Metal–Organic-Framework-Derived Copper Catalysts for the Hydrogenolysis of Lignin into Monomeric Phenols

Abstract

Reductive catalytic fractionation (RCF) of lignocellulosic biomass has emerged as a leading biorefinery strategy. Herein, we present a copper-based catalyst (CuO/C) derived from a metal–organic backbone (HKUST-1) with enhanced catalytic performance for RCF of woody sawdust, which affords high yields of propyl and propanol end-chain monomeric phenols (15.5 wt % in softwoods and 46.7 wt % in hardwoods) via the C–O bond scission. A series of conifer β-O-4 models and their deuterated analogues revealed that the synergistic action of CuO/C and hydrogen could effectively cleave aryl ether linkages. It was deduced that lignin alcoholysis led to partial α-OH etherification of the β-O-4′ units, which promoted the C–O bond breakage of Cα-OMe and Cβ-O, thus giving propanol phenolic compounds through the hydrogenation of coniferyl alcohol over the CuO/C catalyst. When both α- and γ-OH of β-O-4′ motifs were meoxylated, the para-propyl phenolics were obtained through the scission of C–O linkages (Cα-OMe and Cβ-O), followed by the Cγ-OMe cleavage of propenyl ethers and hydrogenation of propenyl phenols. We envision that this work may pave the way for the development of non-noble catalysts with high reactivity and selectively for lignin valorization.

Preparation and Characterization of Bisphenol A-Based Thermosetting Epoxies Based on Modified Lignin

“…For 1 H NMR, 5.0 mg of p -nitrobenzaldehyde (NBA) acting as an internal standard and 30.0 mg of modified lignin samples were dissolved in 0.5 mL dimethyl sulfoxide- d 6 (DMSO- d 6 ). For 2D heteronuclear single quantum coherence spectroscopy (HSQC) NMR, 50.0 mg modified lignin samples were dissolved in 0.5 mL DMSO- d 6 . ,,,, 31 P NMR spectra were acquired after the reaction of lignin with 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane (TMDP) as described previously. , The cross-sectional morphologies of the resin materials were obtained using scanning electron microscopy (SEM), JEOL JSM-7800F (Japan). It should be noted that the resin materials were first cracked in liquid nitrogen to prepare the samples.…”

“…Herein, we reported a simple and effective approach for the preparation and characterization of bisphenol A (BPA)-based thermosetting epoxy-based modified lignin. The technical lignin with lower structural complexity and dispersivity prepared through a pH-controlled precipitation was first modified under a moderate condition to introduce the oxirane moieties on the lignin backbone. , Then, the epoxidized lignin samples were cross-linked with industrial diamines to prepare thermosetting epoxy resins . Consequently, the mechanical and thermal properties of the fabricated thermosetting epoxies were thoroughly investigated to build a correlation with the lignin structure.…”

Lignin-based composites with enhanced mechanical properties by acetone fractionation and epoxidation modification

“…One strategy was to deconstruct lignin into phenolic compounds with low molecular weights by the strategies of catalytic and pyrolytic approaches. 17 , 18 , 19 , 20 , 21 Another alternative route is the crosslinking or blending of lignin with other monomers or polymers to produce thermoset resins, 22 , 23 adhesives, 24 , 25 foams, 26 and thermoplastics. 27 , 28 …”

Catalytic Hydrolysis/Hydrogenolysis of Lignin-Derived Aryl Ethers over Bimetallic Pd-Ni Systems: The Directional Regulation of Reaction Pathways

“…It is of great concern of researchers to select a suitable reaction pathway to obtain high-priced chemical products by cleaving the C–O bond of lignin-related compounds. − Among these C–O bonds in lignin, the highest bond energy of 4–O–5 linkages has been extensively used to explore its reaction mechanism. − A typical model compound of 4–O–5 bond, diphenyl ether (DPE), is prone to direct hydrolysis and hydrogenolysis to cyclohexane and cyclohexanol over the catalyst and solvent. − The direct hydrolysis of DPE is 1 mole of DPE to generate 2 moles of phenol. Phenol is hydrogenated to cyclohexanol.…”