Controlled hydrogenolysis over heterogeneous catalysts for lignin valorization

Lignin to value-added chemicals and advanced materials: extraction, degradation, and functionalization

“…57 For the extraction of lignin from a lignocellulosic source, cellulases and hemicellulases are commonly used to hydrolyze carbohydrates, leaving lignin-enriched solid residues composed of lignin, carbohydrate, protein and ash. 16,40,57,63 To improve the efficiency of the extraction and the purity of lignin, additional pretreatments including hot water treatment, ball-milling, mechanical refining, and ammonia fiber explosion are usually required to decrease the recalcitrance of lignocellulosic biomass and increase the digestibility of the polysaccharides. 40,63 For example, lignin can be obtained by treating ball-milled wood with cellulolytic enzymes, which can hydrolyze carbohydrates.…”

“…16,40,57,63 To improve the efficiency of the extraction and the purity of lignin, additional pretreatments including hot water treatment, ball-milling, mechanical refining, and ammonia fiber explosion are usually required to decrease the recalcitrance of lignocellulosic biomass and increase the digestibility of the polysaccharides. 40,63 For example, lignin can be obtained by treating ball-milled wood with cellulolytic enzymes, which can hydrolyze carbohydrates. 5 The obtained cellulolytic enzyme lignin has low purity due to the presence of protein and carbohydrates impurities.…”

“…Lignin is hydrogenated between 300 °C and 600 °C in the presence of H 2 as a reducing agent. 33,63,66 During the process of hydrogenolysis, the C–O and C–C bonds in lignin are cleaved, resulting in the production of phenolic compounds ( e.g. , phenol and catechol), cyclic alcohols, and cycloalkanes.…”

Catalytic Hydrodeoxygenation of Lignin-Derived Oxygenates: Catalysis, Mechanism, and Effect of Process Conditions

“…Among these three constituents, lignin accounts for up to 40% of the biomass’s energy. It is a highly cross-linked polymer made up of three monomeric units: coumaryl, coniferyl, and sinapyl alcohols. − Currently, 50–70 million tonnes of lignin are produced annually by paper and pulp industries and disposed of by the hollow way of burning. , …”

“…3−5 Currently, 50−70 million tonnes of lignin are produced annually by paper and pulp industries and disposed of by the hollow way of burning. 6,7 Thermal breakdown of lignin is one such strategy to produce bio-oil using fast pyrolysis. 8−10 Nonetheless, in contrast to conventional fuels, biomass pyrolysis oil (also known as bio-oil or pyrolytic oil), possesses high contents of oxygen (up to 40 wt %) and water (up to 25 wt %).…”