Uniqueness of biphasic organosolv treatment of soft- and hardwood using water/1-butanol co-solvent

Abstract

Biphasic organosolv treatment for soft- and hardwood using water/1-butanol was unique based on the correlation between liquid-phase states and solubility of the co-solvents when compared with a monophasic water/ethanol system. First, Pro II process simulator showed that water/1-butanol exhibited a biphasic system in the range of 1.6–19.0 mol/mol at a treatment temperature of 473 K. In addition, solubility of the co-solvents was evaluated using the Hildebrand solubility parameter (δ), which indicated that the biphasic system could simultaneously provide 28.5 and 42.0 MPa1/2 for the 1-butanol and water phase, respectively. Each δ value appeared appropriate for lignin and hemicellulose dissolution because they were similar to those reported for lignin and a typical sugar. While hemicellulose could be removed by increasing water content in an organosolv of Japanese cedar sawdust, high lignin removal was achieved only under biphasic conditions. Carbon yield of each fraction (solid, 1-butanol-, and water-soluble fraction) and Py-GC/MS analysis revealed that lignin and hemicellulose could be recovered in the 1-butanol and water fractions, respectively. The organosolv using Japanese cedar and willow was compared to the results when using monophasic water/ethanol. The results indicated that the co-solvent could not efficiently remove hemicellulose and lignin simultaneously because the monophasic system did not produce the level of solubility needed under the same conditions. In contrast, the biphasic water/1-butanol system achieved greater removal of hemicellulose and lignin compared to water/ethanol. The biphasic system was also applicable to separation of an industrial agricultural waste; sugarcane bagasse. Finally, the 2D-NMR spectra of 1-butanol-soluble lignin showed a trace amount of β-O-4 linkages in the lignin, indicating β-O-4 was cleaved via hydrolysis in the water phase during biphasic treatment.