Junjie Tang,Peiwen Liu,Xiaoling Liu,Lei Chen,Haimeng Wen,Yu Zhou,Jun Wang
Straightforward encapsulation of Pt clusters (∼2 nm) into the pure silica TON-type zeolite (ZSM-22) was reached in a dry gel conversion route, where the ionic liquid template was removed via the hydrocracking-calcination-reduction approach. The obtained Pt@ZSM-22 series possessed high crystallinity, large surface area, and ultrafine Pt clusters inside the zeolite crystals. They exhibited remarkable activity in the semi-hydrogenation of phenylacetylene into styrene; the lead sample with 0.2 wt % Pt loading afforded a large turnover number up to 117,787. The preferential high affinity of the pure silica ZSM-22-encapsulated Pt clusters toward the substrate phenylacetylene rather than the hydrogenated product was derived from the unique space-confinement effect of zeolite microchannels, which is responsible for such excellent performance.
Rapid and straightforward synthesis of all-silica zeolites is essential for scaling up their industrial applications in adsorption and separation. However, the synthesis typically necessitates the use of complex organic structure-directing agents (OSDAs) and/or fluoride, presenting challenges in the development of straightforward strategies. Herein, a siliceous TON zeolite, referred to as Si-TON, is successfully obtained without the need for any costly OSDAs, utilizing seeds and methanol as facilitating agents. Various analyses validate that methanol acts as both a dynamic stabilizer and a solvent, which can be totally removed without high temperature calcination. This approach circumvents the requirement for high-temperature calcination to achieve open channels in the TON zeolite, distinguishing it from traditional synthesis method. Additionally, metal species (Co, Fe, and Zr) can be incorporated into the TON zeolite to form heteroatom-substituted TON samples, thereby offering a viable strategy for the preparation of heteroatom doping catalysts that exhibits excellent performance in various catalytic reactions. Furthermore, the as-synthesized Si-TON zeolite exhibits high methanol adsorption capacity, stands as a candidate adsorbent for methanol removal.
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