Construction And Performance Investigation Of Nano-catalysts In Oxidative Desulfurization Of Diesel

Diesel is a high-energy density fuel widely used in long-distance transportation,engineering machinery,and other fields.Commercial diesel requires pre-desulfurization to reduce environmental harm.Currently,the precise desulfurization of diesel depends on traditional hydrodesulfurization technology,which requires high investment,energy consumption,and operating costs.Among emerging desulfurization technologies,aerobic oxidative desulfurization has become an important development direction for diesel desulfurization due to its mild reaction conditions,low cost,and high reaction activity towards refractory sulfides.This paper focuses on the development of high-performance aerobic oxidative desulfurization catalysts,with a focus on the efficient activation of molecular oxygen（O₂）under mild conditions,and designs and synthesizes a series of two-dimensional nano-catalysts with non-metallic vanadium（V）and molybdenum（Mo）as active sites.Through advanced characterization techniques,the morphology,phase,oxidation state,and surface species of the catalyst were examined.The structure and chemical environment of the active site were investigated to understand the modulation and promotion mechanisms of catalytic performance,in combination with theoretical calculations and reaction kinetics studies.The catalytic reaction mechanism was revealed,and deep oxidative desulfurization of real diesel under mild conditions was achieved.The specific research contents are as follows:（1）Single-layer V₂CT_x MXene nanosheets were prepared as catalysts by hydrochloric acid/sodium fluoride（HCl/Na F）mixed acid etching,organic molecule intercalation,and ultrasonic delamination.In the oxidation desulfurization system with O₂ as the oxidant,the V₂CT_x MXene catalyst exhibited excellent catalytic activity and stability,and could activate O₂ at a low temperature of 70°C,oxidizing thiophene sulfides to the corresponding sulfoxides.The characterization and theoretical calculation results confirmed that the V₂CT_x MXene surface has a low anion vacancy formation energy,inducing the generation of abundant low-valence V sites.The low-valence V sites displayed strong adsorption capacity towards O₂,promoting the activation and dissociation of O₂ and leading to a lower minimum conversion temperature.（2）Co-N co-doped Mo O_x nano-cluster catalyst supported on reduced graphene oxide was prepared by using polyoxometalates as precursors and ammonia reduction.The research results showed that the catalyst could control the exposure of coordinatively unsaturated Mo sites on the catalyst surface,and effectively regulate the electronic structure of the Mo sites under the co-doping effect of Co-N,enhancing the electron-donating ability of the Mo sites,and improving the catalytic activity of the catalyst towards O₂.The oxygen vacancies on the catalyst surface also enhanced the adsorption capacity of the catalyst towards O₂,significantly improving the catalytic activity of the catalyst.The conversion frequency of dibenzothiophene by this catalyst can reach 67.88h^-1,and the catalyst can maintain stability during multiple repeated uses.The transformation of thiophene-type sulfides in real diesel was achieved,and deep desulfurization was realized in combination with solvent extraction.（3）To further enhance the oxygen activation ability under mild conditions,Ag QDs modified cobalt phosphide（Co P）ultrathin nanosheets loaded with Mo-Fe dual-atomic photocatalysts（Ag Fe Mo/Co P）were prepared and applied in the aerobic photocatalytic oxidative desulfurization.This catalyst achieved fast and complete transformation of thiophene sulfides in model oil and real diesel.Through systematic reaction kinetics studies and in situ characterization,it was confirmed that Ag QDs,as co-catalysts,can enhance the light absorption capacity of the catalyst and improve the efficiency of electron-hole separation.Under the assistance of Ag QDs,Co P ultrathin nanosheets can efficiently convert water and O₂ into hydrogen peroxide（H₂O₂）in situ,and then form hydroxyl radicals through Fenton reaction under the Fe site,and finally,through the catalytic action of the Mo site,thiophene-type sulfur compounds are converted into the corresponding sulfones.