Divinyl benzene cross‐linked HTPB‐based polyurethaneurea membranes for separation of p‐/o‐xylene mixtures by pervaporation

Cross‐linked hydroxy terminated polybutadiene (HTPB)‐based polyurethaneurea (PU), HTPB‐divinyl benzene (DVB)‐PU, was synthesized by a three‐step polymerization process. It was first used as membrane material to separate p‐/o‐xylene mixtures by pervaporation (PV). The effects of the content of cross‐linker DVB, feed concentration, and operating temperature on the PV performance of HTPB‐DVB‐PU membranes were investigated. The membranes demonstrated p‐xylene permselectivity as well as high total flux. The introduction of DVB significantly enhanced the temperature resistance ability of the HTPB‐DVB‐PU membranes. With increasing DVB content, the separation factor increased while the total flux decreased a little. The highest separation factor reaches 2.01 and the total flux is 33 g/m²h with feed concentration of 10 wt % p‐xylene at 30°C. These PV performances with increasing DVB content were explained in terms of the view point of chemical compositions and physical structures of the HTPB‐DVB‐PU membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Modified polydimethylsiloxane/polystyrene blended IPN pervaporation membrane for ethanol/water separation

In this article a modified polydimethylsiloxane (PDMS) blended polystyrene (PS) interpenetrating polymer network (IPN) membranes supported by Teflon (polytetrafluoroethylene) ultrafiltration membrane were prepared for the separation of ethanol in water by pervaporation application. The relationship between the surface characteristics of the surface‐modified PDMS membranes and their permselectivity for aqueous ethanol solutions by pervaporation are discussed. The IPN supported membranes were prepared by sequential IPN technique. The IPN supported membrane were tested for the separation performance on 10 wt % ethanol in water and were characterized by evaluating their mechanical properties, swelling behavior, density, and degree of crosslinking. The results indicated that separation performance, mechanical properties, density, and the percentage of swelling of IPN membranes were influenced by degree of crosslink density. Depending on the feed temperature, the supported membranes had separation factors between 2.03 and 6.00 and permeation rates between 81.66 and 144.03 g m^?2 h^?1. For the azeotropic water–ethanol mixture (10 wt % ethanol), the supported membrane had at 30°C a separation factor of 6.00 and a permeation rate of 85 g m^?2 h^?1. Compared to the PDMS supported membranes, the PDMS/PS IPN supported blend membrane ones had a higher selectivity but a somewhat lower permeability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Pervaporation of 50 wt % ethanol–water mixtures with poly(1‐trimethylsilyl‐1‐propyne) membranes at high temperatures

Poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) membranes have been used to separate ethanol–water mixtures by pervaporation. This polyacetylene is known to present high affinity toward ethanol, showing high selectivity and ethanol permeation flux. The performance of this polymer in the separation of alcohol–water solutions has been evaluated over long periods (572 h) at a high temperature (75°C) to examine the deterioration of the transport properties in the separation of 50 wt % ethanol–water solutions. Although PTMSP membranes present good characteristics for the separation of gases and liquid mixtures, their organic selectivity decrease with the operating time because of the relaxation processes of the polymeric chains, which affect the free volume of the polymer, the deterioration being more evident for concentrated solutions. The effects of the operation temperature on the characteristic parameters of pervaporation have also been studied to establish how this variable affects the performance of PTMSP membranes. The selectivity increases slightly with the operation temperature, but the effect of the temperature on the separation factor decreases as membranes are degraded with the operation time. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2843–2848, 2007     

HTPB‐based polyurethaneurea membranes for recovery of aroma compounds from aqueous solution by pervaporation

Hydroxyterminated polybutadiene (HTPB)‐based polyurethaneurea (PU), HTPB‐PU, was synthesized by two‐step polymerization and was firstly used as membrane materials to recover aroma, ethyl acetate (EA), from aqueous solution by pervaporation (PV). The effects of the number–average molecular weight (M_n) of HTPB, EA in feed, operating temperature, and membrane thickness on the PV performance of HTPB‐PU membranes were investigated. The membranes demonstrated high EA permselectivity as well as high EA flux. The DSC result showed two transition temperatures in the HTPB‐PU membrane and contact angle measurements revealed the difference of hydrophobicity of the membrane at both sides, which were induced by glass plate and air, respectively, due to movement of the soft hydrophobic polybutadiene (PB) segments in HTPB‐PU chains. Furthermore, the PV performance of the HTPB‐PU membrane with the hydrophobic surface facing the feed was much better than that with the hydrophilic surface. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 552–559, 2007     

Stabilized production of highly concentrated bioethanol from fermentation broths by Zymomonas mobilis by pervaporation using silicone rubber‐coated silicalite membranes

Since pervaporation performance of ethanol‐permselective silicalite membrane, which is an aluminum‐free hydrophobic zeolite, in the separation of fermentation broths by yeast are negatively affected by succinic acid, the potential of pervaporation using silicone rubber‐coated silicalite membranes of ethanol fermentation broths, not containing succinic acid, by Zymomonas mobilis was investigated for the reliable production of concentrated bioethanol. In the separation of fermentation broths, the pervaporation performance was influenced by nutrients used for the preparation of fermentation broths. In the separation of a broth prepared with yeast extract, pervaporation performance was greatly compromised by accumulation of a substance(s) having an ultraviolet absorption maximum at approximately 260 nm not only in total flux, but also in permeate ethanol concentration compared to the separation of binary ethanol/water mixtures. When supplying a prepared broth with corn steep liquor without the accumulation of a substance(s) having an ultraviolet absorption maximum at approximately 260 nm, the permeate ethanol concentration did not decrease. Treating the prepared broth with activated carbon was effective in restraining the decrease in total flux. Pervaporation performance is also deteriorated by the adsorption of lactic acid contained in corn steep liquor onto the silicalite crystals. In the separation of ternary mixtures of ethanol/water/lactic acid, accomplished by adjusting the ternary mixtures to pH > 5, more than 90% of the permeation flux in the separation of binary ethanol/water mixtures was obtained, and the permeate ethanol concentration was comparable to that obtained in the separation of binary mixtures. For stably performing pervaporation, it is important to prepare ethanol fermentation broths by Zymomonas mobilis in which lactic acid concentration is as low as possible. Copyright © 2007 Society of Chemical Industry     

Hydrophilic/hydrophobic IPN membranes for the pervaporation of ethanol-water mixture

Summary Pervaporation of ethanol-water mixture was examined on IPN membranes composed of hydrophilic polyurethane(PU) and hydrophobia polystyrene(PS). The IPN membranes showed preferential pervaporation of water over ethanol and revealed high permeation rate. As the content of hydrophobic PS was increased, the permeation rate decreased while the separation factor increased, indicating that the PS domains suppressed the swelling of the PU phase and reduced the plasticizing effect. The average diffusion coefficient, computed from the permeation rate and solubility, was highly dependent on the viscosity and concentration of the permeant in the membrane.     

Preparation and characterization of Silicalite‐1/PDMS surface sieving pervaporation membrane for separation of ethanol/water mixture

To improve the pervaporation performance of Silicalite‐1/PDMS composite membrane by adding a small amount of Silicalite‐1 zeolite, novel Silicalite‐1/PDMS surface sieving membranes (SSMs) were prepared by attaching Silicalite‐1 particles on the PDMS membrane surface. The obtained membranes and traditional mixed‐matrix membranes (MMMs) were characterized by SEM, XRD, TGA, FT‐IR, and pervaporation separation of ethanol–water mixture. Effects of Silicalite‐1 particles content, feed temperatures, and feed compositions on the separation performance were discussed. From the cross‐section view SEM images of SSMs, a two‐layer structure was observed. The thickness of the Silicalite‐1 layer was about 300 nm to 2 μm. The TGA analysis indicates that the zeolite concentration in 3 wt % SSM is lower than 10 wt % MMMs. In the ethanol/water pervaporation experiment, the separation factor of Silicalite‐1/PDMS SSMs increased considerably compared with pure PDMS membrane. When the suspensions concentrations of Silicalite‐1 particles reached 3 wt %, the separation factor was about 217% increase over pure PDMS membrane and 52.9% increase over 10 wt % Silicalite‐1/PDMS MMMs. As the ethanol concentration in the feed increases, the separation factor of SSMs increases, whereas permeation flux decreases. At the same time, with increasing operating temperature, the permeation flux of SSMs increased. The stability of SSMs at high temperature is better than the traditional MMMs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42460.     

Ethanol/water mixture pervaporation performance of b‐oriented silicalite‐1 membranes made by gel‐free secondary growth

b‐oriented silicalite‐1 membranes on porous silica supports were synthesized using gel‐free secondary growth. The porous silica supports were made by pressing crushed quartz fibers followed by sintering and polishing, and further modified by slip‐coating three layers of Stöber silica particles (1000, 350, and 50 nm). The b‐oriented seed layers were prepared by rubbing silicalite‐1 particles (2 μm × 0.8 μm × 3 μm along a‐, b‐, and c‐axis, respectively) after depositing a polymeric layer on the support. After silicalite‐1 seed deposition, a final coating of spherical silica particles was applied. Well‐intergrown, μm‐thick, b‐oriented membranes were obtained, which, after calcination, exhibited ethanol permselectivity in ethanol/water mixture pervaporation. At 60°C and for ～5 wt % ethanol/water mixtures, the best membrane exhibited overall pervaporation separation factor of 85 (corresponding to membrane intrinsic selectivity of 7.7) and total flux of 2.1 kg/(m²·h). This performance is comparable to the best performing MFI membranes reported in the literature. © 2015 American Institute of Chemical Engineers AIChE J, 62: 556–563, 2016     

Preparation and pervaporation performances of fumed‐silica‐filled polydimethylsiloxane–polyamide (PA) composite membranes

Fumed‐silica‐filled polydimethylsiloxane (PDMS)–polyamide (PA) composite membranes were prepared by the introduction of hydrophobic fumed silica into a PDMS skin layer. The cross‐sectional morphology of these filled composite membranes was observed with scanning electron microscopy. Their pervaporation performances were tested with aqueous ethanol solutions at 30, 35, and 40°C. Increasing the amount of the fumed silica resulted in significantly enhanced ethanol permeability of the membranes. When the content of the fumed silica in the PDMS skin layer was 20 wt %, the ethanol permeability increased to nearly twice that of the unfilled PDMS–PA composite membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effect of operation conditions in the pervaporation of ethanol–water mixtures with poly(1‐trimethylsilyl‐1‐propyne) membranes

Poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) is known to show preferential permeation of ethanol in the pervaporation of ethanol–water mixture. Although this polymer presents good characteristics for the separation of organic–water solutions, operation conditions and membrane characteristics, such as thickness, affect its pervaporation performance. The effect of temperature and feed concentration on pervaporation was studied. During pervaporation of 10 wt % ethanol–water solution, the separation factor (α_H2O^EtOH) remains almost constant, whereas the permeation flux (F) increases exponentially with operation temperature. On the other hand, the separation factor decreases, whereas the permeation flux increases with ethanol content in the feed mixture. The membrane thickness also affects the performance of PTMSP polymer films: selectivity increases sharply with membrane thickness up to 50 μm, whereas it remains constant for thicker membranes. The permeation flux decreases with membrane thickness in the whole range studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94:1395–1403, 2004     

Stabilization of bioethanol recovery with silicone rubber‐coated ethanol‐permselective silicalite membranes by controlling the pH of acidic feed solution

In order to produce highly concentrated bioethanol by pervaporation using an ethanol‐permselective silicalite membrane, techniques to suppress adsorption of succinic acid, which is a chief by‐product of ethanol fermentation and causes the deterioration in pervaporation performance, onto the silicalite crystals was investigated. The amount adsorbed increased as the pH of the aqueous succinic acid solution decreased. The pervaporation performance also decreased with decreasing pH when the ternary mixtures of ethanol/water/succinic acid were separated. Using silicalite membranes individually coated with two types of silicone rubber, pervaporation performance was significantly improved in the pH range of 5 to 7, when compared with that of non‐coated silicalite membranes in ternary mixtures of ethanol/water/succinic acid. Moreover, when using a silicalite membrane double‐coated with the two types of silicone rubber, pervaporation performance was stabilized at lower pH values. In the separation of bioethanol by pervaporation using the double‐coated silicalite membrane, removal of accumulated substances having an ultraviolet absorption maximum at approximately 260 nm from the fermentation broth proved to be vital for efficient pervaporation. Copyright © 2005 Society of Chemical Industry     

Preparation and pervaporation performance of 3,3‐bis[4‐(4‐aminophenoxy)phenyl] phthalide based polyimide membranes

A series of novel solvent‐soluble polyimides based on the diamine of 3,3‐bis[4‐(4‐aminophenoxy)phenyl] phthalide (BAPP) were prepared. The effects of the dianhydride structures on the pervaporation performance of aqueous alcohol mixtures through these polyimide membranes were studied. The BAPP‐based polyimide membranes exhibited water permselectivity during all process runs. The permeation rate increased with the addition of bulky groups to the polyimide backbone. The effects of the feed solution concentration, feed solution temperature, and carbon atom number of the feed alcohol on the pervaporation performance were also investigated systematically. Optimum pervaporation results, a separation factor of 22 and a permeation rate of 270 g/m² h, were obtained for a 90 wt % feed aqueous ethanol solution through a 3,3′,4,4′‐biphenyl tetracarboxylic dianhydride polyimide membrane at 25°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2046–2052, 2005     

Sodium alginate–poly(hydroxyethylmethacrylate) interpenetrating polymeric network membranes for the pervaporation dehydration of ethanol and tetrahydrofuran

Interpenetrating polymeric network (IPN) membranes of sodium alginate (NaAlg) and various amounts of poly(hydroxyethylmethacrylate) (PHEMA) have been prepared and tested for the pervaporation dehydration of ethanol and tetrahydrofuran (THF). The presence of hydrophilic PHEMA in the IPN matrix was found to be responsible for increase in membrane selectivity to water. NaAlg–PHEMA IPN membrane containing 20 wt % of PHEMA exhibited a selectivity of 571 to water for the water–ethanol mixture and 857 for water–THF mixture. These data are much better than those observed for the pristine NaAlg membrane. However, flux of the IPN membranes was smaller than that of pristine NaAlg membrane. Comparatively higher flux values were observed for water–THF mixture than for water–ethanol mixture. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3324–3329, 2006     

Pervaporation characteristics and structure of poly(vinyl alcohol)/poly(ethylene glycol)/tetraethoxysilane hybrid membranes

Poly(vinyl alcohol) (PVA) blended with poly(ethylene glycol) (PEG) was crosslinked with tetraethoxysilane (TEOS) to prepare organic–inorganic PVA/PEG/TEOS hybrid membranes. The membranes were then used for the dehydration of ethanol by pervaporation (PV). The physicochemical structure of the hybrid membranes was studied with Fourier transform infrared spectra (FT‐IR), wide‐angle X‐ray diffraction WXRD, and scanning electron microscopy (SEM). PVA and PEG were crosslinked with TEOS, and the crosslinking density increased with increases in the TEOS content, annealing temperature, and time. The water permselectivity of the hybrid membranes increased with increasing annealing temperature or time; however, the permeation fluxes decreased at the same time. SEM pictures showed that phase separation took place in the hybrid membranes when the TEOS content was greater than 15 wt %. The water permselectivity increased with the addition of TEOS and reached the maximum at 10 wt % TEOS. The water permselectivity decreased, whereas the permeation flux increased, with an increase in the feed water content or feed temperature. The hybrid membrane that was annealed at 130°C for 12 h exhibited high permselectivity with a separation factor of 300 and a permeation flux of 0.046 kg m^?2 h^?1 in PV of 15 wt % water in ethanol. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Poly(acrylic acid)–poly(vinyl alcohol) semi- and interpenetrating polymer network pervaporation membranes

A series of poly(acrylic acid) (PAA)–poly(vinyl alcoho) (PVA) semiinterpenetrating (SIPN) and interpenetrating (IPN) polymer network membranes were prepared by crosslinking PVA alone or by crosslinking both PVA and PAA. Glutaraldeyde and ethylene glycol were used as crosslinking agents for the PVA and PAA networks, respectively. The presence of PAA increases the permeability of the membranes while the presence of PVA improves their mechanical and film-forming properties. The mechanical properties of the membranes were investigated via tensile testing. These hydrophilic membranes are permselective to water from ethanol–water mixture and to ethanol from ethanol–benzene mixtures. The IPN membranes were employed for the former mixtures and the SPIN membranes for the latter, because the IPN ones provided too low permeation rates. The permeation rates and seperation factors were determined as functions of the IPN or SIPN composition, feed composition, and temperature. For the azeotropic ethanol–water mixture (95 wt % ethanol), the separation factor and permeation rate at 50°C of the PAA-PVA IPN membrane, containing 50 wt % PAA, were 50 and 260 g/m²h, respectively. For the ethanol–benzene mixture, the PAA–PVA SIPN membranes had separation factors between 1.4 and 1200 and permeation rates between 6 and 550 g/m²h, respectively, depending on the feed composition and temperature. © 1996 John Wiley & Sons, Inc.     

Effects of the polymerization and pervaporation operating conditions on the dehydration performance of interfacially polymerized thin‐film composite membranes

The disadvantage of dense polyamide membranes when applied in the pervaporation separation process is their low permeation rates. To improve the pervaporation performance, polyamide thin‐film composite membranes were prepared via the interfacial polymerization reaction between ethylenediamine (EDA) and trimesoyl chloride (TMC) on the surface of modified polyacrylonitrile (mPAN) membranes. These composite membranes were applied in the pervaporation separation of alcohol aqueous solutions. On the basis of the best pervaporation performance, the desired polymerization conditions for preparing the polyamide thin‐film composite membranes (EDA–TMC/mPAN) were as follows: (1) the respective concentration and contact time of the EDA aqueous solution were 5 wt % and 30 min and (2) the respective concentration of and immersion time in the TMC organic solution were 1 wt % and 3 min. The polyamide thin‐film composite membranes (EDA–TMC/mPAN) exhibited membrane durability when applied in the pervaporation separation of a 90 wt % isopropyl alcohol aqueous solution at 70°C, which indicated that the polyamide thin film composite (TFC) membranes were suitable for the pervaporation separation process at a high operating temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

聚氨酯膜的制备及渗透汽化分离水中苯酚性能研究

研究通过两步反应法制备端羟基聚丁二烯基聚氨酯（HTPB-PU）渗透汽化膜,采用红外、热分析、扫描电镜等手段对其结构与性能进行了表征,研究了该膜从水中分离苯酚的渗透汽化性能。结果发现,该膜表现出良好的优先透过苯酚的分离性能。以0.5%苯酚水溶液作为料液,随着操作温度从60℃增加到80℃,渗透通量增加而分离因子下降,在60℃时,分离因子与渗透通量可分别达到23.80与2.85 kg.μm.m-2.h-1。     

Cellulose–poly(acrylamide–acrylic acid) interpenetrating polymer network membranes for the pervaporation of water–ethanol mixtures. II. Effect of ionic group contents and cellulose matrix modification

The separation properties in the dehydration of a water–ethanol mixture and the swelling behavior of interpenetrating polymer network (IPN) pervaporation membranes based on a cellulose or cellulose–hydroxyethyl cellulose (HEC) matrix and poly(acrylamide and/or acrylic acid) were investigated depending on the ionic acrylate groups content (γ) in synthetic polymer chains (0–100 mol %), the HEC content in the matrix (0–50 wt %), and the temperature (25–60°C). The separation factor (α), permeation rate (P), and separation index (αP) significantly improved with increasing γ values only for the separation of concentrated ethanol solutions (～86 wt %). For more dilute solutions of ethanol (～46 wt %), the P and αP values also increased but no considerable increase in α was observed. All types of membranes based on the cellulose matrix were characterized by a drastic decrease in the values of P at [EtOH] ≥90 wt % and, as a result, a decrease in the separation index (kg m^?2 h^?1) from ～2000 (for 86 wt % EtOH, 50°C) to ～240 (for 95 wt % EtOH, 50°C), which correlates with a decrease in the degree of membrane swelling. The modification of the cellulose matrix by introducing HEC into it makes it possible to increase considerably the membrane swelling in concentrated EtOH solutions and, hence, the αP value to ～760 (95 wt % EtOH, 50°C). All types of IPN membranes exhibit a marked increase in both α and P when the temperature increases from 25 to 60°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1452–1460, 2001     

Structure and pervaporation performance of novel quaternized poly(vinyl alcohol)/γ‐aminopropyltriethoxysilane hybrid membranes

Novel hybrid organic–inorganic membranes were prepared via sol–gel reactions of quaternized poly(vinyl alcohol) (q‐PVA) and γ‐aminopropyltriethoxysilane (APTEOS) for pervaporation dehydration of an 85 wt % ethanol solution. The physicochemical structure of the hybrid membranes was characterized by FTIR, XRD, SEM, TG, and TEM. Nanofractal objects originated from self‐assembly of ammonium groups on the q‐PVA chains and amino groups in APTEOS can be observed on the surface of the hybrid membranes. When APTEOS/PVA ratio is 5% (wt/wt), the hybrid membrane has specific nervate networks on its surface and exhibits the highest separation factor. The hybrid membranes have better pervaporation performance than pristine q‐PVA membrane, and their permeation flux was found to increase linearly with increasing APTEOS content. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly(vinyl alcohol)/ZIF‐8‐NH2 mixed matrix membranes for ethanol dehydration via pervaporation

Ethanediamine‐modified zeolitic imidazolate framework (ZIF)‐8 particles (ZIF‐8‐NH₂) is synthesized and incorporated in the poly(vinyl alcohol) (PVA) matrix to fabricate novel PVA/ZIF‐8‐NH₂ mixed matrix membranes (MMMs) for pervaporation dehydration of ethanol. The PVA/ZIF‐8‐NH₂ MMMs exhibit enhanced membrane homogeneity and separation performance because of the higher hydrophilicity and restricted agglomeration of the particles, as compared to corresponding MMMs loaded with unmodified particles. The effect of ZIF‐8‐NH₂ loading in the MMMs is studied and the MMM with a 7.5 wt % ZIF‐8‐NH₂ loading shows the best pervaporation performance for ethanol dehydration at 40°C. Various characterization techniques (Fourier transform infrared, scanning electron microscope, contact angle, sorption test, etc.) are used to investigate the MMMs loaded with ZIF‐8 and ZIF‐8‐NH₂ particles. The impact of operation conditions on pervaporation performance is also performed. The performance benchmarking shows that the MMMs have superior separation factors and comparable flux to most other PVA hybrid membranes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1728–1739, 2016