Role of β-CD Macromolecule Anchored to α-Fe₂O₃/TiO₂ on the Selectivity and Partial Oxidation of Guaiacol to Add-Value Products

Abstract

Biomass is a naturally abundant, sustainable, and clean resource, which has the potential to replace fossil feedstock for sustainable production of high add-value chemicals. However, an efficient conversion process is still difficult to achieve due to the difficult reaction conditions. In this study as a novel and versatile concept, we introduced the use of β-cyclodextrin (β-CD) macromolecule to enhance the photocatalytic behavior of a α-Fe 2 O 3 /TiO 2 heterojunction. The selective conversion of guaiacol was evaluated using 0.2, 1.0, and 2.0 molar ratios of β-CD anchored on 0.7 wt % α-Fe 2 O 3 /TiO 2 under mild reaction conditions. 1.0 molar ratio of β-CD promoted photo-oxidation of guaiacol to mainly produce p-benzoquinone with ∼68% selectivity at ∼10% conversion. To understand this effect, Electron Paramagnetic Resonance Spectroscopy (EPR) in operando mode and Diffuse Reflectance Spectroscopy (DRS) experiments were performed. The results showed that the 1.0 molar ratio of β-CD decreases the bandgap from 3.06 to 2.76 eV and controls the •OH radical concentration due to the formation of a covalent bond between β-CD and semiconductors. The improved guaiacol adsorption capacity on the photocatalyst resulted in the enhancement of the photochemical activity and selectivity. Additionally, a possible pathway of guaiacol transformation was proposed through the oxidation intermediates. Furthermore, the photocatalyst β-CD/α-Fe 2 O 3 /TiO 2 can be recycled efficiently and reused three times, without loss in reactivity.

Role of Nb2O5 Crystal Phases on the Photocatalytic Conversion of Lignin Model Molecules and Selectivity for Value‐Added Products

“…Previous reports have shown that guaiacol photocatalytic oxidation may occur through different mechanisms involving reactive oxygen species such as ⋅OH, O 2 ⋅ − and ⋅OOH, among others [13,68–70] . Conversion rates shown in Table 4 indicate that photocatalytic conversion of guaiacol relays in more than one reactive oxygen species.…”

“…Previous reports have shown that guaiacol photocatalytic oxidation may occur through different mechanisms involving reactive oxygen species such as * OH, O 2 *À and * OOH, among others. [13,[68][69][70] Conversion rates shown in Table 4 indicate that photocatalytic conversion of guaiacol relays in more than one or * OOH for these photocatalyst. Both samples produce hydroquinone (A3), indicating that the main reaction pathway for its production was through O 2 *À or * OOH.…”

A dog nose-inspired high-performance NH3 gas sensor of biomass carbon materials with a pleated structure derived from rose tea

“…The peak at 3428 cm À1 is associated with the stretching and bending vibrations of the O-H groups (hydroxyl and chemisorbed water). 24,25 The peaks at 2924 and 1736 cm À1 for the ORT are attributed to the stretching vibrations of C-H and C]O functional groups, respectively, 26,27 which are the characteristic groups of cellulose. The peaks at 1566 cm À1 for CRT are attributed to C]C vibrations and the peaks at 1028 cm À1 for ORT and CRT are attributed to C-O vibrations.…”

Waste Biomass Selective and Sustainable Photooxidation to High-Added-Value Products: A Review

“…β-Cyclodextrin (β-CD) is essential in photogenerated charge transfer, as it can serve as a hole eliminator to suppress recombination of photogenerated (h + -e − ) pairs. It has also been shown that its presence contributes to a more selective reaction because it prevents the formation of the •OH radical, which is highly reactive but not selective, so its presence contributes to complete degradation reactions, obtaining as final products CO 2 and H 2 O [95,124].…”