Pervaporation Separation of Xylene Isomers by Hybrid Membranes of PAAS Filled with Si lane-Modified Zeolite

Silicalite-1 zeolite was modified with 3-aminopropyltriethoxysilane (APTES) and then loaded into poly(acrylic acid) sodium (PAAS) to prepare PAAS/silicalite-1 hybrid pervaporation membranes for the separation of xylene isomer mixtures. Characterization by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopies confirmed that chemical modification on the zeolite surface had taken place. Based on sorption equilibrium experiments, the diffusion coefficients of permeates in the membrane were obtained, and the order of the diffusion coefficients of xylene isomers was found to be D-o < D-m < D-p An investigation of the effects of the original versus modified zeolite loading on the pervaporation performance was performed. With the original zeolite, the permeation flux of the binary xylene mixtures showed little change, whereas the selectivity of the hybrid membrane exhibited some enhancement. After modification of the zeolite surface, the selectivity of the hybrid membrane was clearly improved, the permeation flux of the membrane decreased slightly, and the maximum separation factors of the p-/o-xylyne (alpha(p/o)) and p-/m-xylene (alpha(p/m)) mixtures were determined to be 2.62 and 2.68, respectively. The experimental results revealed that the modification promoted the compatibility of the PAAS and silicalite-1 zeolite interface.