Supercritical Carbon Dioxide Extraction of Lignocellulosic Bio-Oils: The Potential of Fuel Upgrading and Chemical Recovery

Abstract

Bio-oils derived from the thermochemical processing of lignocellulosic biomass are recognized as a promising platform for sustainable biofuels and chemicals. While significant advances have been achieved with regard to the production of bio-oils by hydrothermal liquefaction and pyrolysis, the need for improving their physicochemical properties (fuel upgrading) or for recovering valuable chemicals is currently shifting the research focus towards downstream separation and chemical upgrading. The separation of lignocellulosic bio-oils using supercritical carbon dioxide (sCO2) as a solvent is a promising environmentally benign process that can play a key role in the design of innovative processes for their valorization. In the last decade, fundamental research has provided knowledge on supercritical extraction of bio-oils. This review provides an update on the progress of the research in sCO2 separation of lignocellulosic bio-oils, together with a critical interpretation of the observed effects of the extraction conditions on the process yields and the quality of the obtained products. The review also covers high-pressure phase equilibria data reported in the literature for systems comprising sCO2 and key bio-oil components, which are fundamental for process design. The perspective of the supercritical process for the fractionation of lignocellulosic bio-oils is discussed and the knowledge gaps for future research are highlighted.

Progressing Plastics Circularity: A Review of Mechano-Biocatalytic Approaches for Waste Plastic (Re)valorization

“…Despite of increased use of scCO 2 in polymer modification, only a limited number of studies are available on the use of scCO 2 for polymer depolymerization. The majority of the studies to date focus on the use of scCO 2 in the pyrolysis of plastic and other waste materials to increase the yield of hydrocarbons and production of nanomaterials ( Feng and Meier, 2017 ; Montesantos and Maschietti, 2020 ). The depolymerization reaction proceeds effectively in the presence of scCO 2 resulting in monomer production, which are recoverable with high yields ( Goto, 2009 ).…”

Valorisation of CO2 into Value-Added Products via Microbial Electrosynthesis (MES) and Electro-Fermentation Technology

“…For the extraction of propionic acid, trioctylamine was used in supercritical CO 2 , high extraction productivity was achieved (97%-propionic acid), only a small portion vanished acid-amine complex formation. Pressure and temperature conditions need to be maintained as they have a high effect on productivity [213][214][215].…”

Supercritical Carbon Dioxide Extracts of Cordyceps sinensis: Chromatography-based Metabolite Profiling and Protective Efficacy Against Hypobaric Hypoxia

“…In this manner, supercritical fluids are capable of solvent power with negligible surface tension as well as excellent mass transfer properties ( Pronyk and Mazza, 2009 ). Although supercritical water and carbon dioxide (CO 2 ) have garnered major attention amongst researchers for extracting superior quality cosmeceuticals, essences, fragrances, pharmaceuticals from medicinal herbs, CO 2 happens to be advantageous in industrial bioprocessing owing to its comparatively moderate supercritical temperature, better diffusivity, low viscosity and easy recovery in addition to being an economical solvent, nonflammable and recyclable gas ( Montesantos and Maschietti, 2020 ). Previous literature evidence that CO 2 is contemplated to be a better supercritical fluid than other solvents like water ( Kumoro et al, 2010 ).…”