A study of the dealumination methods for zeolite L

The dealumination of zeolite L was attempted by steaming, treatment with am monium hexafluorosilicate, and with silicon tetrachloride. The zeolite fram ework can be dealuminated most effectively through ion exchange into the so dium form followed by treatment with silicon tetrachloride. The crystalline structure remains essentially intact. FTIR spectroscopy and Si-29 MAS-NMR attest to the most intense dealumination. However, after the treatment with silicon tetrachloride, the zeolite loses its nitrogen adsorption capacity almost entirely, probably because of pore blockage by amorphous silica and/ or alumina. Steaming leads to intense structural collapse, as does treatmen t with ammonium hexafluorosilicate beyond a limited extent. (C) 2000 Elsevi er Science B.V. All rights reserved.