ALKYLAMMONIUM POLYCATIONS AS STRUCTURE-DIRECTING AGENTS IN MFI ZEOLITE SYNTHESIS

Silicate and aluminosilicate MFI-type zeolites are synthesized with di - and triquaternary ammonium cations as structure-directing agents (SD A). Solid-state NMR spectra show that polycations are intact in the as -synthesized zeolites. Materials synthesized with polycationic molecul es are compared to zeolites synthesized with tetrapropylammonium, the normal SDA for MFI-type zeolite. The zeolite nucleation rates and part icle sizes decrease as the net charge of the organic cation increases, i.e. SDA(n+) where n=1, 2 or 3. (C) 1998 Elsevier Science B.V. All ri ghts reserved.