聚乙烯醇辐照交联共聚物渗透气化分离膜

研究了聚乙烯醇(PVA)与丙烯酰胺丙烯酸钠共聚物(PcoAANa)的辐照交联共聚物膜用于水-乙醇混合物的渗透气化分离,随着PcoAANa在共聚物中的含量由0%上升到35%,透量及分离系数同时增大,膜材料对混合物中水及乙醇的选择性溶解,对渗透气化过程起重大影响。求出了水、乙醇及其混合物的表现透过活化能.水,乙醇和混合物的平均扩散系数在水含量为40%时出现极大值。     

渗透气化源及其分离过程

渗透气化过程(简称PV过程)是一种早为人知而近期才得以发展的膜分离过程,它是利用混合液中各组分被高分子膜选择吸附溶解,及在膜中扩散速度的不同,从而分离或富集有机液体混合物中的某一组分。1850年Graham等首先利用这一原理进行了液体混合物的分离,然而直到本世纪五十年代,PV过程才被Binning等人进行了较系统的研究。近十年来,     

丙烯酸交联壳聚糖渗透汽化膜研究（Ⅰ）——膜结构及交联机理

报道了一种新型渗透汽化膜－－丙烯酸交联壳聚糖膜，通过溶胀、拉伸、渗透汽化分离以及红外光谱等手段研究了膜的结构和交联机理。实验结果表明，交联反应由两部分组成：丙烯酸的双键和壳聚糖的氨基的加成反应和丙烯酸另一端的羧基和壳聚糖的氨基的酸碱中和反应。     

用聚电解质渗透汽化膜进行乙醇脱水

渗透汽化 (PV)膜过程由于可用于有机 /有机及有机 /水的恒沸或近沸混合物的分离而成为近年来膜技术研究开发的热点[1,2 ] .德国 GFT公司所制的富马酸交联 PVA脱水膜[3] 对温度为 80℃的 80 %Et OH料液 ,其分离因子为 350 ,渗透通量为 2 0 0 g/ (m2 ·h) .优秀的分离膜要求渗透通量大 ,同时具有较高的分离因子和良好的稳定性 .因此 ,提高膜的分离性能是渗透汽化技术开发应用的关键 .周继青等 [4 ]研究了 PVA/ PVP互穿网络膜的渗透汽化性能 ,发现膜的渗透通量虽有明显提高 ,但膜的选择性下降 .聚电解质具有优良的亲水性 ,可制得高水通…     

酯化交联聚乙烯醇膜用于渗透气化法分离EtoH／H2O的研究

合成了一系列磷酸和二元羧酸酯化交联改性的聚乙烯醇(PVA)膜,研究了它们用于水-乙醇混合液的渗透气化分离规律。磷酸改性的PVA膜具有较大的通量,当料液浓度为50%时,通量可达1200g/m~2·hr.,分离系数α_(H_2O/EtOH)=10。丙二酸改性PVA膜在料液浓度为50%时,通量可达800g/m~2·hr.,且α_(H_2O/EtOH)=18。并作了这两种膜的通量和分离系数随料液浓度的变化曲线。草酸交联的PVA膜具有较高的分离系数,但通量很小。求出了水、乙醇及总的表现渗透活化能。     

渗透气化法分离液体混合物

渗透气化法是一种用来分离液体混合物的膜分离方法。本综述简要地讨论了渗透气化法的机理。本法用于乙醇-水混合物的分离,对于从生物源生产乙醇具有重要意义。乙醇-水混合物的分离膜可以分成二类:亲水性膜和亲乙醇膜。使用若干物理方法可改进渗透气化过程。最后,作者认为渗透气化膜的发展趋势是从均质膜,不对称膜向复合膜过渡。     

为什么要引入溶剂的渗透因子

阐明了引入溶剂渗透因子的必要性,较详细地介绍了两种渗透因子及它们间的关系。     

渗透汽化过程中传递耦合现象的研究

多元分离体系在膜内传递过程中 ,其分离特性不仅受渗透组分与膜材料之间的相互作用的影响 ,同时也受控于膜内组分间的耦合效应的影响 .研究了渗透组分在膜界面上的溶胀分配关系 ,从理论上描述了溶胀过程中的耦合效应 .讨论了渗透组分在扩散传递过程中膜内各组分所形成的浓度场分布 ,以此研究了强相互作用下膜过程中的传递行为 .对乙醇 水体系在壳聚糖膜和硫酸交联壳聚糖膜的渗透汽化实验结果表明了耦合效应的存在以及对分离性能的影响     

用于渗透气化法分离水—乙醇混合物的含离子膜

合成了乙烯醇和顺丁烯二酸的交替共聚物,并制成膜,使其与BaCl_2,CaCl_2,SrCl_2及CuSO_4的水溶液反应。将反应产物—含离子聚合物膜用于渗透气化法分离乙醇-水混合物。结果表明,离子膜在渗透速率及分离系数两方面均好于纯聚合物膜。在以上四种离子膜中,含Ba~(2 )离子膜的性能最好,这表明Ba~(2 )离子不仅使膜更加亲水,增加了对水的溶解度,而且由于Ba~(2 )离子引起聚合物分子链间的交联,而使膜变得更加致密,从而提高了膜的分离系数。     

渗透汽化汽油脱硫膜材料

渗透汽化膜法汽油脱硫技术是一种新型汽油脱硫技术,具有投资和操作费用低、辛烷值损失小等显著优点,受到人们的广泛关注。本文简要介绍了渗透汽化膜法脱硫的研究背景,基于溶解-扩散模型,以溶解度参数原则为理论指导,分析了聚合物脱硫膜材料的选择,结合近二十年来文献报道的渗透汽化脱硫膜研究进展,详细介绍了用于膜法脱硫的聚合物膜材料(聚二甲基硅氧烷、聚醚嵌段酰胺、聚乙二醇、醋酸纤维素、聚酰亚胺、聚磷腈等)及有机/无机复合膜材料的结构特点、改性方法及膜材料结构与性能间的关系,并将不同膜材料的脱硫性能进行了对比研究,在此基础上总结了目前渗透汽化脱硫膜存在的问题,并对其未来的研究方向和发展前景进行了展望。     

磺化聚乙烯离子交换膜渗透汽化分离二氧六环／水混合物研究

本文用非均相光化学氯磷化反应制得了亲水的耐有机溶剂耐酸碱的磺化聚乙烯离子交换膜．膜截面离子基因密度与反应程度有关．该膜对近恒沸组成的二氧六环／水混合液显示出很高的渗透汽化分离系数和透过速率．研究了对离子、离子交换容量、料液浓度和温度对分离性能的影响．通过膜内水合离子形成“水通道”模型讨论了渗透机理．膜内离子基团密度估计及水的表观渗透活化能的大小支持“水通道”的存在．     

On the mutual diffusion properties of ethanol-water mixtures

The structural organization, the number of hydrogen bonds (H bond), and the self- and mutual diffusion coefficients of ethanol-water mixtures were studied by molecular dynamics simulation. It was found that both the numbers of H bonds per water and per ethanol decrease as the mole fraction of ethanol increases. The composition dependences and the relationships between the self- and the mutual diffusion coefficients were further discussed. The self-diffusion coefficient of water has a large drop as the concentration of ethanol increases from 0 to 0.3 and then it nearly keeps constant, while that of ethanol has a minimum around ethanol mole fraction of 0.5. The mutual diffusion coefficient could be divided into two parts, the kinematic factor and the thermodynamic factor. Both the kinematic and thermodynamic factors for ethanol-water mixtures were calculated. It was found that the change trend of mutual diffusion coefficients with the composition is mainly dependent on the thermodynamic factors.     

A Thermo-Chemical Reactor for analytical atomic spectrometry

A novel atomization/vaporization system for analytical atomic spectrometry is developed. It consists of two electrically and thermally separated parts that can be heated separately. Unlike conventional electrothermal atomizers in which atomization occurs immediately above the vaporization site and at the same instant of time, the proposed system allows analyte atomization via an intermediate stage of fractional condensation as a two stage process: Vaporization → Condensation → Atomization. The condensation step is selective since vaporized matrix constituents are mainly non-condensable gases and leave the system by diffusion while analyte species are trapped on the cold surface of a condenser. This kind of sample distillation keeps all the advantages of traditional electrothermal atomization and allows significant reduction of matrix interferences. Integration into one design a vaporizer, condenser and atomizer gives much more flexibility for in situ sample treatment and thus the system is called a Thermo-Chemical Reactor (TCR).     

ORGANIC PERMSELECTIVE PERVAPORATION CHARACTERISTICS OF POLY(SILYLPROPYNE) AND COPOLYMER DENSE MEMBRANES

An investigation into the organic permselective separation through poly [1-trimethylsilyl-1-propyne] (PTMSP) and (1-trimethylsily1)-1-(1-penta-methyl-disilyl)-1-propyne copoly-mer (TMSP-PMDSP) dense membranes was made to gain an insight into the effect ofthe chemical structure of membrane materials on pervaporation (PV) characteristics. Theresults show that the copolymer has a higher separation factor α_(org/water) but with a rela-tively lower value of flux J_t (g/m~2·h) than pure PTMSP. This phenomenon may be at-tributed to the introduction of side chain with large bulk volume in copolymer, whichbrought about a decrease of excess free volume and the improvement of diffesion selectivityto some extent. With the same molar concentration of organic liquids in feed, THF/watersolutions have the highest value of α_(org/water) as well as J_t in comparison with ethanol/water,iso-propanol/water and THF/water mixtures.     

QPVA/SMPVA自组装聚离子复合物膜对乙醇中水的渗透汽化性能研究

聚乙烯醇-N,N-二甲基-3-氨基-2-羟基丙基醚的季铵化产物(quaternized PVA-N,N-dimethyl-3-amido-2-hydroxy-propyl ether,简称QPVA)与硫酸单酯化聚乙烯醇(sulphate monoesterified polyvinyl alcohol,简称SMPVA)自组装聚离子复合物(self-assembled polyion complex,简称SAPIC),自组装溶液pH=7时,膜在水中的溶胀度最小.SAPIC均质膜在60vol%～90vol%(间隔10%)乙醇中浸泡48h,观察不同浓度乙醇中水在均质膜中的扩散行为.SAPIC均质膜在95%乙醇中浸泡48h,在20～120℃(间隔20℃)下,观察乙醇中水在膜中的汽化行为.应用FTIR技术跟踪两类吸水膜,确认了水和膜内聚离子基的吸收.改变浓度的一维(1D)和二维(2D)FTIR相关分析表明,渗透过程中形成两种状态的水,游离水和缔合水,随乙醇中水的增加游离水优先变化.游离水靠静电作用与膜内聚离子基优先缔合形成缔合水;改变温度的1D-和2D-FTIR显示,汽化过程中也存在两种状态的水,游离水和缔合水,随温度升高游离水优先变化.游离水较缔合水优先挥发,脱离膜与乙醇分离.同时测定了SAPIC复合膜对95%乙醇/水的渗透汽化性能,分离因子870,渗透通量1400g/(m2·h).为SAPIC膜用于乙醇脱水的渗透汽化过程研究提供了一种简便的方法.     

PERVAPORATION SEPARATION FOR TOLUENE/n-HEPTANE MIXTURE BY POLYIMIDE MEMBRANES CONTAINING FLUORINE

Five kinds of polyimides were synthesized using five dianhydrides (including 2,2-bis[4-(3,4-dicarboxyphenoxy)- phenyl] propane dianhydride (BPADA),3,3',4,4'-diphenylsulfone-tetracarboxylic dianhydride (DSDA),4,4'- (hexafluoroisopropylidene)-diphthalic anhydride (6FDA),1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride (HQDPA), and 4,4'-oxydiphthlic dianhydride (ODPA)) and 2,2-bis[4-(4-aminophenoxy)phenyl] hexafluoropropane (BDAF) via the two- step method that included polyaddition to form the polyamic aci...     

Preferential sorption of modified PVA membrane in pervaporation

The swelling processes of an annealed poly(vinyl alcohol) membrane, a NaOH-crosslinked poly(vinyl alcohol) membrane, a poly(vinyl alcohol)-N,N′-methylene bisacrylamide irradiation-crosslinked membrane and a poly(vinyl alcohol)/poly (AMcoAANa) blend membrane were investigated. Water was preferentially sorbed by all four membranes. The selective sorption factor ^s and the selective diffusion factor ^d were defined, and were used to characterize the effects of sorption and diffusion on selectivity. The results have shown that preferential sorption has a marked effect on selectivity. The mean diffusion coefficients and pervaporation properties of the four membranes are also discussed.     

醇／水混合液分离用聚乙烯醇复合膜的渗透汽化特性

制备了聚乙烯醇（ＰＶＡ）／聚丙烯睛（ＰＡＮ）渗透汽化复合膜，研究了交联剂用量、底膜结构、进料液组成、操作温度等因素对膜的渗透汽化性能的影响．发现ＰＶＡ／ＰＡＮ复合膜对水／醇混合液表现为水优先透过，进料液中乙醇浓度在６０～９９ｗｔ％的范围内，渗透通量Ｊｔ与温度之间符合Ａｒｒｈｅｎｉｕｓ关系，选择分离系数αＷ／Ｅ也随温度上升而增大．进料液为９５ｗｔ％的乙醇／水混合液时，７５℃下Ｊｔ高达３００～４５０ｇ／ｍ２ｈ，αＷ／Ｅ为８００～１１００．对异丙醇／水、异丁醇／水及甘油／水混合体系，复合膜显示出更为优秀的透过、分离性能．就膜的化学、物理结构与其渗透汽化性能间的关系进行了讨论．