蒸汽渗透技术在燃料乙醇生产中的应用研究进展

蒸汽渗透作为一种新型膜分离技术,可有效解决生物燃料乙醇生产中发酵产物浓度低、能源消耗量大、污染环境等诸多瓶颈问题。与渗透蒸发相比,蒸汽渗透技术具有分离性能好、进料清洁、能量损耗低、操作弹性大等优点,在燃料乙醇生产领域具备更广阔的应用前景。本文在比较渗透蒸发和气体分离技术的基础上,简述了蒸汽渗透过程的机理和特点。介绍了优先透水膜和优先透醇膜两类应用于燃料乙醇生产不同阶段的蒸汽渗透膜和这两类膜材料当前的研究进展,重点阐述了有机/无机杂化膜在成膜方法、杂化材料选择等方面的最新成果。回顾了蒸汽渗透在乙醇脱水方面的工业应用成果,指出该技术在发酵原位分离乙醇和替代精馏工艺方面所具有的优势,探讨了与固态发酵技术相结合进行一次相变生产燃料乙醇工艺实现的可能性,并提出未来亟待研究和解决的问题,为蒸汽渗透技术在燃料乙醇生产领域大规模发展提供参考。     

生物乙醇原位分离技术的研究进展

生物乙醇是一种重要的可再生生物燃料,使用生物乙醇可大幅减少温室气体排放。为了建立更高效低能耗的生物乙醇回收工艺,原位分离（ISPR）技术应运而生。本文综述了近年来乙醇原位分离的研究进展,从原理及应用等进行多方面详细地介绍,包括气提、真空发酵、吸附、液-液萃取、渗透汽化、膜蒸馏等分离技术。针对分离性能、能耗成本等问题分析了不同分离技术耦合发酵过程的优势及不足,重点回顾了以渗透汽化为代表的膜分离技术,总结了渗透汽化膜材料的选择以及膜的制备方法,旨在提升乙醇分离膜性能优化乙醇分离工艺。为整合不同分离技术的特点及优势,聚焦多级耦合分离系统的开发对各级分离技术联用的性能及潜力进行剖析与评价,并在此基础上研判其发展前景。     

渗透气化膜分离技术在乙醇-水体系中的应用

渗透气化是一种新型的膜分离技术,因其具有独特的优势已被广泛应用于乙醇-水的分离.从渗透气化的原理和特点出发,介绍了渗透气化膜材料以及渗透气化与精馏、化学反应耦合等技术,并概述了国内外渗透气化膜分离技术在乙醇-水分离中的应用现状.     

渗透蒸发与化学反应耦合过程的研究进展

渗透蒸发膜分离过程往往不是单独应用 ,而是与其它的分离或反应过程进行耦合的。着重介绍了渗透蒸发膜分离过程与精馏和反应耦合过程的研究现状 ,以及讨论了渗透蒸发膜分离过程与化学反应耦合过程的数学模型和常用的渗透蒸发膜材料。     

分子筛膜渗透蒸发技术研究进展

概述了渗透蒸发膜分离过程和分子筛膜的优点,重点综述了沸石分子筛膜在渗透蒸发中的传输机理和传质模型,以及温度、压力、组成等对渗透蒸发膜分离性能的影响因素,介绍了分子筛膜渗透蒸发技术在有机溶剂脱水、水中脱除有机物和有机混合物分离等方面的应用,展望了分子筛膜在渗透蒸发膜分离技术中的发展方向。     

浓乳液聚合制备优先脱醇渗透蒸发分离膜

提出了一种以浓乳液聚合直接浇注制备新型有机硅类渗透蒸发分离膜的新方法。考察了乙醇浓度、分离时间与渗透蒸发分离性能之间的关系,表征了有机硅浓乳液聚合过程中的乳胶粒子形态与成膜后粒子堆砌的微观结构。结果表明,利用膜中乳胶粒子间微通道的极性效应可以有效地分离醇/水混合物中的醇,且优先脱醇效果明显,分离性能良好。在乙醇/水混合物的渗透蒸发膜分离实验中,其渗透通量为4.7～165g·m-2·h-1,分离因子为1.0～11.3,分离选择性最好时的料液中乙醇的质量分数为33.41%。     

渗透汽化在生物燃料乙醇制备中的研究进展

渗透汽化作为一种新型的膜分离技术应用于发酵法制备生物燃料乙醇,不但能减少产物对微生物的抑制作用,而且可以脱水制备高纯度燃料乙醇,因而具有显著的优势。本文对渗透汽化在发酵法制备燃料乙醇中所涉及的膜材料、耦合工艺、应用现状和经济评价进行了详细的综述,并对发展趋势作了展望。     

渗透蒸发的原理及其应用

渗透蒸发过程是近几年来在国内外膜分离技术中研究比较活跃的课题。由于该过程具有选择性好、传质速率大、热效率高和易于操作等优点,因而具有广泛的应用前景。尤其在有机共沸物分离、水中有机物的脱除等方面,有其独到之处。特别是七十年代以后,能源危机的出现,而且以石油、天然气为燃料的能源又容易污染环境,因此,以美国为首的西方工业化国家,正在寻找生物能源——醇类物质(甲醇、乙醇等)作为下一个世纪的新能源,因而用渗透蒸发方法使醇类脱水,成为人们普     

改性壳聚糖渗透蒸发膜用于酯化反应过程强化

壳聚糖(chitosan, CS)作为渗透蒸发膜材料来源广泛、亲水性好,但结构致密、渗透性较低。为改善CS膜的分离性能,将CS与聚醚-聚酰胺嵌段共聚物Pebax 1657共混,涂覆在NaOH水解处理的聚丙烯腈(polyacrylonitrile,PAN)超滤膜表面制备复合膜,用于渗透蒸发醇水分离过程,并进一步用渗透蒸发方法对乳酸-乙醇酯化反应进行强化。Pebax的聚酰胺与聚醚链段分别发挥调节膜结构与促进水跨膜传递的作用,有效地提高了膜分离性能。CS与Pebax质量比为2:1时,渗透蒸发醇水分离性能及对酯化反应强化的性能达到最优:渗透通量703 g·m^-2·h^-1、分离因子308,较未改性CS膜分别提高61%、65%;反应8 h后的乳酸乙酯产率由58%提高至73%。     

用膜渗透蒸发过程分离乙醇-水混合物的研究

本文报导了用膜渗透蒸发过程进行乙醇-水混合物分离的实验结果。对用CA,CTA,PSf等透水膜分离稀醇水溶液,用PDMS,PVA等透醇膜分离醇-水恒沸物的可行性和经济性进行了初步分析。用基本溶解扩散模型和修正的溶解扩散模型对分离过程的机理作了初步的探讨。     

A Review of Membrane Materials for Ethanol Recovery by Pervaporation

Due to an emerging scarcity of oil resources and an associated increase of oil prices, biofuels (e.g., ethanol) play an important role in the energy crisis. Fermentation is a common process for producing ethanol from renewable biomass. Pervaporation is an attractive technique for the recovery of ethanol from the fermentation systems. Separation membrane is the key element in the pervaporation separation equipments. In this article, the pervaporation performances of ethanol-permselective membranes presented in the recovery of ethanol from dilute ethanol aqueous solution are reviewed. An analytical overview on the challenges and opportunities, and the prospect of ethanol-permselective membranes by pervaporation is also discussed.     

Wettability switchable metal-organic framework membranes for pervaporation of water/ethanol mixtures

To evaluate the effect of MOF surface wettability for the purification of ethanol from water/ethanol mixtures, the hydrophilic Ni₂(l-asp)₂bipy membrane is switched to hydrophobic Ni₂(l-asp)₂bipy@PDMS membrane via vapor deposition of PDMS. The PDMS coating can improve the hydrothermal stability of MOF membranes. The stable Ni₂(l-asp)₂bipy membrane exhibits a high flux of H₂O and acceptable separation factor. The pervaporation studies based on the both two membranes provide insight into the effect of surface wettability on the bio-ethanol purification performance.     

Characterization of sodium alginate and poly(vinyl alcohol) blend membranes in pervaporation separation

By blending a rigid polymer, sodium alginate (SA), and a flexible polymer, poly(vinyl alcohol) (PVA), SA/PVA blend membranes were prepared for the pervaporation separation of ethanol–water mixtures. The rigid SA membrane showed a serious decline in flux and a increase in separation factor due to the relaxation of polymeric chains, whereas the flexible PVA membrane kept consistent membrane performance during pervaporation. Compared with the nascent SA membrane, all of the blend membranes prepared could have an enhanced membrane mobility by which the relaxation during pervaporation operation could be reduced. From the pervaporation separation of the ethanol–water mixtures along with the temperature range of 50–80°C, the effects of operating temperature and PVA content in membrane were investigated on membrane performance, as well as the extent of the relaxation. The morphology of the blend membrane was observed with PVA content by a scanning electron microscopy. The relaxational phenomena during pervaporation were also elucidated through an analysis on experimental data of membrane performance measured by repeating the operation in the given temperature range. SA/PVA blend membrane with 10 wt % of PVA content was crosslinked with glutaraldehyde to enhance membrane stability in water, and the result of pervaporation separation of an ethanol–water mixture through the membrane was discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:949–959, 1998     

Application and development of synthetic polymer membranes. II. Separation of aqueous ethanol solution through poly(tert-butyl methacrylate-co-styrene) membranes

Separation of aqueous ethanol solution was carried out by pervaporation using a membrane which consisted of common polymer membranes. A membrane obtained from poly(tert-butyl methacrylate-co-styrene) was effective for a selective separation of ethanol from aqueous ethanol solution by pervaporation technique. The pervaporation ethanol–water mixture through the present membranes was analyzed as a solution–diffusion process, on the assumption that the both diffusion coefficients of each component are an exponential function of ethanol concentration.     

Membrane materials in the pervaporation separation of aromatic/aliphatic hydrocarbon mixtures—A review

The separation of aromatic/aliphatic hydrocarbon mixtures is a significant process in chemical industry,but challenged in some cases.Compared with conventional separation technologies,pervaporation is quite promising in terms of its economical,energy-saving,and eco-ffiendly advantages.However,this technique has not been used in industry for separating aromatic/aliphatic mixtures yet.One of the main reasons is that the separation performance of existed pervaporation membranes is unsatisfactory.Membrane material is an important factor that affects the separation performance.This review provides an overview on the advances in studying membrane materials for the pervaporation separation of aromatic/aliphatic mixtures over the past decade.Explored pristine polymers and their hybrid materials (as hybrid membranes) are summarized to highlight their nature and separation performance.We anticipate that this review could provide some guidance in the development of new materials for the aromatic/aliphatic pervaporation separation.     

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     

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。     

Processing of ethanol fermentation broths by Candida krusei to separate bioethanol by pervaporation using silicone rubber‐coated silicalite membranes

BACKGROUND: Pervaporation employing ethanol‐permselective silicalite membranes as an alternative to distillation is a promising approach for refining low‐concentration bioethanol solutions. However, to make the separation process practicable, it is extremely important to avoid the problems caused by the adsorption of succinate on the membrane during the separation process. In this work, the pervaporation of an ethanol fermentation broth without succinate was investigated, as well as the influence of several fermentation broth nutrient components. RESULTS: Candida krusei IA‐1 produces an extremely low level of succinate. The decrease in permeate ethanol concentration through a silicone rubber‐coated silicalite membrane during the separation of low‐succinate C. krusei IA‐1 fermentation broth was significantly improved when compared with that obtained using Saccharomyces cerevisiae broth. By treating the fermentation broth with activated carbon, bioethanol was concentrated as efficiently as with binary mixtures of ethanol/water. The total flux was improved upto 56% of that obtained from the separation of binary mixtures, compared with 43% before the addition of activated carbon. Nutrients such as peptone, yeast extract and corn steep liquor had a negative effect on pervaporation, but this response was distinct from that caused by succinate. CONCLUSION: For consistent separation of bioethanol from C. krusei IA‐1 fermentation broth by pervaporation, it is useful to treat the low nutrient broth with activated carbon. To further improve pervaporation performance, it will be necessary to suppress the accumulation of glycerol. Copyright © 2009 Society of Chemical Industry