SYNTHESIS OF LEV-TYPE ZEOLITE FROM AQUEOUS NONALKALINE FLUORIDE ALUMINOSILICATE GELS

By using an original synthesis procedure in which the OH- ions are rep laced by the F- anions as the mineralizing agent, the preparation of a LEV-type zeolite was possible from near-neutral nonalkaline reaction mixtures containing 1-azabicyclo[2.2.2]octane (quinuclidine) and optio nally methylamine. The LEV-type zeolite could be synthesized only with a very narrow range of Si/Al molar ratios in the framework, i.e., bet ween about 8 and 11. The obtained products appear as bail-like aggrega tes of platelet crystallites. The samples were characterized through t he usual techniques, e.g., XRD, STEM, d.t.a., and t.g.a., C-13, Si-29, Al-27, and F-19 MAS n.m.r. spectroscopy. In the presence of quinuclid ine alone, the occluded species is the quinuclidinium cation. In the p resence of quinuclidine and methylamine simultaneously, a transformati on reaction takes place during the synthesis, and the incorporated org anic species are, besides the still preponderant quinuclidinium ion, t he N-methylquinuclidinium ion and a cationic polymer identified as pol yethylene piperidine. The low content of incorporated fluoride (0.3-0. 6 wt%) corresponds to a variety of species, for instance to AlF to SiF groups, and also possibly to a F- ion trapped in the structure.