Effective aerobic oxidative denitrogenation of model fuel with metal-free porous carbon derived from phytic acid-loaded polyaniline

Aerobic oxidative denitrogenation (ODN) of a model fuel was first done with metal-free P and O co-doped carbon catalysts. The catalysts, phytic acid (PA)-loaded polyaniline-derived carbons (PPDCs), were firstly prepared by high-temperature pyrolysis of polyaniline with phytic acid (as P/O sources). One material, PPDC-2 showed a conversion of 95 % and 86 % for indole (IND) and quinoline (500 ppm each), respectively, at 100 °C, with O₂ as an oxidant. A very small activation energy of 26.6 kJ mol⁻¹ was observed in the IND oxidation. Radical trapping experiments and electron spin resonance spectroscopy analyses supported the formation of superoxide anion radicals (O₂^[rad]−) from the fed O₂, which was responsible for the IND oxidation. A plausible reaction mechanism was proposed by analyzing the experimental results and DFT calculations on charge separations on carbons. Defect sites also could play an important role in the activation of O₂ since PPDC-2 showed higher defect sites compared to the non-doped carbon. PPDC-2 was also found to be recyclable for the ODN, by simple acetone soaking, without a considerable loss in performance.