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

Abstract

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 Ea (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).