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

Abstract

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−) 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.