Production of light hydrocarbons from organosolv lignin through catalytic hydrogenation and subsequent fast pyrolysis

Abstract

Valorization and utilization of lignin have been drawing increasing attention recently. Hydroprocess is one of the main technologies, which can reduce organic compounds and partially depolymerize the macromolecular structure of lignin. The mechanism of lignin hydroprocess has been extensively discussed focusing on hydrogenolysis. In contrast, the solid residue regarded as unreacted or depolymerized lignin has drawn less attention so far. This study proposes an integrated process that consists of catalytic hydrogenation and subsequent fast pyrolysis for valorizing lignin. The results showed that 48−87 wt.% of solid product could be recovered as hydrogenated lignin (H-EOL) after hydrogenation at 200–250 ℃ for 1−7 h. Chemical structure of H-EOL was comprehensively investigated by means of elemental analysis, FTIR, 13C &1H NMR, and TGA. Furthermore, behavior of fast pyrolysis of H-EOL was detected here for the first time. H-EOL has higher hydrogen to carbon atomic effective ratio(H/Ceff ratio) and achieves the increasing reactivity of thermal decomposition. H-EOL yields light olefins double as much as raw ethanol organosolv lignin (EOL). And the formation of alkanes (C1-C4), benzene, and toluene was promoted to various degrees, while the yield of carbon monoxide, carbon dioxide, and vapor decreased. A novel and efficient pretreatment method has been provided to valorize lignin, which is instructive for subsequent research.