The use of bimetallics to control the selectivity for the upgrading of lignin-derived oxygenates: Reaction of anisole on Pt and PtZn catalysts

• Bonding configuration of anisole on Pt facilitates ring hydrogenation under HDO reaction conditions.
• Bonding configuration of anisole on PtZn limits ring hydrogenation under HDO reaction conditions.
• Zn-modified Pt exhibits high selectivity for CO bond scission in anisole.

The adsorption and reaction of anisole on Pt and PtZn catalysts were investigated using both model single crystal and high surface area supported metal catalysts. Temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS) studies of the interaction of anisole with Pt(1 1 1) demonstrated that there is a strong interaction between the phenyl ring of anisole and the surface, resulting in CO and CH bond scission at relatively low temperatures. In contrast, anisole was observed to bond to a Zn-modified Pt(1 1 1) surface primarily via the oxygen at Zn sites or possibly adjacent Pt sites, with the phenyl ring tilted away from the surface. Such bonding configuration facilitated selective CO bond cleavage producing phenyl groups and methoxide groups with the latter being bonded to the Zn sites. These results suggested that PtZn may be an effective catalyst for hydrodeoxygenation (HDO) of lignin-derived aromatic oxygenates with low activity for ring hydrogenation. This hypothesis was then tested and verified by investigating the reaction of anisole and H2 over high surface area carbon-supported Pt and PtZn catalysts.

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