The presence of nitrogen compounds in fossil fuels leads to the formation of NOx during combustion, harmful pollutants that represent a significant challenge for the environment and health, making its removal very important. Hydrotreatment, currently the most common strategy for denitrogenation, requires severe operating conditions, which motivates the search for more sustainable alternatives. This study investigates oxidative denitrogenation (ODN) as a promising strategy, analyzing the oxidation of quinoline, a nitrogen-containing compound common in fossil fuels, using catalysts based cobalt ferrite and its variants coated with silica (CoFe2O4@SiO2) and carbon (CoFe2O4@C), applied in a biphasic system containing isooctane as the organic phase and hydrogen peroxide as the oxidant. Cobalt ferrite was synthesized using the sol-gel method, followed by silica and carbon coatings. Characterization techniques such as XRD, FTIR and contact angle measurements confirmed the successful synthesis of core-shell structures, with crystallite sizes in the 19-20 nm range. The coatings significantly modified the surface properties, reducing the hydrophobicity of the ferrite, with the contact angle reduced from 130° to 40° with silica. Quinoline adsorption tests revealed a low adsorption capacity of the materials, in line with the low surface area and low pore volume determined by N2 adsorption isotherms at 77 K (SBET = 9-10 m2/g). In the oxidation reactions, CoFe2O4@SiO2 showed the best catalytic performance removing 74% of quinoline in 8 hours, likely due to its hydrophilic surface, favorable to the generation of reactive oxygen species through the decomposition of H2O2 and consequent greater quinoline removal. GC-MS identified intermediate degradation products, including species suggesting the opening of pyridine rings, while TOC analysis confirmed significant quinoline mineralization. The study highlights the potential of oxidative denitrogenation systems, combined with coated catalysts, to effectively remove nitrogen impurities from liquid fuels, offering a promising alternative to conventional hydrotreatment.
