Bo Shuang,Wang Tianlong,Lv Tianming,Wu Huifang,Feng Ziyi,Miao Lei,Feng Zhaochi,Ren Limin,Meng Changgong
ERB-1 zeolite emerges as a key bridging material for crafting heteroatom-containing MWW for versatile catalytic applications. In this study, we developed a solvent-free strategy facilitated by high-temperature condition and seed assistance, streamlining the synthesis of ERB-1 zeolite. This novel approach not only significantly reduces the growth time to 12 h compared to the conventional 168-h hydrothermal synthesis but also enhances product yield while minimizing waste generation. Benefiting from the platelet seeds and the grinding force, a distinct non-classical growth pathway, involving nanoparticle attachment, epitaxial growth, anisotropic assembly, and crystallization, was observed in the solvent-free synthesis. Through heteroatom substitution, pillared Sn-MWW was successfully prepared, exhibiting remarkable stability and catalytic performance in the Bayer-Villiger oxidation reaction of 2-adamantanone. Our findings present a simple and cost-effective way for rapid synthesis of MWW zeolite, with implications extending to diverse catalytic applications.
As robust heterogeneous catalysts, stannosilicate zeolites (in particular Sn-Beta) exhibit excellent catalytic performance in aqueous Baeyer-Villiger oxidation due to their unique activation ability of carbonyl group. For a specific Sn-containing zeolite, pore-engineering and hydrophobicity are generally two coupled factors to impact catalytic behavior. How to distinguish the function of each factor in this selective oxidation is still a pending question. Bearing this in mind, five stannosilicate zeolites (Sn-MFI, Sn-MWW, Sn-Beta, Sn-MCM-41, and Sn-Y) were prepared to establish the relationship between the structure (Lewis acidity, pore-engineering, and hydrophobicity) and catalytic performance. Particularly, hierarchical Sn-Y zeolite was post-synthesized by a simple solid-state ion-exchange method, where Sn 4+ ions were incorporated into zeolite framework via reacting with silanol nests derived from dealumination process. In comparison with other stannosilicate zeolites, the obtained Sn-Y possessed excellent catalytic activity in Baeyer-Villiger oxidation irrespective of using aqueous hydrogen peroxide or bulky tert -butyl hydroperoxide as the oxidant. Structure-performance relationship revealed that Lewis acid site was the catalytically active center and the catalytic activity was depended on zeolite pore-engineering and hydrophobicity in aqueous B-V oxidation system. The relatively high catalytic activity of Sn-Y zeolite was ascribed to its excellent hydrophobicity and opened channel system. The former can be further enhanced by silanization treatment. Finally, the recyclability and deactivation mechanism were given insight. This work is aimed to provide some guidance for elaborately designing efficient stannosilicate zeolite catalyst for Baeyer-Villiger oxidation by precisely modulating pore-engineering and hydrophobicity.
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