Protic ionic liquid-based biorefinery—pathways for cellulose and hemicellulose valorization
File(s)
Author(s)
Zhang, Chaoyue
Type
Thesis
Abstract
Lignocellulosic biomass is a carbon-neutral feedstock for biofuels and biochemicals, but its potential depends on cost-effective fractionation and the full valorization of each component. Our group has developed low-cost protic ionic liquids (PILs), such as N,N-dimethylbutylammonium hydrogen sulfate ([DMBA][HSO4]), that extract hemicellulose and lignin in a one-pot ionoSolv process, leaving a cellulose-rich pulp.
First, we evaluated probe sonication to accelerate the ionoSolv process at mild temperatures. The sonication effect was strongly feedstock-dependent: for Miscanthus, acceleration was confined to the early stage (0–1 h), whereas for recalcitrant spruce, it remained pronounced after 4 h at 130 °C. Quantitative analysis indicated that sonication-induced heating, rather than mass transfer enhancement, was the main driver.
Second, using the same PIL platform, we targeted hemicellulose valorization via furfural production. Prior work has confirmed furfural formation but faced side reactions due to inadequate in situ furfural separation, which forced low biomass loadings. We therefore coupled hemicellulose hydrolysis–dehydration with steam stripping to remove furfural as it formed and implemented strict process control with stepwise biomass feeding. At 30 wt% biomass loading, the system delivered a >75% isolated yield by minimizing the furfural residence time in the acidic, recyclable [DMBA][HSO4], suppressing condensation with substrates and intermediates. A techno-economic analysis suggested that co-recovering cellulose would be essential for the process’s commercial viability.
Finally, to extend the value chain, we developed a continuous process for oxidizing furfural to furoic acid, a higher-value intermediate for biopolymers and bio-based surfactants. Using a robust Ru/C catalyst in a high-pressure continuous-flow system, the process achieved a >90% furfural conversion and a >90% furoic acid yield with stable operation, successfully scaling the technique to the liter level and offering guidance for further industrial deployment.
Collectively, these results support the development of an integrated PIL-based biorefinery for efficient cellulose and hemicellulose valorization.
First, we evaluated probe sonication to accelerate the ionoSolv process at mild temperatures. The sonication effect was strongly feedstock-dependent: for Miscanthus, acceleration was confined to the early stage (0–1 h), whereas for recalcitrant spruce, it remained pronounced after 4 h at 130 °C. Quantitative analysis indicated that sonication-induced heating, rather than mass transfer enhancement, was the main driver.
Second, using the same PIL platform, we targeted hemicellulose valorization via furfural production. Prior work has confirmed furfural formation but faced side reactions due to inadequate in situ furfural separation, which forced low biomass loadings. We therefore coupled hemicellulose hydrolysis–dehydration with steam stripping to remove furfural as it formed and implemented strict process control with stepwise biomass feeding. At 30 wt% biomass loading, the system delivered a >75% isolated yield by minimizing the furfural residence time in the acidic, recyclable [DMBA][HSO4], suppressing condensation with substrates and intermediates. A techno-economic analysis suggested that co-recovering cellulose would be essential for the process’s commercial viability.
Finally, to extend the value chain, we developed a continuous process for oxidizing furfural to furoic acid, a higher-value intermediate for biopolymers and bio-based surfactants. Using a robust Ru/C catalyst in a high-pressure continuous-flow system, the process achieved a >90% furfural conversion and a >90% furoic acid yield with stable operation, successfully scaling the technique to the liter level and offering guidance for further industrial deployment.
Collectively, these results support the development of an integrated PIL-based biorefinery for efficient cellulose and hemicellulose valorization.
Version
Open Access
Date Issued
2025-10-03
Date Awarded
2026-05-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Hallett, Jason
Fennell, Paul
Publisher Department
Department of Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)