Study On Preparation, Dilute Solution Property Of Membrane Materials And Pervaporation Behavior Of Their Membranes For Organic Mixtures (MeOH/MTBE,Benzene/Cyclohexane)

Two approaches for improved pervaporation performances were developed, which involved the preparation new membrane materials, and amendatory formation process of membrane.All cellulose acetate (CA) membranes were prepared by dry-cast process in three type of casting solvent mixtures AC/THF, AC/CF, AC/CYH and pure solvent AC, respectively. The CA-AC membrane morphology looks like dense, smooth and homogenous, and the morphologies of other three kinds of membranes from CA-AC/THF, CA-AC/CF and CA-AC/CYH seem to be loose and irregular and like cellular, leafy and pore-like, respectively. The average size of the nodule from AFM photography increases with the second solvent, THF, CF, and CYH in order. The permeation flux of CA membranes from the solvent mixture was always higher than that from pure solvent AC, and the flux of methane (JMeOH) increases (the a decreases) with increasing the volume fraction of the second solvent (φsecond solvent) The trend of the JMeOH is Jcyh>Jcf>Jthf at the same φsecond solvent in the casting solvent mixture. JMeOH increases (the a decreases) with increasing operation temperature. The results from dilute solution study for CA polymer display that the Huggins constant kH and association constant km increases with the solvent AC, AC/THF, AC/CF and AC/CYH in order. Thus, JMeOH kH or km, and vice versus for intrinsic viscosity,Blend membranes of CA/ethylene-co-vinylacetate(EVA) from dioxane (DIO)/l,2-dichloroethane (DEC) and DIO/cyclohexane(CYH) were successfully prepared using selective casting solvents and by a novel solution method. The pervaporation performance was studied for separating MeOH/MTBE (methyl tert-butyl ether) mixture with 5 (wt)% MeOH at 35℃. Results showed that the pervaporation properties of blend membranes from DIO/DCE solvent mixture were better than that of blend membrane from DIO/CYH solvent mixture. An optimal composition of blend membrane(CA/EVA WEva=0.1) from DIO/DCE ((φDCE = 0.1) could give high JMeOH = 158 gm-2h-1 compared to pure CA membrane, and maintain large a = 204. The compatibility of blends membrane CA/EVA in different solvent mixture was investigated by viscometry. It was found that CA was compatible withthe EVA in DIO/DCE solvent mixture, and CA was incompatible with EVA in DIO/CYH solvent mixture. The distinct compatibility was due to the different conformation of EVA in two kinds of solvents DCE and CYH. The rule of JMeOH kH or km and Jmcoh was also obtained for blend membrane (CA/EVA) from DIO/DCE solvent mixture, but not obtained from DIO/CYH solvent mixtureBinary blends and their blend membranes of poly (vinyl chloride) and low molecular weight ethylene-co-vinyl acetate copolymer with 38 (wt)% VA content (HPVC/EVA) have been prepared by solution blending. The compatibility of the blends was investigated by viscometry and Fourier transform infrared (FTIR). It was found that the PVC is compatible with the EVA when EVA weight fraction (Weva) is less than 0.20 or larger than 0.50. The blend membranes with Weva 0.15 have good resistance to benzene/cyclohexane mixtures with benzene content up to 50 (wt)% at 30°C. The blend membrane with Weva=0.15 has better pervaporation performance, Jbenzene=65g/m2h and a=15, for the feed with 10 wt % benzene compared to the PVC membranes modified chemically. Meanwhile, the rule of Jbenzene kH and Jbenzene exsits for PVC/EVA in tetrahydrofunan and its membrane performance.Polyacrylonitrile (PAN) was successfully synthesized in DMF by RAFT employing azobis(isobutyronitrile) (AIBN) as the initiator and 2-cyanopropyl-2 dithiobenzoate (CPDB) as the chain transfer agent. Influence of AIBN and CPDB dosage on the polymerization kinetics was discussed. It was found that the polymerization rate was directly proportional to [AIBN]094 and negative exponent to [CPDB], and a kinetic equation was obtained as Rp = k[AJBN]0.94[CPDB}-0.43[M] at65. Number-average molecular weigh of PAN increases with increasing monomer conversion and molecular weight could be controlled and the MWD was narrow (<1.2). The block polymer P(AN-b-MA) wi...