SYNTHESIS OF ZSM-5 FILMS AT ELEVATED GRAVITY

ZSM-5 zeolite films, with a thickness from 100 to 1,000 mu m, have bee n synthesized in a colloidal silica-TPABr gel system without a support and under elevated gravity (16 G). Under high gravity, the films obta ined were completely crystallized and were stronger than those produce d under normal gravity. Parameters that influence the film crystalliza tion process such as water content(H2O/SiO2 ratio), alumina to silica ratio, and the reaction gel alkalinity were investigated. The optimum value of the water content was found to be approximately 33 in the syn thesis of these films. The film growth became difficult with increasin g aluminum content in the reaction mixture. The alkalinity of the reac tion gel had to be increased at a higher aluminum content to form a co ntinuous film. The alkalinity of the synthesis mixture was also used t o control the thickness of the film. In zeolite film formation, the ef fect of providing seeds in the reaction mixture was also investigated. The thickness of the resulting films varied with the configuration of seeds used. In addition, thick zeolite films were produced when a vyc or glass plate treated by a leaching and an unconsolidating process wa s used as a support. (C) Elsevier Science Inc. 1997.