锡硅分子筛：新型杂原子分子筛催化材料

锡硅分子筛能高效催化含氧烃转化，因此其具有重要潜在工业应用价值。本文简述了锡硅分子筛的骨架锡判定、合成方法、多级孔合成研究及应用领域。XRD、NMR和EXAFS等表征方法可以判别锡硅分子筛内锡原子的配位形式及落位。合成锡硅分子筛通常采用水热晶化法、后插入法和干胶转化法。碱性水热合成过程中匹配锡源和硅源的水解速率是使锡原子高效插入分子筛骨架的关键。中性水热合成方法制备的锡硅分子筛结晶度较高，但存在使用剧毒含氟试剂和晶粒较大等问题。干胶转化法可在短时间内制备高结晶度含锡分子筛，但该法存在传质传热差等弊端。采用后插入法可将锡原子插入到不同拓扑结构的分子筛骨架，但锡原子易发生聚集。同时，采用碱处理、硬模板剂法和软模板剂法合成多级孔锡硅分子筛，可提升骨架锡活性中心的可接近性。其中，采用软模板剂法展示出独特的优势，其可制备介孔分布均匀且贯通性良好的多级孔锡硅分子筛。另外，锡硅分子筛的骨架锡原子对含氧官能团具有优异的活化作用，因此其在Meerwein-Ponndorf-Verley-Oppenauer反应、葡萄糖异构化反应、乳酸及乳酸酯制备及Baeyer-Villiger氧化反应中都展示了良好的催化效果。

Stannosilicate molecular sieve:a new star in heteroatom incorporated zeolite family

Stannosilicate zeolites show excellent catalytic performance in transformation of oxygenated hydrocarbon, hence they are of great industrial application potential. Characterization, synthesis methods, hierarchical stannosilicate zeolites and their applications were reviewed in detail. Various characterization methods (such as XRD, NMR, and EXAFS) are employed to determine the coordination and location of tin atoms in stannosilicate zeolites. Tin-containing zeolites can be prepared by several methods, including hydrothermal crystallization, post-synthesis and dry-gel conversion methods. In basic hydrothermal crystallization process, it is key to match the hydrolysis and crystal growth rates between tin and silicon sources, so as to make Sn atoms efficiently insert into the zeolite framework. Tin-containing zeolite prepared by neutral hydrothermal synthesis method in the presence of fluorine-containing agents is of high crystallinity, but it suffers from the use of toxic fluorine reagent and large size particles. Dry-gel conversion method favors to synthesize highly crystalline stannosilicate zeolites within short time, but it is of poor heat and mass transfer performance. Meanwhile, Sn atoms are also incorporated into the framework of various topological zeolites, yet the Sn species are easily to aggregate. Hierarchical stannosilicate zeolites are synthesized by alkali treatment, hard-template method and soft-template method to improve the accessibility of framework tin atoms. Among them, soft-template approach shows promising prospect, with narrow mesopore distribution and good connection. In addition, framework tin atoms of stannosilicate zeolite tend to interact with oxygen-containing functional groups, which renders them good catalytic performance in Meerwein-Ponndorf-Verley-Oppenauer reaction, glucose isomerization to fructose, the synthesis of lactic acid and tis lactate and Baeyer-Villiger reaction.