Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Hydrothermal pretreatment of lignocellulosic biomass removes and solubilizes hemicellulose fraction of the biomass. The majority of the solubilized hemicellulose is present as oligomeric sugars which need to be further hydrolyzed to monomeric sugars prior to be converted to fuels and other chemicals. In this study, we evaluate the performance of three different acids, sulfuric acid and two dicarboxylic acids (maleic and oxalic acid) on the hydrolysis of pentose sugar oligomers derived from steam pretreated mixed hardwood. Temperature and pH was varied between 140-180oC and pH 1.3-2.2, respectively. We present a homogeneous, consecutive pseudo first-order kinetic model to describe the catalytic behavior of these acids. Based on the model, we determine the kinetic parameters of each acid and compare their effectiveness. The empirical and model-based analysis indicates that xylose yield is maximized with increase of acid loading and low temperature. Maleic and oxalic acids outperform sulfuric acid by preventing xylose degradation, as indicated from an inverse correlation between xylose degradation rates and acid loadings (or pH). Other key factors to be considered in process design and catalyst selection are also discussed.