Crystallization Model for the SUZ-4 Zeolite and Its Application in the Synthesis of Materials with an Increased Si-to-Al Ratio

Athree-step crystallization model of theSUZ-4 zeolite was clarified based on the evolution of solid and liquidphases in UV-Raman spectra, and the key species, spatiallyorganized 4 MRs, was extracted for synthesizing the SUZ-4with an increased Si-to-Al ratio. The zeolite SUZ-4, with intersecting 10- and 8-memberring (MR)channels, represents an interesting topology with potential in industrialcatalysis. The synthesis of SUZ-4 with a less organic template anda broader elemental composition is essential for its application inthe industry. Understanding the crystallization mechanism of SUZ-4is therefore not just of academic interest. In this study, we proposea three-stage model to categorize the crystallization period of SUZ-4based on the evolution of ultraviolet (UV) Raman spectra: (1) theformation of 4 MR species, (2) the spatial organization of 4 MRs throughthe interaction with an organic template, and (3) the growth of SUZ-4crystals. This model successfully explains the function of the tetraethylammoniumhydroxide (TEAOH) template: accelerating the generation of 4 MRs,directing the formation of the nucleus, and filling the 10 MR channelsin tt.tt. conformation. Based on this knowledge,precursor species at the very beginning of stage 3 were extractedand put into a further period of crystallization with replenishedSi and reduced TEAOH, resulting in an increase of bulk nSi/nAl by 17% and a reduction by 72% of the originalamount of the template.

Automated summary

A three-step crystallization model of SUZ-4 zeolite was proposed based on the evolution of solid and liquid phases in UV-Raman spectra. The spatially organized 4 MRs key species was extracted for synthesizing the SUZ-4 with increased Si-to-Al ratio. Understanding the crystallization mechanism of SUZ-4 is important for its practical application in the industry.