Supported chromium nitride: A new catalyst for oxidative desulfurization of liquid fuel

Desulfurization of fuel is very important for our sound health and environment; oxidative desulfurization (ODS) can be one of the solutions. In this work, ODS or oxidation of thiophenic S-compounds was done firstly with a CrN catalyst, dispersed on carbon, which was prepared via pyrolysis of a MOF (composed of Cr₂O₃ and melamine), even without ammonia flow. Of note, ODS has been very seldom studied with Cr-based catalysts, so far. One CrN@carbon (named CrN@C-6) was highly effective in ODS with very low E_a (which is not far from that of simple diffusion in the liquid phase). Additionally, the catalyst showed rapid kinetics even at low temperatures (for example, 96 % of dibenzothiophene (1000 mg/L) was oxidized in 30 min at 60 °C; 83 % dibenzothiophene oxidation was possible at 30 °C in 60 min). The oxidation mechanism over the CrN@C-6 catalyst was interpreted with radical scavengers and electron spin resonance; the ODS was carried out through a non-radical mechanism probably through Cr-peroxo species. Calculation also supported that the Cr-nitride was more effective than Cr-oxide (that can be a representative Cr-based catalyst for ODS) in both H₂O₂ adsorption and ODS. The effective ODS catalysis could be explained with the contribution of well-dispersed active CrN with the electronegative nitrogen atom of the CrN and the high porosity of the catalyst. Finally, the invented CrN@C-6 can be suggested as a promising catalyst for ODS based on its remarkable activity even at low temperatures and ready recyclability (after simple solvent washing).