聚乙烯基咪唑/陶瓷复合膜的渗透汽化性能

通过自由基接枝聚合反应在硅烷化处理的沉积有SiO2活性层的无机陶瓷微孔膜上接枝乙烯基咪唑（VI）,经质子化后,制备出一种聚电解质亲水性有机-无机复合膜。用FT-IR表征了接枝PVI前后化学组成的变化;用TGA 测定了单体在二氧化硅粉末上的接枝率;用SEM观察了接枝反应前后膜表面形态的变化;系统研究了操作条件对膜的渗透汽化分离性能的影响。结果表明,这种膜用于醇/水、酸/水等水溶液的分离有很好的选择性和渗透性,膜的渗透性随操作温度的变化表现异常,结合SEM的结果可以推断有机单体主要是在无机膜的孔内接枝形成活性分离层。     

苯乙烯/马来酸酐和苯乙烯/甲基丙烯酸二甲氨基乙酯二元体系在聚四氟乙烯多孔膜上的γ辐射接枝

在氮气的氛围下用γ辐照的方法在聚四氟乙烯多孔膜上接枝苯乙烯 马来酸酐、苯乙烯 甲基丙烯酸二甲氨基乙酯二元单体 .并且研究了剂量、剂量率、溶液中单体的浓度和二元单体的摩尔比等条件对接枝率的影响 .探讨了两种单体的竞聚率对接枝率、接枝膜的组成及性能的影响 .结果表明 ,苯乙烯 马来酸酐二元体系对接枝率有协同效应 ,苯乙烯 甲基丙烯酸二甲氨基乙脂二元体系对接枝率表现为加合效应 .制备的二元接枝的聚四氟乙烯多孔膜可以进一步磺化来制备用于质子交换膜燃料电池的质子交换膜 .     

无光敏剂光引发亲水性单体在嵌段聚醚氨酯膜上接枝聚合的研究

<正> 嵌段聚醚氨酯(SPEU)是一类应用广泛的医用高分子材料。用亲水性单体进行表面接枝改性,已有不少研究,接枝聚合方法有铈盐引发、辐射引发以及光敏引发等。 本文研究一种新的接枝方法,不加光敏剂,用紫外光照射,直接引发亲水性单体接枝于SPEU膜上、接枝的单体有丙烯酰胺(AAM)与N,N-二甲基丙烯酰胺(DMAA),从接枝前后膜的性能变化可以证实接枝反应的发生。文中研究了反应条件与单体结构对接枝率的影响,并通过模型化合物,对接枝部位进行了研究。     

聚砜与丙烯酸的紫外光辐射接枝共聚及其表征

在均相溶液体系下,运用紫外光辐射引发合成了聚砜与丙烯酸的接枝共聚物。用化学滴定、漫反射傅立叶变换红外光谱和热分析等技术对接枝聚合物进行了表征。结果表明:丙烯酸被接枝在聚砜链上;光照时间、单体浓度和光引发剂浓度对接枝率均有较大影响。膜表面接触角的研究表明,接枝共聚物膜的亲水性比改性前有所提高。     

N,N-二乙基丙烯酰胺与丙烯酸在聚丙烯薄膜表面光接枝制二元接枝膜及其温度、pH值敏感特性研究

以二苯甲酮为引发剂,聚丙烯薄膜(CPP)为基材,通过紫外光接枝的方法制备了具有温度和pH值双重敏感特性的聚N,N-二乙基丙烯酰胺(PNDEA)与聚丙烯酸(PAA)二元接枝膜.在PNDEA一次接枝膜的制备过程中,引发剂与单体配比相同时,本体接枝方法的接枝速率在反应初期明显高于溶液接枝方法;采用溶液法时,增大引发剂与单体配比等可提高接枝率.用本体法所制得的PNDEA一次膜光活化接枝PAA时接枝速率较溶液法高,并且能够实现较高的PAA接枝率.用红外光谱(FTIR)、X射线光电子能谱化学分析(ESCA)对接枝层组成的表征结果证实了二元接枝层的存在.在不同温度下,PNDEA一次接枝膜的FTIR谱图中酰胺Ⅰ带特征吸收峰发生位移表明它具有温度敏感特性.用扫描电子显微镜(SEM)对PNDEA接枝层表征结果表明,用不同接枝手段所制备的接枝膜具有不同的表面形貌.通过吸水率测定研究了二元接枝膜的温度及pH值敏感特性.     

N,N-二乙基丙烯酰胺与丙烯酸在聚丙烯薄膜表面光接枝制备二元接枝膜及其温度、pH值敏感特性研究

以二苯甲酮为引发剂,聚丙烯薄膜(CPP)为基材,通过紫外光接枝的方法制备了具有温度和pH值双重敏感特性的聚N,N-二乙基丙烯酰胺(PNDEA)与聚丙烯酸(PAA)二元接枝膜.在PNDEA一次接枝膜的制备过程中,引发剂与单体配比相同时,本体接枝方法的接枝速率在反应初期明显高于溶液接枝方法;采用溶液法时,增大引发剂与单体配比等可提高接枝率.用本体法所制得的PNDEA一次膜光活化接枝PAA时接枝速率较溶液法高,并且能够实现较高的PAA接枝率.用红外光谱(FTIR)、X射线光电子能谱化学分析(ESCA)对接枝层组成的表征结果证实了二元接枝层的存在.在不同温度下,PNDEA一次接枝膜的FTIR谱图中酰胺Ⅰ带特征吸收峰发生位移表明它具有温度敏感特性.用扫描电子显微镜(SEM)对PNDEA接枝层表征结果表明,用不同接枝手段所制备的接枝膜具有不同的表面形貌.通过吸水率测定研究了二元接枝膜的温度及pH值敏感特性.     

紫外辐照接枝制备亲水性荷正电纳滤膜

通过在酚酞基聚芳醚酮超滤膜表面紫外辐照接枝亲水性单体二烯丙基二甲基氯化铵(DADMAC)制备了一种表面荷正电的纳滤膜. ATR-FTIR和表面水接触角的研究结果表明膜表面的接枝率和亲水性随着辐照时间和单体在接枝溶液中的浓度的增加而增加. 荷正电纳滤膜对盐溶液有很好的截留, 对盐溶液中的高价阳离子和低价阳离子的截留率分别为95%和65%. 但当溶液中存在高价负离子时, 膜的截留性能会明显下降. 表明静电效应在荷电纳滤膜的分离过程中起了重要的作用.     

聚环氧乙烷大单体与丙烯酸乙酯的共聚及其规整接枝共聚物的表征

本工作研完了末端为甲基丙烯酸酯型的聚环氧乙烷大单体与丙烯酸乙酯的溶液自由基共聚。结果表明,大单体接枝效率和共聚物分子量受单体总浓度、投料比、大单体分子量及引发剂等的影响,接枝效率最高可达90％以上,分子量可在5-15×10~4范围内变化。丙烯酸乙酯与大单体共聚的竞聚率为0.83。共聚物用萃取法精制后,用IR、~1H-NMR、裂解色谱、GPC和膜渗透压计等进行了表征。证实产物有预期的规整接枝共聚物结构。平均接枝数为2—11。     

芴酮引发光接枝改性LDPE膜的研究

采用紫外光引发接枝表面改性的方法,以芴酮(FL)为引发剂,在低密度聚乙烯(LDPE)薄膜表面上接枝丙烯酸(AA)、甲基丙烯酸(MAA)、丙烯酸甲酯(MA)、甲基丙烯酸甲酯(MMA)、丙烯酰胺(AM)等单体,以赋予薄膜表面新的化学性质.考察了引发剂浓度、紫外光的辐照时间、辐照强度、单体种类对LDPE薄膜接枝程度的影响.结果表明,在一定范围内,增加芴酮浓度,可以提高单体的接枝率,但当芴酮浓度达到5%时,接枝率反而下降.延长辐照时间至4 min和提高紫外光的辐照强度达100 W/m2,均有利于接枝反应的进行.不同单体在LDPE膜上的接枝能力与单体的活性、单体与基材的相容性等因素有关.接枝后,LDPE与水的接触角下降程度不仅与单体在膜上的接枝量有关,还与接枝单体的亲水性能密切相关.     

二元单体在棉纤维上的γ辐射接枝

在氮气气氛下用γ射线辐照的方法在棉纤维上接枝苯乙烯/马来酸酐、苯乙烯/甲基丙烯酸二甲胺乙酯、苯乙烯/醋酸乙烯酯二元单体. 研究了溶液中单体的浓度和二元单体的摩尔比等条件对接枝率的影响, 并探讨了两种单体的竞聚率对接枝率、接枝膜的组成及性能的影响. 结果表明决定二元接枝生成物结构比例的是二元单体的比例及其竞聚率. 接枝产物的红外、热重分析进一步佐证了竞聚率对不同二元单体体系接枝生成物结构的影响. X射线衍射结果表明棉纤维素上接枝不同的二元单体后均引起结晶度的下降, 而且结晶度随接枝率的增加而降低, 证明二元接枝反应是从纤维素无定型区通过第三相向结晶区逐步扩展的.     

二次生长法制备高分离性能的PHI分子筛膜

通过二次生长法在α-Al2O3支撑体表面合成了PHI分子筛膜,考察了晶种合成方式、二次生长合成温度及时间对形成PHI分子筛膜的影响.采用X射线衍射(XRD)、扫描电子显微镜(SEM)对合成膜进行表征.结果表明:载体表面合成出了PHI分子筛;二次生长法合成出的PHI分子筛膜连续、致密,膜厚约为20 μm.利用渗透汽化技术对甲醇、乙醇、异丙醇和叔丁醇等不同分子尺寸的醇/水体系进行分离性能的研究,同时考察原料液中水含量对所制备的PHI分子筛膜的分离性能的影响.结果表明:PHI分子筛膜对几种醇水体系都具有良好的分离效果,随着水含量的增加,水的渗透通量呈增大趋势,乙醇和甲醇的理想分离因子有所降低,异丙醇和叔丁醇的理想分离因子增大.     

季胺盐对共混聚酰亚胺膜气体除湿性能的影响

季胺盐对共混聚酰亚胺膜气体除湿性能的影响;共混改性;聚酰亚胺;季胺盐;亲水性;除湿     

Relations between structure, acidity, and activity of WOx/TiO2: influence of the initial state of the support, titanium oxyhydroxide, or titanium oxide

Two series of WO(x)/TiO(2) catalysts, containing W surface densities up to 4.4 W atoms/nm(2), were prepared by pore volume impregnation of two different supports, titanium oxyhydroxide (amorphous) or titanium oxide (crystallized, 100% anatase). The influence of W surface density and the nature of the support on the surface structure, development of the acidity, and catalytic performances were examined. The texture and structure of the catalysts were investigated by Brunauer-Emmett-Teller measurements, X-ray diffraction (XRD), and Raman and infrared spectroscopy. The catalytic activity was tested for 2-propanol dehydration and n-hexane isomerization. For catalysts obtained by impregnation of titanium oxide, XRD and Raman results showed that W was present as a surface phase. Infrared spectra indicated an increase in the degree of polymerization of W species with increasing W surface density. CO and lutidine adsorption, followed by infrared spectroscopy, showed an increase in the strength and abundance of Br?nsted acid sites (measured after lutidine desorption at 573 K) with the W surface density above a threshold of 1.3 W atoms/nm(2). The development of Br?nsted acidity correlated with the evolution of the infrared bands attributed to polymerized W species. A direct relationship was observed between the concentration of Br?nsted acid sites and the catalytic activity for 2-propanol dehydration. Catalytic activity, for n-hexane isomerization, appears to be associated with the presence of highly condensed W species. The catalysts synthesized by impregnation of titanium oxyhydroxide exhibited a comparable behavior. Hence, for a given W surface density, the W surface structure, concentration of Br?nsted acid sites, and catalytic performances were similar. Thus, no significant effect of the initial form of the support (titanium oxyhydroxide versus titanium oxide; 100% anatase) was evidenced.     

紫外辐照接枝制备亲水性两性纳滤膜

通过紫外辐照在酚酞基聚芳醚酮(PEK-C)超滤膜表面引发自由基共聚反应, 依次接枝二甲基二烯丙基氯化铵(DADMAC)和对苯乙烯磺酸钠(SSS), 制成亲水性、表面载有两种不同电荷的纳滤膜. 通过测定膜的纯水通量和对不同盐溶液表观截留率的变化, 系统研究了单体浓度和接枝时间对膜的分离性能的影响. 结果表明, 用这种方法制成的亲水性两性纳滤膜对盐溶液的截留作用与两种单体在接枝液中的浓度和接枝时间有关. 膜对由高价同离子和高价反离子组成的盐表现出优良的截留作用.     

Dehydration of aqueous acetonitrile solution by pervaporation using PVA–iron oxide nanocomposite membrane

Pervaporative performances were investigated for dehydration of water–acetonitrile using nanocomposite metal oxide and Pervap^® 2202 membranes. Poly (vinyl alcohol) based nanocomposite metal oxide membranes were prepared through co-precipitation of different amounts of Fe (II) and Fe (III). The freestanding nanocomposite metal oxide membranes were characterized by Transmission electron microscopy and X-ray diffraction. Sorption studies evaluated the extent of interaction and degree of swelling of the membranes. Fe containing PVA polymer matrix showed improved flux and selectivity. In order to observe simultaneous effect of flux and selectivity, pervaporation separation index showed 10 wt.% iron oxide containing membrane is the most amongst all tested. The diffusion coefficients were calculated using pervaporation results and sorption kinetics data. An attempt was made to predict sorption selectivity thermodynamically. PV separation factor was observed to be governed by sorption and/or diffusion phenomena and sorption selectivity was found to be higher than PV separation factor. Prediction of concentration profile in the membrane was also attempted and the results showed that water concentration in the membrane drops down with increase in membrane thickness.     

具有界面交联结构藻酸钠复合膜的制备与性能

报道了一种具有界面交联结构的新型藻酸钠复合膜及其对醇水和其它有机物水体系的渗透汽化分离性能.该膜的活性层为藻酸钠,支撑层为氨化聚丙烯腈(PAN)多孔膜,在这两层之间存在着界面交联结构.研究了PAN多孔膜的水解时间、进行氨基化的二元胺种类及浓度对复合膜分离性能的影响,用己二胺进行氨基化所得到的复合膜的分离性能明显优于用乙二胺的结果.扫描电镜照片显示水解及氨基化改变了PAN超滤膜的孔结构,这也是影响新型复合膜性能的一个重要原因.     

Comparison of membrane processes with distillation for alcohol/water separation

The overall objectives of this study were to summarize and evaluate the performance of currently available membranes for purification of fermentation alcohol and to compare the economics of membrane processes with a modern-day energy-efficient distillation scheme.Literature survey showed that very little work had been done on the development of membrane processes for alcohol concentration.Based on laboratory work, it was found that the present-day thin-film composite desalination membranes can be used for partial concentration of beer solution to about 20 to 30% alcohol concentration. The water permeation coefficient for these membranes in reverse osmosis with 7.6% alcohol feed at 60 atm was about 10 kg/m²-day-atm (2 lb/ft²-day-atm).Due to the high osmotic pressures of ethanol/water mixtures, reverse osmosis can be used only for the initial concentration of beer solution and for the final dehydration of 95% alcohol to produce 199 proof alcohol. Thus, a distillation unit would have to be used for the intermediate concentration of alcohol solution. Membrane concentration schemes using distillation for intermediate concentration were prepared for comparison with a conventional distillation process. Based on preliminary analysis it was concluded that while the capital cost of the membrane-augmented distillation schemes can be significantly than that of the conventional system, the annualized cost of these schemes will be approximately equal to that for distillation. The capital and the annualized costs of the membrane process for the final dehydration of alcohol can be significantly lower than those for the conventional dehydration still.     

Caractérisation des propriétés électriques des parois de pores d’une membrane

The characterisation of the surface electrical properties of membrane materials is critical for understanding and predicting the filtration performances of membranes. In this paper, four simple experimental methods – streaming potential, electro-osmosis, pore conductivity and membrane potential –, allowing the characterisation of the charge state of membrane pore walls are presented. The four experimental parameters provide information about the sign of the electrical net charge. Examples illustrating the influence of the pH, electrolyte concentration and nature on the four experimental parameters are given. The zeta potential can be then deduced from these measurements by means of a model.     

Pervaporation dehydration of isopropanol with chitosan membranes

Homogeneous and composite chitosan based membranes were prepared by the solution casting technique. The membranes were investigated for the pervaporation dehydration of isopropanol-water systems. The effects of feed concentration and temperature on the separation performance of the membranes were studied. In terms of the pervaporation separation index (PSI), the composite membrane was more productive than the homogeneous membrane for pervaporation of feed with high isopropanol content. It was observed that permeation increased and the separation factor decreased with the temperature. Modification of the homogeneous chitosan membrane by chemical crosslinking with hexamethylene diisocyanate improved the permselectivity but reduced the permeation rate of the membrane.     

稀土超强酸SO42-/TiO2-Nd2O3催化合成环己烯

环己烯是重要的一种有机合成中间体,具有活泼的双键,作为有机化工原料,可广泛应用于医药、农药、农用化学品、饲料添加剂、聚酯和其他精细化学品的生产。人们曾对环己醇脱水制环己烯反应使用过多种酸性催化剂及固体催化剂,固体超强酸就是其中之一,虽然已有许多关于固体超强酸应