Furan Distribution as a Severity Indicator upon Organosolv Fractionation of Hardwood Sawdust through a Novel Ternary Solvent System.

Beech sawdust was treated with a ternary solvent system based on binary aqueous ethanol with partial substitution of ethanol by acetone at four different water contents (60, 50, 40, and 30%v/v). In addition to standard, i.e., noncatalyzed treatments, the application of inorganic acid in the form of 20 mm H 2 SO 4 was evaluated. The various solvent systems were applied at 180 °C for 60 min. The obtained biomass fractions were characterized by standard biomass compositional methods, i.e., sugar monomer and oligomer contents, dehydration product contents of the aqueous product, and lignin, cellulose, and hemicellulose contents in isolated solid fractions. More advanced analyses were performed on the lignin fractions, including quantitative 13 C NMR analyses, 1 H- 13 C HSQC analysis, size exclusion chromatography, and pyrolysis-GC/MS, and the aqueous product, in the form of size exclusion chromatography and determination of total phenol contents. The picture emerging from the thorough analytical investigation performed on the lignin fractions is consistent with that resulting from the characterization of the other fractions: results point toward greater deconstruction of the lignocellulosic recalcitrance upon higher organic solvent content, replacing ethanol with acetone during the extraction, and upon addition of mineral acid. A pulp with cellulose content of 94.23 wt % and 95% delignification was obtained for the treatment employing a 55/30/15 EtOH/water/acetone mixture alongside 20 mm H 2 SO 4 . Furthermore, the results indicate the formation of two types of organosolv furan families during treatment, which differ in the substitution of their C 1 and C 5 . While the traditional lignin aryl-ether linkages present themselves as indicators for process severity for the nonacid catalyzed systems, the distribution of these furan types can be applied as a severity indicator upon employment of H 2 SO 4 , including their presence in the isolated lignin fractions.