Tuning the selectivity of phenol hydrogenation on Pd/C with acid and basic media

- Phenol hydrogenation on Pd/C in acid and basic media was investigated.
- Acid and basic media saw opposite trend in activity and selectivity.
- Substrate-media interactions correlate to activity.
- Keto-enol tautomerization correlates to selectivity.

The selectivity of phenol hydrogenation over Pd/C was successfully tuned by various Bronsted acid and base additives. Compared with neutral reaction condition, the basic condition witnessed decreased catalytic activity and cyclohexanone selectivity while the opposite trend was observed under acidic condition. Mechanistic studies indicated the varied interaction of substrate with acid and base is responsible for the activity difference, while the changed keto-enol tautomerization correlates directly to the selectivity variation.