Electronic Structure Calculations of the Decomposition of Xylose During Acid Pretreatment of Biomass

Dilute acid pretreatment of biomass is an effective tool for converting hemicellulose and amorphous cellulose into their constituent sugars and exposing crystalline cellulose to enzymatic hydrolysis. The resulting sugars provide a platform for chemical and biological proceses to produce renewable fuels and chemicals. The preliminary chemical processes that occur during the decomposition of protonated xylose were studied using electronic structure techniques. This served as a model of the decomposition of xylose during the acid pretreatment of biomass. O₂ had the largest proton affinity (PA = 191.3 kcal/mole), and this oxygen atom is the most likely site for addition. Protonation at the O1 was least likely because the PA at this site was lowest. Loss of water from xylose protonated at O1 had the lowest activation energy, followed by ring opening from xylose protonated at O5. Water addition to reform xylose was possible, resulting in no net reaction. Loss of water from protonation at O₂ was accompanied by addition of O5 to C2 forming a furanyl compound. This is an abstract of a paper presented at the ACS Fuel Chemistry Meeting (San Diego, CA Spring 2005).