Synthesis and characterization of silicalite membrane for separation of mixed xylenes

Abstract

To synthesize the silicalite membrane for the separation ofmixed xylenes. The silicalite membrane was prepared by the hydrogel formula. Thecomposition of the gel was 0.1TPABr-0.05Na(,2)O-SiO(,2)-80H(,2)O. Supports used inthis research were borosilicate discs and silica fiber. It was found that the surfacearea of the borosilicate disc facilitated the crystal growth of silicalite more thanthat of the silica fiber. The silicalite membrane was calcined at 500 (+,ฐ)C for 6hours to remove organic templates inside the pores of silicalite crystals. SEM andXRD were used to characterize the membranes. The SEM results showed that thetreatment of the support affected the coating of the silicalite membrane onto thesupport. It was also found that the pore size of the support had an effect on thesize of the crystal and the thickness of membrane. Silicalite membrane formed on thesupport with larger pore size had bigger crystal size and more thickness than the onewith small pore size. The XRD patterns corresponded to that of the standardsilicalite. The silicalite membrane was sealed with 3-way Pyrex glass by gas weldingor epoxy resin. The better results were obtained when epoxy resin was used as abinder. The separation of mixed xylenes using this membrane was investigated by gaschromatographic technique. The experiments were carried out at 140 (+,ฐ)C withcarrier gas pressure of 0.5 bar. The chromatograms showed that pxylene and m-xylenein mixed xylenes could be separated from o-xylene by using this synthesizedsilicalite membrane. The separation factor of p-xylene and m-xylene to mixed xyleneswas 1.47 and that of o-xylene to mixed xylenes was 0.04.