(207g) Design of Active and Stable Catalysts for the Hydrodeoxygenation of m-Cresol

Pyrolysis is an emerging technology for the conversion of biomass
to liquid fuel products. However, due to the oxygen content of these
biomass-derived liquids they are acidic, highly viscous, prone to
polymerization, and have a low heating value (1). For
these reasons, oxygenates present in ?pyrolysis oils? must be upgraded to
hydrocarbons before consideration as potential transportation fuels. Hydrodeoxygenation (HDO) is a potential route for the oxygenate
upgrading, but the design of active, stable HDO catalysts that operate with
minimal H₂ consumption is still a challenge (2).

Phenolic compounds account for a large fraction of biomass
pyrolysis oils. The phenolic C-O bond is particularly strong, and thus HDO must
occur by hydrogenation of the phenolic aromatic ring followed by dehydration to
remove oxygen (3). This path suggests the need for a catalyst active for
hydrogenation of aromatics and with acid sites able to catalyze dehydration
reactions. As a model for the phenolics from
pyrolysis oil, we have studied the HDO of m-Cresol (3-methylphenol) over
Pt-based supported catalysts in a lab-scale flow reactor. Modification of the
Pt catalyst by bimetallic formation with 3d metals has a significant impact on
the overall activity for HDO. Pt-Ni/Al₂O₃ and Pt-Co/Al₂O₃
are both more active (63% and 60% conversion of m-Cresol, respectively, under
conditions tested) for HDO than a monometallic Pt catalyst (38% conversion),
but also are more selective towards fully hydrogenated products. Similarly, increasing
the acidity of the Al₂O₃ support by F^- washing
increases HDO activity, and improves selectivity towards the aromatic
hydrocarbon product. We have further investigated the role of the support by testing
alternative supports such as SiO₂ and ZrO₂. We will report
an investigation of the structure-function properties of the metal particles in
the catalysts and their synergy with acid sites on the support to maximize stability
and selectivity for desired products.

References

1. Zhang Q,
Chang J, Wang T, Xu Y. Review of biomass pyrolysis
oil properties and upgrading research. Energy Conversion and
Management. 2007;48:87-92.

2. Elliott DC.
Historical Developments in Hydroprocessing
Bio-oils. Energy & Fuels. 2007;21(3):1792-815.

3. Massoth FE, Politzer P, Concha MC, Murray JS, Jakowski J, Simons J. Catalytic Hydrodeoxygenation
of Methyl-Substituted Phenols: Correlations of Kinetic Parameters with
Molecular Properties. Journal of Physical Chemistry B. 2006;110:14283-91.