Germanosilicate zeolite ITQ-44 with extra-large 18-rings synthesized using a commercial quaternary ammonium as a structure-directing agent

Abstract

Germanosilicate zeolite ITQ-44 with extra-large 18-rings has been hydrothermally synthesized by using a commercial benzyltriethylammonium bromide (denoted as SDA-1) as structure-directing agent (SDA). The crystallization field and the influence of various synthetic factors on the synthesis of ITQ-44, such as the crystallization temperature, the crystallization time, the Si/Ge ratio, and the amount of the F⁻ and water have been studied. The as-synthesized ITQ-44 has been characterized by XRD, ICP, CHN, TG, SEM, NMR, N₂ adsorption and NH₃-TPD. The results indicate that use of SDA-1 cations could lead to a pure phase of ITQ-44 in a wide synthetic range and remain intact in the final product. The framework structure of ITQ-44 is maintained at 500 °C. B, Al and Ga atoms can be introduced into the framework of germanosilicate ITQ-44, which produces Lewis acid sites in the framework. This work offers the possibility to synthesize extra-large pore germanosilicate zeolites with simple and commercial SDAs, which is important for the practical applications of germanosilicate zeolites.