Boron Nitride Supported Heteropoly Acid For Catalytic Oxidative Deep Desulfurization Of Fuels

Recent years,sulfur content in oil is becoming increasingly higher with aggravation of inferior oil.The sulfur compounds can turn into SOx after burning,which will generate serious environmental pollution.Hence,the removal of sulfides attracts increasing attentions.Mercaptan and thioether can be removed by simple physical or chemical methods,but thiophene and its derivatives are difficult to remove by traditional hydrogenation desulfurization technology.So many desulfurization techniques arise at the historic moment,such as biological desulfurization,adsorptive desulfurization,extractive desulfurization and oxidative desulfurization,etc.Among them,oxidative desulfurization?ODS?with mild operating conditions and high-activity for aromatic sulfides,has become a technology to produce ultra low sulfur fuel.The core of ODS is looking for an efficient stable catalyst.In current thesis,a series of boron nitride supported heteropoly acid heterogeneous catalysts have been designed,synthesized and applied in deep desulfurization of fuel.First,the few-layer hexagonal boron nitride?h-BN?was chose as carrier to immobilize phosphotungstic acid?HPW?by solvent thermal method.The prepared HPW/h-BN heterogeneous catalyst has been characterized by SEM,TEM and XRD.Results showed that HPW was successfully confined into micropores of h-BN,and the structure of h-BN was not changed after heterogenization.HPW/h-BN presented excellent catalytic activity for dibenzothiophene?DBT?and4,6-dimethyldibenzothiophene?4,6-DMDBT?in ODS system.The catalyst presented¹00% of sulfur removal for DBT,and can be recycled for 6 times without noticeable decrease in reactivity.Reaction mechanism were exhibited as follows: DBT and H₂O₂ were adsorbed onto the surface of catalyst,then [PW12O40]3-accept active oxygen of H₂O₂ to form peroxide species W?O?2,finally DBT was oxidate into DBTO2 by W?O?2.Next,silicotungstic acid?HSiW?was dispersed into h-BN by impregnation method to prepare HSiW/h-BN heterogeneous catalyst.Using FT-IR,XRD,SEM and TEMmethods to analyze morphology and structure,results showed that the immobilization process not only gave rise to the promising dispersion of HSiW,but also produced valence alternation of tungsten in HSiW.HSiW/h-BN exhibited ¹00% of sulfur removal for DBT and 4,6-DMDBT in ODS system.And the sulfur removal for DBT can still reach to 93% after recycled for 9 times.The excellent dispersion of HSiW and valence variation of tungsten species in HSiW are beneficial to operation of catalytic reaction.Finally,the ionic liquid-modified hexagonal boron nitride?BN-IL?was prepared as carrier to immobilize phosphomolybdic acid?HPMo?.Analyzing by XRD,TEM,XPS and Raman methods,the HPMo/BN-IL catalyst maintained the lamellar and mesoporous structure of h-BN after heterogenization.Results showed that HPMo/BN-IL presented excellent catalytic activity for 4,6-DMDBT,DBT and 3-MBT,and the sulfur removal of 4,6-DMDBT only reduced 3.7 % after recycled for 5 times.In addition,the introduction of IL can improve the stability of HPMo/BN-IL catalyst.The HPMo/BN-IL possessed excellent resistibility to olefins and aromatic hydrocarbon.