Controllable Synthesis Of Tungsten Oxide Nano-catalyst And Its Application In Catalytic Oxidation Desulfurization Of Fuel Oil

Fuel combustion has brought many hazards to human society,such as soil acidification,engine corrosion and air pollution,which is a serious threat to human health.For the series of the resulting environmental problems,how to achieve the deep desulfurization of fuel oil has become one of the main global concerns.In order to cope with the growing demand for deep desulfurization,it is urgent to seek efficient desulfurization technologies.At present,the commly used technology is the traditional hydrodesulfurization（HDS）.However,HDS is difficult to remove thiophene sulfide in fuel oil due to its harsh reaction conditions,an alternative technique is desirable.Oxidative desulfurization（ODS）has attracted the attention on account of its mild and environmentally friendly reaction conditions as well as high desulfurization efficient.In this paper,a series of oxidative desulfurization catalysts are designed for tungsten oxide(W₁₈O₄₉).The desulfurization performance of prepared catalysts under the condition of oxygen（O₂）as oxidant,and properties of the catalysts and the reaction mechanism of were through a series of characterization.The main findings are as follows:1.The low-coordinated atoms such as edges,single atoms and vacancies have been widely determined as reactive sites for catalytic oxidative desulfurization.However,the grain boundaries（GB）as a favorable atomic configuration have been ignored.In the first work,a universal strategy was proposed to engineer grain boundaries into oxides via facile two-step growth.Based on the W₁₈O₄₉nanowires,the engineered GB can work as reactive sites to build stronger interfacial molecular interactions with dibenzothiophene（DBT）due to the low-coordinated W atoms with local electron-rich state,promoting the surface adsorption and activation performance towards DBT.Moreover,the molecular oxygen activation capacity is improved by GB to yield more·O₂^-compared to W₁₈O₄₉.Benefiting these features,the GB-W₁₈O₄₉deliver a greatly improved catalytic oxidative desulfurization behavior than W₁₈O₄₉nanowires,in which 98%DBT can be removed by GB-W₁₈O₄₉in 5 h while 40%can be achieve by W₁₈O₄₉nanowires.2.Developing catalyst with abundant surface active sites is the core issue to achieve efficient catalytic oxidative desulfurization performance,In the second work,Mo doped W₁₈O₄₉ultrathin nanowires is fabricated through solvothermal method to provide plentiful low coordinated metal atoms around oxygen vacancies to trigger oxidative desulfurization reaction.As a non-stoichiometric oxide,the discorded lattice microstructure in W₁₈O₄₉endows the formation of oxygen vacancies neighboring low-valence W atoms,while the ultrathin structure ensures the fully exposure of surface atoms.Moreover,the doped Mo atoms will tune the surface atomic structure and electronic state of W₁₈O₄₉nanowires,leading to the higher oxygen vacancy concentration and strengthened interaction with target sulfide molecules.Benefiting from these features,the higher molecular oxygen activation capacity can be realized over Mo-W₁₈O₄₉nanowires to yield more superoxide radical（·O₂^-）,resulting in improved oxidative desulfurization performance.The optimized 2%Mo-W₁₈O₄₉catalyst shows nearly 100%removal of dibenzothiophene within 5 h and maintain the good cycle stability.This work supplies new insights for the design of catalytic sites towards selective catalytic oxidative desulfurization.3.Improving the surface oxygen vacancy is one of the common methods to enhance the oxidation performance of the catalyst.In the third work,the W₁₈O₄₉surface was reconstructed through the synergy of Mo doping and plasma-induced.The incorporation of Mo species into the W₁₈O₄₉surface in the form of replacing W species adjusted the atomic and electronic structure of the catalyst surface to form more oxygen vacancies.On this basis,the plasma induced the surface of material to destroy and reconstruct part of the surface structure,thus producing the active site with low coordination,further generating more oxygen vacancies,thus greatly improving the catalyst activity.Compared with pure W₁₈O₄₉,Mo-W₁₈O₄₉-P is significantly more active,and can achieve deep desulfurization within 3 h.Mo-W₁₈O₄₉-P with better stability than pure W₁₈O₄₉,can be recycled 12 times.This work provides more possibilities to further improve the oxidation properties of transition metal oxide catalysts.