Spectators Control Selectivity in Surface Chemistry: Acrolein Partial Hydrogenation Over Pd
Karl-Heinz Dostert1, Casey P O'Brien1, Francisco Ivars-Barceló1
1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
Journal of the American Chemical Society
|October 21, 2015
Summary
Selective hydrogenation of acrolein to propenol is achieved over modified Palladium(111) surfaces. A unique oxopropyl spectator layer enables near-perfect C═O bond selectivity, forming unsaturated alcohols.
Area of Science:
- Heterogeneous catalysis
- Surface science
- Organic synthesis
Background:
- Acrolein hydrogenation is crucial for producing valuable chemicals.
- Achieving high selectivity for C═O bond hydrogenation over C═C bond hydrogenation remains challenging.
- Palladium (Pd) based catalysts are widely studied for hydrogenation reactions.
Purpose of the Study:
- To investigate the mechanism of selective acrolein hydrogenation over model Pd surfaces.
- To identify conditions and surface species enabling selective C═O bond hydrogenation.
- To understand the role of surface modifications in directing reaction pathways.
Main Methods:
- Mechanistic study using single crystal Pd(111) and supported Pd nanoparticles.
- Pulsed multimolecular beam experiments.
- In situ infrared reflection-absorption spectroscopy (IRRAS).
Main Results:
- Nearly 100% selectivity for C═O hydrogenation to unsaturated alcohol (propenol) achieved on Pd(111).
- Surface modification with an oxopropyl spectator overlayer is essential for selectivity.
- Identification of oxopropyl spectator and propenoxy reactive intermediate.
- Simultaneous monitoring of intermediate evolution and product formation.
Conclusions:
- Selective hydrogenation of acrolein's C═O bond is feasible over Pd(111) under specific surface conditions.
- Surface-mediated spectator species can effectively control catalytic selectivity.
- The findings provide fundamental insights into designing selective hydrogenation catalysts.
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