/permeability and permselectivity relationship of polyetherimides from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride. I

Gas permeability coefficients of a series of aromatic polyetherimides, which were prepared from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride (HQDPA) and various aromatic diamines, to H₂, CO₂, O₂, N₂ and CH₄ have been measured under 7 atm pressure and over the temperature range 30–150°C. A significant change in permeability and permselectivity, which resulted from a systematic variation in chemical structure of the polyetherimides, was found. Generally, increases in permeability of the polyetherimides are accompanied by decreases in permselectivity. The order of decrease of the permeability coefficients is as follows: HQDPA–IPDA > HQDPA–DDS > HQDPA–MDA > HQDPA–ODA > HQDPA–DABP > HQDPA–BZD. However, HQDPA–DMoBZD and HQDPA–DMoMDA, with bulky methoxy side-groups on the aromatic rings of the diamine residue, display both high permeability coefficients and high permselectivity. The favourable gas separation property, excellent thermal and chemical stability, and high mechanical strength make HQDPA–DMoBZD and HQDPA–DMoMDA promising candidates for membrane-based gas separation applications.     

Gas permeability and permselectivity of photochemically crosslinked copolyimides

A series of copolyimides were prepared from 2,4,6-trimethyl-1,3-phenylenediamines (3MPDA), 3,3′,4,4′-benzophenone tetracarboxyl dianhydride (BTDA), and pyromellitic dianhydride (PMDA). Modification of the copolyimides by ultraviolet irradiation were carried out. Gas permeabilities of H₂, O₂, and N₂ through the copolyimides and photochemically crosslinked copolyimides were measured at temperatures from 30 to 90°C. The relationships between gas permeabilities and temperature are in agreement with the Arrhenius equation. The structure of photochemically crosslinked copolyimides were characterized by Fourier transform infrared and gel measurement methods. Linear relationships between both log P and E_p and the volume fraction of PMDA–3MPDA exist. Photochemically crosslinking modification result in a decrease in gas permeability and an increase in E_p and α(H₂/N₂) for all the copolyimides. For H₂/N₂ separation, photochemically crosslinked copolyimides are of higher gas permeabilities and permselectivities simultaneously than normal polyimides. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 521–526, 1999     

Synthesis and characterization of end‐capped polyimides and their gas permeability properties

Polyimides (PIs) based on 3,3′,4,4′‐oxydiphthalic anhydride (ODPA) and 4,4′‐oxydianiline (ODA) end capped with two new monoamines and other four different monoamines have been synthesized with a view to study the effect of different functional groups at the end of polymer chain on solubility, gas permeability, and thermal properties. The new monoamines have been synthesized from 3‐pentadecylphenol, obtained by hydrogenation of cardanol, a major constituent of cashew‐nut shell liquid. Introduction of different functional groups at the end of polyimide (PI) based on ODPA and ODA, by end capping with different monoamines, alters oxygen and nitrogen gas permeability, solubility, and thermal properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 627–635, 2000     

Gas transport property of homo- and copolyimides from isomeric thiaphthalic dianhydride and oxydianiline

Gas transport properties of homo- and copolyimides prepared from 3,3′,4,4′- and 2,2′,3,3′-thiaphthalic dianhydride (p-TDPA and m-TDPA, respectively) with 4,4-oxydianiline (ODA) were investigated. The fractional free volume of m-TDPA-ODA is larger than that of p-TDPA-ODA, and the chain segmental mobility of the former is lower than that of the latter. The permeability coefficients of m-TDPA-ODA to H₂, CO₂, and O₂ are more increased by 48, 69 and 75%, at 30°C and 10 atm, respectively, than those of p-TDPA-ODA; but the permselectivities of m-TDPA-ODA for H₂, CO₂, and O₂ toward N₂ are more decreased by 33, 77, and 26%, respectively, than those of p-TDPA-ODA. The permeability coefficients and the diffusion coefficients of the copolyimides can be described by the following equations: log P = Φ_p log P_p + Φ_m log P_m and log D_a = Φ_p log(D_a)p + Φ_m log(D_a)_m, respectively. The variation of the permselectivity is controlled predominantly by diffusivity selectivity. These observations are interpreted in terms of variations in the fractional free volume of polyimides. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1821–1826, 1997     

Gas Permeation Properties of Copolyimides from 1,4-Bis(3,4-dicarboxyphenoxy)benzene Dianhydride and 2,2-Bis(3,4- dicarboxyphenyl)hexafluoroisopropane Dianhydride

A series of aromatic copolyimides was prepared from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA) and 2,2-bis(3,4-dicarboxy-phenyl)hexafluoroisopropane dianhydride (6FDA) with 3,3′-dimethyl-4,4′-methyl-ene dianiline (DMMDA) by a chemical imidization. The gas permeability coefficients of the copolyimides to H₂, CO₂, O₂, N₂ and CH₄ were measured under 7atm. pressure. The fractional free volume of 6FDA–DMMDA is larger than that of HQDPA–DMMDA, while the chain segmental mobility of 6FDA–DMMDA is lower than that of HQDPA–DMMDA. The gas permeability of 6FDA–DMMDA is much higher than that of HQDPA–DMMDA but the perm-selectivity of 6FDA–DMMDA for H₂, CO₂, O₂, N₂ over CH₄ is lower than that of HQDPA–DMMDA. The experimental values of the gas permeability coefficients of the copolyimides are in satisfactory agreement with the values estimated from the gas permeability coefficients of the constituent homopolyimides and their weight fractions. © of SCI.     

The Effect of Hydrotalcite Content in Microporous Composite Membrane on Gas Permeability and Permselectivity

Microporous silica membrane containing hydrotalcite (HT) was prepared successfully without losing the former’s molecular sieving property. The microporous HT-silica membrane (200 nm in thickness) was formed on the surface of mesoporous γ-alumina layer (9 μm in thickness) and supported by macroporous α-alumina substrate (ca. 2 mm in thickness). The pore size of the microporous HT-silica membrane was 8.5Å, slightly larger than the pristine silica membrane (5Å). The composite membrane was found to enhance the permeability of gases and permselectivity of carbon dioxide from gas mixture comprising methane, hydrogen or nitrogen. Microporous HT-silica membrane with 15 vol.% HT displayed the highest permselectivities in the order of CO₂/CH₄ > CO₂/N₂ > CO₂/H₂ and the permselectivities decreased with increasing HT content.     

合成氨吹除气氢回收技术应用

比较几种氢气回收方法的优劣,确定选用膜分提氢技术回收合成氨系统合成塔吹除气中的氢气,作为合成氨原料气使用,达到了节能降耗的目的。     

膜法技术在甲醇弛放气回收氢气中的应用

针对新能凤凰(滕州)能源有限公司煤制甲醇生产中存在的弛放气放空问题,为回收弛放气中的氢气,引进了膜法氢气回收技术。介绍了膜法氢回收工艺及该技术的应用情况,对膜分离氢回收装置采取了增加尾气管线、改造氢压机负荷开关、更换氢压机后水冷器、富氢气同时进入两期合成系统等改进措施。改进后,优化了循环气组成,提高了甲醇产量,具有较好的经济效益。     

PTFE多孔膜气体渗透数学模型和膜孔结构的影响

Membrane-based separation processes are new technology combined membrane separation with conventional separation. Hydrophobic porous membranes are often used in these processes. The structure of hydrophobic porous membrane has significant effect on mass transfer process. The permeabilities of five kinds of gas, He, N2,O2, CO2 and water vapor, across six polytetrafluoroethylene(PTFE) fiat membranes were tested experimentally.Results indicated that the greater the membrane mean pore size and the wider the pore size distribution are, the higher the gas permeability. A gas permeation model, including the effects of membrane structure parameter and gas properties, was established. A comprehensive characteristic parameter (including porosity, thickness and tortuosity) was found more effective to express the influence of membrane structure in gas permeation process. The predicted permeation coefficients were in good agreement with experimental data.     

醋酸装置放空尾气回收技术开发与应用

通过对醋酸合成系统放空尾气气体成分的测定,在3000m^3／h和5000m^3／h工况下,模拟计算了采用膜分离纯化系统分离回收放空尾气各项工艺指标,并确定了关键设备的选型依据和工艺流程,据此建设了普里森膜分离纯化尾气装置。装置投用以采,运行稳定,年可实现毛收益2320万元,减排CO2 170×10^3m’,经济效益和社会效益显著。     

单外皮层PES中空纤维气体分离膜制备的研究

以聚醚砜(PES)作膜材料,N-甲基吡咯烷酮(NMP)为溶剂,乙醇(Ethanol)作非溶剂,NMP-Water为芯液,获得PES/NMP/Ethanol铸膜液[m(PES)∶m(NMP)∶m(Ethanol)=35∶57∶8],采用相转化法制备了PES中空纤维气体分离不对称膜,研究了保存时间、硅橡胶种类、芯液浓度、芯液流量和凝胶温度等对PES中空纤维膜O2/N2渗透性能的影响。同时,分析了单外皮层PES中空纤维气体分离膜的结构,讨论了PES中空纤维气体分离膜的机械性能。当芯液组成的m(NMP)∶m(H2O)=86∶14和凝胶温度17℃时,涂3%硅橡胶A后的PES中空纤维气体分离膜气体分离性能如下:αO2/N2=6.68,JO2=2.26GPU,JN2=0.33GPU。     

富含二氧化碳的天然气分离及其利用

论述了国内外对富含二氧化碳的天然气分离技术的研究进展,包括：膜分离法、变压吸附（PSA）法、物理吸收法和化学吸收法等,并分析了天然气资源的深加工利用及其产品开发前景。     

天然气净化膜及膜内气体传质机理研究

作者以碳氟高分子聚合物为膜材,通过辐射接枝技术,得到含氟羧酸膜（ＰＦＣＭ）,并分别用乙二胺（ＥＤＡ）、三乙醇胺（ＴＥＡ）、三乙烯二胺（ＴＥＤＡ）等三 活性载体,对ＰＦＣＭ进行改性,得到了酸性气体促进传质优先渗透酸性组份的特征。可用于 天然气净化。本文以ＣＨ４、ＣＯ２和Ｈ２Ｓ为对象,测定了上述几种膜内的吸收等温线数据和渗透动力学数据。分别考察了活性载体种类和改性度以及温度等参数对膜性能的影响。进而阐     

Effect of Feed Composition on the Gas Separation Performance of Binary and Ternary Mixed Matrix Membranes

Binary and ternary component mixed matrix membranes comprised of zeolite 4A and p-nitroaniline (pNA) in the polycarbonate (PC) matrix were prepared and appraised in gas separation. For comparison, homogenous membranes of PC and PC/pNA membranes were also investigated. The membranes were utilized to separate binary mixtures of CO₂/CH₄, H₂/CH₄, and CO₂/N₂. The effect of feed composition on the separation performance of membranes was investigated. Separation factors and ideal selectivities were similar for the PC membrane. A similar trend was also observed with the PC/pNA membrane. The separation factors of the PC/pNA membrane for CO₂/CH₄ were almost twice as high as those of the PC membrane regardless of the feed composition. The ideal selectivities were, however, higher than separation factors for PC/zeolite 4A and PC/pNA/zeolite 4A membranes. The PC/ pNA/zeolite 4A membrane has separation factors of 18 for 77% CO₂/ 23% CH₄ mixture, and 40 for 20% CO₂/ 80% CH₄ mixture, respectively. The separation factors of the mixed matrix membranes depended on the feed composition strongly. The PC/ pNA/zeolite 4A membrane had higher separation factors and lower permeabilities than the PC/zeolite 4A membrane. pNA assisted to eradicate partly the detrimental effects of interfacial voids and improved the molecular sieving effect of zeolite 4A dispersed in the PC.     

Effect of H+ and N+ Irradiation on Structure and Permeability of the Polyimide Matrimid®

Abstract

This paper presents a comparison of the impact of H⁺ and N⁺ ion irradiation on the chemical structure, microstructure, and gas permeation properites of the polyimide, Matrimid®. While irradiation with both ions resulted in evolution of chemical structure with loss of functional groups and crosslink formation, there was greater modification of polyimide structure following N⁺ irradiation at similar total deposited energy. Irradiation with N⁺ resulted in simultaneous large increases in permeance and permselectivity at comparatively low ion fluences or irradiation time. For example, irradiation at 4 × 10¹⁴ N⁺/cm² resulted in a 2.5 fold increase in He permeance with a selectivity of He/CH₄ of 340. Much higher H⁺ fluences were required to achieve similar total deposited energy and combined increases in permeance and permselectivity. The larger modification in chemical structure and gas permeation properties following N⁺ irradiation was attributed to the relatively large energy loss and damage from the nuclear energy relative to electronic energy loss.     

Polyether-segmented nylon hemodialysis membranes. II. Morphologies and permeability characteristics of polyether-segmented nylon 610 membrane prepared by the phase inversion method

The relationships between the morphologies and the permeability characteristics as dialysis membrane of polyether-segmented nylon 610 (PE-Ny610) have been investigated. PE-Ny610 used are poly(propylene oxide) (PPO)-segmented nylon 610 containing 25 wt % PPO (PPO-Ny610) and poly(ethylene oxide) (PEO)-segmented nylon 610 containing 15 wt % PEO (PEO-Ny610). The morphologies in the cross section of the membranes exhibit the cellular porous structures due to liquid-liquid phase separation. On the other hand, the structures of the surfaces are mainly composed of the crystalline spherulite due to liquid-solid phase separation. These morphologies are little affected by the composition ratio of the coagulant, calcium chloride/methanol/water mixture. PEO-Ny610 membranes have shown superior membrane performances to the PPO-Ny610 membrane. The effect of PEO content in PEO-Ny610 on the adhesion of platelet onto the PEO-Ny610 film surface was investigated and it is concluded that PEO-Ny610 having > 10 wt % PEO shows a good nonthrombogenicity equal to PPO-Ny610. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1713–1721, 1997     

Gas‐permeation performance of metal organic framework/polyimide mixed‐matrix membranes and additional explanation from the particle size angle

With MOFs of Cu₃(BTC)₂ and ZIF‐8 as the dispersed phases and four polyimides with CO₂ permeabilities ranging from 1.36 to 564 barrer as the continuous phase, the influence of metal organic frameworks on the gas‐separation properties of mixed‐matrix membranes (MMMs) was investigated. The results show that the gas permeabilities of all of the prepared MMMs greatly increased and even largely exceeded the predicted value of the Bruggeman model; for example, with the same Cu₃(BTC)₂ loading of 21.3 vol %, the O₂ permeability increase rate of our prepared Cu₃(BTC)₂/Matrimide 5218‐20 MMMs was 2.26 times, whereas that predicted by the Bruggeman model was only 1.05 times. In addition, when the gas permeability of the polymeric phase was far lower than the dispersed phase of ZIF‐8 or Cu₃(BTC)₂ compared with ZIF‐8, which had a particle size (R) around 150 nm, Cu₃(BTC)₂ of 5–15 µm showed a little better enhancing effect on the gas‐permeation performance of the MMMs. In addition to the properties of the dispersed and continuous phases, we speculated that the ratio between R of the dispersed phase to the membrane thickness (L) played an important role for MMMs; the larger R/L was, the greater the gas permeability of the MMMs was. This speculation was initially evidenced by the ZIF‐8/ODPA/TMPDA‐20 MMMs with different Ls. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45728.     

Effects of membrane thickness and heat treatment on the gas transport properties of membranes based on P84 polyimide

P84 polyimide membranes with thicknesses ranging from 6 to 310 μm were successfully fabricated by spin coating. The glass transition temperature of the P84 powder was found to be 315°C using differential scanning calorimetry, whereas its decomposition temperature was 536°C using thermogravimetric analysis. Scanning electron microscopy was used to examine the morphology of the membranes. The permeability of single gas (He, N₂, O₂, and CO₂) and the ideal selectivity of gas pair (O₂/N₂, He/CO₂, CO₂/N₂, and He/O₂), as a function of membrane thickness, were determined. The results showed that the permeability of a single gas increased with increasing membrane thickness, whereas the selectivity of a given gas pair was nearly independent of the membrane thickness. The average selectivity of O₂/N₂, He/CO₂, CO₂/N₂, and He/O₂ were found to be 8.2, 10.0, 12.9, and 15.8, respectively. The effects of heat treatment on the membrane morphology and gas transport properties were investigated for three annealing temperatures, i.e., 80°C, 200°C, and 315°C. The membrane annealed at 315°C was cracked due to the stress sustained either during heating or cooling, thereby resulting in little or no selectivity. The permeabilities of P84‐118 membrane (118 μm thickness) annealed at 80°C were 16.2, 0.196, 1.20, and 2.01 Barrer for He, N₂, O₂, and CO₂, respectively. The permeabilities of P84‐118 membrane annealed at 200°C decreased by 9.75%, 47.96%, 25.83%, and 30.85% for He, N₂, O₂, and CO₂, respectively, as compared with those at 80°C, whereas the ideal selectivities increased by 42.65%, 30.52%, 32.85%, and 21.63% for O₂/N₂, He/CO₂, CO₂/N₂, and He/O₂, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Gas chromatographic separation of the fatty acid methyl esters prepared from dairy products,partially hydrogenated oils,and refined vegetable oils applying a negative temperature gradient

To date no single gas chromatographic method can simultaneously measure all fatty acids (FA), including trans-FA (TFA), that are contained in dairy products, partially hydrogenated oils (PHO), and refined vegetable oils. Using 100% poly(biscyanopropyl siloxane) capillary columns, ruminant and dairy fats are preferentially analyzed by applying temperature programs that separate short chain FA, but not trans-18:3 from 20:1. Refined vegetable oils and PHO are preferentially analyzed by applying isothermal elutions that provide quantification of all 18 carbon TFA including trans-18:3 FA, but not of all short chain FA. In this short communication, we propose a temperature program method capable of simultaneously measuring short chain FA and all 18 carbon TFA including trans-18:3 by applying a negative temperature gradient after the elution of trans-18:1. A simplified version of the method is also described for equipment not able to perform negative temperature gradients.