Bio-oils must be upgraded if they are to be used as a replacement diesel and gasoline fuel. The overall goal of this project is to examine the feasibility of steam reforming the aqueous fraction of bio-oils. Fast pyrolysis bio-oils can be separated into aqueous and organic fraction by the addition of water or a solvent or hydrotreating to less than 20 wt.% O. While other liquefaction technologies, such as hydrothermal liquefaction and some permutations of catalytic pyrolysis, directly yield biphasic bio-oils. The loss of organic species in the aqueous phase that would otherwise need to be treated in order to reclaim the water is potentially a negative economic impact. The higher value predominantly organic fraction can be used to make chemicals or upgraded to produce gasoline, diesel, or jet fuels. The lower value predominantly aqueous fraction can be converted into syngas by steam reforming, producing hydrogen which can be recycled in-plant for hydrogenation purposes (e.g. hydrodeoxygenation upgrading). Process hydrogen would otherwise be supplied from either natural gas, or steam reforming of the entire bio-oil, which includes the higher value organic fraction.
The steam reforming of model biomass compounds, including acetic acid, acetone, phenol, cresol, ethanol, and sugars, has been carried out with Ni and noble metal catalysts, including Pt, Rh, and Pd. Coking problems have largely been reported on the Ni catalyst surfaces. The steam reforming of model compounds over noble metal catalysts have been reported with some degree of success, given suitable operating conditions. Steam-to-carbon molar ratio in excess of 6 has been reported as typically necessary to avoid coking. However, there is a trade-off with the energy penalty associated with water vaporization. Thus, robust reforming catalysts are desired that allow stable reforming operation at low steam-to-carbon ratios. The objective of this work is to develop active and stable catalysts for the steam reforming of oxygenated species specifically found in the aqueous fraction of bio-oils. Combined experimental-theoretical studies will be performed in order to better understand the interaction been catalytic structure and chemical reactivity.