1-Benzyl-1-methyl-hexamethylenammonium and some of its fluorine-containing derivatives as structure directing agent for the synthesis of all-silica zeolites

Abstract

The 1-benzyl-1-methyl-hexamethylenammonium (BMHM) cation under the appropriate synthesis conditions is a good structure directing agent (SDA) for the synthesis of pure silica zeolite beta in fluoride media. The chemical properties of this cation change with the replacement of a fluorine atom by a hydrogen atom in the aromatic ring and the nature and morphology of the crystal phases thus obtained are affected. The 1-orthofluorobenzyl-1-methyl-hexamethylenammonium allows the crystallization of all-silica beta zeolite but the morphology of crystals is very different from that of beta obtained with the all-hydrogen counterpart. The meta-F derivative leads to a mixture of three phases, Beta, nonasil (NON) and a characteristic unidentified phase, whereas by using the para-F cation only, nonasil is obtained.