CO2 fractionation of biocrude produced from liquefaction of weeping lovegrass

Abstract

Currently, there is a growing demand andresearch effort to reduce the utilization of fossil resources. Bio-crudes orbio-oils, produced from second-generation biomass, are considered aninteresting alternative. Thermochemical processes, such as hydrothermalliquefaction and pyrolysis, have demonstrated their capacity to yield highamounts of bio-crudes from low-cost lignocellulosic biomass that does notcompete with food production. Bio-crudesobtained through thermochemical processes require significant hydrogenationtreatment in biorefineries to upgrade them to a fuel grade and make the productcompatible with engine fuels and mineral oils. One viable alternative is toseparate the biocrude to obtain a fraction of components with lower density,reduced acidity, and low oxygen content, which simplifies the hydrotreatmentprocess. The heavy fraction obtained in the separation process as well as thesolid residue of the liquefaction can be used as a precursor for activatedcarbon. Inthis study, we have assembled a semi-continuous bench scale liquefaction unitto investigate the production of biocrude from biomass. We obtained biocrudesfrom weeping lovegrass biomass straw through a hydrothermal liquefactiontreatment at 280 ºC and 170 bar using an atmospheric azeotropic composition ofethanol+water (89.4 mol% ethanol) + CO2 mixture prepared in a tankat 30 bar. Biomass liquefaction using water + etanol in presence of CO2significantly increases biocrude production compared to the liquefactionprocess using pure water. Following the hydrothermal process,the biocrude is treated in a bench-scale semicontinuous high-pressure extractorwith supercritical CO2 at different temperatures (25 to 40 ºC) andpressures (65 to 150 bar) to evaluate the fractionation of low-molar massaromatic components, and its solubility in supercritical CO2. Theproducts obtained under different operating conditions are analyzed by GC-MS tocharacterize the extracts and assess their overall valorization.