Effects of surface functional groups of the N-containing carbon support on the catalytic properties of supported palladium

Nitrogen-containing mesoporous carbons (SNMC) were shaped by the drop ball method. A SNMC and a commercial coconut shell carbon (CSC) were oxidized by nitric acid to obtain the OSNMC and OCSC supports. Then, the Pd/OSNMC, Pd/SNMC, Pd/OCSC and Pd/CSC catalysts (5%wt) were prepared to study the effects of carboxyl group on the hydrogenation of C=C double bond. The results showed that both the doped N and surface O-containing functional groups increased the dispersion and surface electron density of supported Pd, leading to the increased heats for the adsorption of hexene and H-2 and thus the increased intrinsic activity for the hydrogenation of hexene on Pd. The pre-adsorption of propionic acid (PA) significantly inhibited the adsorption of hexene and H-2 and decreased the conversion of hexene on Pd. However, the surface O-containing functional groups inhibited the adsorption of carboxyl groups and offset the inhibition effect of carboxyl groups on the hydrogenation of hexene on Pd, while the doped N atoms played the opposite role. Thus, it is expected that the surface O-containing functional groups are beneficial to the hydrogenation of unsaturated fatty acids on Pd/C catalysts.