Separation of a C_(3)H_(6)/C_(2)H_(4) mixture using Pebax^(■) 2533/PEG600 blend membranes

In industry, ethylene(C_(2)H_(4))/propylene(C_(3)H_(6)) separations are usually performed by a cryogenic process,which is energy intensive. Membrane separation technology is an alternative separation process that saves energy and is efficient. In this study, blend membranes were prepared by doping polyethylene glycol(PEG600) into a poly(ether-block-amide)(Pebax^(■) 2533) matrix and were used to separate the C_(2)H_(4)/C_(3)H_(6) mixture. The PEG 600 and Pebax^(■) 2533 polymers have good compatibility because they share hydrogen bonds. The addition of PEG600 is conducive to the hydrophilicity and the free volume of blend membranes, and it is also conducive to the solubility of C_(2)H_(4) and C_(3)H_(6) in the membranes, which improves the ability of the membranes to separate this gas pair. The Pebax^(■) 2533/PEG600 blend membrane with 15%(mass) PEG600 showed the highest separation performance in our investigated membranes, with a C_(3)H_(6)/C_(2)H_(4) selectivity of 8.9 and a C_(3)H_(6) permeability of 196 barrer(1 barrer = 1.33×10^(14)m^(3)(STP)·m·m^(-2)·s^(-1)·kPa^(-1)) at 238 K and 0.2 MPa, which is higher than that of the Pebax^(■) 2533/NaY-6%(mass) membrane(α_(C_(3)H_(6)/C_(2)H_(4)) =6.5, P_(C_(3)H_(6))=211 barrer) reported in our previous work. It is confirmed that incorporating PEG600 into the Pebax^(■) 2533 matrix to fabricate blend membranes is an efficient strategy for separating light olefins.

PREPARATION OF HIGH DENSITY POLYETHYLENE/POLYETHYLENE-BLOCK-POLY(ETHYLENE GLYCOL)COPOLYMER BLEND POROUS MEMBRANES VIA THERMALLY INDUCED PHASE SEPARATION PROCESS AND THEIR PROPERTIES

High density polyethylene （HDPE）/polyethylene-block-poly（ethylene glycol） （PE-b-PEG） blend porous membranes were prepared via thermally induced phase separation （TIPS） process using diphenyl ether （DPE） as diluent. The phase diagrams of HDPE/PE-b-PEG/DPE systems were determined by optical microscopy and differential scanning calorimetry （DSC）. By varying the content of PE-b-PEG, the effects of PE-b-PEG copolymer on morphology and crystalline structure of membranes were studied by scanning electron microscopy （SEM） and wide angle X-ray diffraction （WAXD）. The chemical compositions of whole membranes and surface layers were characterized by elementary analysis, Fourier transform infrared spectroscopy-attenuated total reflection （FTIR-ATR） and X-ray photoelectron spectroscopy （XPS）. Water contact angle, static protein adsorption and water flux experiments were used to evaluate the hydrophilicity, antifouling and water permeation properties of the membranes. It was found that the addition of PE-b-PEG increased the pore size of the obtained blend membranes. In the investigated range of PE-b-PEG content, the PEG blocks could not aggregate into obviously separated domains in membrane matrix. More importantly, PE-b-PEG could not only be retained stably in the membrane matrix during membrane formation, but also enrich at the membrane surface layer. Such stability and surface enrichment of PE-b-PEG endowed the blend membranes with improved hydrophilicity, protein absorption resistance and water permeation properties, which would be substantially beneficial to HDPE membranes for water treatment application.

Study on PVA Membranes Blended with Acrylic Ester-Acrylic Acid Copolymer for Dehydration of Ethanol

The viability of polyvinyl acetate (PVA) membranes blended with acrylic ester-co-acrylic acid copolymers (AE-co-AA), for ethanol dehydration was examined. The effects of the operating temperature on the permeate flux and separation factor of the membranes were investigated. The pervaporation separation characteristics of PVA/(AE-co-AA) membranes were related to the blend ratio, the dose of crosslinking agents and the operating temperature.

Polyvinyl acetate/poly(amide-12-b-ethylene oxide) blend membranes for carbon dioxide separation

In this paper,blend membranes from polyvinyl acetate(PVAc)and block copolymer poly(amide-12-b-ethylene oxide)(Pebax1074)are prepared by solution casting and solvent evaporation method.Although they are homogeneous on a macro-scale,the observations from DSC and SEM indicate micro-phase separation for PVAc/Pebax1074 blend membranes.With the increase of Pebax1074 content,gas permeabilities of CO2,H2,N2and CH4all increase greatly.PVAc/Pebax1074 blend membranes with high PVAc content are appropriate for CO2/CH4separation.The temperature dependence of gas permeability is divided into rubbery region and glassy region.The activation energies of permeation in rubbery region are smaller than those in glassy region,and they all decrease with increasing Pebax1074 content.For N2,H2and CH4,their gas permeation properties are mainly influenced by the dual-mode sorption and hydrostatic pressure effect.But for CO2,its permeability increases with the increase of pressure due to CO2-induced plasticization effect,which is more obvious for PVAc/Pebax1074 blend membranes with high PVAc content.

Proton-exchange Sulfonated Poly（ether ether ketone）/Sulfonated Phenolphthalein Poly（ether sulfone） Blend Membranes in DMFCs

A sulfonated poly（ether ether ketone） （SPEEK） membrane with fairly high degree of sulfonation （DS） swells excessively and even dissolves at high temperature. To solve these problems, sulfonated phenolphthalein poly（ether sulfone） （SPES-C, DS= 53.7%） is blended with the SPEEK matrix （DS= 55.1%, 61.7%） to prepare SPEEKJSPES-C blend membrane. The decrease in swelling degree and methanol permeability of the membrane is dose-dependent. Pure SPEEK （DS = 61.7%） membrane dissolves completely in water at 70℃, whereas the swelling degree of the SPEEK （DS = 61.7%）/SPES-C （40%, by mass） membrane is 29.7% at 80℃. From room temperature to 80℃, the methanol permeability of all SPEEK （DS = 55.1%）/SPES-C blend membranes is about one order of magnitude lower than that of Nafion 115. At higher temperature, the addition of SPES-C polymer increases the dimensional stability and greater proton conductivity can be achieved. The SPEEK （DS = 55.1%）/SPES-C （40%, by mass） membrane can withstand temperatures up to 150℃. The proton conductivity of SPEEK （DS = 55.1%）/SPES-C （30%, by mass） membrane approaches 0.16 S·cm^-1, matching that of Nafion 115 at 140℃ and 100% RH, while pure SPEEK （DS = 55.1%） membrane dissolves at 90℃. The SPEEK/SPES-C blend membranes are promising for use in direct methanol fuel cells because of their good dimensional stability, high proton conductivity, and low methanol permeability.

Poly(amide-6-b-ethylene oxide)/[Bmim][Tf2N] blend membranes for carbon dioxide separation

Poly（amide-6-b-ethylene oxide）（Pebax1657）/1-butyl-3-methylimidazo-lium bis[trifluoromethyl）sulfonyl]-imide（[Bmim][Tf2N]） blend membranes with different [Bmim][Tf2N] contents were prepared via solution casting and solvent evaporation method. The permeation properties of the blend membranes for CO2, N2,CH4 and H2 were studied, and the physical properties were characterized by differential scanning calorimeter（DSC） and X-ray diffraction（XRD）. Results showed that [Bmim][Tf2N] was dispersed as amorphous phase in the blend membranes, which caused the decrease of Tg（PE） and crystallinity（PA）. With the addition of [Bmim][Tf2N], the CO2 permeability increased and reached up to approximately 286 Barrer at 40 wt%[Bmim][Tf2N], which was nearly double that of pristine Pebax1657 membrane. The increase of CO2 permeability may be attributed to high intrinsic permeability of [Bmim][Tf2N], the increase of fractional free of volume（FFV） and plasticization effect. However, the CO2 permeability reduced firstly when the [Bmim][Tf2N]content was below 10 wt%, which may be due to that the small ions of [Bmim][Tf2N] in the gap of polymer chain inhibited the flexibility of polymer chain; the interaction between Pebax1657 and [Bmim][Tf2N]decreased the content of EO units available for CO2 transport and led to a more compact structure. For Pebax1657/[Bmim][Tf2N] blend membranes, the permeabilities of N2, H2 and CH4decreased with the increase of feed pressure due to the hydrostatic pressure effect, while CO2 permeability increased with the increase of feed pressure for that the CO2-induced plasticization effect was stronger than hydrostatic pressure effect.

Effect of Heat Treatment on Structures and Properties of Polyurethane Blend Ultrafiltration Membranes

The polyurethane/polyacrylonitrile (PU/PAN) and polyurethane/cellulose acetate (PU/CA) blend ultra filtration membranes were prepared based on Loeb-Sourirajan phase transition method. The change of the structures and properties of the PU/PAN and PU/CA membranes with the heat treatment process was studied. The results showed: the water flux decreased and retention increased with the increase of heat treatment temperature of PU/PAN blend membrane, but the water flux of PU/CA blend membrane got the maximum with heat treatment temperature of 60℃ and decreased rapidly with the heat treatment temperature of 100 ℃. The interfacial microvoid structure and its influence on the properties of PU/PAN and PU/CA blend membranes were studied.

Effect of poly(ethylene glycol) molecular weight on CO_2/N_2 separation performance of poly(amide-12-b-ethylene oxide)/poly(ethylene glycol) blend membranes

Membranes from block copolymer poly(amide-12-b-ethylene oxide)(Pebax1074) and its blends with different molecular weight poly(ethylene glycol)(PEG)(200, 400, 600, 1500, 4600 and 8000) were prepared. The thermal properties and structures of Pebax1074/PEG blend membranes were characterized by DSC and SEM, and the gas permeation properties of CO_2 and N_2 were also investigated at different temperatures. For Pebax1074/PEG blend membranes with low molecular weight PEG(MW≤ 600), higher gas permeabilities than Pebax1074 were achieved. The permeability increased with the increase of PEG molecular weight. The addition of low molecular weight PEG resulted in decrease in activation energy of permeation. For Pebax1074/PEG blend membranes with high molecular weight PEG(MW≥ 1500), due to the melt of PEO phase crystals, the gas permeation properties of blend membranes were temperaturedependent, which could be divided into crystalline region, transition region and amorphous region according to two different transition temperatures. PEG molecular weight and operation temperature determined different gas permeation properties of Pebax1074/PEG blend membranes in three regions. The activation energies of permeation in crystalline region were larger than those in amorphous region.

Fabrication of polymer/fluoride-containing salts blend composite membranes for CO_2 separation

Poly （N,N-dimethylaminoethyl methacrylate）-poly （ethylene glycol methyl ether methacrylate） （PDMAEMA-PEGMEMA） and cesium fluoride （CsF） were blended and used as the separation material of composite membranes.Hollow fiber composite membranes were fabricated by coating the blend on polysulfone （PSf） hollow fiber substrate.Introduction of fluorine ion improved the separation performance of the membrane.The concentration of coating solution was adjusted to obtain a membrane with high permeance.The composite membrane showed good performance with the CO2 permeance of 30.4 GPU （1 GPU=10-6 cm3 （STP）/（cm 2 s cmHg））,and selectivities to CO2/N2,CO2/CH4,CO2/H2 and O2/N2 of 47.2,37.6,1.75 and 4.70,respectively.Potassium fluoride （KF）,due to its low cost,was also used as a substitute of CsF to prepare composite membrane and the permeation data showed that CsF can be replaced by KF.The effect of operating temperature on the permeation properties of the composite membrane was also investigated.

PREPARATION AND ELECTROCHEMICAL CHARACTERISTICS OF POLYMER ELECTROLYTE MEMBRANES BASED ON SAN/PVDF-HFP BLENDS

A copolymer of poly（acrylonitrile-co-styrene） （SAN） was synthesized via an emulsion polymerization method. Novel polymer electrolyte membranes cast from the blends of poly（vinylidene fluoride-co-hexafluoropropylene） （PVDF- HFP）, SAN and fumed silica （SIO2） are microporous and can be used in polymer lithium-ion batteries. The membrane shows excellent characteristics such as high ionic conductivity and good mechanical strength when the mass ratio between SAN and PVDF-HFP and SiO2 is 3.5/31.5/5. The ionic conductivity of the membrane soaked in a liquid electrolyte of 1 mol/L LiPF6/EC/DMC/DEC is 4.9 × 10^-3 S cm^-1 at 25℃. The membrane is electrochemical stable up to 5.5 V versus Li^＋/Li in the liquid electrolyte. The influences of SiO2 content on the porosity and mechanical strength of the membranes were studied. Polymer lithium-ion batteries based on the membranes were assembled and their performances were also studied.

SYNTHESIS OF AN AMPHIPHILIC PPESK-g-P(PEGMA)GRAFT COPOLYMER VIA ATRP AND ITS USE IN BLEND MODIFICATION OF PPESK MEMBRANES

Preparation of an amphiphilic graft copolymer having poly(phthalazinone ether sulfone ketone)(PPESK) as main chains was carried out by atom transfer radical polymerization(ATRP).The precursor,chloromethylated PPESK (CMPPESK),was prepared by using chioromethylether as chloromethylation agent.Then,poly(ethylene glycol) methyl ether methacrylate(PEGMA) was used as monomer to synthesize PPESK-g-P(PEGMA) by ATRP method under the catalysis of a cuprous chloride/2,2'-bipyridyl system.PPESK/PPESK-g-P(PEGMA) blend m...

Fabrication of Poly(vinylidene fluoride) /Polysulfone Flat Blend Membranes via Thermally Induced Phase Separation Process for Water Treatment

Poly(vinylidene fluoride) /polysulfone(PVDF/PSF) flat blend membrane was prepared via thermally induced phase separation(TIPS) technique.The membrane formation mechanism and membrane structure were investigated and the effects of PSF/PVDF weight ratio on morphology,crystallinity,porosity,and mechanical properties of the membrane were discussed.The relationship between membrane structure and performances,such as pure water flux and the rejection of carbonic black,was also discussed.It was found that solid-liquid(S-L) phase separation occurred for the PVDF/PSF/diluent system.The addition of PSF influences structure and crystallinity of the membrane,which in turn influences mechanical properties and performances of the membrane.The results reveal that it is possible to obtain network structure via S-L phase separation by blending the polymer,which has a partial compatibility with PVDF.

Effects of F127 on Properties of PVB/F127 Blend Hollow Fiber Membrane via Thermally Induced Phase Separation

Hydrophilic poly(vinyl butyral)(PVB) /Pluronic F127(F127) blend hollow fiber membranes were prepared via thermally induced phase separation(TIPS) ,and the effects of blend composition on the performance of hydrophilic PVB/F127 blend hollow fiber membrane were investigated.The addition of F127 to PVB/polyethylene glycol(PEG) system decreases the cloud point temperature,while the cloud point temperature increases slightly with the addition of F127 to 20%(by mass) PVB/F127/PEG200 system when the concentration of F127 is not higher than 5%(by mass) .Light scattering results show that the initial inter-phase periodic distance formed from the phase separation of 20%(by mass) PVB/F127/PEG200 system decreases with the addition of F127,so does the growth rate during cooling process.The blend hollow fiber membrane prepared at air-gap 5mm,of which the water permeability increases and the rejection changes little with the increase of F127 concentration.For the membrane prepared at zero air-gap,both water permeability and rejection of the PVB/F127 blend membrane are greater than those of PVB membrane,while the tensile strength changes little.Elementary analysis shows that most F127 in the polymer solution can firmly exist in the polymer matrix,increasing the hydrophilicity of the blend membrane prepared at air-gap of 5mm.

STUDY OF COMPOSITE MEMBRANE OF CELLULOSE ACETATE OR POLYVINYL ALCOHOL BLENDED WITH METHYLMETHACRYLATE-ACRYLIC ACID COPOLYMER FOR PERVAPORATION SEPARATION

In this paper, methylmethacrylate-acrylic acid MMA-AA hydrophilic and hydrophobic copolymers were prepared by copolymerization for preparing membrane materials. The composite membrane of cellulose acetate (CA) blended with MMA-AA hydrophobic copolymer was used for the separation of methanol from pentane-methanol mixture. When the methanol concentration was only 1 wt%, the permeate flux still maintained at 350 g/m(2)h and separation factor was as big as 800. The composite membrane of PVA (polyvinyl alcohol) blended with MMA-AA hydrophilic copolymer was used for the separation of ethanol-water mixture. The permeate flux was increased to 975 g/m(2)h at 74 degrees C and the separation factor reached 3000 at 25 degrees C. The PVA/MMA-AA blended membrane surface modified by ammonia plasma was also investigated for separating ethanol-water mixture. Both permeate flux and separation factor of the membrane was improved. However, there was no obvious difference of plasma treatment time in the interval of 20 similar to 40 min.

Research and Application Progress of Silk Fibroin Membranes

This paper mainly introduced the preparation of silk fibroin membranes and their structural change characteristics.Silk fibroin membranes can be used as tissue engineering materials,enzyme-immobilizing membranes,biosensors and drug controlled-release membranes and other different materials.They have excellent characteristics such as non-toxic,non-polluting and degradable,and thus have broad application prospects.

TIPS behavior for IPP/nano-SiO_2 blend membrane formation and its contribution to membrane morphology and performance

In the present work, the TIPS behavior of isotactic polypropylene(iP P)/di-n-butyl phthalate(DBP)/dioctyl phthalate(DOP)/nano-SiO_2 system and the competition relation between liquid–liquid phase separation and polymer crystallization are successfully adjusted by adding nano-SiO_2. The liquid–liquid phase separation temperature of the system increases with increasing nano-SiO_2 content. Besides, iP P crystallization temperature is also changed after adding nano-SiO_2. IPP/nano-SiO_2 blend hollow fiber microporous membrane is prepared via TIPS method. SEM photos show that the membrane exhibits mixed morphology combining cellular structure relating to liquid–liquid phase separation and branch structure originating from polymer crystallization. The relative weight of cellular structure first decreases and then increases with the increase of nano-SiO_2 content. Furthermore, porosity, connectivity among pores and pure water flux of the membrane first increase and then decrease with increasing nano-SiO_2 content. However, mechanical performance of the membrane is improved at all times with increasing nano-SiO_2 content.

Study on Pervaporation Membranes for Removing Methanol from C_5 or Methyl Tert-butyl Ether Mixtures

Several pervaporation membranes, cellulose acetate (CA), polyvinylbutyral (PVB), poly(MMA-co-AA), MMA-AA-BA, CA/PVB blend and CA/poly(MMA-co-AA) blend, were prepared, and their pervaporation properties were evaluated by separation of methanol/C5 or methanol/MTBE (methyl tert-butyl ether). The results shows that the CA composite membrane has a high separation performance (flux Jmenthanol =350g.m-2.h-1 and separation factor a > 400) for methanol/C5 mixtures, and the pervaporation characteristics of MMA-AA-BA copolymer membranes changes with the ratio of copolymer. For CA/poly(MMA-co-AA) blend membrane, the pervaporation performance is improved in comparison with CA or poly(MMA-co-AA) membrane. From the experiment of CA/PVB blend membranes for methanol/MTBE mixture, it is found that the compatibility of blends may affect the separation features of blend membrane.

Quadrature Element Vibration Analysis of Arbitrarily Shaped Membranes

The aim of the present study is to develop an efficient weak form quadrature element for free vibration analysis of arbitrarily shaped membranes.The arbitrarily shaped membrane is firstly mapped into a regular domain using blending functions,and the displacement in the element is assumed as the trigonometric functions.Explicit formulations are worked out for nodes of any type and a varying number of nodes.For verifications,results are compared with exact solutions and data obtained by other numerical methods.It is demonstrated that highly accurate frequencies can be obtained with a small number of nodes by present method.

A Simple and Effective Method to Fabricate Separation Membranes for Dehydration of Natural Gas

PBT/PEG_(1000)composite membranes were prepared by the phase inversion method and were used to dehydrate natural gas.In this study,evaporation time,coagulation bath concentration,and additives in casting solution were investigated,respectively,on the selectivity and permeability of separation membranes,and optimal conditions were found to include an evaporation time of 30 sec,an 100%PEG400-containing coagulation bath and 2%of PVA used as the additive.The H_(2)O/CH_(4)selectivity reached over 3600,which is about 20 times more selective than the original membrane.It provides a simple and effective preparation method to fabricate membranes for dehydration of methane gas.