Yi-Chieh Wang

Dehydration of acetic acid by pervaporation through an asymmetric polycarbonate membrane

Abstract Dehydration of acetic acid by pervaporation through an asymmetric polycarbonate membrane was investigated. Investigations focused on the effects of feed composition, degree of swelling, and the molar volume of non-solvent additive on the pervaporation performances. The membrane formation systems are discussed in terms of the presence of a nonsolvent in the casting solution, the kinds of coagulation media, and the polymer concentration. The rate of liquid–liquid demixing decreases with increasing alcohol molar volume of the coagulation medium. The durability of the asymmetric polycarbonate membranes with n -hexanol additive was tested for 3 wt.% aqueous acetic acid solution at 25°C for two months and it was found to be stable.

Dehydration of water–alcohol mixtures by pervaporation and vapor permeation through surface resintering expanded poly(tetrafluoroethylene) membranes

For the purpose of separating aqueous alcohol mixtures by the use of the pervaporation and vapor permeation techniques, a surface resintering expanded poly(tetrafluoroethylene) (e-PTFE), membrane was investigated. The surface properties of the modified e-PTFE membranes were characterized by atomic force microscopy, scanning electron microscopy, and contact angle meter. The X-ray diffraction measurements show that the crystallinity of the e-PTFE membrane decreases with increasing the surface resintering temperature. The surface roughness decreases with the surface resintering temperature increases. The membrane exhibited water selectivity during all process runs. The effects of feed composition, surface resintering temperature, and molar volume of the alcohols on pervaporation and vapor permeation were investigated. Compared with the e-PTFE membrane without surface modified, the e-PTFE membrane with surface resintering treatment effectively improve the separation factor for pervaporation of aqueous alcohol mixtures. The separation performances of e-PTFE membranes in vapor permeation are higher than that in pervaporation.

Application of aromatic polyamide membranes for pervaporation and vapor permeation

Abstract In this article, three types of aromatic polyamides were prepared by the direct polycondensation of bis[4-(4-aminophenoxy) phenyl] diphenyl methane (BAPDM) with various of aromatic diacids such as terephthalic acid (TPAc), 5-tert-butylisophthalic acid (TBPAc), and 4,4′-hexafluoroisopropylidenedibenzoic acid (6FDAc). The pervaporation and vapor permeation performance of the above novel aromatic polyamide membranes for dehydrating an aqueous alcohol solution was investigated. Compared with pervaporation, vapor permeation effectively increases the perm-selectivity of water. Moreover, the effect of aromatic diacids on the polymer chain packing density, pervaporation, and vapor permeation performance was investigated. It was found that the permeation rate can be increased by introduction of a bulky group into the polymer backbone.

APPLICATION OF PERVAPORATION AND VAPOR PERMEATION PROCESSES TO SEPARATE AQUEOUS ETHANOL SOLUTION THROUGH CHEMICALLY MODIFIED NYLON 4 MEMBRANES

ABSTRACT The pervaporation performance of a nylon 4 membrane, chemically grafted by N,N-dimethylaminoethyl methacrylate (DMAEM), DMAEM-g-N4, was studied by measurement of the permeation ratio and the pervaporation separation index. It was found that the water permselectivity and permeationrate for the chemically modified Nylon 4 membrane were higher than those of the unmodified Nylon 4 membrane. Optimum pervaporation results, a separation factor of 28·3, and a permeation rate of 439 g/m2-h, were obtained when the degTee of grafting was 12·7%. It was also found that all the permeation ratios at low temperature were less than unity. In addition, compared with pervaporation, vapor permeation effectively increases the permselectivity of water.

Pervaporation of aqueous alcohol mixtures through a chemically grafted glycidyl methacrylate on to poly(4-methyl-1-pentene) membrane

Abstract To improve the pervaporation performances of a poly(4-methyl-1-pentene) (TPX) membrane, this study attempts to utilize chemical initiation which includes a hydrophilic monomer of glycidyl methacrylate (GMA) homografted on to poly(4-methyl-1-pentene) (TPX-g-PGMA). The sulfonating process was also applied to improve the hydrophilicity of the TPX-g-PMGA membrane. The effects of feed composition, feed temperature and molar volume of alcohol on the pervaporation performances of the modified TPX membrane were investigated. The water permselectivity and permeation rate for both modified TPX membranes were higher than those of the unmodified TPX membrane. The separation factor towards water and the permeation rate through the sulfonated TPX-g-PGMA membrane (TPX-g-PGMAS) with a degree of grafting 5.8% were 49 and 100 g/m2hr, respectively.

EFFECT OF SURFACE RESINTERING ON THE SURFACE MORPHOLOGY AND VAPOR PERMEATION PROPERTIES OF SKIVED POLY(TETRAFLUOROETHYLENE) MEMBRANES

Surface sintering of skived poly(tetrafluoroethylene) membrane was carried out to improve the water permselectivity of the membrane. The surface morphologies of the modified and unmodified membranes were studied by scanning electron and atomic force microscopy. The results indicate that the surface sintering process can make the surface denser and smoother, resulting in higher water permselectivity but lower permeation rate. In addition, the vapor permeation performances were strongly related to the surface resintering temperature.

Pervaporation of aqueous alcohol mixtures through functionalized syndiotactic poly(styrene-co-4-methylstyrene) membrane

Abstract The pervaporation performances of a series of functionalized syndiotactic poly(styrene-co-4-methylstyrene) (SPSM) membranes for various alcohol mixtures were investigated. The effect of functionalization on the thermal properties and polymer structure of the SPSM membranes were also investigated. The crystallinity of the functionalized SPSM membrane is lower than that of the unfunctionalized SPSM membranes. The water molecules preferentially permeate through the SPSM membranes. Compared with unfunctionalized SPSM membranes, the functionalized SPSM membrane effectively increases the membrane formation performances and the pervaporation performances. The optimun pervaporation performance (a separation factor of 510 and permeation rate of 220 g/m2h) was obtained by the bromination of SPSM (SPSMBr) membrane with a 90wt% aqueous ethanol solution.