Friday October 8
Chem. Sci. & Engineering Room 211
Presenter: Dr. Daniel Resasco, Univ. of OklahomaSchool of ChemicalBiological & MaterialsEngineering
Abstract: Pyrolysis oil is a complex mixture of oxygenated compounds with up to ~30-40% of water. Depending on the cooling process used in the condensation of the pyrolysis vapors, the crude bio-oil can generate a biphasic system, in which molecules are distributed, between the two phases, depending on their solubility. It is desirable to conduct reactions at the water/oil interface that can both enhance the fuel value of the molecules and effect phase migration, based on solubility, avoiding fractionation by heating, which is known to negatively impact bio-oil.We have developed a new reaction/separation concept based on a family of recoverable nano-hybrid catalysts that simultaneously stabilize emulsions in biphasic bio-oil. These nanostructured solid particles exhibit a unique advantage in streamlining biomass refining, where the immiscibility and thermal instability of crude bio-oil greatly complicates purification procedures. These novel catalyst/emulsifier hybrids can catalyze reactions with high “phase-selectivity” either in the aqueous or organic phases.These catalysts are obtained by fusing carbon nanotubes with metal-oxide particles, which results in twofaced nanohybrid solids that are able to stabilize water/oil emulsions by forming a rigid film at liquidliquid interface of the droplets and increasing the apparent viscosity of the system (1).The metal oxide in the nanohybrid acts both, as the hydrophylic side of the emulsifier, and as a catalyst for condensation reactions in the aqueous phase. Accordingly, small oxygenates soluble in water, with low fuel value, condense via aldol-condensation, ketonization, or etherification resulting in products, which are no longer water-soluble molecules and therefore migrate to the organic phase. The oxide used can vary in acid/base characteristics. Some of the metal-oxides tested are; MgO, SiO2, TiO2 and ZnO.In the organic phase, transition metals such as Pd, Ni and Cu have been deposited onto the hydrophobic carbon nanotube of the nanohybrids to catalyze deoxygenation reactions including hydrogenation, hydrogenolysis, or decarbonylation occurring on the oil side of the emulsion.We have accomplished biphasic hydrodeoxygenation and condensation catalysis in high yields, using these nono-hybrid catalysts for several systems of interest in biomass refining (2). Reactions were conducted in a semi-batch reactor with the liquid composed of three layers oil/emulsion/water and with continuous flow of hydrogen, at temperatures in the range 80- -900 psi) high enough to maintain the water in the liquid state.