Pyridinic nitrogen dominated doping on Pd/carbon catalysts for enhanced hydrogenation performance.

The hydrogenation of 4-carboxylbenzaldehyde over Pd catalysts is a crucial process during the production of pure terephthalic acid. Herein, ZIF-8 derived carbon materials (NC) with adjustable N types were synthesized and used as the supports of Pd catalysts. Pd supported on NC with 50.5% of pyridinic N exhibited best hydrogenation activity with a TOF value of 4.1 min. The microstructures of NC support and electronic structures of Pd in Pd/NC were investigated by techniques such as XRD, N physisorption, XPS, H-O titration and TEM. The nitrogen species in CN surface not only can adjust chemical state and dispersion of Pd nanoparticles (NPs), but also promote the adsorption and activation capability of H molecular. Besides, the ratio of Pd/Pd and Pd dispersion were closely correlated with pyridinic nitrogen content. The improvement in hydrogenation activity and stability of Pd/CN catalyst in relative to Pd/C were ascribed to the synergistic effect of pyridinic nitrogen and active site Pd.