Hydrogen-Free Production of 4-Alkylphenols from Lignin via Self-Reforming-Driven Depolymerization and Hydrogenolysis

Abstract

Lignin is constructed from methoxylated phenylpropanoid with plenty of hydroxys and methoxys. Its conversion to valuable products is extremely attractive but especially challenging without additional hydrogen sources. Herein we report a hydrogen-free production of 4alkylphenols directly from native lignin via self-reforming-driven depolymerization and hydrogenolysis over Pt/NiAl 2 O 4 . This is the first example of acquiring 4-alkylphenols from native lignin. Using this strategy, high yields of 4-alkylphenols, 17.3 wt %, were obtained from birch lignin. Reaction pathway and mechanism studies revealed that this strategy initiates from the reforming of aliphatic hydroxys, followed by the cleavage of C−O linkages, and ends via demethoxylation over Pt/NiAl 2 O 4 . Moreover, the subsequent aqueous phase reforming of the as-formed methanol accelerates the whole process. This strategy realizes the one-pot production of 4-alkylphenols from lignin by fully utilizing the structural hydrogen in lignin and H 2 O, providing a low-cost and safe method of lignin valorization.

Catalytic self-transfer hydrogenolysis of lignin with endogenous hydrogen: road to the carbon-neutral future

“…1b). [4][5][6] From the perspective of the reaction process, the in situ hydrogen species generation from lignin with subsequent self-transfer hydrogenolysis in one pot has several good advantages: (1) simplification of the complex lignin depolymerization process and decrease of the overall energy input in separation and purification; (2) the absence of high-pressure H 2 undoubtedly improves the safety of operation. From the perspective of the molecule, the utilization of internal hydrogen from lignin for its depolymerization, which can avoid the question of the dissolution and accessibility of H 2 , can increase the intrinsic kinetics of lignin depolymerization.…”

“…However, the natural recalcitrance and complexity of the lignin structure make its valorisation a tremendous challenge. [4][5][6] Some value-added chemicals have been produced through the initial depolymerization of lignin into platform chemicals, then upgrading to targeted products through functionalization or defunctionalization. 7 The state-of-the-art strategies developed for lignin deconstruction mainly involve catalytic oxidation/ reduction, acid/base-catalysed hydrolysis, and pyrolysis.…”

Unexpected Formation of Organic Siloxanes alongside Ethylphenols in the Catalytic Hydrogenation of Waste Enzymatic Lignin

“…The hydrogenolysis of methoxy groups in G and S units has also been reported in Wang's work, where Pt/NiAl 2 O 4 promoted the cleavage of methoxy group to produce methanol, which then underwent aqueous methanol reforming affording H 2 . [24] In fact, according to the proportion of H-, G-, and S-type phenols in the reaction products (Table S6, Supporting Information), the proportion of H-type monophenols in pure ethanol solvent (%50%) is significantly higher than that in water/ethanol mixed solvent (%40%), which seems to confirm the cleavage of the methoxy group.…”

H2‐free Plastic Conversion: Converting PET back to BTX by Unlocking Hidden Hydrogen

“…[11] More encouragingly, we have realized a hydrogen-free production of 4-alkylphenols from lignin by sufficiently using the structural hydrogen of lignin via self-reforming-driven depolymerization and hydrogenolysis over Pt/NiAl 2 O 4 . [12] It is therefore reasonable to explore the availability of Pt/NiAl 2 O 4 to convert PET back to BTX by unlocking hidden hydrogen. Over Pt/NiAl 2 O 4 , 70.2 % monomer yield was obtained, but the selectivity towards BTX (3.6 %) was extremely low.…”