Selective separation of n‐butanol from aqueous solutions by pervaporation using silicone rubber‐coated silicalite membranes

BACKGROUND: To use butanol as a liquid fuel and feedstock, it is necessary to establish processes for refining low‐concentration butanol solutions. Pervaporation (PV) employing hydrophobic silicalite membranes for selective recovery of butanol is a promising approach. In this study, the adsorption behavior of components present in clostridia fermentation broths on membrane material (silicalite powder) was investigated. The potential of PV using silicone rubber‐coated silicalite membranes for the selective separation of butanol from model acetone–butanol–ethanol (ABE) solutions was investigated. RESULTS: The equilibrium adsorbed amounts of ABE per gram of silicalite from aqueous solutions of binary mixtures at 30 °C increased as follows: ethanol (95 mg) < acetone (100 mg) < n‐butanol (120 mg). The amount of butanol adsorbed is decreased by the adsorption of acetone and butyric acid. In the separation of ternary butanol/water/acetone mixtures, the enrichment factor for acetone decreased, compared with that in binary acetone/water mixtures. In the separation of a model acetone–butanol–ethanol (ABE) fermentation broth containing butyric acid by PV using a silicone rubber‐coated silicalite membrane, the permeate butanol concentration was comparable with that obtained in the separation of a model ABE broth without butyric acid. The total flux decreased with decreasing feed solution pH. CONCLUSION: A silicone rubber‐coated silicalite membrane exhibited highly selective PV performance in the separation of a model ABE solution. It is very important to demonstrate the effectiveness of PV in the separation of actual clostridia fermentation broths, and to identify the factors affecting PV performance. Copyright © 2011 Society of Chemical Industry     

聚偏氟乙烯/聚二甲基硅氧烷渗透气化膜在丁醇分离中的应用

通过相转化法制备PVDF多孔支撑膜,在其上涂覆致密的PDMS分离层制备得到PVDF/PDMS复合膜,用于丁醇的分离纯化。以丁醇水溶液为原料液,流速为1.6 L·min^-1,丁醇浓度为15 g·L^-1,温度为37℃时, PVDF/PDMS复合膜的总通量为158.2 g·m^-2·h^-1,分离因子为17.3。向丁醇水溶液中按丁醇：丙酮：乙醇比例为6：3：1添加丙酮和乙醇模拟发酵液,PVDF/PDMS复合膜的总通量升高到189.5 g·m^-2·h^-1,分离因子降低到14.8。进一步考察了以丙酮-丁醇-乙醇（ABE）发酵液为原料液的渗透气化膜分离性能,发酵液中不存在菌体时,PVDF/PDMS复合膜的总通量和分离因子分别为120.2 g·m^-2·h^-1和19.7,而菌体存在时,复合膜的总通量和分离因子分别为122.1 g·m^-2·h^-1和16.7。与PDMS均质膜相比,PVDF/PDMS复合膜在丁醇分离过程中的分离性能有了显著的提升, 具有潜在的应用价值。     

Characterization of poly(dimethylsiloxane)‐poly(methyl hydrogen siloxane) composite membranes for organic water pervaporation separation

Hydrophobic composite membranes with a crosslinked poly(dimethylsiloxane)‐poly(methyl hydrogen siloxane) selective layer were prepared by using a new laboratory made catalyst agent. The pervaporation separation of five organic solvent–water mixtures was carried out with these composite membranes, together with swelling experiments in the same feed mixtures. The volatile organic compounds employed were ethanol, methanol, 1‐butanol, acetone, and ethyl acetate. The pervaporation and swelling experiments revealed that both the 1‐butanol and the ethyl acetate solutions showed the highest affinity for the composite membrane. When these components were employed as feed solutions, the membranes showed both high selectivity and high permeation. Mechanical–dynamical experiments of swollen and nonswollen composite membranes were also performed. The relaxation spectra were analyzed in terms of the interaction of the components of the different mixtures with the composite membrane, and the free volume corresponding to the each sample was obtained. Once the membranes had reached an equilibrium swelling, a decrease in the free volume was observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 546–556, 2001     

ZIF-L/PDMS混合基质膜蒸气渗透耦合发酵强化乙醇生产效率的研究

蒸气渗透（VP）膜分离不存在膜污染风险,在生物乙醇生产中具有广阔的应用前景。将聚二甲基硅氧烷（PDMS）膜和以二维沸石咪唑骨架（ZIF-L）为填充基质制备的PDMS（ZIF-L/PDMS）混合基质膜,分别用于VP膜分离与菊粉水解液发酵制乙醇过程的耦合,分析了二者在耦合过程中的分离性能和发酵性能。探究了不同膜分离方式、不同类型膜及操作条件对膜分离性能的影响。实验结果表明,当料液浓度为5%（质量）、蒸气循环流量为1.5 L·min^-1时,ZIF-L/PDMS混合基质膜的VP性能高于渗透汽化（PV）,归一化总通量达到1148.78 g·m^-2·h^-1,分离因子高达19.14,显著提升了乙醇分离性能。ZIF-L/PDMS混合基质膜用于VP耦合发酵,实现了耦合过程的高渗透性和乙醇选择性,与文献报道相比,乙醇移除效果最优,乙醇产率和时空产率分别达到0.421 g·g^-1、3.07 g·L^-1·h^-1,两个指标明显高于单独发酵,极大地提高了乙醇生产效率。因此,ZIF-L/PDMS混合基质膜在原位分离发酵乙醇方面具有很大的应用潜力。     

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     

Pervaporative enrichment of 2,3‐butanediol from its mixture with 1‐butanol using a polydimethylsiloxane and ZSM‐5 mixed matrix membrane: Effects of ethanol as a by‐product

A ZSM‐5 filled polydimethylsiloxane membrane with 44.4 wt.% zeolite loading was used in the pervaporative removal of 1‐butanol from its mixtures with 1‐butanol. A small quantity of ethanol was added to the feed as a by‐product to test the response of the membrane. It was found that the permeation behaviour of other feed components was changed and membrane selectivity decreased. This change was attributed to the frequently‐observed inter‐component coupled transport in multi‐component feed systems. The impact of ethanol on recovery of 2,3‐butanediol was evaluated using a simulated continuous operation, which enriched 2,3‐butanediol to 99.5 wt.% from a feed containing 5 wt.% 2,3‐butanediol and less than 1.0 wt.% ethanol. It was observed that membrane selectivity improves as ethanol concentration decreases in the stream due to its preferential removal. The final recovery of 2,3‐butanediol was not significantly reduced as the concentration of ethanol was below 1.0 wt.%. © 2011 Canadian Society for Chemical Engineering     

丙酮、乙醇对丁醇渗透汽化性能的影响

考察了全硅沸石silicalite-1对丁醇-水、丙酮-水、乙醇-水、丙酮-丁醇-水、乙醇-丁醇-水5种体系中各溶剂的吸附作用。采用自制的silicalite-1/硅橡胶杂化渗透汽化透醇膜,研究了温度对丙酮、丁醇、乙醇分离性能的影响以及不同分离温度下丙酮、乙醇的浓度对丁醇、水渗透汽化性能的影响,结果表明丙酮和乙醇的存在会促进丁醇的透膜性。     

Selective recovery of acetone-butanol-ethanol from aqueous mixture by pervaporation using immobilized ionic liquid polydimethylsiloxane membrane

An effective in situ recovery of acetone, butanol and ethanol (ABE) from fermentation broth is requisite to overcome the low productivity of ABE production. Pervaporation has proven to be one of the best methods for recovering ABE from fermentation broth. We fabricated an immobilized ionic liquid-polydimethylsiloxane (PDMS) membrane in which a [Tf₂N]^? based ionic liquid covalently bound to the PDMS backbone polymer and used it to recover ABE from aqueous solution by pervaporation. Permeate flux of immobilized IL-PDMS membrane was 7.8 times higher than that of conventional supported IL-PDMS membrane (where ILs are physically absorbed on the supported membrane). Butanol enrichment factor of immobilized IL-PDMS membrane was three-times higher than that of PDMS membrane. In addition, high enrichment factor both to acetone and ethanol as well as high operational stability of immobilized IL-PDMS membrane can enhance the efficacy of ABE recovery by employing this membrane.     

Recovery of alcohols from water using polydimethylsiloxane–silica nanocomposite membranes: Characterization and pervaporation performance

Different polydimethylsiloxane (PDMS) nanocomposite membranes were synthesized by incorporating various contents of nanosized silica particles to improve the PDMS pervaporation (PV) performance. A uniform dispersion of silica nanoparticles in the PDMS membranes was obtained. The nanocomposite membranes were characterized morphologically by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results showed that surface roughness increases by incorporating silica, and this decreases absorption of penetrants on the membrane. Swelling studies showed that the presence of silica nanoparticles into the PDMS membranes decreases degree of swelling, which can be attributed to rigidification of the PDMS matrix. Additionally, the results revealed that helium permeability decreases through the nanocomposite membranes, due to the more polymer chains packing. Effects of silica on recovery of isopropanol (IPA) from water mixtures were also investigated. Based on the results, incorporating silica nanoparticles promotes significantly the PDMS membrane selectivity because the polymer chains are rigidified and also the polymer free volume decreases. However, permeation flux decreases as diffusion of the penetrants reduces in the presence of silica nanoparticles within the PDMS membranes. As PV performance depends on operating conditions, effects of feed composition, and temperature were also studied. Moreover, recoveries of IPA, ethanol, and methanol from water mixtures were compared using the PDMS‐silica nanocomposite membranes. The results demonstrated that polarity and solubility of alcohols affect permeation flux and selectivity resulting in the higher permeation flux and selectivity for IPA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

硅橡胶渗透汽化复合膜在丁醇发酵中的应用

丁醇发酵受产物丁醇的抑制,产率和产物浓度低,过程经济性差,为减轻丁醇的抑制,制备了聚二甲基硅氧烷/聚偏氟乙烯(PIMS/PVDF)复合膜用于丙酮-丁醇-乙醇-水体系有机成分的分离.以分离因子和渗透通量为评价指标,考察了料液温度、质量分数和pH值对复合膜渗透汽化分离性能的影响.结果表明:料液温度升高能提高膜的分离性能;料...     

The Effect of Process Parameters on the Pervaporation of Alcohols through Organophilic Membranes

Abstract

Several organophilic membranes were utilized to selectively permeate ethanol, n-butanol, and t-butanol from dilute aqueous mixtures using pervaporation (PV). Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) membranes were utilized to investigate the effect of temperature, pressure, and start-up/transient time on the separation of aqueous ethanol mixtures. Results indicate optimal ethanol selectivity and flux at the lowest permeate-side pressure. Increased temperature significantly enhanced the productivity of PTMSP, but extended operation of the PTMSP membranes at high temperatures resulted in flux degradation. Two other hydrophobic membranes, poly(dimethyl siloxane) (PDMS) and a poly(methoxy siloxane) (PMS) composite, were used to separate n-butanol and t-butanol from dilute aqueous mixtures. The effect of feed concentration on the flux and selectivity was investigated. Both membranes were found to be more permeable to n-butanol than t-butanol. The PDMS membrane was found to be more effective than the PMS membrane in terms of flux and selectivity. The effect of membrane thickness on water permeation and on organic selectivity was also studied using the PDMS membrane.     

Polyvinylpyrrolidone–polydimethylsiloxane amphiphilic co‐networks: Synthesis,characterization, and perm‐selective behavior

An amphiphilic co‐network (APCN) membrane has been synthesized through end‐crosslinking of amphiphilic grafts of polyvinylpyrrolidone (PVP) backbone carrying polydimethylsiloxane (PDMS) branches fitted with terminal vinylsilyl groups via free radical polymerization. The synthesis strategy has been carried out by the free radical polymerization of N‐vinylpyrrolidone (VP) with methacrylate allyl terminated polydimethylsiloxane (MA‐PDMS‐V) and dimethacrylate terminated polydimethylsiloxane (MA‐PDMS‐MA) to form a soluble graft consisting of PVP main chains carrying vinyl terminated PDMS branches, which is crosslinked with polymethylhydrosiloxane through hydrosilylation. The resulting APCN membrane exhibited a combination of unique properties, that is, high transparency, high mechanical properties, and high permeation rate to inulin. Notably, the mechanical properties and inulin permeability of fabric‐support APCN membrane were higher than that of pure APCN membrane. As a result of their unique performance, the resulting APCN membranes showed a wide range of potential applications in drug release vectors, soft contact lenses, and biomedical separation materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42985.     

Preparation of polydimethylsiloxane/polystyrene interpenetrating polymer network membranes and permeation of aqueous ethanol solutions through the membranes by pervaporation

Polydimethylsiloxane (PDMS)/polystyrene (PSt) interpenetrating polymer network (IPN) membranes were prepared by the bulk copolymerization of styrene and divinylbenzene in the PDMS networks. The interpenetration of PDMS and PSt resulted in the improvement of mechanical properties of PDMS. Transmission electron microscope (TEM) observation demonstrated that the PDMS/PSt IPN membranes have microphase-separated structures consisting of a continuous PDMS phase and a discontinuous PSt phase. When an aqueous ethanol solution was permeated through the PDMS/PSt IPN membranes by pervaporation, the PDMS/PSt IPN membranes exhibited ethanol permselectivity, regardless of the PDMS content. The effects of their microphase-separated structures on the permeability and selectivity for aqueous ethanol solutions are discussed experimentally and theoretically. © 1996 John Wiley & Sons, Inc.     

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     

PDMS复合膜从发酵液中渗透汽化回收乙醇

The pervaporation behavior of fermentation broth was investigated experimentally and compared with those started with ethanol mixtures. Ethanol was produced by Saccharomyces cerevisiae utilizing technical grade glucose and recovered by pervaporation using a composite polydimethylsiloxane (PDMS) membrane prepared in our laboratory. Ethanol concentration in fermentation broth decreased to a relatively low level when pervaporation was coupled with fermentation. The more active cells appeared in the fermentation broth, the better the membrane performance was.     

乙醇/水及乙酸/水体系的渗透汽化分离

以乙醇/水及乙酸/水体系为研究对象,研究了渗透汽化过程中料液浓度、温度因素对分离效果的影响;结合乙醇、乙酸对聚二甲基硅氧烷(PDMS)膜的溶胀特性差别,分析并讨论了两者在渗透汽化过程中可能的分离机理. 研究表明,PDMS膜能够优先透醇,但乙酸分子的缔合物以及羧基与疏水PDMS膜高分子链的强相互作用降低了其在膜中的扩散速率,使低温时乙酸/水体系优先透水,只有当温度在60℃以上时才表现出优先透酸,且分离效果较差.     

PDMS/ceramic composite membrane for pervaporation separation of acetone–butanol–ethanol (ABE) aqueous solutions and its application in intensification of ABE fermentation process

Pervaporation (PV) has attracted increasing attention because of its potential application in bio-butanol recovery from fermentation process. In this work, PDMS/ceramic composite membrane was employed for PV separation of acetone–butanol–ethanol (ABE) aqueous solutions. The influence of coupling effect on the molecular transport during the PV process was systematically investigated. The separation performance and transport phenomena of ABE molecules were discussed based on the analysis and calculation of physicochemical properties such as solubility parameter, polarity parameter, interaction parameter, activity coefficient. The results suggested that the ABE separation factor was mainly determined by the intrinsic solubility parameter and driving force. Coupling effect in the ABE multicomponent system was closely related to the interaction parameters between components themselves and between component and membrane. Also, the PDMS membrane was integrated with ABE fermentation to construct an efficient intensification process. It was found that the rate matching of fermentation and in situ removal could improve the ABE productivity by 2 times.     

Pervaporative separation of butanol using a composite PDMS/PEI hollow fiber membrane

In the study, the separation and purification of butanol was carried out using the composite hollow fiber membrane having the active layer of polydimethylsiloxane (PDMS) on the macroporous support of polyetherimide (PEI). The pervaporation results with the initial butanol concentration showed a trade-off between flux and separation factor. However, both the flux and the separation factor increased as the operating temperature increased. The pervaporation results showed the butanol flux and the separation factor were higher than those of the reported results. In this study, butanol was concentrated by the pervaporation as a feasibility study for the biofuel applications.     

Chemical modification of poly(substituted-acetylene). IV. Pervaporation of organic liquid/water mixture through poly(1-phenyl-1-propyne)/polydimethylsiloxane graft copolymer membrane

Poly(1-phenyl-1-propyne)/polydimethysiloxane (PPP/PDMS) graft copolymer membranes having various PDMS content were prepared by solvent casting method, and the permeation characteristics at pervaporation were examined upon the aqueous solutions containing organic liquids such as alcohols, acetone, dioxane, acetonitrile, pyridine, and DMF. At pervaporation of ethanol/water mixture, preferential permeation of ethanol was observed for all the copolymer membranes, although PPP membrane showed water permselectivity. The permselectivity of the copolymer membrane also depended on operation temperature, but was independent on the thickness of the membrane. Furthermore, an excellent permselectivity of organic liquids was observed at the pervaporation of several organic liquid/water mixtures except in the case of DMF/water mixture. Observed high selectivity is thought to be due to the depression of the membrane swelling and the high solubility of the liquids into the membrane.     

PDMS/陶瓷复合膜用于正丁醇-水体系的渗透汽化分离

Pervaporation has attracted considerable interest owing to its potential application in recovering biobutanol from biomass acetone-butanol-ethanol (ABE) fermentation broth. In this study, butanol was recovered from its aqueous solution using a polydimethylsiloxane (PDMS)/ceramic composite pervaporation membrane. The effects of operating temperature, feed concentration, feed flow rate and operating time on the membrane pervaporation per-formance were investigated. It was found that with the increase of temperature or butanol concentration in the feed, the total flux through the membrane increased while the separation factor decreased slightly. As the feed flow rate increased, the total flux increased gradually while the separation factor changed little. At 40 &#61616;C and 1% (by mass) butanol in the feed, the total flux and separation factor of the membrane reached 457.4 g&#8226;m&#61485;2&#8226;h&#61485;1 and 26.1, respec-tively. The membrane with high flux is suitable for recovering butanol from ABE fermentation broth.