Roles of N on the N-doped Ru/AC catalyst in the hydrogenation of phthalate esters

A series of N-modified Ru/N x -AC catalysts were prepared by ammonia treatment method and applied in dioctyl phthalate hydrogenation, which is a cascade reaction system involving partial hydrogenation of aromatic ring and the further saturated hydrogenation of the formed intermediate bis(2-ethylhexyl) cyclohexene-1,2-dicar-boxylate (DH 4 ) to dioctyl di-2-ethylhexylcyclohexane-1,4-dicar-boxylate (DEHCH). N doping was found to be able to increase the nitrogen-containing pyridine groups on the activated carbon (AC) surface, resulting in the abundance of binding sites for anchoring Ru and exceptionally enhancing the dispersion of Ru nanoparticles. Furthermore, the N-modified Ru/N 12 -AC catalyst exhibited a significantly higher turnover frequency value (1260.06 h −1 ) than Ru/AC catalyst (913.64 h −1 ). It was deduced that the presence of the pyridine groups could improve the adsorption of intermediate DH 4 by promoting the coverage of DH 4 on the catalyst surface. The environment of surface-enriched DH 4 accelerated the reaction rate of DH 4 hydrogenation and increased the selectivity to DEHCH. Therefore, the cooperation between highly dispersed Ru nanoparticles and pyridine groups supports remarkably enhanced the activity and selectivity. In addition, the Ru/N 12 -AC catalyst presented excellent catalytic activity and versatility in the hydrogenation of other phthalates such as dimethyl phthalate, diethyl phthalate, and dibutyl phthalate, demonstrating its prospective application in phthalate esters hydrogenation. Graphical abstract Description N-doping exceptionally improved Ru dispersion and the adsorption of the intermediate product in DOP hydrogenation, leading to a higher activity and selectivity to saturated product.