Designing ABC-6 family small pore zeolites by epitaxial growth approach

Abstract

Aluminosilicate small pore zeolites belonging to ABC-6 family play crucially important roles in the high methanol conversion with the high selectivity of light olefins, gas separation and storage, and selective catalytic reduction of NOx. In this work, we report a general method, called the epitaxial growth approach, for designing ABC-6 family small pore zeolites. It is mainly realized through the epitaxial growth on the nonporous SOD-type zeolite in the presence of inorganic cations (Na+ and K+) combined with a variety of organic structure directing agents (OSDAs). In this case, a series of ABC-6 family small pore zeolites such as ERI-, SWY-, LEV-, AFX-, and PTT-type zeolites have been successfully synthesized within a few hours. More importantly, the advanced focused ion beam (FIB) and the low-dose high-resolution transmission electron microscopy (HRTEM) imaging technique have been utilized for unraveling the zeolite heterojunction at the atomic level during the epitaxial growth process. It turns out (222) crystallographic planes of the SOD-type zeolite substrate provide unique pre-building units, which facilitate the growth of targeted ABC-6 family small pore zeolites along its c-axis. Moreover, the morphologies of ERI-type zeolite can also be tuned through the epitaxial growth approach, achieving a longer lifetime in the methanol conversion.