Aromatic Hydrocarbons for Jet Fuels from Lignin Fast Pyrolysis and Upgrading

Jet fuels have never been entirely substituted by biomass (viz. bio-jet fuel) due to the absence of aromatic hydrocarbons and cycloparaffins in biomass-derived oils. Currently, this problem can only be mitigated by blending bio-jet fuel with at least 50% traditional petroleum-based jet fuels. To produce 100% non-petroleum-based jet fuels, a suitable source of bio-based aromatic hydrocarbons and cycloparaffins is needed. Lignin is the only component in biomass rich in benzene-ring structures linked via ether bonds. Lignin is frequently underutilized due to its heterogeneity and resistance to chemical conversion; most of the lignin extracted from biomass is burned as low-value, stationary energy.

In this paper, we explore the opportunity of a four-step pathway to convert lignin into jet-fuel-range molecules aromatic hydrocarbons and cycloparaffins. Once produced, these molecules can be blended with bio-jet fuels to create 100% non-petroleum-based jet fuel that meets the technical specifications of Jet A. The production pathway consists of four steps: biomass pretreatment, lignin depolymerization, hydrodeoxygenation (HDO), and alkylation. During biomass pretreatment, lignin will be the final product rather than a waste. During HDO, the two-phase bio-crude oil derived from lignin depolymerization is used as feedstock. The bottom phase, dominated by heavier phenols as the main components from depolymerization, will be targeted. The mixture of lignin-derived bio-oils from HDO will serve as the feedstock for alkylation. In addition, the mutual influences of multi-components on desired product yields will be considered in HDO and alkylation of lignin-derived bio-oil. The review on each process is conducive to direct the pathway optimization to produce jet-fuel-range molecules from lignin in future research through a simplified and integrated pathway.