Lignin waste processing into solid, liquid, and gaseous fuels: a comprehensive review

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

“…92 The supercritical water acts as both a reactant and reaction medium, and thus lignin with a high water content can be used directly without drying. 93–95 In the process of supercritical water gasification, catalysts play a role in lowering the reaction temperature and improving the gasification efficiency and hydrogen selectivity. 93,95 Alkali catalysts such as KOH, NaOH, K 2 CO 3 , Na 2 CO 3 , and Ca(OH) 2 , metal catalysts such as Ni, Pt, Ru and Rh, and metal oxide catalysts such as CuO–ZnO and Fe 2 O 3 –Cr 2 O 3 have been proven to be effective for the supercritical water gasification of lignin.…”

“…93–95 In the process of supercritical water gasification, catalysts play a role in lowering the reaction temperature and improving the gasification efficiency and hydrogen selectivity. 93,95 Alkali catalysts such as KOH, NaOH, K 2 CO 3 , Na 2 CO 3 , and Ca(OH) 2 , metal catalysts such as Ni, Pt, Ru and Rh, and metal oxide catalysts such as CuO–ZnO and Fe 2 O 3 –Cr 2 O 3 have been proven to be effective for the supercritical water gasification of lignin. 95,96 For example, an Ni catalyst showed high catalytic activity in supercritical water gasification.…”

Insight into the Mechanism of Humic Acid’s Dissolution Capacity for Lignin in the Biomass Substrates

“…To counter the adverse effects of lignin, research has turned to the development of practices capable of fractionating and/or transforming it into chemical products . Essentially, lignin is a high-molecular-weight polymer constituted with phenylpropane units, which can potentially become a renewable source of aromatic compounds if an economic process could be developed .…”

“…To counter the adverse effects of lignin, research has turned to the development of practices capable of fractionating and/or transforming it into chemical products . Essentially, lignin is a high-molecular-weight polymer constituted with phenylpropane units, which can potentially become a renewable source of aromatic compounds if an economic process could be developed . In traditional technical methods, the lignin is usually extracted or removed by cracking it into lower molecular units through violent pretreatment at a high temperature and pressure, which causes a severe waste of resources, enhancing the cost of lignocellulosic conversion and polluting the environment .…”

“…7 Essentially, lignin is a high-molecular-weight polymer constituted with phenylpropane units, which can potentially become a renewable source of aromatic compounds if an economic process could be developed. 7 In traditional technical methods, the lignin is usually extracted or removed by cracking it into lower molecular units through violent pretreatment at a high temperature and pressure, which causes a severe waste of resources, enhancing the cost of lignocellulosic conversion and polluting the environment. 2 Therefore, an effective and ecofriendly technical method is urgently needed to improve the utilization of lignin in the biorefinery process to fully embrace the potential of lignocelluloses as a high-value feedstock.…”