A d-Electron Deficient Pd Trimer for Exceptional Pyridine Hydrogenation Activity and Selectivity.

Area of Science:

• Catalysis
• Materials Science
• Organic Chemistry

Background:

• Selective hydrogenation of pyridines, like 2-phenylpyridine (PPY), is challenging due to nitrogen coordination and over-hydrogenation.
• Existing methods often suffer from low yields and poor selectivity.

Purpose of the Study:

• To develop a novel catalyst for efficient and selective hydrogenation of PPY.
• To investigate the structure-activity relationship of the new catalyst.

Main Methods:

• Synthesis of a novel Pd trimer catalyst via confined growth on an ordered mesoporous carrier.
• Characterization of the catalyst, focusing on its d-electron deficiency (0.42).
• Evaluation of catalytic performance in liquid-phase hydrogenation of PPY, including batch and continuous flow tests.

Main Results:

• Achieved nearly complete conversion of PPY and high selectivity to 2-phenylpiperidine (PPD).
• Demonstrated remarkable stability over eight batch cycles and 800 hours of continuous flow with negligible activity loss.
• Identified d-electron deficiency and specific active site structures as key factors for enhanced performance.

Conclusions:

• The d-electron deficient Pd trimer catalyst overcomes limitations in pyridine hydrogenation.
• Catalyst design, including electron charge and ensemble structure, is crucial for activity and selectivity.
• The findings offer a pathway for developing advanced hydrogenation catalysts.