Separation Of Ethanol-water Mixtures Research Articles

Water Removal from an Ethanol-Water Mixture at Azeotropic Condition by Adsorption Technique

The separation of ethanol-water mixture is employed in the present work to produce pure ethanol, the present investigation on the separation of water from the ethanol to achieve pure ethanol by adsorption process. The different parameters like quantity of adsorbent, flow rate of feed mixture, and different adsorbents which are zeolite 3A, zeolite 4A, and silica gel are selected to study purification of ethanol by adsorption. The effect of process parameter for purification is also recorded and studied to evaluate the performance of adsorption equipment and adsorbent. The experiments are conducted at 30°C. The feed mixture is 95.6% (v/v) concentration of ethanol and 4.4% (v/v) of water. The designed adsorption column is suitable for purification of ethanol. The highest ethanol concentration 99.9443% obtained at 20 ml/min flow rate of feed mixture using 50 g of zeolite.

A ZIF-71 Hollow Fiber Membrane Fabricated by Contra-Diffusion.

As a subclass of metal-organic framework materials, zeolitic imidazolate frameworks (ZIFs) have exhibited great potential for numerous applications because of their special three-dimensional structure. Up to now, utilizing ZIF membranes for liquid separations is still limited because it is very difficult to select suitable materials and to fabricate integrated membranes. In this work, a modified contra-diffusion method was carried out to prepare ZIF-71 hollow fiber membranes. The metals Zn(2+) and the organic links imidazole would meet and react on the interface of ceramic hollow fiber through diffusion. The as-prepared ZIF-71 membrane exhibits good performance in separation of ethanol-water mixtures.

<b>Separation of Ethanol-Water Mixtures by the Membranes Prepared from Liquid Silk</b>

Silk-based membranes with the thickness of around 6 micrometers were prepared from the silk glands of fully grown larvae of domestic Bombyx mori silkworm instead of its fibers, and the fundamental vapor permeation as well as pervaporation experiments of ethanol-water mixtures were performed. The permselectivity of water for the membranes developed was almost comparable to that for chitosan and a little superior to PVA. The observed ATR-FTIR spectra bands in the range of amide I and II frequencies for the silk-based membranes were unchanged after the treatments with ethanol. The membranes produced from liquid silk seem to be fairly stable against ethanol.

Poly(vinyl Alcohol)/Cellulose Nanocomposite Pervaporation Membranes for Ethanol Dehydration

In this study, pervaporation membranes were prepared from poly( vinyl alcohol) (PVA) with different amounts of cellulose nanocrystals as filler, and characterized by scanning electron microscopy (SEM). The characterization results demonstrated that cellulose nanocrystal particles dispersed homogeneously within the PVA matrix. Moreover, the pervaporation performance of these membranes was investigated using the separation of ethanol-water mixture as model system. Among all the prepared membranes, PVA/cellulose nanocomposite membrane containing 1 wt% cellulose nanocrystals exhibited the best pervaporation performance, whose averaged permeation flux reduced slightly but separation factor was increased from 83 to 163 for 80% aqueous solution of ethanol at 80 °C respectively.

New composite membranes based on crosslinked poly(acrylic acid) and porous polyethylene films

A process for the preparation of new composite membranes via free-radical copolymerization of acrylic acid with a macromolecular crosslinker (allyloxyethylcellulose) on the surface of porous polyethylene films was proposed. To reveal the effect of the porous matrix on the properties of the composites, homogeneous hydrogel membranes based on crosslinked poly(acrylic acid) were studied. The swelling ratio and transport characteristics of the membranes during separation of ethanol-water mixture by pervaporation were determined depending on the ethanol concentration. It was found that all membranes at low ethanol concentrations (0–30 vol %) exhibited high swelling ratios, which drastically decreased in the range 30–40 vol % as a result of gel collapse. The composite membranes had a higher selectivity for water over a broad range of ethanol concentrations than homogeneous membranes, but a lower flux. It was found that the strength and elasticity of porous matrices was retained in the composite membranes, which became mechanically more isotropic owing to the presence of the crosslinked component.

Pervaporation of aqueous ethanol solutionthrough poly(amidesulfonamide)s (PASAs) membranes

Symmetric non-porous membranes derived from five poly(amidesulfonamide)s were prepared for the separation ofethanol-water mixtures by the use of the pervaporation technique. It was found that water preferentially permeated through all PASA membranes in all ranges of feed compositions. The relationship between the polymer structure and its pervaporation performance will be discussed. The dependence of permeation rate on the feed composition was explained by the ‘carrier-mediated’ mechanism. The effect of temperature on the pervaporation characteristics of the materials was investigated in details. Experimental results revealed that the polymer based on the diamino monomer containing the piperazine moiety and isophthaloyl chloride emerged as the best system in terms of separation factor and permeation rate in the dehydration of ethanol.

Vapor permeation of ethanol-water mixtures using sodium alginate membranes with crosslinking gradient structure

For the vapor permeation of ethanol-water mixtures, two types of dense sodium alginate (SA) membranes have been prepared: a nascent SA membrane and crosslinked SA membranes with glutaraldehyde (GA). In the vapor permeation of the concentrated ethanol-water mixtures through the SA membranes, the effects of feed temperature, cell temperature and crosslinking density in the membrane were investigated on the membrane performance, and a comparison of vapor permeation process was made with pervaporation. SA membranes having different crosslinking gradients have been fabricated by exposing the nascent membrane to different GA content of reaction solutions. The extent of the gradient was controlled by the exposing time. The permeation performance of the membranes will be discussed with the extent of the gradient. An optimal crosslinking gradient was determined in terms of flux and membrane stability. The separation of ethanol-water mixtures through the membrane with the optimal crosslinking gradient was carried out by vapor permeation and the permeation performance will be discussed, and compared with pervaporation.

Preparation of N-methylol nylon-6 membranes for pervaporation of ethanol-water mixtures

N-methylol nylon 6 membranes were prepared by reacting nylon-6 with formaldehyde. Elemental analysis, used to analyze the composition of modified membranes, showed that the degree of substitution increased with formaldehyde content in the reaction solution. The modified nylon-6 membranes exhibited a high affinity to ethanol. Pervaporation results for the separation of ethanol-water mixtures showed that these membranes were water-selective, indicating that the diffusion property is the dominant factor. An N-methylol nylon-6 membrane with 33% degree of substitution showed the best membrane performance. In order to control the swelling of N-methylol nylon-6 membranes in the feed solutions of high ethanol content, thermal crosslinking was applied at 180°C for different times. It was found that heat treatment of 10 minutes gave the optimal permselectivity. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 855–863, 1997

A MODIFIED SOLUTION-DIFFUSION MODEL FOR SEPARATION OF ETHANOL-WATER AZEOTROPIC MIXTURES IN PERVAPORATION

A modified solution-diffusion model is presented which describes separation of ethanol-water mixtures. The model is particularly useful in predicting the solute (ethanol) flux as the mixture approaches the azeotrope point where ethanol activity is greater than 0 6. Based on the experimental observations obtained from the literature, the model assumes that polymers of about seven molecules of ethanol are formed, which are then transported through the membrane along with water and ethanol monomers and dimers. It is shown that the ethanol flux can be predicted more accurately as compared with the existing model. Comparisons with experimental data from the literature confirms this model.

96/05378 Sorptive separation of ethanol-water mixtures with a bi-dispersed hydrophobic molecular sieve, silicalite: Determination of the controlling mass transfer mechanism

96/05378 Sorptive separation of ethanol-water mixtures with a bi-dispersed hydrophobic molecular sieve, silicalite: Determination of the controlling mass transfer mechanism

96/05379 Sorptive separation of ethanol-water mixtures with a bi-dispersed hydrophobic molecular sieve, silicalite: Measurement and theoretical analysis of column dynamics

96/05379 Sorptive separation of ethanol-water mixtures with a bi-dispersed hydrophobic molecular sieve, silicalite: Measurement and theoretical analysis of column dynamics

Pervaporation Properties of Dense Polyamide-6 Membranes in Separation of Water-Ethanol Mixtures

Abstract Several dense polyamide-6 membranes were prepared by casting 7 wt% and/or 10 wt% solutions of polymer in trifluoroethanol. The cast membranes were dried at different temperatures from 25 to 80°C. Sorption and pervaporation properties of PA-6 membranes in water-ethanol mixtures were obtained. The data obtained showed that water was preferentially sorbed into the membrane and transported through the membrane; however, the pervaporation selectivity factor αPV was close to unity at higher concentrations. The selectivity parameters in pervaporation were improved for membranes obtained from 10 wt% polymer and dried at higher temperatures.

放射線グラフト重合法により合成したアクリル酸グラフト膜によるエタノール水溶液からの水選択分離

放射線前照射法を適用して,ポリエチレンフィルムにアクリル酸をグラフト重合した.得られた親水性の膜を使って,パーベーパレーション法により,エタノール水溶液からの水の選択分離性を検討した.その結果,分離係数および透過遠度は,グラフト膜中のカルボキシル基濃度の増加にともなって増大した.例えば,グラフト率220%の膜を使った場合,30wt%エタノール水溶液の分離係数,透過速度はそれぞれ6および4.6kg/(m2・h)であった.さらに,膜への放射線架橋が水の選択分離性に及ぼす効果を調べた.グラフト鎖導入前の架橋と導入後の架橋とを比較した結果,後者の架橋法がエタノール水溶液からの水のパーベーパレーション選択分離に有効であった.グラフト率220%の未架橋膜と後架橋膜の分離性能を70wt%のエタノール水溶液で比較した結果,後架橋膜の分離係数は10倍になった.

Separation of water-ethanol mixtures by pervaporation through composite membranes prepared by concentrated emulsion polymerization: Improvement of the permeation rate with a porogen

The sorption and pervaporation characteristics of hydrophilic-hydrophobic composite membranes are investigated for the water-ethanol mixture. The membranes have been prepared using a concentrated emulsion as precursor. In this emulsion, an aqueous solution of sodium acrylate (SA), N,N′-methylene-bisacrylamide and an initiator constitutes the dispersed phase, and a mixture containing styrene, butylacrylate, hexane and an initiator the continuous phase. The polymerization of this emulsion generates a composite which is used to prepare a membrane in which hydrophilic cells are separated by hydrophobic films. The porogen (hexane) does not participate in the polymerization process and was introduced in the continuous phase of the emulsion in order to generate pores in the films and thus to increase the permeation rate through the membrane. It was found that with increasing SA content of the membrane, both the equilibrium swelling ratio S e and the equilibrium sorption selectivity α s increase monotonically; there is a slight decrease of α s but almost no change of S e with increasing amount of porogen (hexane). The permeation rate Q increases and the separation factor α p decreases with increasing contents of SA and porogen in the emulsion. The best performance, hence the highest value of α p Q, was 67 kg/m 2-hr. The prepared membranes have not changed their pervaporation characteristics after 250 hr of operation.

Optimization of the mechanical properties of polymeric composite membranes prepared via emulsion pathways

A novel composite membrane which is effective in the separation of ethanol-water mixtures by pervaporation was prepared by the concentrated emulsion polymerization pathway. In this method, a concentrated emulsion is employed as a precursor for a hydrophilic-hydrophobic composite from which subsequently the membrane is prepared by polymerization. A mixture of styrene (St) and butyl acrylate (BA) constitutes the continuous phase of the emulsion, while an aqueous solution of sodium acrylate (SA) forms the dispersed phase. The presence of BA in the continuous phase profoundly affects the mechanical properties of the membranes. In its absence, the membrane is brittle; it becomes more rubber like as the concentration of BA increases without becoming too large. It was found that water causes the swelling of the membrane to a much greater extent than ethanol does. The separation factor (α) increases markedly, and the permeation rate through the membrane decreases gradually as the water concentration decreases in the feed. Increasing the content of polysodium acrylate (PSA) results in a higher permeation rate, but the separation factor (α) decreases. At room temperature, the separation factor (α) varies between 23 and 724, and the permeation rate varies between 13 and 246 g/m 2-hr.

Pervaporation of water-ethanol through poly(vinyl alcohol)/chitosan blend membrane

Blend membrane consisting of poly(vinyl alcohol)(PVA) and chitosan was prepared from solvent casting technique for effective separation of ethanol-water mixture by pervaporation. Selectivity toward water and the flux through the blend membrane, crosslinked with glutaraldehyde at the concention of 4×10-6 mol/g, were∼450 and 0.47 kg/m2.hr, respectively.

Separation of ethanol-water mixtures by vapor permeation through cellophane membrane.

Vapor permeation (VaP) using cellophane membrane was compared with pervaporation (PV) for ethanol-water mixtures under isothermal conditions (Mode I). The selectivity of VaP was higher than that of PV through whole feed composition, while the permeation rate of VaP was lower than that of PV. It was observed that the membrane in PV was more swollen than in VaP. In the case (Mode II) which feed vapor was superheated in VaP under keeping downstream pressure constant, the selectivity increased remarkably and the permeation rate decreased. In another case (Mode III) which downstream temperature near the membrane was dropped and the temperature gradient was generated through the membrane in VaP, the permeation rate increased and the selectivity decreased. The influence of temperature to the permeation rate could be expressed by the Arrhenius' correlation only for Mode I. With regard to the influence of downstream pressure, the selectivity of Mode II showed only a slight decrease with downstream pressure, not so much decrease as the usual condition (Mode I).

Separation of ethanol from culture broth by pervaporation with hydrophobic porous membrane.

Separation of ethanol-water mixture from alcoholic fermentation broth in which yeast is suspending is carried out by pervaporation, using hydrophobic microporous hollow fiber membrane of polypropylene. Results show that this membrane has a selective permeation ability of ethanol and has a potential to be applied as a new fermentation system.