Catalytic Reformation of the Bio-oil Aqueous Fraction: Reforming Catalyst Development
EMSL Project ID
47689
Abstract
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 the bio-oil. Fast pyrolysios bio-oils can be separated into aqueous and organic fraction by the addition of water or a solvent or hydrotreating to less than 20wt % O. While other liquefaction technologies such as, hydrothermal liquefaction and some permutations of catalytic pyrolysis directly yield biphasic (predominantly aqueous and predominantly organic) bio-oils. The loss of organic species in the aqueous phase that would 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 provide 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. Reformation of the bio-oil aqueous fraction would increase overall biomass carbon utilization, decrease hydrogen requirement for the overall liquefaction process, and reduce aqueous stream waste processing cost.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. Temperature, steam-to-carbon ratios, and space velocity are important operating parameters. Steam-to-carbon molar ratio in excess of 6 has been reported as typically necessary to avoid coking. Since water addition to the bio-oil is necessary, in order to separate the aqueous and organic fraction, allowing use of the dilute aqueous stream with no water removal required prior to reforming is advantageous. 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.
Little has been reported for the steam reforming of actual aqueous fraction of the products that result from direct liquefaction processes (fast pyrolysis, catalytic fast pyrolysis, hydro-pyrolysis and hydrothermal liquefaction). At the same time, very little characterization data has been published on the composition of these aqueous streams. This project will leverage other projects being performed at PNNL that will produce and characterize bio-oil aqueous fractions.
In this project catalysts will be developed for the steam reforming of species specifically found in the aqueous fraction of the bio-oil. This project will also leverage previous work at PNNL engaged in developing active and stable noble metal based catalysts for light hydrocarbon and tar reforming of gasifier-derived syngas.
Project Details
Start Date
2012-10-05
End Date
2013-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Mei D, VA Glezakou, VMC Lebarbier, L Kovarik, H Wan, KO Albrecht, MA Gerber, RJ Rousseau, and RA Dagle. 2014. "Highly Active and Stable MgAl2O4 Supported Rh and Ir Catalysts for Methane Steam Reforming: A Combined Experimental and Theoretical Study." Journal of Catalysis 316:11-23. doi:10.1016/j.jcat.2014.04.021