Tuning of Sn-BEA Reactivity by Controlling Tin Location in the BEA Framework

The combined application of 119Sn MAS NMR spectroscopy, adsorption of probe molecules, and catalytic testing in the MPVO conversion of cyclohexanone into cyclohexanol have been used to uncover T-positions in the zeolite Sn-BEA structure, providing for Sn-sites responsible for its high catalytic activity. The results reveal that tin atoms located in T3, T4, and T9 positions (group I) and in T1, T2, and T8 positions (group II) of the zeolite BEA structure generate Sn-sites with the highest Lewis acidity and the highest ability to hydrolyze, respectively, and therefore provide for the highest catalytic activity. In contrast, the sites in T5–T7 positions (group III) occupy more energetically favorable T-positions, leading to less reactive Sn-sites. Besides that, it has been shown that the content of different Sn-sites can be altered by the variation of the duration of hydrothermal synthesis of Sn-BEA and that the highest content of the most reactive sites can be achieved at the end of crystallization and the onset of the postcrystallization period.