Graphene-like Hexagonal Boron Nitride Based Catalysts For Ultra-deep Oxidative Desulfurization In Fuels

With the continuous development of the world economy,the demand for energy is also continues to rise.To date,fossil fuels are still the most important energy components.However,the combustion of sulfur-containing compounds in fuel will produce sulfur oxides（SO_x）,which caused serious problems such as acid rain and haze,thereby,damaging the ecological environment and affecting human health.Therefore,the production of clean fuels is essential to maintaining a healthy life in today’s world.At present,the hydrodesulfurization（HDS）technology adopted in the industry needs to be carried out under the conditions of high temperature and high pressure and the participation of hydrogen,which leads to the high cost.Meanwhile,the refractory aromatic sulfides cannot be removed effectively by HDS process.Oxidative desulfurization（ODS）technology has attracted wide attention due to its mild reaction conditions and high desulfurization efficiency.Therefore,a series of graphene-like hexagonal boron nitride based（h-BN）catalysts was designed in this work and the performance of h-BN as catalyst and active center carrier for oxidative desulfurization of fuel was investigated,respectively.The catalytic mechanism was also researched systematically.The main research contents and conclusions of this thesis are as follows:（1）The modulation of the surface electronic structure of h-BN was achieved by simple organic modifications.The deep eutectic solvents（DES）were uniformly dispersed on the surface of h-BN by impregnation method.The composition and structure of the catalyst were determined by the characterizations of SEM,TEM,XRD,FT-IR,XPS,UV-Vis DRS,N₂ adsorption and desorption.The results confirmed that DES had been dispersed on the surface of h-BN successfully,and the electronic structure of h-BN was changed at the same time.The prepared catalysts was used in the oxidation desulfurization system with H₂O₂ as oxidant and the effects of different reaction parameters on the catalytic performance of the catalyst were investigated in detail.The experimental results suggested that under the optimal reaction conditions,the sulfur removal of DBT can reach to 97.5%.The mechanism of oxidative desulfurization was studied by EELS and XPS characterizations that with the DES dispersed,the electronic structure of h-BN was changed,which promoted the transfer of electrons and facilitated the generation of HO·radicals.（2）A kind of heterogeneous catalyst NHPI/BN-x supported by commercial grade BN was synthesized by impregnation method.The synthesized catalysts were characterized by SEM,XRD,FT-IR,¹HNMR to confirme the successful loading of NHPI.The experimental results suggested that the optimal loading amount was 30%and the sulfur removal of DBT could achieve to 95%after 6 h.GC-MS analysis confirmed that the oxidation product was only DBTO₂.It can be detected by ESR that the O₂^·-radicals played the main role in the reaction process.The mechanism of the oxidation reaction was then studied by ESR.（3）The modulation of the electronic structure of h-BN was realized by heteroatoms doping.The BCN-x catalysts with different carbon content was synthesized by pyrolysis method using ionic liquid[C₁₆mim]Cl as carbon source.The successful incorporation of C atoms into h-BN framework was proved by a series of characterizations.Subsequently,the prepared catalyst was used in oxidative desulfurization with O₂ as oxidant.Experiments results confirmed that the catalyst BCN-20 has the best catalytic performance and total sulfur removal of DBT can be achieved at low temperature（100 ^oC）.And it also has excellent catalytic performance to the removal of refractory sulfur compounds 4-MDBT and 4,6-DMDBT.Based on the analysis of ESR and XPS,it is confirmed that the delocalization of electrons is enhanced after the doping of C atoms,which facilicate the transfer of electrons.In addition,the catalyst has outstanding regenerative properties and exhibits similar catalytic activity to the original catalyst after heat treatment.