CA膜分离MeOH/MTBE混合体系的渗透汽化传质模型

根据UNIQUAC模型和溶解扩散模型,建立了CA膜分离MeOH/MTBE混合体系的渗透汽化(PV)传质模型,模型计算值与试验值吻合良好.采用UNIQUAC模型关联MeOH-MTBE混合液的汽液平衡数据以及MeOH和MTBE在醋酸纤维素膜内的等温吸着数据,得到UNIQUAC相互作用参数,预测混合物组分在膜内的溶解度.用溶液吸着溶胀试验测得了MeOH/MTBE混合物在CA膜内的扩散系数,由6参数模型回归得到各个相互作用参数.     

CA和CTA膜分离MeOH/MTBE混合物渗透汽化性能研究

分别研究了甲醇(MeOH)和甲基叔丁基醚(MTBE)纯纽分在二醋酸纤维素(CA)和三醋酸纤维素(CTA)膜内的吸着性能、扩散系数及渗透通量.结果表明,活度在0.2～1.0范围内,MeOH在CA和CTA膜内的平衡吸着质量分数分别为0.018～0.172和0.032～0.175,远大于MTBE,而组分在2种膜中的溶解度无明显差别,2种组分在CTA膜中的扩散系数和渗透通量均大于CA膜.考察了进料温度在25℃、32℃和40℃下,料液中MeOH质量分数为5%～35%时,MeOH/MTBE混合物在CA膜中的渗透通量和分离系数,结果表明,随着进料温度和料液中MeOH浓度的升高,通量增加,分离系数减小.     

纤维素酯膜的有机物渗透性

本文研究了经丙酮水溶液改性处理后的醋酸纤维素（CA）反渗透（RO）膜的有机物渗透性，在丙酮改性处理过程，透过CA－RO膜的丙酮溶剂量，开始时迅速下降，然后逐渐趋于零，多孔膜变成了致密均相膜，非对称性的超滤（UF）膜，纳滤（NF）膜，RO膜，分别经丙酮改性处理后，甲苯透过膜的渗透速率依次减少。孔径越小，脱盐率越低的RO膜，经改性处理后，甲苯渗透速率越小，三醋酸纤维素（CTA）与醋酸丁酸纤维素（CAB）二组分混的CTACAB膜，或者与醋酸丙酸纤维素（CAP）三组分共混的CTACABCAP膜，随着实验时间的延长，甲苯的渗透速率，前者逐渐下降到接近零时趋于稳定，后者没有变化，改性的CA膜和CTACAB共混膜分离甲基叔丁基醚（MTBE）／甲醇（MeOH)混合物时，渗透能量分别为835和226（g/m^2.h)，渗透物中MeOH浓度都达到88wt％。     

分离有机／有机混合物的PVA，CA系列膜及其渗透汽化性能研究（I）膜材料与成膜工艺

依据溶度参数原则和分离甲基叔丁基醚（MTBE）/甲醇（MeOH）混合物的选择渗透性,选择了聚乙烯醇（PVA）为复合膜的分离层材料,聚丙烯腈（PAN）、醛酸纤维素（CA）系列为支撑层的膜材料。初步讨论了膜材料和复合膜结构对分离性能的影响,给出了用不同成膜工艺制备的膜性能。获得了可用于有机/有机体系分离的性能优良的PVA/PAN和PVA/CA复合膜,以及CTA中空纤维渗透汽化膜。     

乙醇和水在聚酰亚胺膜中的溶解和传递现象研究(Ⅰ)——吸收和解吸实验

用石英弹簧法测定了298.15 K、308.15 K和313.15 K下乙醇和水在聚酰亚胺膜中的吸收平衡数据和吸收解吸动力学数据,结果表明乙醇和水在聚酰亚胺膜中以吸附态和溶解态两种形式存在;乙醇和水在膜中的传质过程比较复杂,既有费克扩散类型也有非费克扩散类型;含交联剂的聚酰亚胺膜对水有溶解选择性,乙醇的解吸速度受交联剂的影响较大,表明交联剂的加入有利于提高聚酰亚胺膜的分离性能。     

分离有机/有机混合物的PVA、CA系列膜及其渗透汽化性能研究(Ⅰ)膜材料与成膜工艺

依据溶度参数原则和分离甲基叔丁基醚(MTBE)/甲醇(MeOH)混合物的选择渗透性,选择了聚乙烯醇(PVA)为复合膜的分离层材料,聚丙烯腈(PAN)、醋酸纤维素(CA)系列为支撑层的膜材料.初步讨论了膜材料和复合膜结构对分离性能的影响,给出了用不同成膜工艺制备的膜性能,获得了可用于有机/有机体系分离的性能优良的PVA/PAN和PVA/CA复合膜,以及CTA中空纤维渗透汽化膜.     

异戊二烯在聚苯乙烯高分子膜中的扩散系数测定

为了探讨在反应挤出过程中异戊二烯在聚苯乙烯中的扩散传递机理,采用石英弹簧法测定了298.15K、308.15K和318.15K下异戊二烯在聚苯乙烯膜中的吸收动力学曲线。探讨了温度、压力、分子量对扩散吸收的影响,并对实验结果进行了关联。结果表明异戊二烯在聚苯乙烯膜中的扩散吸收呈S型吸收,由吸收曲线获得了平均扩散系数和平衡溶解度。     

甲基叔丁基醚-苯、甲基叔丁基醚-甲基环己烷二元系在293～313K温度范围的密度和过剩摩尔体积

用液体比重天平测定了甲基叔丁基醚（MTBE）－苯二元系，甲基叔丁基醚－甲基环已烷二元系在293．15－313．15K下的密度值，求得过剩摩尔体积V^Em。对MTBE－苯二元系，所测定的V^Em都是负值，且随着温度升高，V^Em的绝对值稍有增加；而对MTBE－甲基环已烷二元系，所测定的V^Em都是正值，且随温度升高，V^Em的值稍有增加，实验数据用Redlich-kister方程关联，用非线性回归方法求得参数。     

热活化凹凸棒土对磷吸附性能的研究

将凹凸棒土高温煅烧活化,通过静态实验研究其对磷的吸附行为。结果表明,温度773 K时热活化效果显著。在研究的浓度范围内,吸附平衡数据显著符合Langmuir、Freundlich和Dubinin-Radushkevich模型(P<0.01),优惠吸附过程,磷吸附量随试验温度的升高而增加,328 K时理论饱和吸附量为2 408 mg P/kg。吸附动力学数据显著符合Lagergren伪二级动力学、Elovich和Kannan颗粒内扩散模型(P<0.05),非均相扩散、物理吸附过程,主要控速步骤为液膜扩散和颗粒内扩散联合控制。吸附热力学参数ΔG<0、ΔH>0、ΔS>0,热活化凹凸棒土对磷的吸附为自发吸热反应。研究结论为凹凸棒土在提高磷肥与复混肥料养分利用率中的应用提供了科学依据。     

柠檬酸改性聚乙烯醇制备可生物降解膜的研究

选择柠檬酸（CA）作为单体在聚乙烯醇（PVA）水溶液中制备柠檬酸改性的聚乙烯醇交联聚合物,并用红外光谱表征膜的结构：重点考察了反应时间和反应温度对柠檬酸改性聚乙烯醇键合度的影响;使用淀粉与聚乙烯醇交联聚合物共混,制备了柠檬酸改性聚乙烯醇（CA—SP）,并将其延流成膜,采用溶菌酶体外降解实验,测定CA—SP膜的降解性能,与柠檬酸键合量对生物降解的影响。测试了降解的CA—SP膜的力学性能考察。结果表明：柠檬酸的多羧基结构,能与PVA的羟基发生酯化,从而改性淀粉／聚乙烯醇（SP）;在60℃下,反应3h时,柠檬酸的键合量可达到最大,为3．92g/g。使用溶菌酶对其进行降解,通过降解的失重率测定,发现柠檬酸的键合量越高,膜降解性能越好。柠檬酸改性的SP膜几乎可以达到完全降解。     

Pervaporation of methanol/methyl tert‐butyl ether mixtures through agarose/hydroxyethylcellulose blended membranes

In this study, we investigated methanol (MeOH)/methyl tert‐butyl ether (MTBE) separation with hydroxyethylcellulose (HEC)/agarose blended membranes by applying a pervaporation technique. The membranes permeated MeOH in preference to MTBE from MeOH/MTBE mixtures. From pervaporation and sorption data, the permselectivity of HEC/agarose blended membrane was dominantly due to solubility selectivity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3408–3411, 2002     

Pervaporation separation of MTBE–methanol mixtures using cross‐linked PVA membranes

Poly(vinyl alcohol)(PVA)/poly(acrylic acid)(PAA) and PVA/sulfosuccinic acid (SSA) membrane performances have been studied for the pervaporation separation of methyl tert‐butyl ether (MTBE)/methanol (MeOH) mixtures with varying operating temperatures, amount of cross‐linking agents, and feed compositions. Typically, the separation factor, about 4000, and the permeation rate, 10.1 g/m²/h, were obtained with PVA/PAA = 85/15 membrane for MTBE/MeOH = 80/20 mixtures at 50°C. For PVA/PAA membranes, it could be considered that the flux is affected by the structural changes of the membranes due to the cross‐linking and the free carboxylic acid group also took an important role in the separation characteristics through the hydrogen bonding with PVA and the feed components leading to the increase of flux. The latter membrane of the 5% SSA membrane shows the highest separation factor of 2095 with the flux of 12.79 g/m²/h for MTBE/MeOH = 80/20 mixtures at 30°C. Besides the swelling measurements were carried out for pure MTBE and MeOH, and MTBE/MeOH = 90/10, 80/20 mixtures using PVA/SSA membranes with varying SSA compositions. It has been recognized that there are two factors, the membrane network and the hydrogen bonding in the swelling measurements of PVA/SSA membranes. These two factors act interdependently on the membrane swelling. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1699–1707, 2000     

KINETICS OF THE SIMULTANEOUS SORPTION OF NONIONIC SURFACTANT AND COPPER(II) BY POLY ACRYLIC ACID - FUNCTIONALIZED ION EXCHANGER

ABSTRACT

Kinetics of the simultaneous sorption of nonionic surfactant oxyethylated alcohols (OS-20) and copper(II) by hydrogen containing form of Purolite C 106 polyacrylic acid-functionalized cation exchanger was investigated: kinetic curves measured, effective coefficients of intraparticle diffusion (D), effective kinetic coefficients of the external mass transfer ((β) were calculated. The sorption of copper (II) and OS-20 is controlled by the intraparticle diffusion. The diffusion rate depends on the solution acidity: on increasing the acidity both the rate of copper (II) intraparticle diffusion and the equilibrium sorption decrease while the rate of intraparticle diffusion and the equilibrium sorption of OS-20 increase. The presence of copper (II) results in an increase in OS-20 diffusion rate but leads to a decrease in the equilibrium sorption of OS-20. The action of OS-20 results in the decrease in the equilibrium sorption of copper (II).The simultaneous sorption of oxyethylated alcohols and copper (II) by Purolite C 106 can be applicable for the purification of sewage including copper plating rinsewater A column filled with Purolite C 106 would not limit the productivity if integrated into the system of sewage purification by ion exchange |The simultaneous sorption of OS-20 and copper (II) by Purolite C 106 ion exchanger can be applicable for the purification of sewage including copper plating rinsewater. With respect to the coefficients of intraparticle diffusion for both copper (II) and OS-20 the column filled with Purolite C 106 would not limit the productivity if integrated into the system of sewage purification using ion exchange,     

Copolyimide molecular brushes with poly(methacrylic acid) side chains as additive to polyphthalamide membrane: Organization,physical, and transport properties

Macromolecules of complex architecture find application as modifiers of commercial polymeric membrane materials. In this work, copolyimide molecular brushes (coPI) composed of polyimide backbone and poly(methacrylic acid) side chains were used to modify poly(m-phenylene iso-phthalamide) (PPA). Structure, physical, mechanical, and transport properties of dense nonporous PPA/coPI membranes containing up to 10 wt% coPI were studied. The effect of included coPI on the membrane structure was estimated using atomic force microscopy and mechanical tests. The coPI modifier contributes to the additional formation of free volume elements evenly distributed throughout the membrane. Transport properties of PPA/coPI membranes were investigated via sorption tests and pervaporation separation of methanol (MeOH) and methyl tert-butyl ether (MTBE) mixtures. The inclusion of coPI modifier in the PPA membrane leads to an increase in the total flux of the membrane. The highest separation factor was found for the PPA/coPI membrane containing 10 wt% coPI; transport properties of the best membrane were compared with the literature data on separation of the azeotropic MeOH–MTBE mixture.     

Pervaporation separation of meOH/MTBE through CTA membrane

In the present work, the pervaporation (PV) separation of a MeOH/MTBE mixture system was studied using a CTA dense membrane. The PV performances were characterized by changing the operating conditions, such as the feed composition and permeation temperature. The results show that the CTA membrane favors MeOH permeation and exhibits specificity during the PV separation process for the MeOH/MTBE system due to the existence of the plasticization effect from the MeOH component. Furthermore, the swelling sorption measurements reaffirm that the plasticization effect has a dominant effect on the transport of the penetrants through the membrane and substantially determines the PV permeation properties. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 377–386, 1999     

An experimental study on the application of polymer membranes to the catalytic decomposition of MTBE (methyl tert.-butyl ether)

In this experimental study, the methyl tert.-butyl ether (MTBE) decomposition was carried out in various inert membrane reactors composed of H₃PW₂O₄₀ and a polymer membrane. Polycarbonate (PC), polyarylate (PA) and cellulose acetate (CA) membranes were used in the membrane reactor. It was revealed that all the tested polymer membranes showed larger permeability of methanol than that of either MTBE or isobutene, and the membrane reactor showed better performance than the corresponding fixed bed reactor. The perm-selectivity of methanol/MTBE was in the order of CA > PC > PA, and the permeation ratio of product/MTBE was in the order of CA > PA > PC. Among the membrane reactors tested CA membrane reactor showed the best performance. The enhanced performance of the membrane reactor was mainly due to the selective permeation of methanol that made a methanol-deficient phase suppressing MTBE synthesis reaction in the reversible reaction.     

Experimental study of vapor permeation of C5C7 alkane through PDMS membrane

Vapor permeation through dense membrane is regarded as an effectively way to separate volatile organic compounds (VOC) from industrial gas stream. This study proposes a new method to get the solubility and diffusivity of pure VOC vapor in dense membrane. C₅H₁₂, C₆H₁₄ and C₇H₁₆ were selected as sample VOC components to conduct newly developed sorption experiment with polydimethylsiloxane (PDMS) membrane. For each considered VOC component, its solubility was obtained from measured sorption equilibrium concentration in PDMS membrane, and its diffusivity was determined by fitting diffusion equation to the measured transient concentration of VOC component. The permeation behavior of VOCs in PDMS membrane was analyzed in terms of their solubility, diffusivity and permeability. Furthermore, the obtained solubility of these VOC components was utilized to get the vapor–membrane interaction parameters in UNIQUAC model. This opens an effective way to obtain the activity coefficient of VOC components for predicting their permeation performance in PDMS membrane.     

Synthesis of MTBE in zeolite membrane reactors

A zeolite membrane was employed to selectively remove water from the reaction atmosphere during the gas-phase synthesis of methyl-tert-butyl ether (MTBE) from tert-butanol and methanol. This reaction was carried out over a bed of Amberlyst™ 15 catalyst packed on the inside of a zeolite tubular membrane. The results obtained with different hydrophilic membranes (mordenite or NaA zeolite) are presented. Prior to reaction, the zeolite membranes were characterized by measuring their performance in the separation of the equilibrium mixture containing water, methanol, tert-butanol, MTBE and isobutene. The results obtained with zeolite membrane reactors (ZMR) were compared with those of a fixed bed reactor (FBR) under the same operating conditions. MTBE yields obtained with the ZMR at 334 K reached 67.6%, under conditions where the equilibrium value without product removal (FBR) would be 60.9%.