Efficient Lignin Depolymerization Process for Phenolic Products with Lignin-Based Catalysts and Mixed Solvents

Abstract

Due to their diverse functional groups and structural composition, carbon-based catalysts exhibit superior performance in various catalytic reaction systems, such as hydrogenolysis, hydrogenation, and oxidation. Herein, we propose an effective strategy of lignin liquid-phase depolymerization by applying the designed lignin-based carbon catalysts to produce aromatic chemicals. A series of Ni–Mo bimetallic carbon-based catalysts were synthesized to explore the effect of different preparation methods on the catalytic activity. The results demonstrate that the embedded Ni–Mo/C-WMO catalyst with multi-active sites of Ni, MoO3, and Mo2C results in a prominent catalytic effect on lignin depolymerization. The Ni–Mo/C-WMO catalyst can achieve a lignin conversion of 87.62% with a 42.25% monophenol yield in the methanol and water system. With the synergistic contribution of multiple active sites of the catalyst and the mixed-solvent system (water, methanol, and 1, 4-dioxane), a remarkably high yield of 62.95% of mono-phenolic compound was achieved at 260 °C and 3 MPa N2 with a reaction time of 4 h. The selectivity of 2-methoxy-4-methylphenol and 2-methoxy-4-ethylphenol in liquid products was 40.85 and 36.42%, respectively. Vanillin, a typical product from lignin depolymerization reported in the literature, was further degraded to monophenol in this system. The outcomes also confirmed that the in situ hydrogen production system of methanol and water coupled with 1,4-dioxane facilitated the lignin depolymerization significantly.

Review on Catalytic Cracking of Lignin for the Production of Fuels and High-Value-Added Chemicals: Advances, Challenges, Opportunities, and Outlook

“…Additionally, certain carbon materials derived from biological sources exhibit remarkable catalytic activity after modification, attributed to their high resistance to thermal decomposition. Wu et al 152 made efforts in this regard. Their experiments were successfully applied to the pyrolysis process of lignin by designing related carbon catalysts.…”

Kinetic Analysis of Hydrogen Transfer Route from Hot-Compressed 2-Propanol to Diphenyl Ether over NiCo/C Catalyst

“…Lignin, which accounts for about 10 to 35% of lignocellulosic biomass, , is a promising biomass fraction to produce valuable chemicals and fuels owing to its high content of aromatic structures. − It has been reported that about 100 million tonnes of lignin are produced annually on a global scale, , which may have the ability to afford the worldwide BTX production. However, its cross-linked heterogeneous phenolic polymer structures have made it difficult to depolymerize lignin into the desired monomers such as phenols and BTX. ,, Therefore, such produced lignin is generally destined for incineration as a low-valued fuel. − Considering the continuous demands for BTX and phenolic compounds as chemical feedstock, it is crucial to develop lignin depolymerization technologies for the achievement of a sustainable supply of aromatic chemicals.…”

Lignin Catalytic Depolymerization for Guaiacols and Alkylphenols over Co–Zr/Sepiolite under Supercritical Ethanol

“…This catalytic system suppressed the polymerization of ester structures in lignin and improved the conversion efficiency of lignin to fuel. In addition, some other solvents including n -hexane, diisopropyl ether, ethyl acetate, methanol, and acetone cooperated with hydrogen pressure (3–5 MPa) were developed for lignin depolymerization. − Although the HHV of the liquid product or monomer selectivity was clearly improved by employing the complex solvent systems and the high hydrogen pressure, the high cost of solvent and downstream product separation and the urgent need for delicate catalysts that can efficiently activate hydrogen become a great challenge.…”