The role of the support in the gas phase hydrogenation of butyronitrile over Pd/Al2O3 and Pd/C (2.5–3.0 nm mean Pd size) has been studied, taking bulk Pd as benchmark. Catalyst activation by temperature programmed reduction was monitored and the metal and acid functions characterized by H2 and NH3 chemisorption/temperature programmed desorption and electron microscopy (STEM/TEM). Butyronitrile hydrogenation was stable with time on-stream to deliver butylamine where consecutive condensation with the intermediate butylidenimine generated dibutylamine and tributylamine. Condensation can occur on bulk Pd but selectivity is influenced by the support and reaction over Pd/Al2O3 generated dibutylamine as principal product. Preferential tertiary amine formation was observed over Pd/C and attributed to greater surface acidity that favors the condensation step. Increased hydrogen spillover and acidity (associated with Pd/C) elevated butyronitrile consumption rate.
The authors acknowledge EPSRC support for free access to the TEM/SEM facility at the University of St Andrews and financial support to Y. Hao and X. Wang through the Overseas Research Students Award Scheme (ORSAS).
- Bulk PD
- butyronitrile hydrogenation
- surface acidity
- spillover hydrogen