(118a) Insights into the Incorporation and Removal of Heteroatoms in Zeolite Catalysts

Metal-incorporation in zeolites can yield promising materials for diverse catalytic applications due to their enhanced physiocochemical properties. Optimization of these properties requires unravelling the complex crystallization mechanism(s) of heteroatom incorporation in zeolite structures, which is relatively elusive owing to the challenges of characterizing zeolite growth from diverse precursor species. The majority of zeolite studies rely on ex situ techniques as a result of the complex growth media and conditions employed in zeolite syntheses. We have pioneered methods to probe zeolite growth in situ using high temperature atomic force microscopy (AFM) to visualize zeolite surface growth at a near molecular level. We have shown that zeolite crystallization is predominantly a result of nonclassical pathways (e.g., crystallization by particle attachment) with minor contributions from classical layer-by-layer growth via monomer incorporation.

In this presentation, we report our recent observations of zeolite faujasite (FAU) growth. We recently showed that FAU stability and corresponding catalytic performance is enhanced by the incorporation of zinc; however, the mechanism of FAU formation in the presence of Zn remains unclear. Here we will present our study of Zn-FAU crystallization using in situ AFM to probe the inhibitory effect of metal incorporation. We will also discuss demetallation approaches for various heteroatoms in commercially relevant zeolites of different pore sizes, such as *BEA, MFI, and CHA frameworks. The removal of these metals has the potential to introduce defects in the zeolite structures that can stabilize extra-framework metals (i.e., active sites for reactions), thereby tuning physicochemical properties beyond their pristine crystalline counterparts.