(285a) Permeation and Separation Characteristics of Mfi Type Zeolite Membranes on Zirconia Intermediate Layer by Template-Free Secondary Growth Method

Silicalite membranes were prepared by template-free secondary growth method in order to minimize the chance for defects and intercrystalline pores that form during the template removal step by calcinations. The phase structure, the morphology and thickness of the supported membranes were characterized by using XRD and SEM. Membrane quality was examined by pervaporation of 1,3,5-triisopropylbenzene (TIPB), p-xylene and o-xylene and gas permeation/separation test. XRD patterns indicated that silicalite film could grow well without an organic template on the surface of the silicalite seeded alumina support and the thickness of silicalite membrane was around 3 µm. Reproducibility of preparation of silicalite membranes was confirmed and membrane thickness could be controlled by dip coating times with stable suspension. Pervaporation results showed good quality of silicalite membranes (TIPB flux: <0.01 kg×m-2×s-1, p/o-xylene separation factor: ~20) and the membrane performance was largely affected by the dip coating times of silicalite suspension. The p-xylene separation performance (p/o-xylene selectivity, p-xylene flux) for silicalite membranes with ZrO2 intermediate layer was not as good as that for the membranes without ZrO2 intermediate layer, however, membrane quality could be improved by annealing the membranes (silicalite seed layer) prior to template removal. Thermal and hydrothermal stability of silicalite membranes will be also examined.