Chromatographic Recovery of Monosaccharides for the Production of Bioethanol from Wood

Abstract

Chromatographic recovery of monosaccharides from concentrated-acid hydrolysates of spruce and birch was investigated for the production of bioethanol from lignocellulose. The effects of resin cross-linkage, column loading, and hydrolysate composition on the yield of monosaccharides and the productivity of the process were of particular interest. Three strong acid cation-exchange resins (gel type) were used. Chromatographic separation experiments were done in a batch column. Monosaccharides were recovered as a “center cut” between sulfuric acid and acetic acid. Hydroxymethyl furfural and furfural, which inhibit the fermentation of monosaccharides, were completely separated from the other components. The highest H2SO4−monosaccharide separation efficiency was obtained with a 6 wt % cross-linked resin. The monosaccharide−acetic acid separation efficiency was found to improve with increasing resin cross-linkage. In the case of high amounts of acetic acid in the hydrolysate, a resin with a high cross-link density is needed for a good yield of monosaccharides. With hydrolysates containing small amounts of acetic acid, a 6 wt % cross-linked resin was found to give the highest yield. The productivity of the process was found to increase with the resin cross-linkage (up to 8 wt %). The optimum column loading depends on whether a high monosaccharide yield or high productivity is desired. The highest yield is obtained with a low loading. As to the productivity, the optimum loading was found to be approximately 10 vol % of the bed volume.