Solvolysis of lignocellulose by anhydrous hydrogen fluoride vapor: Yield comparisons from four cellulosic substrates

Abstract

Water soluble sugar yields and total product recoveries from the vapor-phase HF solvolysis of four ligno-cellulose substrates were compared: Bigtooth Aspen wood, prehydrolyzed Bigtooth Aspen wood, filter paper, and a synthetic lignocellulose composite substrate containing 23·3% wt lignin. The lignocellulose composite substrates were prepared by solvent-impregnating milled wood lignin onto filter paper. Single wafers of each substrate were contacted with an 100% HF vapor stream at 30°C and 1·0 atm and reacted to completion. After mild posthydrolysis of water-soluble products, glucose yields averaged 84% of theoretical for wood (87% including glucose trapped in solid fraction) and 93–94% of theoretical for prehydrolyzed wood, filter paper, and the lignocellulosic composite substrate. Total measured product recoveries averged 85% for wood vs 93–94% for the other three substrates. Reactions of HF vapor with the lignocellulosic composite substrate indicated that glucosyl fluoride from solvolysis of the cellulose fraction did not condense with lignin to form a water-insoluble adduct. Lowered glucose and xylose recoveries from wood may be due to uncertainties in composition of wood and possible reactions of HF with hemicellulose/lignin fractions.