Separation of various alcohols and water through a membrane was carried out by means of a hydrogen‐bonding interaction. A membrane obtained from poly(maleimide‐co‐acrylonitrile) was effective for a selective separation of water from aqueous alcohol solution by pervaporation technique. Spectroscopic analyses verified that this high selectivity was attributed to the hydrogen‐bonding interaction between water and maleimide units in the membrane.
A new polymer containing the N-substituted succinimide moiety poly(1-[ (2-methylpropenoyl)oxy]succinimide-co-acrylonitrile) (poly( 1-co-2)) was synthesized. The sequence distributions of the copolymers were investigated by 13C NMR spectroscopy. A terminal model was used to interpret the propagation process in the copolymerization. The reactivity ratios in the solution polymerization at 60 "C were evaluated rl = 2.40 and r2 = 0.42. Radical reactivity indices and frontier eledron densities were calculated. The membrane prepared from this copolymer showed a selective separation of water from a water-ethanol mixture by a pervaporation technique. The separation factor toward water reached over 2000.
IntroductionSelective separations of water from aqueous ethanol solution is of great interest in connection with the production of ethanol via fermentation of biomasses that are rich in sugar and starch.On the basis of this point of view, we have prepared polymer membranes containing a pendant imide g r~u p , l -~ a N-substituted imide group,l or a carbonyl group6p6 that have a strong interaction with water through hydrogen bonding. Poly(maleimide-co-acrylonitrile)1v2 and poly-(acrylic a~id-co-acrylonitrile)~~~ membranes gave high separation factors, which reached over 700 for water. We concluded that high selectivity toward water through these two membranes was attained by the selective hydrogenbonding interaction between water and maleimide or carboxylic acid in these membranes.2p6 It was also found that not only the amount of functional groups, which interacted preferentially with water in the membrane, but also the environment (membrane polarity) around functional groups influenced the separation characterization for the water-ethanol m i~t u r e .~ The present paper reports the pervaporation of a novel synthetic membrane containing not only pendant a Nsubstituted succinimide moiety but also a pendant ester group and its use for separation of a water-ethanol mixture by pervaporation.
ABSTRACT:Pervaporation of aqueous ethanol solution was carried out through three synthetic polymer membranes each containing an imide group, poly(N-phenylmaleimide-costyrene)s and a polymer having an N-substituted phthalimide group. These membranes selectively permeated water. The water was assumed to be permeated by a carrier mechanism utilizing a carbonyl moiety of the imide group as a carrier, while ethanol was permeated through membranes without specific interaction between ethanol and membranes.KEY WORDS Pervaporation I Permselectivity I N-Substituted Imide Group I Carrier Mechanism I Michaelis-Menten Type Profile I Separation technique by membranes are regarded as very promising means for energy saving conservation because of their high separation efficiency. The pervaporation technique is a potential method for specific and selective separation of neutral organic compounds such as organic mixtures.In a previous paper, the authors reported the separation of water from aqueous alcohol solutions by pervaporation through poly-(maleimide-co-acrylonitrile ), 1 -3 poly(maleimide-co-styrene),3 and poly(acrylic acid-coacrylonitrile)4 membranes. In particular, poly(maleimide-co-acrylonitrile) and poly-(acrylic acid-co-acrylonitrile) membranes gave high separation factors, exceeding 700 for water. The authors concluded that the high selectivity toward water through poly(maleimide-co-acrylonitrile) membrane was possible by the selective hydrogen-bonding interaction between water and maleimide units in the poly(maleimide-co-acrylonitrile) membrane. 2 Not only the number of functional groups, which interact preferentially with water in the membrane, but also the environment (membrane polarity) surrounding the functional groups have been found to determine the separation characteristics of water-alcohol (ethanol) binary mixtures. 3In the present paper, attention is focussed on the N-substituted imide group as a carrier and poly(N-phenylmaleimide-co-styrene)s and the polymer containing the N-substituted phthalimide group as a side chain. The permeation and separation of water-ethanol mixtures through these polymer membranes are discussed.
EXPERIMENTAL
MaterialsN-phenylmaleimide (1) was purified by recrystallization from cyclohexane solution and melted at 89.5-90.0°C. Styrene (2) and 2,2'-azobisisobutyronitrile (AIBN) were purified by the usual methods. Mixtures of 4-and 3-363
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