Designing Fast and Efficient Hausmannite Mn₃O₄ Driven CuO-C3N4 Catalyst-NaClO System for the Oxidative Desulfurization of Commercial Fuels

Sulfur rich fuels produce harmful gaseous oxides on combustion leading to significant environmental and mechanical problems. Conventional desulfurization methods are often time and energy intensive, lack effective catalyst-oxidant synergy and are not readily applicable to real transportation fuels. Herein, a hausmannite manganese (Mn3O4) driven copper oxide (CuO) based C3N4 composite-sodium hypochlorite (Mn₃O₄-CuO/C₃N₄-NaClO) system was developed for the oxidative desulfurization (ODS) of naphthenic sulfur compounds in transportation fuels. The metal oxides were synthesized using a wet impregnation technique while C₃N₄ was prepared using urea as the precursor. The synthesized catalysts were characterized using various techniques which confirmed the incorporation of Mn3O4 and CuO species, and the uniform modification of the morphology and surface characteristics of pristine C₃N₄, resulting in enhanced crystallinity and surface functionalities. The Mn₃O₄-CuO/C₃N₄-NaClO system achieved 100% removal of dibenzothiophene (DBT) from model fuels, as well as 100% sulfur removal from gasoline and kerosene and 97.7% from diesel fuel. The system was optimized at 30 °C for 5 min using 0.1g of catalyst per 15 mL of fuel at an O/S ratio 1.5. The ODS process followed first-order kinetics, with an activation energy of 27 kJmol^-1. The catalyst maintained high activity over five consecutive cycles, demonstrating excellent recyclability with minimal loss in ODS performance. The enhanced efficiency is attributed to the synergistic interaction among the highly active Mn²⁺/Mn³⁺ and Cu²⁺ species and the NaClO oxidant, which facilitated the rapid oxidation of DBT to dibenzothiophene sulfone (DBTO₂). Thus, the Mn3O4-CuO/C₃N₄-NaClO system represents a potentially cost-effective and environmentally friendly alternative for large-scale oxidative desulfurization of transportation fuels.