A study of the dealumination methods for zeolite L

Abstract

The dealumination of zeolite L was attempted by steaming, treatment with ammonium hexafluorosilicate, and with silicon tetrachloride. The zeolite framework can be dealuminated most effectively through ion exchange into the sodium form followed by treatment with silicon tetrachloride. The crystalline structure remains essentially intact. FTIR spectroscopy and 29Si 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 treatment with ammonium hexafluorosilicate beyond a limited extent.