Acid pretreatment of biomass is necessary in many cellulosic ethanol processes. This step hydrolyzes the hemicellulose to form fermentable sugars and exposes cellulose for subsequent enzymatic hydrolysis steps. A key to the economic success of cellulosic ethanol production is the efficient hydrolysis of xylans into the monomer, xylose. The yield of xylose is reduced by dehydration reactions, which form furfural; and reversion reactions, which are the reverse of hydrolysis reactions. Reversion reactions occur in high concentration xylose solutions (~200 g/L) and result in formation of xylooligomers. In this study, experimental measurements were used in conjunction with quantum mechanical molecular modeling to explore the fate of xylan, xylooligomers, and xylose in acidic solutions. Experiments were conducted using highly agitated microwave-heated reactor vessels. This reactor set up allowed rapid heating of the sample and limited the effects of mass transport, thus permitting the measurement of intrinsic kinetics. The experimental kinetics and activation energies will be compared to the results of quantum mechanical calculations. We used both static electronic structure theory and quantum mechanical molecular dynamics simulations to obtain activation energies and free energies for these important reactions.

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