Promoting tin into the framework of β zeolite via stabilizing Sn species and its catalytic performance for the conversion of ethyl levulinate to γ-valerolactone

Tin-containing β zeolite exhibits excellent catalytic performance in various biomass conversions to high-value chemicals due to its strong Lewis (L) acidity produced by framework Sn 4+ sites. However, it is difficult to incorporate Sn species into the framework of β zeolite due to that the ionic radius of Sn (0.69 Å) is larger than that of Si (0.40 Å). Herein, organic additives with carbonyl, hydroxyl , aldehyde or amine groups were used to stabilize Sn species in the gel and framework Sn 4+ in the zeolite. Among all additives, acetone (AC) has the best stabilizing effect on Sn species. The stabilization effect between AC and Sn 4+ sites was observed by FT-IR. The characterization results indicate that more tin species were incorporated into β framework and the L acid density increased due to the complexation between carbonyl group and Sn species. Compared to Sn-β-3d synthesized without additive, the L acid density of Sn-β-AC-3d increased by ∼50% (from 21 μmol g −1 to 34 μmol g −1 ). For the conversion of ethyl levulinate to γ-valerolactone, the reaction reached equilibrium faster over Sn-β-AC-3d than over Sn-β-3d at the investigated reaction temperatures. A yield of 98% was obtained over Sn-β-AC-3d at 110 °C. Besides, Sn-β-AC-3d exhibited good stability and reusability.