Selective Fractionation of Larch into Oligosaccharides and Less-Condensed Lignin in a Novel Molten Salt/n-Butanol System

Efficient fractionation of lignocellulosic components is a prerequisite for full-component utilization. Conventional methods rely on harsh conditions, causing severe degradation of cellulose and hemicellulose and lignin condensation, while milder conditions compromise fractionation efficiency. To balance native structure preservation and fractionation efficiency, a biphasic system composed of lithium bromide molten salt hydrate (MSH) and n -butanol was developed. At 110 ° C for 1 h, cellulose and hemicellulose were selectively hydrolyzed into oligosaccharides in the MSH phase with yields of 81.4% and 88.1%, respectively. The isolated lignin retained 96.1% of β-O-4 ether bonds (38.5/100 C9 units), and its catalytic hydrogenolysis delivered a monophenol yield of 82.1% to the theoretical value. The light-colored lignin (Δ E = 31.28) achieved SPF 28.2 as a sole sunscreen active ingredient, demonstrating commercial potential. This biphasic system enables highly selective fractionation of lignocellulosic components with limited condensation, yielding key feedstocks for bioenergy and biorefinery, including oligosaccharides and native structure-preserved lignin.