Selectivity in Hydrogenation Catalysis with Unsaturated Aldehydes: Parallel versus Sequential Steps.

Area of Science:

• Surface chemistry
• Catalysis
• Reaction kinetics

Background:

• Catalytic hydrogenation is crucial for chemical synthesis.
• Understanding reaction mechanisms on metal surfaces is key to catalyst design.
• Crotonaldehyde hydrogenation involves C═C and C═O bonds.

Purpose of the Study:

• To investigate the reaction kinetics and selectivity of crotonaldehyde hydrogenation on platinum.
• To elucidate the reaction mechanism under single-collision conditions.
• To determine the role of dual hydrogenation pathways.

Main Methods:

• Utilized a high-flux molecular beam setup.
• Performed steady-state catalytic hydrogenation experiments.
• Analyzed reaction products under single-collision conditions on platinum surfaces.

Main Results:

• Detected formation of saturated aldehyde, unsaturated alcohol, and saturated alcohol.
• Identified dual hydrogenation (C═C and C═O bonds) as a primary pathway.
• Observed pressure-dependent selectivity shift from saturated alcohol to saturated aldehyde.

Conclusions:

• Dual hydrogenation is a primary reaction pathway, not a secondary process.
• Proposed a mechanism involving parallel formation of monohydrogenated intermediates.
• Surface reaction kinetics and selectivity are influenced by reactant partial pressure.