Monday, April 30, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Ching-Shuan Lau1, Kris Bunnell1, Edgar Clausen2 and Danielle Julie Carrier1, (1)Department of Biological and Agricultural Engineering, University of Arkansas, Fayetteville, AR, (2)Ralph E. Martin Department of Chemical Engineering, University of Arkansas, Fayetteville, AR
Dilute acid hydrolysis is a common pretreatment method for cellulosic ethanol production by hydrolyzing hemicellulose into simple monomeric sugars, such as xylose, which can be fermented to produce ethanol. However, the severity of pretreatment generates degradation by-products such as furfural and formic acid, which reduce yields of monomeric sugars and inhibit the fermentation process. Conversely, if pretreatment conditions are less severe, a high accumulation of oligomers, the intermediate products of hemicellulose depolymerization into monomers, will inhibit the enzymatic hydrolysis of cellulose. Therefore, studying the kinetics of xylose oligomers degradation is critical to describe hemicellulose depolymerization because these results will help optimize the monomeric sugar yields from biomass.
Birchwood xylan was partially hydrolyzed to produce xylose oligomers, which were then fractionated using centrifugal partition chromatography (CPC). A solvent system of butanol: methanol: water (5:1:4, V/V/V) was used in the CPC instrument to produce high purity fractionated xylose oligomers, which were subsequently hydrolyzed using sulfuric acid concentrations ranging from 0 to 0.5% at 120 to 200 ˚C for 0 to 60 min. The hydrolysates were analyzed for xylose monomer, oligomers, and by-products to determine rates of formation and degradation.
The depolymerization of xylose monomer and oligomers was found to follow first order kinetics. Using water at 160 ˚C, the degradation rates of xylose (DP1), xylobiose (DP2), and xylotriose (DP3) were 0.0040, 0.0391, and 0.0155 min-1, respectively. Our future work will focus on expanding the kinetic model of xylose monomer and oligomers decomposition to different pH and temperature conditions.
