Complete valorization of lignocellulosic biomass through integrated reductive catalytic fractionation and microwave-assisted pyrolysis

Abstract

Reductive catalytic fractionation (RCF) of lignocellulosic biomass produces phenolic-rich lignin oil and carbohydrate pulp, but catalyst separation is usually required for pulp utilization. This study introduces an integrated process combining RCF with microwave-assisted pyrolysis (RCF-MAP), enabling complete biomass valorization without catalyst separation. Using Ni/AC, RCF generates phenolic-rich lignin oil and high-quality carbohydrate pulp. The RCF-derived carbohydrate pulp can be directly subjected to microwave-assisted pyrolysis, producing syngas yields of 49.5 wt% with a high H₂ to CO ratio of approximately 1:1, suitable for hydroformylation. The Ni/AC catalyst can be recycled back into the MAP process, preventing deactivation seen in conventional thermal pyrolysis. On-line gas analysis revealed that the microwave environment enhances secondary cracking of liquid products, contributing to the hydrogen formation. Mass flow analysis reveals that birch biomass yields approximately 18.9 wt% of lignin oil, 29.6 wt% of syngas (H₂ and CO), 20.1 wt% of bio-oil, and 4.9 wt% of char. This integrated RCF-MAP approach efficiently produces both phenolic chemicals and high-quality syngas, supporting industrial-scale utilization of all biomass fractions.