Sulfuric acid-sugar separation by ion exclusion

Abstract

Abstract Biomass conversion continues to have significant potential in the production of fuel ethanol by fermentation. A major cost in acid hydrolysis of biomass to fermentable sugars is the acid itself. Separation and recyle of the acid could reduce ethanol production costs by $0.10 / gallon or more. In this context, a process that separates sulfuric acid from glucose using ion-exclusion technology is presented. A 61 cm long, fixed-bed of Rohm and Haas Amberlite IR-118, strong cation-exchange resin in the hydrogen form was used. Samples containing 7.7% H2SO4 and 1.0% glucose, at sample volumes of 10% to 50% of the column void volume gave separation of H2SO4 from glucose at column temperatures ranging from 27 to 81°C with water as eluent at a superficial velocity of 0.6 cm/min. Skewing of the H2SO4 peak was observed and traced to a sharp density gradient between the acid and the water eluent while the glucose peak was sufficiently symmetric to be fitted by an axial dispersion model. This work shows that a chromatographic resin having a particle size range of 300 to 1200 micrometers can give complete recovery of sulfuric acid with 94% recovery of glucose. This case study has interesting implications for both the practice of process chromatography, using a resin with large particle size at gross loading conditions, and the prospects of further reducing fermentable sugar costs in biomass conversion.