Effect of the Surface Functionality of Nanoglobular Carbon Altered by its Thermal Treatment on the Formation and Performance of the Pd/NGC Hydrogenation Catalyst

It was established that the surface functionality of nanoglobular carbon (NGC) can be effectively altered by treatment at temperatures of 573 – 1173 K in an inert atmosphere, without affecting the structure and morphology of the material as a whole. The destruction and loss of surface oxygen groups occurs as a result of this treatment, which is accompanied by a decrease in the concentration of paramagnetic centers. At a temperature of 1173 K, a restructuring and “smoothing” of the carbon surface apparently takes place, which is expressed by annealing of defects (sources of EPR signal). It was found that changes in the surface functionality of NGC affect the reducibility of supported palladium precursor and the formation of palladium nanoparticles, without causing changes in palladium dispersion state. The study of the obtained Pd/NGC catalysts in the practically important hydrogenation of 4-nitrobenzoic acid ethyl ester and furfural showed that thermal pre-treatment of the support affects the catalytic performance in these reactions. It is important that varying temperature of such pre-treatment over a fairly wide range, which has a significant impact on the functionality of the support surface, leads to only relatively small changes in the activity and selectivity of the resulting catalysts. In this regard, thermal pre-treatment of carbon support should be considered as an approach to fine tune the performance of carbon-supported palladium catalysts.

Graphical Abstract