(206e) Upgrading of Short Oxygenates From Pyrolysis Oil Via Condensation Reactions for the Refining of Biofuels

Torrefaction of biomass between 270-290 ^oC produces significant amounts of short oxygenates including acetol, acetic acid and acetone together with large amounts of water. The carbon number and energy content of these oxygenates are too low to be directly utilized for the production of transportation fuels and there is a need to build the carbon chain of these oxygenates.  Condensation reactions are an important route to build the carbon chain to produce molecules in the gasoline and diesel range without the external addition of hydrogen and it is of interest to perform these reactions in-situ after the pyrolysis of biomass to prevent degradation reactions within the liquid bio-oil product. To do this, a suitable catalyst has to be designed that will selectively perform condensation reactions in the presence of a large excess of water, while resisting deactivation by furfural and phenolic compounds. In this work, a model study of pure and mixed feeds of acetol, acetic acid and water were carried out over metal oxides, with the aim of maximizing the yield to acetone. Acetone is a useful intermediate that can be further upgraded via self aldol condensation reactions and cross aldol condensation reactions with furfural to form fuel range carbon chains. It can also be hydrogenated to iso-propanol, which is a good alkylating agent for phenolic compounds. From the reaction of the mixed feed, acetone was obtained as the major product, with small amounts of cyclopentanones and other oxygenates. From the reaction of pure acetol, the yields of acetone, cyclopentanones and other oxygenates were comparable. It is believed that the pathway to acetone from acetol involves several possible steps. The dehydrogenation of acetol produces 2-oxopropanal that undergoes decarbonylation to give acetaldehyde. The ketonization of acetaldehyde gives acetone. Acetol also apparently undergoes cyclization through a series of steps to give various cyclic ketones. These are believed to form a surface pool that undergoes cracking to yield acetone.