Vapor-phase HF solvolysis of cellulose: Modification of the reversion oligosaccharide distribution by in-situ methanolysis

Abstract

The solvolysis of cellulose by anhydrous hydrogen fluoride (HF) vapor produces water-soluble oligosaccharides generated by repolymerization of the primary solvolysis product, glucosyl fluoride. In-situ methanolysis of glucosyl fluoride in the HF-reacting cellulose substrate reduced the extent of this reversion reaction and increased the recovery of monomers (as glucose and 1- O-methyl glucose) in the water-soluble reaction products. Single cellulose filter paper wafers both with and without absorbed methanol were reacted with an HF vapor stream at 30°C and 1·0 atm for reaction times varying from 2 to 12 min. The oligosaccharide product distribution in the water-soluble reaction products was then profiled by HPLC. The cellulose substrate was completely converted to water-soluble products within 4 min exposure to HF vapor, but the oligosaccharide product distribution did not reach equilibrium until 10 min exposure to HF vapor. Absorbed methanol (5 mole methanol to 1 mole glucan) in the cellulose substrate increased the monomer recovery of the water-soluble reaction products from 30 mole % to 60 mole %.