Preparation of supported Sil-1, TS-1 and VS-1 membranes - Effects of Ti and V metal ions on the membrane synthesis and permeation properties

The incorporation of titanium and vanadium metal ions into the structural f ramework of MFI zeolite imparts the material with catalytic properties. The se zeolites are good candidates for catalytic membranes. The Sil-1, TS-1 an d VS-1 membranes were grown on pre-seeded porous stainless steel support us ing hydrothermal synthesis method. The effects of silica and metal (i.e. Ti and V) contents, template concentration and temperature on the zeolite mem brane growth and morphology were investigated. The addition of Ti and V met al ions inhibits the zeolite growth and, thus, restricting the amount of me tals (i.e. Ti and V) that can be effectively incorporated into the membrane without compromising its separation performance. Optimum Si and TPAOH conc entrations were identified for the synthesis of well-intergrown zeolite mem branes. An increase in the synthesis temperature can result in a change in film crystallographic orientation and the appearance of imperfections in th e form of imbedded zeolite crystals. Single gas permeation experiments were conducted for noble gases (He and Ar), inorganic gases (H-2, N-2, SF6) and hydrocarbons (methane, n-C-4, i-C-4) to determine the separation performan ce of these membranes. The results indicate that the gas transport through Sil-1 and VS-1 membranes is predominantly through the zeolite pores and tha t the presence of vanadium in VS-1 has significant influence on the permean ce of adsorbed gases (e.g. hydrocarbons). Laminar flow is important for the TS-1 membrane that exhibited microscopic cracks. (C) 2001 Elsevier Science B.V. All rights reserved.