(222b) Condensed Phase Ketonization of Bio-Oil Model Compounds: Catalysis by Ceria Nanoparticles
Bio-oil, made from the fast pyrolysis of biomass, suffers from low energy density and high acidity due to the large number of oxygen containing functionalized molecules and low molecular weight carboxylic acids. While hydrodeoxygenation could potentially solve these problems, it would be an expensive option. Condensed phase catalytic conversion of these undesirable molecules to increase the carbon-carbon chain length as well as remove oxygen would be a desirable alternative. Ketonization, taking two organic acids and creating a ketone, carbon dioxide, and water, would be an ideal reaction for this application as it is environmentally clean and efficiently removes acidity and oxygen from the oil. Unfortunately high temperatures have been necessary for the ketonization reaction, thus the vapor phase has almost exclusively been used with the coupling of low molecular weight acids. A number of different metal oxides have been found to catalyze this particular reaction, but cerium oxide is particularly active. Despite a significant amount of research, the exact mechanism of ketonization has not been determined and much about the reaction remains unknown.
In order to make condensed phase ketonization of low molecular weight acids more feasible, a significant lowering of the reaction temperature is necessary. Therefore a more active catalyst must be designed. Further understanding of the oxides role in the reaction, particularly in the condensed phase is thus crucial. The work presented here focuses primarily on the condensed phase reactions and potential applications of shape selective ceria nanocatalysts. Pre- and post-reaction characterization has demonstrated that the condensed phase ketonization reaction may proceed through a different mechanism than has been typically proposed in the vapor phase.