Effects of surface oxygen-containing groups of the flowerlike carbon nanosheets on palladium dispersion, catalytic activity and stability in hydrogenolytic debenzylation of tetraacetyldibenzylhexaazaisowurtzitane

The influence of the surface chemical properties of the carbon support on the Pd dispersion, activity and stability of Pd(OH)₂ /C catalyst for the hydrogenolytic debenzylation of tetraacetyldiben-zylhexaazaisowurtzitane (TADB) was studied in detail. The flowerlike nanosheet carbon material (NSC) was chosen as the pristine support, meanwhile chemical oxidation with nitric acid and physical calcination at 600^◦ C treatments were used to modify its surface properties, which were denoted as NSC_ox-2 (treated with 20 wt% HNO₃) and NSC-600, respectively. The three carbon supports and the corresponding catalysts of Pd/NSC, Pd/NSC-600, and Pd/NSC_ox-2 were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), nitrogen sorption isotherm measurement (BET), powder X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectra (XPS), temperature-programmed desorption (TPD), temperature-programmed reduction (H₂-TPR), thermogravimetric analysis (TG), and element analysis. The debenzylation activities of Pd/NSC, Pd/NSC-600, and Pd/NSC_ox-2, as well as the three catalysts after pre-reduction treatment were also evaluated. It was found that the activity and stability of the Pd(OH)₂ /C catalysts in the debenzylation reaction highly depended on the content of surface oxygen-containing groups of the carbon support.