Silicalite-1/PDMS Hybrid Membranes on Porous PVDF Supports: Preparation, Structure and Pervaporation Separation of Dichlorobenzene Isomers

Separation of dichlorobenzene (DCB) isomers with high purity by time- and energy-saving methods from their mixtures is still a great challenge in the fine chemical industry. Herein, silicalite-1 zeolites/polydimethylsiloxane (PDMS) hybrid membranes (silicalite-1/PDMS) have been successfully fabricated on the porous polyvinylidene fluoride (PVDF) supports to first investigate the pervaporation separation properties of DCB isomers. The morphology and structure of the silicalite-1 zeolites and the silicalite-1/PDMS/PVDF hybrid membranes were characterized by XRD, FTIR, SEM and BET. The results showed that the active silicalite-1/PDMS layers were dense and continuous without any longitudinal cracks and other defects with the silicalite-1 zeolites content no more than 10%. When the silicalite-1 zeolites content exceeded 10%, the surfaces of the active silicalite-1/PDMS layers became rougher, and silicalite-1 zeolites aggregated to form pile pores. The pervaporation experiments both in single-isomer and binary-isomer systems for the separation of DCB isomers was further carried out at 60 degrees C. The results showed that the silicalite-1/PDMS/PVDF hybrid membranes with 10% silicalite-1 zeolites content had better DCB selective separation performance than the silicalite-1/alpha-Al2O3 membranes prepared by template method. The permeate fluxes of the DCB isomers increased in the order of m-DCB < o-DCB < p-DCB both in single-isomer and binary-isomers solutions for the silicalite-1/PDMS/PVDF hybrid membranes. The separation factor of the silicalite-1/PDMS/PVDF hybrid membranes for p/o-DCB was 2.9 and for p/m-DCB was 4.6 in binary system. The permeate fluxes of the silicalite-1/PDMS/PVDF hybrid membranes for p-DCB in p/o-DCB and p/m-DCB binary-isomers solutions were 126.2 g center dot m(-2)center dot h(-1) and 104.3 g center dot m(-2)center dot h(-1), respectively. The thickness-normalized pervaporation separation index in p/o-DCB binary-isomers solutions was 4.20 mu m center dot kg center dot m(-2)center dot h(-1) and in p/m-DCB binary-isomers solutions was 6.57 mu m center dot kg center dot m(-2)center dot h(-1). The results demonstrated that the silicalite-1/PDMS/PVDF hybrid membranes had great potential for pervaporation separation of DCB from their mixtures.