The Current Understanding of Mechanistic Pathways in Zeolite Crystallization

Abstract

Zeolite catalysts and adsorbents have been an integral part of many commercial processes and are projected to play a significant role in emerging technologies to address the changing energy and environmental landscapes. The ability to rationally design zeolites with tailored properties relies on a fundamental understanding of crystallization pathways to strategically manipulate processes of nucleation and growth. The complexity of zeolite growth media engenders a diversity of crystallization mechanisms that can manifest at different synthesis stages. In this review, we discuss the current understanding of classical and nonclassical pathways associated with the formation of (alumino)silicate zeolites. We begin with a brief overview of zeolite history and seminal advancements, followed by a comprehensive discussion of different classes of zeolite precursors with respect to their methods of assembly and physicochemical properties. The following two sections provide detailed discussions of nucleation and growth pathways wherein we emphasize general trends and highlight specific observations for select zeolite framework types. We then close with conclusions and future outlook to summarize key hypotheses, current knowledge gaps, and potential opportunities to guide zeolite synthesis toward a more exact science.

A dual growth mode unique for organic crystals relies on mesoscopic liquid precursors

“…The proposed evolution of the mesoscopic clusters is similar to previous observations, in aqueous solutions, with mesoscopic clusters and dense liquids of lysozyme and olanzapine 31,37,69,112 . Importantly, these observations indicate that amorphous particles are poor precursors for crystal growth in organic media, unlike observations for minerals, e.g., zeolites, that form in aqueous environments via CPA involving disorder-to-order transition of amorphous particles 52,113 . Besides the failure of etioporphyrin-I particles to integrate in the crystal lattice and contribute to growth, they may become embedded within it as gross defects and diminish the crystal quality.…”

Research progress on the preparation of transition metal-modified zeolite catalysts and their catalytic performance for the purification of engine exhausts

“…The general formula of zeolite is M x / n [(AlO 2 ) x (SiO 2 ) y ]· z H 2 O. T represents Si 4+ ions or another trivalent (or tetravalent) cation of an appropriate size and with suitable coordination ability, such as Al 3+ ions, where M is an exchanged cation and the catalytic activity of a zeolite typically depends on the atoms that replace the M position. 25–27 Typically, small-pore zeolites have pore sizes in the range of 0.30–0.45 nm, while medium-pore zeolite openings range from 0.45–0.60 nm and large pore materials have their largest pores in the range from 0.60–0.80 nm. In light of the different pore sizes of small and large pore materials, the entrance to and exit from the intracrystalline void spaces have been defined.…”

Recent advances in zinc-ion dehydration strategies for optimized Zn–metal batteries

“…As one of the most mature porous products for commercialization, zeolites with a variety of ordered sub-nanochannels modified by a variety of functional groups have attracted interest from researchers. 215–217 Zhou's group employed a commercially available 3.0 Å zeolite to further promote the pre-desolvation of Zn 2+ for AZMBs. 205 Raman spectroscopy was also used to study the coordination environment of the electrolyte inside the zeolite channels (Fig.…”