Influence of Hydrophilicity on the Snβ‐Catalyzed Baeyer–Villiger Oxidation of Cyclohexanone with Aqueous Hydrogen Peroxide

Abstract

Snβ zeolites are amongst the most effective heterogeneous catalysts for the Baeyer–Villiger (BV) oxidation of ketones with aqueous hydrogen peroxide (H2O2). The high selectivity is rooted in the activation of the carbonyl substrate through interaction with the isolated SnIV sites. However, these sites are also accessible to other molecules in the reaction mixture (in particular the co‐solvent and product). In this contribution, we report the impact of competitive adsorption on the Snβ‐catalyzed BV oxidation of cyclohexanone with aqueous H2O2. We furthermore prepared a series of Snβ zeolites with varying amounts of framework silanols and quantified their hydrophilicities with water adsorption and IR experiments. By correlating the results with catalytic data, we show that Snβ zeolites with an intermediate hydrophilicity achieve the highest activity. Our adaptable post‐synthetic synthesis allows us to tune the material synthesis, resulting in enhanced activity compared with conventional hydrothermal Snβ.

Influence of Composition and Preparation Method on the Continuous Performance of Sn-Beta for Glucose-Fructose Isomerisation

“…It is generally recognised that Sn-Beta materials prepared by classical hydrothermal synthesis possess different intrinsic characteristics to those prepared by emerging post-synthetic methods such as SSI. For example, hydrothermally synthesised materials are reportedly more hydrophobic than postsynthetically prepared ones [34][35][36][37]. In several reports, the intrinsic activity of the hydrothermal synthesised catalyst also differs to that of its post-synthetic counterpart.…”

Controllably Confined ZnO on USY Zeolites (USY@ZnO/Al2O3) as Efficient Lewis Acid Catalysts for Baeyer–Villiger Oxidation

“…[43] Consequently,w hen the reaction proceeded with TBHP in decane, the USY@ZnO/Al 2 O 3 catalysts with Zn contents of 3.2 and 7.8 wt %e xhibited ah igher conversion than that of the pristine USY zeolite;i np articular the USY@ZnO/Al 2 O 3 -7.8 catalyst showed ap erformance comparable to that of the reported Sn-zeolite catalyst. [52] Therefore, duet ot heir hierarchical structurea nd intrinsic Lewis acidity,t hese novel USY@ZnO/ Al 2 O 3 catalysts exhibited outstanding performance for B-V oxidation reactions, particularly for bulky oxidantsa nd substrates. For TBHP in water (65 wt %), the ketone conversionf or all the catalysts decreased remarkably due to the competitive adsorption of water molecules versus organic substrate in catalysts that contained ah ydrophilic zeolite component.…”

“…For TBHP in water (65 wt %), the ketone conversionf or all the catalysts decreased remarkably due to the competitive adsorption of water molecules versus organic substrate in catalysts that contained ah ydrophilic zeolite component. [52] Therefore, duet ot heir hierarchical structurea nd intrinsic Lewis acidity,t hese novel USY@ZnO/ Al 2 O 3 catalysts exhibited outstanding performance for B-V oxidation reactions, particularly for bulky oxidantsa nd substrates.…”

Baeyer–Villiger Oxidation of Cyclic Ketones by Using Tin–Silica Pillared Catalysts

“…Taking into account the promising results obtained with the Sn‐ BEA zeolite catalyst on the one hand and considering pore‐diffusion limitations, characteristic for conventional zeolites on the other hand, Sn‐containing hierarchical or lamellar materials could be effective catalysts for the oxidation of bulky ketones. Highlighting the role of diffusion in the tin‐zeolite catalysis, Conrad et al . studied the kinetics of the Baeyer–Villiger oxidation of cyclohexanone over Sn‐ BEA (Si/Sn molar ratio 217), showing that the reaction occurs in kinetic regime only at temperatures below 65 °C under the used conditions and also that the hydrophilicity of the material influences the reaction.…”

“…Highlighting the role of diffusion in the tin-zeolite catalysis, Conrade tal. [11] studied the kinetics of the Baeyer-Villiger oxidation of cyclohexanone over Sn-BEA (Si/Sn molar ratio 217), showingt hat the reactiono ccurs in kinetic regime only at temperatures below 65 8Cu nder the used conditions and also that the hydrophilicity of the material influences the reaction.…”