Synthesis and Physicochemical Characterization of an Aluminosilicate Zeolite with IFR Topology, Prepared by the Fluoride Route

Abstract

An aluminosilicate zeolite with IFR topology can be synthesized in a wide range of Si/Al ratios (Si/Al ≥ 20) using benzylquinuclidinium as a structure-directing agent in the presence of fluoride anions. The phase selectivity of the crystallization depends on both the Al and the water content of the synthesis mixture, and by adjustment of the degree of dilution of the mixture, it is also possible to obtain zeolite Beta. The isomorphous substitution of Si by Al in the IFR framework and the acidity of the calcined zeolite has been confirmed by a number of physicochemical techniques. The calcined IFR material contains acid sites of medium strength with large pores and a large void volume. Partial dealumination occurs during calcination, but N2 and pyridine adsorption experiments do not indicate any pore blocking. The aluminosilicate IFR zeolite contains unusual acid sites that are involved in relatively strong hydrogen bonds. Besides the well-known 1H NMR chemical shift for acid sites at 3.9 ppm and the IR band at 3629 cm-1, the hydrogen-bonded acid sites are characterized by 1H NMR chemical shifts of 5.2 and 6.3 ppm and a broad unresolved IR band at 3488 cm-1.