CuSO₄/H₂O₂-Catalyzed Lignin Depolymerization under the Irradiation of Microwaves

Abstract

The increasing demand for renewable materials in the world has resulted in sustained efforts to utilize biomass in a better way. Lignin, a natural and abundant polymer in plants, has provided an ongoing challenge for many researchers seeking ways to better utilize this abundant resource. Here, we report a very efficient lignin depolymerization strategy with the assistant of microwave radiation. Copper sulphate (CuSO 4 ) and hydrogen peroxide (H 2 O 2 ) were used to generate hydroxyl radicals to depolymerize lignin under the irradiation of microwaves. Three different types of lignin, organosolv lignin, kraft lignin, and alkali lignin, were all successfully depolymerized using microwave irradiation at a temperature of 110 °C for 7 min. The use of 1 H/ 13 C two-dimensional nuclear magnetic resonance spectroscopy enabled the confirmation of structural changes, comparing before and after depolymerization. Liquid chromatography–mass spectrometry was used to characterize the products. Both monomers and oligomers were detected after depolymerization.

Production of polyurethane elastomer from highly reactive acetic acid lignin‐derived polyols with reduced molecular weights

“…The free radicals generated by the reaction between H 2 O 2 and iron ions could react with lignin to break the ether linkage during hydroxylation 37 . The double bond and carbonyl group could be oxidized by H 2 O 2 to form new hydroxyl groups on the side chain of lignin 38 .…”

H2O2-Triggered Rapid Deposition of Poly(caffeic acid) Coatings: A Mechanism-Based Entry to Versatile and High-Efficient Molecular Separation

“…These two fragments were attributed to the elimination of CO 2 from partial decarboxylation at 300 °C. The dimer was dominant regardless of the non-triggered or H 2 O 2 -triggered polymerization pathway, consistent with free radical-induced polymerization of natural phenolic compounds . The peak corresponding to m / z 453.4 (M3) might represent an oxidized product of trihydroxy benzacridine derivative formed by Michael addition and intermolecular Diels–Alder cyclization between two CA esters and a primary amine of Tris molecule.…”

“…The dimer was dominant regardless of the non-triggered or H 2 O 2 -triggered polymerization pathway, consistent with free radical-induced polymerization of natural phenolic compounds. 23 The peak corresponding to m/z 453.4 (M3) might represent an oxidized product of trihydroxy benzacridine derivative formed by Michael addition and intermolecular Diels−Alder cyclization between two CA esters and a primary amine of Tris molecule. Tris molecule was incorporated into the PCA structure during the relatively slow oxidation of the CA in the non-triggered polymerization pathway.…”

“…It is well-known that a suitable cation (such as iron or copper) can deprotonate plant-derived polyphenol and serves as a metal−ligand to form polyphenol−metal coordination complexes. 23 Since copper sulfate (CuSO 4 ) is an excellent catalyst for quantitative oxidation, enabling soluble in water to be used as a reaction recipient. Besides, CuSO 4 can be reused by a simple extraction from the residual solvent after the deposition process.…”

Tandem Triphosgene-Assisted Metal-Free One-pot Preparation of Nitriles and Amides from Aldehydes and Ketones

“…[20][21][22][23][24][25] Among the alternatives from biomass valorization, the production of 5-hydroxymethylfurfural (HMF) from hexoses is a versatile platform for the synthesis of furan-based chemicals such as furyl diamide, diamidine, diimidate, and diformylfuran. [26][27] Therefore, oxidative depolymerization of lignin and lignin model compounds can obtain aromatic aldehydes and ketones [28][29][30][31][32][33][34][35][36][37][38] such as vanillin veratraldehyde, acetovanillone, acetosyringone, and syringaldehyde. To further demonstrate the utility of our protocol, we used our one-pot strategy for the efficacious synthesis of 2,5-dicyanofuran from biomass-derived 2,5-diformylfuran.…”