Permselectivity of Liquid–Polymer Hybrid Membrane Composed of Carbon Tetrachloride and 2-Hydroxyethyl Acrylate– Acrylonitrile Graft Copolymer for Ethanol–Water Mixture

Abstract

ABSTRACT:A membrane with selective permeability for ethanol was designed for the separation of ethanol from its aqueous solution by pervaporation on the basis of the difference in solubility between two components of the membrane. A liquid membrane was introduced to extend this difference and ethanol in the liquid membrane was isolated by the polymer membrane; that is, a liquid-polymer hybrid membrane was formed. Carbon tetrachloride was used as a liquid membrane, and 2-hydroxyethyl acrylate (HEA) (branch)-acrylonitrile (AN) (backbone) graft copolymer membrane was used as a polymer membrane. The effect of the microphase separated structure of the graft copolymer membrane on permselectivity was studied. The microdomain of the AN moiety displayed more dispersion and a smaller microdomain with decreasing chain length of the backbone polymer. It was found that the plasticizing effect was suppressed effectively by the microphase separated structure and the permselectivity of the graft copolymer membrane for ethanol was higher. When pervaporation of the ethanol-water mixture was carried out using the liquid-polymer hybrid membrane, ethanol completely permeated the liquid-polymer hybrid membrane.KEY Recently, a method has been found for ethanol production by the fermentation of starch, sugar, and cellulose. 1 This method requires a separation process, since ethanol is obtained in about a 5% aqueous solution. An enormous amount of energy is consumed by the distillation generally used for the separation of ethanol and this has prompted the development of a difference separation process. For a continuous and economical operation, a separation process using a polymer membrane has been found. This pervaporation method does not require isolation of the permeate and can be applied to various organic liquid mixtures. 2 Separation of an ethanol-water mixture using various polymer membranes by pervaporation has been reported. These generally involve water permeation through the membrane.3.4 However, it is more practical to permeate ethanol through the membrane since it is a minor component in the mixture produced by biomass.Permselectivity of the polymer membrane for the solvent takes place by two steps in the permeation process, i.e., dissolution and diffusion of the membrane. Therefore, the selectivity of a liquid mixture through the polymer membrane is a function of the difference in solubility and diffusivity of the solvents.5 However, in the case of ethanol permeation from an ethanol-water mixture, even if the solubility of ethanol toward the membrane is practical, the permselectivity of ethanol is not enhanced because of the poor diffusivity of ethanol owing to its molecular size. If a component with low diffusivity such as ethanol in an ethanol-water system is permeated selectively, it is necessary to design a 827

Dielectric and relaxation processes in PEG based polymeric networks

“…The polymer of n-butyl acrylate is still softer and rather tacky at room temperature. These trends to tackier, softer polymer continue to n-dodecyl (lauryl) ester [13][14][15][16][17][18][19][20].…”