Nano WO₃‐Catalyzed One‐Pot Process for Mild Oxidative Depolymerization of Lignin and its Model Compounds

Abstract

Despite challenges related to the robust and irregular structure of lignin, the valorization of this aromatic biopolymer has aroused great interest. However, the current methods exhibit problems such as harsh reaction conditions, complicated operation, and difficult recovery of catalyst. Herein we present a one-pot process for the mild oxidative depolymerization of lignin and lignin model compounds catalyzed by nano WO 3 , along with tert-butyl hydrogen peroxide (TBHP) as the oxidant and NaOH as the additive, which exhibits advantages of both homogeneous and heterogeneous catalysis. Under the optimized condition, it yielded 80.4 wt % of liquid oil from organo-solv lignin with 7.6 wt % of vanillic acid as the main monomer product, accounting for 91.6 wt % monomeric selectivity. Mechanism studies on the model substrate suggest that the reaction proceeds via an oxidation of C α À OH to C=O followed by CÀ O bond cleavage to afford phenol and ketone products which may undergo further oxidation to produce aromatic carboxylic acids. We have developed an operationally simple procedure for mild fragmentation of lignin and lignin model compounds with excellent yields, which provides the potential to expand the existing lignin usage from energy source to value-added commodity chemicals.

Reversible hydrogen spillover in Ru-WO3-x enhances hydrogen evolution activity in neutral pH water splitting

“…Moreover, Ru-WO 3 /CP keeps stable in the long-term stability test, and no obvious HER activity decay is observed. In addition, WO 3 or WO 3−x gradually dissolves in alkaline electrolyte 48 , 49 . Thus, it is not appropriate to apply Ru-WO 3−x in alkaline condition because of the stability issue.…”

Oxidative Cleavage of β‐O‐4 Linkage in Lignin via Co Nanoparticles Embedded in 3DNG as Catalyst**

“…As shown in Table S1, the turnover frequency (TOF) of Co/NG@3DNG-900 (1.0 h À 1 ) is higher than those of Pd/CeO 2 (0.6 h À 1 ), [6] Co@CN (0.5 h À 1 ), [14] VB12@C-900 (0.3 h À 1 ), [12] LCN (0.4 h À 1 ), [26] and NENU-MV-5 (0.4 h À 1 ) [27] as catalysts for the PP-ol cleavage. Although some catalysts used for PP-ol cleavage showed higher TOFs than that of Co@NG/3DNG-900, such as Au/CeO 2 (14.8 h À 1 ), [8] AuÀ Pd-CTF (19.4 h À 1 ), [9] CoÀ NÀ C (4.4 h À 1 ) [13] and nano WO 3 (1.6 h À 1 ), [28] the reactions were conducted under harsh conditions. For instance, the oxidative cleavage of PP-ol with Au/CeO 2 and AuÀ Pd-CTF as catalysts were conducted at 160 and 180 °C, and the oxidation of PP-ol using CoÀ NÀ C as catalyst was proceed at 150 °C in the presence of NaOH.…”

Ionic Liquid-Stabilizing Vanadium Oxo-Cluster Catalysts for One-Step Selective Oxidative Cleavage of β–O–4 Lignin Model Compounds

“…Oxidative cleavage of the linkages was thought to be a very effective method of cleaving lignin’s β–O–4 linkages since it resulted in aromatic molecules that maintained active functional groups (like methoxy groups) . For the oxidative cleavage linkages, the different oxidants such as hydrogen peroxide, molecular oxygen, , ozone, and tert -butanol hydrogen peroxide have been frequently utilized. Since molecular oxygen is rich in natural concentration, cheap, easy to obtain, green, and environmentally friendly, it was regarded as the most ideal oxidant.…”