Pervaporative Separation Of Methanol Research Articles

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

AbstractMacromolecules 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.

Methanol/dimethyl carbonate separation using graphene oxide membrane via cationic control of molecular transport channels

The separation of small molecular organic-organic mixtures by membranes show considerable potential in energy efficiency, while the performance of polymeric membranes is unattractive. Two-dimensional (2D) graphene oxide (GO) membranes having ultra-fast and selective molecular transport channels could be an ideal platform for separating the organic-organic mixtures, however, such potential is not fully explored. In this paper, towards pervaporation separation of methanol (MeOH)/dimethyl carbonate (DMC) solvents, GO membrane with tunable interlayer and stable structure was prepared by anchoring metal ions between GO sheets. The introduced cations formed cation-π interaction with the sp2 region of GO, and electrostatic attraction with carboxyl, hydroxyl and epoxy groups on GO sheets. The molecular transport channels of GO membrane was optimized by optimizing the cation species (Na+, K+, Zn2+, Ca2+), cation content and GO flake sizes. The total flux of GO-Zn2+ membrane is 707.3 g/(m2·h) as well as separation factor is 61.9 for separation of 10 wt% MeOH/DMC mixtures by pervaporation at 50 °C. Meanwhile, the cationic control highly enhanced the stability of the GO membrane during continuous pervaporation process. This work reveals that GO membranes are the feasible for the application in pervaporation separation of organic-organic mixtures.

Pervaporative Separation of Methanol–Methyl Acetate Mixtures with Commercial PVA Membranes

Pervaporation may successfully be implemented for the separation of azeotropic mixtures which generally requires energy intensive separation procedures. Separation of methanol from methyl acetate by pervaporation is a representative application. In this study the commercial polyvinyl alcohol (PVA)-based membranes PERVAPTM 4155-30, PERVAPTM 4155-70, and PERVAPTM 4155-80 were used to recover methanol from binary methanol–methyl acetate mixtures. The separation performance was investigated for various operating parameters such as feed composition, feed temperature, and permeate pressure and discussed in terms of permeance and selectivity. An empirical model was developed to quantify the effect of membrane swelling on the permeate flux.

Separation of Toluene-Methanol Mixtures by Pervaporation Using Semi-IPN Polymer Membranes

Polyvinyl alcohol (PVOH) has been chemically modified by polymerizing hydroxyethylmethacrylate (HEMA) in aqueous solution of PVOH and finally crosslinking PVOH with glutaraldehyde to produce a semi-interpenetrating network (SIPN) membrane. Accordingly, three such SIPN membranes, namely SIPNI, SIPNII, and SIPNIII were synthesized with different weight ratio of PVOH: HEMA i.e., 1:0.25 (SIPNI), 1:0.50 (SIPNII), and 1:0.75 (SIPNIII). These SIPN membranes were used for pervaporative separation of methanol from its mixtures with toluene. The flux and methanol selectivity of these SIPN membranes were found to be much higher than conventional PVOH membrane crosslinked with glutaraldehyde. Among the three membranes, SIPNIII with 75 wt% HEMA incorporation shows optimum performance in terms of flux and methanol selectivity. The permeability of the membranes was also found to increase with increase in HEMA content in PVOH matrix. The novelty of the work lies in synthesis and characterization of a new kind of membrane and its potential for selective removal of methanol from its mixtures with toluene.

Analysis of the membrane thickness effect on the pervaporation separation of methanol/methyl tertiary butyl ether mixtures

The effect of the membrane thickness on the pervaporation separation of methanol and methyl tertiary butyl ether mixtures through membranes was studied. Membranes of a wide range of thicknesses were prepared from two different polymers: cellulose acetate and poly(2,6-dimethyl-1,4-phenylene oxide). For each membrane, the experiments were performed at the same feed pressure, feed temperature and permeate pressure. The results showed that the permeate flux through both membrane types decreased markedly with increasing the membrane thickness, while the separation factor remained nearly constant. This behavior was discussed in terms of a resistance-in-series model.

Preparation and application of dense poly(phenylene oxide) membranes in pervaporation.

Dense flat-sheet membranes were prepared from poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) using the casting solvents chloroform and 1,1,2-trichloroethylene. X-ray diffraction, tapping mode atomic force microscopy (TM-AFM), and contact angle studies were used to characterize the membranes. The surface energy and the solubility parameters of the PPO membranes were determined from the measured contact angles and compared with the predicted ones from the group contribution method. Swelling experiments and pervaporation separation of methanol from its mixture with ethylene glycol over the entire range of concentration, 0-100%, were conducted using these membranes. Flory-Huggins theory was used to predict the sorption selectivity. The results are discussed in terms of the solubility parameter approach and as function of the morphological characteristics of the membranes. It was found that PPO membranes prepared with chloroform exhibited better pervaporation performance than PPO membranes prepared with 1,1,2-trichloroethylene.

Development of co-polymer membranes for pervaporative separation of methanol from methanol–benzene mixture—a solubility parameter approach

Abstract Pervaporative separation of methanol–benzene over the satire range (0–100%) is studied with polyacrylonitrile homo-polymer and four of its different co-polymer membranes, i.e. acrylonitrile with 2-hydroxyethylmethacrylate, maleic anhydride, acrylic acid and methacrylic acid, respectively prepared through emulsion polymerization. The effect of co-polymer morphology on sorption of the solutes has been studied. The permeation, selectivity, and flux variation with methanol concentration has been explained using the solubility parameter approach. For this purpose the component group contribution, solubility parameter and interaction parameter values have been employed. All the membranes were stable during experimentation.

Pervaporation separation of methanol from methanol/ tert-amyl methyl ether mixtures with a commercial membrane

Tertiary ethers have attracted much attention as octane boosters, due to their pollution reduction and excellent blending capabilities. Although much research has been done in the area of pervaporation, not much attention has been given to the separation of organic–organic mixtures with commercially available membranes. In this study, the pervaporation and sorption characteristics of a commercial PVA-based membrane with methanol/ tert-amyl methyl ether (TAME) mixtures were investigated by varying the feed composition and the feed temperature, and measuring quantities such as flux and selectivity. The membrane was found to be highly methanol selective, with the separation factor varying between 30 and 175, and a flux of 1–4 kg m −2 h −1. The flux was found to increase with an increase in temperature and with an increase in weight fraction methanol in the feed. The selectivity decreased with an increase in weight fraction methanol in the feed and increased with an increase in temperature. Sorption data showed that there was only a minor difference in the sorption of both molecules at equilibrium, indicating a diffusion-controlled transport mechanism. Deviation coefficients showed that the plasticisation of TAME has a retarding effect on methanol permeation, and that methanol has an enhancing coupling effect on TAME. Approximated diffusion coefficients confirmed diffusion-controlled transport mechanism and explained why the methanol partial flux was so much higher than that of TAME. It was finally shown that pervaporation can easily be used to break the azeotrope of methanol and TAME, and that the membrane shows potential for being used in an industrial hybrid distillation–pervaporation system.

Development of methanol selective membranes for separation of methanol-methyl tertiary butyl ether mixtures by pervaporation

Several copolymers of acrylonitrile (AN) were synthesized. Methanol selective membranes were prepared from these copolymers of AN. The other monomers in the copolymers were selected on the basis of their solubility parameter values relative to those of methanol. These were hydroxyethyl methacrylate, methacrylic acid, and vinyl pyrrolidone. Thus, pervaporative separation of methanol from its mixture with methyl tertiary butyl ether over the entire concentration range of 0-100% methanol was studied using these copolymer membranes of AN. For each copolymer of AN three different membranes with different copolymer compositions were prepared. Copolymers of AN with hydroxyethyl methacrylate and methacrylic acid showed high selectivity and moderate flux for methanol (2561, 773, 0.057, and 0.045 kg/m 2 h, respectively, with a membrane of 50-μm thickness for a feed mixture containing 5% methanol at 30°C). A copolymer of AN with vinyl pyrrolidone showed comparable flux, but methanol selectivity of this membrane was poor.

Methanol selective membranes for separation of methanol–ethylene glycol mixtures by pervaporation

Several copolymers of acrylonitrile were synthesized. Methanol selective membranes were prepared from these copolymers of acrylonitrile. The other monomers in the copolymers were selected on the basis of their solubility parameter values relative to those of methanol. These were hydroxy ethyl methacrylate, methacrylic acid and vinyl pyrrolidone. Thus, pervaporative separation of methanol from its mixture with ethylene glycol over the entire concentration range 0–100% methanol was studied using these copolymer membranes of acrylonitrile. For each copolymer of acrylonitrile three different membranes with different copolymer compositions were prepared. Copolymers of acrylonitrile with hydroxy ethyl methacrylate and methacrylic acid showed good selectivity and moderate flux for methanol (14.74, 11.3 and 0.108 kg/m 2 h, 0.0813 kg/m 2 h, respectively, with membrane of 50 μm thickness for feed mixture containing 50% methanol). Copolymer of acrylonitrile with vinyl pyrrolidone showed comparable flux but methanol selectivity of this membrane was poor.

Pervaporation Separation of Methanol from Methanol-t-Amyl Methyl Ether Mixture by Polyion Complex Membrane.

Pervaporation separation of methanol (MeOH) from methanol-t-amyl methyl ether (TAME) mixtures is carried out using polyion complex (PIC) hollow fiber membrane. The sorption experiment is performed to observe the equilibrium relations between solute concentrations in the solution and in the membrane phase. With increasing MeOH weight fraction in the feed solution, the permeation flux of MeOH increases, but that of TAME remains almost constant. Considering the swelling effect by MeOH component, the flux model is described using diffusion coefficients dependent on MeOH concentration in the membrane and it can be successfully fitted to experimental data. The separation factor of MeOH ranges from 12 to 73, and decreases with increasing MeOH weight fraction in the feed solution.