SDA-Free Hydrothermal Synthesis of High-Silica Ultra-nanosized Zeolite Y

Despite having been used in hydrocracking processes for decades, zeolite Y is still nowadays the subject of intense research aiming at improving its physicochemical properties. Here, and for the first time, the synthesis of zeolite Y nanocrystals prepared in organic template-free medium, featuring both extremely reduced dimensions (mean diameter below 30 nm) and a high silicon to aluminum ratio (Si/Al ≈ 2.2), is reported. The singularity of the protocol lies in the progressive adding of a silica source during synthesis combined with the use of prolonged aging times. These high-silica ultra-nanosized zeolite Y crystals display excellent textural properties (V_micropore = 0.33 cm³/g and S_BET = 830 m²/g), comparable to their microsized counterparts. In this work, the extensive study of the influence of various parameters (i.e., gel composition, aging time, and crystallization conditions) intended for the optimization of the synthesis protocol is also presented.