Reactive catalytic fast pyrolysis (RCFP) of biomass with atmospheric pressure hydrogen was investigated in a lab-scale fluidized bed reactor with varying reaction conditions (temperature and hydrogen concentration) and catalysts. Presence of atmospheric hydrogen with candidate RCFP catalysts was found to improve the yield and quality of bio-crude and minimize the char and coke formation. A molybdenum-based catalyst was the most effective at hydrodeoxygenating biomass pyrolysis vapors to produce a hydrocarbon-rich bio-crude intermediate with low oxygen content (<10 wt%). Higher hydrogen concentration and moderate reaction temperature (450 °C) favored higher bio-crude yields and quality. A yield of 43.2 C% in the C₄₊ organic fraction with as low as 6.2 wt% oxygen in the liquid was obtained under optimized reaction conditions. The resulting bio-crude contained primarily aliphatic and aromatic hydrocarbons, with small amounts of simple ketones, furans, and phenols. Up to 41.5% carbon in the biomass feed was converted into gas and condensable hydrocarbons with 29.7% in the condensable C₄₊ fraction. The improved bio-crude quality is expected to be more compatible with existing petroleum refining infrastructure.

Driven by the excessive consumption of fossil resources and environmental pollution concerns, a large amount of biorefinery research efforts have been made for converting lignocellulosic biomass into fuels and chemicals. Recently, a strategy termed “lignin-first,” which allows for realizing high-yield and high-selectivity aromatic monomers, is regarded as one of the best prospective strategies. This review summarizes recent research advances in lignin-first biorefinery, starting from the raw lignocellulose through lignin-first processing and moving to downstream processing pathways for intermediate compounds. In particular, for the core purpose of producing liquid fuels, the corresponding downstream processing strategies are discussed in detail. These are based on the structural properties of the intermediates derived from lignin-first biorefinery, including the catalytic conversion of lignin and its derivatives (aqueous phase system and pyrolysis system) and the cascade utilization of carbohydrate residues (fermentation, pyrolysis, and hydrothermal liquefaction). We conclude with current problems and potential solutions, as well as future perspectives on lignin-first biorefinery, which may provide the basis and reference for the efficient utilization of lignocellulosic biomass.