Adsorption of fructose in Sn-BEA zeolite from periodic density functional calculations

Abstract

Fructose is regarded as a key intermediate for transformation of cellulosic biomass to downstream products. In the gas phase, D-fructofuranose conformers that predominate in biochemically relevant polysaccharides are strongly disfavoured, and the condition improves slightly by inclusion of bulk solvent effects. The various O sites in four selected fructose conformers are accessible to the Sn Lewis acidic site of Sn-BEA zeolite except five cases mainly as a result of steric hindrances from the adjacent groups. The adsorption energies of fructose in Sn-BEA zeolite are calculated within −73.3 to −161.5 kJ mol⁻¹ that may differ substantially for the various conformers and various O sites. D-Fructofuranose rather than D-fructopyranose conformers are significantly preferred in Sn-BEA zeolite and this fundamentally alters the conformational preference of gas phase, as corroborated by the computational relative stabilities ranking as F4 ≤ F3 < F1 < F2. Accordingly, D-fructofuranose conformers that predominate in biochemically relevant polysaccharides exist favorably in Sn-BEA zeolite. Dispersion interactions in gas phase can alter the relative stabilities of fructose conformers not more than 5.6 kJ mol⁻¹; however, dispersion interactions play a considerably larger role during the interaction with Sn-BEA zeolite that are averaged at −123.8, −123.4, −125.6 and −127.5 kJ mol⁻¹ for F1, F2, F3 and F4, respectively.