SYNOPSISThe dehydration of aqueous alcohol solutions through asymmetric nylon 4 membranes were investigated using pervaporation processes. The formation of asymmetric pervaporation membranes are discussed in terms of the content of the nonsolvent in the casting solution, polymer concentration, and compositions of the coagulation medium. The effects of the feed composition, feed temperature, and molar volume of the alcohols on the pervaporation performances of the asymmetric membranes are discussed. A separation factor of 4.72 and a permeation rate of 0.78 kg/m2 h for the asymmetric membrane were obtained. Compared to the conventional homogeneous nylon 4 membrane, the asymmetric membrane can effectively overcome the pervaporation performances of the nylon 4 membrane for separation of water-alcohol mixtures. 0 1994 John Wiley & Sons, Inc. I NTRO DUCT1 0 NPervaporation is an attractive separation process for the close boiling-point mixtures, heat-sensitive mixtures, azeotropic and isomeric mixtures, the removal of water from organic liquids, and the removal of organic contaminants from waste Recently, the separation of alcohol/ water mixtures by a pervaporation technique using a dense homogeneous membrane has been given much attention. In a previous article, we investigated various ways such as plasma deposition, homografting and heterografting of 6oCo y-ray irradiation, 5,6 and chemical grafting7 to improve the membrane morphology and pervaporation performances of a dense homogeneous nylon 4 membrane. One of the disadvantages of the dense homogeneous membrane for pervaporation is the low permeation rate, especially with highly selective membrane materials. Thus, we attempted to prepare an asymmetric nylon 4 membrane via a wet phase inversion method to increase the permeation rate for pervaporation of aqueous alcohol solutions, while the selectivity remains the * To whom correspondence should be addressed. Vol. 53, 999-1009Vol. 53, 999- (1994 The objective of this article was concerned with the preparation of asymmetric membranes via a wet phase inversion method. The effects of the feed composition, swelling degree, and molar volume of the alcohols on the pervaporation performances for the asymmetric nylon 4 membranes were studied. Journal of Applied Polymer Science,

ABSTRACT:The membranes of pure poly(4-methyl-l-pentene) (TPX) and the 4-vinylpyridine (4-VP) modified TPX membranes, TPX/P4-VP, were prepared for pervaporation. The introduction of high hydrophilic 4-VP monomer into the TPX matrix was done by free radical polymerization to form the TPX/P4-VP membrane. The separation factor and the permeation rate of TPX/P4-VP membranes are higher than those of the unmodified TPX membranes for pervaporation of aqueous acetic acid solution. FTIR spectra and water permeation behavior were utilized to study the permeation mechanism of aqueous acetic acid solution through the TPX/P4-VP membranes. A good relationship was obtained between the feed water concentration and water permeation rate by applying the Michaelis-Menten equation.KEY WORDS TPX / Acetic Acid-Water Mixture/ Poly(4-m_ethyl-l-pentene) / 4-Vinylpyridine / Pervaporation / The membrane separation technique is considered for the separation of organic mixtures, such as the azeotropic and close boiling point mixtures or structural isomers. Recently, most efforts on pervaporation have focused on water/ethanol separation. 1 -3 Nevertheless, among the organic liquids, acetic acid is an important commodity product in the chemical industry. Therefore, much attention has been directed to the separation of the acetic acid-water mixture by pervaporation. 4 So far, membrane materials, such as polyimide, 5 poly( 4-vinylpyrine-ca-acrylonitrile ), 6 poly(vinyl alcohol), 7 poly(acrylic acid-ca-acrylonitrile), 4 etc., were effectively used for the dehydration of the acetic acid-water mixtures by pervaporation. We reported previously that the performance of TPX membranes for the acetic acid/water separation can be improved using TPX/Ethylene vinylacetate membranes. 8 Yoshikawa et al. 9 examined two special interactions assuming a fixed carrier mechanism, that is, hydrogen bonding and coulombic t To whom correspondence should be addressed.interaction. Thus, the objective of this article is to utilize the TPX/P4-VP membrane which possesses high chemical resistance, hydrophilicity, and mechanical strength for the dehydration of acetic acid by pervaporation. The hydrogen-bonding interaction between the pyridine moiety of membrane and carboxylic acid in the feed is discussed. In addition, the permeation mechanism of aqueous acetic acid solution through modified TPX membranes was characterized by FTIR spectra and water permeation behavior. EXPERIMENT AL Material4-Vinylpyridine ( 4-VP), cyclohexene, and chloroform were purchased from Merck Company. TPX (MX-002) was supplied by Mitsui Company in Japan. The initiator, dibenzoylperoxide (BPO), was purified by traditional methods and the 4-VP monomer was distilled under reduced pressure in vacuum.

SYNOPSISFor dehydrating separation aqueous alcohol solution by the pervaporation technique, a chemical modified poly(4-methyl-1-pentene) (TPX) membrane was synthesized with 4vinylpyridine (4-VP). The morphology, crystallinity, and thermodegradation properties were investigated by scanning electron microscopy, X-ray, and thermogravimetric analysis, respectively. The modified T P X membrane possessed higher stability than that of the unmodified T P X membrane. The effects of feed temperature and poly(4-VP) (P4-VP) content of the modified T P X membranes on the performances of pervaporation were studied.A separation factor of 133 and a permeation rate of 115 g/m2h can be obtained for the TPX/P4-VP membrane with 3.0 wt % P4-VP content. 0