Aqueous phase processing of lignocellulosic biomass for biofuel production
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This thesis studied the catalytic upgrading of pyrolysis oil derived from both ethanol organosolv (EOL) lignin and whole biomass. There are four major components of this thesis. In the first part, several lignin model compounds and the commonly used noble metal catalysts were evaluated. During the reaction, coke formation deactivated several catalysts. The reaction pathway of the coke formation was proposed. Ruthenium/activated carbon can hydrogenate the aromatic ring and remove the methoxyl group as well due to its unique catalytic behavior. The reaction mechanism was deduced based on the products distribution of the model compounds. The second part of this study focuses on the catalytic HDO reaction with real EOL pyrolysis oil. The results indicate the reaction mechanism with EOL pyrolysis oil is similar to the results of the model compound study. Due to the deactivation of the Ru/C catalyst by tar produced during the upgrading, two-step hydrodeoxygenation at different temperature was adopted in this study. The second part mainly discussed the first-step HDO reaction. The upgraded pyrolysis oil was analyzed using GC-MS, ¹H, ¹³C, and HSQC ²D NMR. The chemical structure change after the first-step upgrading and the cleavage of the inter-linkages were included. The third part focuses on the product analysis after the second-step HDO. All the products were completely hydrogenated. The molecular weight of the upgraded oil is in the monomer range and the GC-MS study provided detailed compound structures. However, some of them still contain oxygen atoms. To produce completely deoxygenated products, alkali treated ZSM-5 was used as a supporting material and it was effective in catalyzing the dehydration reaction and producing deoxygenated compounds. In the fourth part, light oil derived from whole biomass also underwent treatment under the same HDO reaction conditions as those used in upgrading EOL pyrolysis oil. In this reaction, the biomass were separated into three components: stem, residue and bark. The compound structures of the three different types of light oil were analyzed by GC, ¹H and ¹H-¹³C HSQC-NMR. Then the light oil was processed under the same condition as the heavy oil upgrading. The reaction mechanisms with cellulose and hemicellulose were also studied. These results will be of value in developing of complete hydrogenation of whole biomass pyrolysis oils.