(435d) Dilute Acid Hydrolysis of Xylose Oligomers Fractionated by Centrifugal Partition Chromatography
Xylose oligomers, which are chains of xylose molecules linked with β-1,4-bonds with a degree of polymerization greater than two, are the intermediate products of xylan depolymerization into xylose monomer. Studying the kinetics of xylose oligomers is critical to describe hemicellulose depolymerization because these results will help researchers understand how the formation of inhibitory by-products occurs. The objective of this research is to determine the rate of depolymerization of xylose oligomers under commonly used dilute acid hydrolysis conditions. The understanding of the depolymerization rate as a function of the hydrolysis conditions will help us determine the optimum range of dilute acid pretreatment conditions, which will hopefully result in the maximum conversion of hemicellulose into xylose monomer.
Xylose oligomers, fractionated by centrifugal partition chromatography (CPC) using a solvent system of dimethyl sulfoxide-tetra hydrofuran-water, were hydrolyzed using sulfuric acid concentrations ranging from 0 to 4%, at 121 to 240 ˚C for 0 to 120 minutes. The hydrolysates were analyzed for the xylose monomer, oligomers and by-products concentrations to determine the individual rate of degradation and the formation rate of the by-products. Mass balance closure of xylose oligomers before and after the hydrolysis was performed to account for the majority of the oligomer’s mass during the hydrolysis process. The results indicated that the use of National Renewable Energy Laboratory’s total sugar analysis method, which hydrolyzes the biomass sample in 4% sulfuric acid, at 121˚C for 60 minutes resulted in a 10% loss of xylose, which can be mostly accounted for by the formation of furfural. Moreover, the xylose loss rates were 26% and 5% for pure xylobiose and xylotriose, respectively, when used in the total sugar analysis.