Lignocellulose, mainly composed of cellulose, hemicellulose and lignin, is the most abundant form of biomass. Utilizing lignocellulose to produce chemicals and fuels reduces the reliance on nonrenewable fossil resources, and hence has been an intensively explored topic in recent years. Nowadays, second-generation (2G) biorefineries using agricultural and forestry residues have been successfully built for the conversion of cellulose and hemicellulose into bio-ethanol as a gasoline blend, but it leaves the enzymatic hydrolysis lignin (EHL), as a large volume solid waste. Lignin is generally an amorphous tridimensional polymer composed of aromatic units. Due to the aromatic feature, lignin has the great potential to replace fossil feedstocks for producing aromatic-based fuels and chemicals. Recently efficient strategies for the conversion of EHL into value-added chemicals and fuels via catalytic solvolysis are explored, though EHL solvolysis product distributions strongly depend on the solvent, catalyst, reaction atmosphere and temperature. For instance, when using ethanol as the solvent, EHL was depolymerized into C8-C16 aliphatic and aromatic ranged products either on the unsupported Ni or γ-Al2O3 supported Ni and WO3 or Mo-based catalysts. On the other hand, EHL was converted into jet fuel ranged cycloalkanes over Ni-Mo alloy catalyst using cyclohexane under 3 MPa H2. Overall, our previous work provides an efficient strategy for EHL utilization, which could improve the economy and sustainability of biorefineries, despite the exploitation of EHL for chemical and fuel commodities is still progressing in the research communities, as compared to other technical lignins such as Kraft and lignosulfonates.

Depolymerization of enzymatic hydrolysis lignin into aromatic chemicals and fuels

ACS Spring 2022

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