Almond-based activated carbon/MIL-125(Ti) composite as a beneficial catalyst for oxidative denitrogenation of model fuel

• Oxidative denitrogenation of model fuel was carried out over almond-based activated carbon/MIL-125(Ti) catalyst. • Under optimal conditions, 99.7 % conversion of indole was obtained. • The high apparent reaction rate constant of 2.130 h⁻¹, and low activation energy of 25.41 kJ/mole were resulted. • Catalyst could be regenerated for at least four cycles, maintaining over 93 % efficiency. • The catalyst showed a beneficial solution for the purification of fuels. Oxidative denitrogenation (ODN) of fuel was studied with an almond-based activated carbon/MIL-125(Ti) catalyst. The synthesized catalysts were analyzed through different characterization techniques, including XRD, FT-IR, FE-SEM, EDX, TEM, and BET, confirming the sufficient synthesis of X %-ACTiM. 20 %-ACTiM showed the best activity in the ODN of model fuel. This high performance can be ascribed to its sufficient BET specific surface area of 639.27 m²/g, total pore volume of 0.5950 cm 3 /g, high apparent reaction rate constant of 2.130 h −1 , and low activation energy of 25.41 kJ/mole. The presence of activated carbon, Ti 2+ sites, and an oxidant, promoted the production of sufficient radicals such as •O 2 − and •OH. The conversions for indole (IND), quinoline (QUI), and carbazole (CBZ) were 99.7 %, 93.2 %, and 82.5 %, respectively. Under optimal conditions, in ODN over 20 %-ACTiM, the conversion of IND, QUI, and CBZ were 99.7 %, 93.2 %, and 82.5 %, respectively, at 2 g/L catalyst dosage, temperature of 60 °C, O/N ratio of 4, V MeOH /V Fuel ratio of 0.5, and IND initial concentration of 500 ppm over 120 min. Additionally, 20 %-ACTiM could be regenerated for at least four cycles, maintaining over 93.4 % efficiency in the ODN of IND. A new mechanism for Ti-based MOF has been promoted as follows: protonation and dehydration of Ti-OH sites, creating unsaturated Ti sites as Lewis acids, which react with H 2 O 2 to generate peroxometallic complexes (Ti-OOH); The O O bond in Ti-OOH breaks, generating radicals of •OH; Ti-O• interacts with oxidant, producing •O 2 − radicals; and oxidizing with •OH and •O 2 − , leading to the creation of 2-oxiindole, hydrogen and oxygen gas from. This catalyst's high catalytic performance for removing IND is useful for practical applications.