Direct liquefaction of Dunaliella tertiolecta for bio-oil in sub/supercritical ethanol–water

Hydrothermal Conversion of Lipid-Extracted Microalgae Hydrolysate in the Presence of Isopropanol and Steel Furnace Residues

“…Compared to previous studies using ethanol-water solvent mixtures, commonly seen as the best solvent and which reported maximum oil yield increases of around 25% at optimized ethanol-water ratio, compared to the water-only reactions [13,30], the increase in total oil yields obtained in the present study (111%) is highly promising. However, it should be noted that due to the nature of the feedstock, the final yields of 28.3% are still significantly below the yields obtained in the cited studies (57.3 and 63%), and therefore it is not possible to distinguish between the effect of the solvent (IPA vs. ethanol) or the differences in the feedstock.…”

“…Operating at 50 vol% IPA therefore ensured that the maximum possible IPA concentration in the liquid phase was achieved, without causing excessive evaporation of IPA, resulting in operation above the design pressure of the reactor. Finally, results from previous HTL studies conducted in water-solvent mixtures suggested that maximum bio-oil yields were obtained when the critical temperature of the mixture corresponded to the reaction temperature [13].…”

“…Consequently, it may be desirable to conduct the HTL of this algae residue in the presence of polar organic solvents, such as ethanol, acetone, or ethylene glycol, or organic waste products, such as glycerol, which have been previously found to enhance bio-oil yields, compared to water-only reactions [9][10][11][12]. These enhancements have been generally associated with reduced critical temperatures and pressures allowing the use of milder reaction conditions and lower dielectric constants, helping to dissolve high-molecular-weight products [13]. It has also been suggested that the hydrogen donation abilities of certain solvents such as ethanol could help to improve the quality of the final bio-oil [14].…”

“…Instead, the liquefaction could be conducted in solvent-water mixtures, which were often found to produce higher yields than the reactions in the pure solvent [10,12,13,15]. In these studies, the optimal solvent-water ratios were found to be strongly dependent on both the solvent, and the selected reaction temperature, and it was suggested that the optimal solvent concentration is governed by the proximity of the critical temperature of the mixture to the reaction temperature [13]. However, for polar solvents, the subsequent recovery of the bio-oil and reaction solvent may be more challenging, compared to conventional HTL reactions, due to the high miscibility of the solvent with the aqueous phase.…”

Liquefaction of Fir Sawdust in Supercritical Ethanol with Dissolved Phosphotungstic Acid

“…Lignin shows distinct bands at 1599, 1506, 1422, and 814 cm -1 ). The broad absorption peak near 3392 cm -1 may be due to O-H stretching originating from the presence of cellulose and/or polysaccharide compounds (hemicellulose) (Chen et al 2012). The strong absorbance at 2915 cm -1 , attributed to the C-H stretching vibrations, indicates the presence of methyl and methylene groups (Brand et al 2013).…”