Production of Glucose from the Acid Hydrolysis of Anhydrosugars

Abstract

Two anhydrosugar model compounds (cellobiose and levoglucosan) and a mixture of anhydrosugars from the fast pyrolysis of birch wood were subjected to acid hydrolysis using sulfuric acid as a catalyst. The anhydrosugar mixture or bio-oil aqueous fraction was found to contain mainly levoglucosan with a concentration of 30 g L–1. Hydrolysis temperature, reaction time, and catalyst to substrate molar ratios (c/s) were varied to identify their influence for glucose production. At 120 °C, 60 min, and a 0.9 c/s ratio, glucose yields of 98.55% and 96.56%, and substrate conversions of 100% and ∼92%, were achieved when hydrolyzing cellobiose and levoglucosan, respectively. An increase in the temperature to 135 °C resulted in a decrease in both glucose yield and selectivity, whereas substrate conversions around 90% were maintained for both anhydrosugars. During the hydrolysis of the bio-oil fraction, a range of conditions to achieve glucose yields above 90% was depicted. It was found that c/s ratios between 0.17 and 0.90 and temperatures between 118 and 126 °C were suitable to achieve glucose yields around 100% (30 g L–1). Furthermore, glucose concentrations of ∼117% (35 g L–1) and levoglucosan conversions above 90% were attained at 135 °C, 20 min, and a 0.2 estimated c/s ratio.