Influence Of CA Preparing Method And Modified β-CD Blend Membrane On Pervaporation

The substitution of pervaporation for traditional separation in organic mixtures is of energy-saving and environment-protecting significance.In this paper, pervaporation of two kinds of organic mixtures is investigated: one is using CA membrane and CA-EVA (ethylene-co-ethylene acetate) composite membrane for methanol removal from MTBE (methyl t-butyl ether), focused on the influence of casting solvent mixtures; the other is utilizing proper membrane stuff and additive to separate p-xylene from m-xylene.For the separation of methanol/MTBE, the casting solvent mixtures were investigated in detail, it was found that the positive relationships between Huggins parameter (kH) and permeation flux (J) were due to the casting solvent mixtures. Thus, the separation performance could be improved by adjusting the casting solvent mixtures. At the same time, it was indicated that the improved separating properties of membranes that had been marinated in methanol was pertinent to the degree of crystallization of polymer chains in membrane. Also the effect of temperature and solvent mixtures on the performance of CA-EVA composite membrane was related with reciprocity of polymer chains in membrane.As to the separation of p-xylene/m-xylene, in order to blend polymer hydrophobe with P -CD which is preferential to adsorb p-xylene , etherified P -CD was synthesized using benzyl chloride (PhCH2Cl). The influences of etherification conditions on the reaction conversion and the degree of substitution of etherified P -CD were investigated. The reaction conversion increases with the increasing of molar ratio of PhCr^Cl: P -CD and the concentration of P -CD. The degree of substitution of etherified P -CD increases greatly with the increasing of molar ratio of PhCFbCl: P -CD ,but there is no significantly change on the degree of substitution with other reaction conditions such as temperature, time and concentration of P -CD. Meanwhile, the pervaporation of PVB membrane containing etherified P -CD and CA membrane containing etherified P-CD were measured respectively, obtaining a permeation flux greater than other membranes with P-CD.