Snβ is probably one of the best water tolerating heterogeneous Lewis acids for liquid phase catalysis. Instead of applying the usual lengthy hydrothermal synthesis to prepare Snβ, this contribution uses a more hands-on two-step synthesis method, involving the grafting of Sn precursors in isopropanol under reflux conditions on a commercial β zeolite that was dealuminated in acid. Among several reference synthesis procedures, this Sn introduction method resulted in active Sn catalytic sites. Taking advantage of this practical method, several synthesis parameters were explored and their impact on the catalytic activity in four different Lewis acid catalyzed reactions is discussed. The adsorption isotherm of SnIV in isopropanol over a broad range of Sn salt concentrations at reflux temperature is presented and discussed in relation with FTIR spectroscopy, UV–vis absorption characteristics and the porosity of the materials. The study reveals a selective Sn uptake, up to 2 wt% Sn loading, into silanol nests of the dealuminated precursor, forming a diversity of mononuclear SnIV. Higher Sn loadings result in less active Sn (hydrous) extraframework oxide phases, which also cause partial blockage of the zeolite micropores. Depending on the reaction type under study, space time yield may increase with increasing Sn loading, but the activity per Sn is always lower. Therefore it is concluded that a preferred synthesis should form high contents of isolated Sn active sites, especially for sugar isomerization and intermolecular Meerwein–Ponndorf–Verley, while the other reaction types like Baeyer–Villiger is also sufficiently catalyzed by the small Sn oxide clusters, albeit less actively.

中文翻译：

Snβ可能是液相催化中最好的耐水多相路易斯酸之一。代替了应用通常的冗长的水热合成来制备Snβ的方法，该贡献使用了更为实际的两步合成方法，该方法涉及在回流条件下将Sn前驱体在异丙醇中接枝到在酸中脱铝的商用β沸石上。在几种参考合成程序中，这种Sn引入方法产生了活性Sn催化位点。利用这种实用的方法，探讨了几个合成参数，并讨论了它们对四种不同的路易斯酸催化反应中催化活性的影响。Sn IV的吸附等温线本文介绍并讨论了在回流温度下，异丙醇中锡盐浓度范围较宽的情况，并结合FTIR光谱，UV-vis吸收特性和材料的孔隙率进行了讨论。该研究表明，脱铝前体的硅烷醇巢中选择性地吸收了高达2 wt％的锡的锡，形成了单核Sn IV的多样性。。较高的锡含量会导致活性较低的锡（含水）骨架外氧化物相，这也会导致沸石微孔的部分堵塞。根据所研究的反应类型，时空产率可能会随着Sn含量的增加而增加，但每Sn的活性始终较低。因此得出的结论是，优选的合成方法应形成高含量的分离的Sn活性位点，尤其是对于糖异构化和分子间Meerwein–Ponndorf–Verley，而其他反应类型（如Baeyer–Villiger）也可以由小的Sn氧化物簇充分催化，尽管不太积极。