A novel application of phosphonate-based self-assembled monolayers (SAMs) for chemoselective hydrogenation has been investigated. The SAMs were formed on the support of Pt/Al2O3 catalysts after immersing the catalyst into a phosphonate solution followed by baking and washing. CO chemisorption suggested that the active site concentration was minimally decreased by the coating. The SAMs were stable up to 400 °C during temperature programmed hydrogenation. Uncoated and coated Pt/Al2O3 catalysts were used for liquid-phase hydrogenation of cinnamaldehyde, resulting in an improved selectivity towards the desired product, cinnamyl alcohol, without compromising the catalytic activity. The Pt/Al2O3 with the longest-chain, most ordered SAM, octadecylphosphonic acid (ODPA), showed a large improvement in selectivity compared to the uncoated Pt/Al2O3. Interestingly, the selectivity improved during the 2nd and 3rd cycle of reuse of the ODPA coated Pt/Al2O3, without any catalyst deactivation. Catalyst performance was found to vary significantly when different phosphonic acid SAMs were used. These results indicate that the performance of supported metal catalysts can be significantly altered via attachment or organic ligands to the support, complementing prior work in which SAMs have been directly attached to the metal.

Application of phosphonate-based self-assembled monolayers for chemoselective hydrogenation

251st National Meeting (2016)

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