Oxidative Desulfurization Of Sulfur-Containing Compounds In Diesel Using Molybdenum-Based Catalysis

In recent years,the acid rain and photochemical smog pollution which were leaded to the SOx from the burning of fuel of sulfur-containing compounds damage the ecological environment.It is a research hot spot to reduce the content of sulfur-containing compounds of diesel oil in petroleum chemical industry.As the standard of sulfur content is more severe in the world,the limitations of the traditional hydrodesulfurization(HDS)is becoming more and more serious.Hence,oxidation desulfurization(ODS)arose gradually in the sights of the researchers because of its mild conditions and high desulfurization efficiency.The Mo-based catalysts were prepared by wet impregnation method in the industry.This method usually exerts unevenly dispersion Mo species on the surface of supports.Meanwhile,these oxidative products(sulfones species)are more easily adsorbed on the hydrophilic surface of catalysts which leads to the decrease of both effectively active sites and stability.Therefore,the catalysts with highly dispersed Mo species and hydrophobic character still need to be further exploited.In this paper,the SiO2 support was modified by KH550,and obtained the modified support NH2-SiO2.Mo-NH2-SiO2 catalyst has been synthesized via bonding Mo species onto the surface of NH2-SiO2 support through coordination with amino ligands.The NH2-SiO2 was characterized by Fourier transform infrared(FT-IR)and X-ray photoelectron spectroscopy(XPS).It is shown that KH550 combined with SiO2 in the form of chemical bond,and its' surface binding is closest to tridentate form Structure and properties of Mo-NH2-SiO2 and Mo/SiO2 catalysts were illuminated by X-ray diffractometer(XRD),transmission electron microscope(TEM),XPS,FT-IR,and N2 adsorption-desorption.The hydrophilic/hydrophobic characters of the catalysts were also tested.The as-synthesized Mo-NH2-SiO2 catalyst possessed of both highly dispersed Mo species and hydrophobic character.By comparing the sulfur removal of Mo-NH2-SiO2 and Mo/SiO2 catalysts on DBT and the results of XPS analysis.It is concluded that the reason for the high activity of Mo-NH2-SiO2 catalysts is that the active Mo species are in the electron rich state.The catalytic performance of the Mo-NH2-SiO2 catalyst was evaluated in ODS.These results suggested that DBT almost was oxidized completely at the reaction temperature was 60?,n(O)/n(S)was 4,the catalyst dosage was 13.34 g/L.The selectivity of DBT removal and the oxidation removal activity of different sulfur-containing compounds over Mo-NH2-SiO2 catalyst were also investigated,Compared with Mo/SiO2 catalyst,Mo-NH2-SiO2 catalyst exhibited high stability,and the two catalysts of fresh and spent were also characterized by FT-IR and XPS.These results indicated thatt the hydrophobic Mo-NH2-SiO2 catalyst weakened the adsorption of sulfone product on the catalyst,and the catalyst life was significantly enhanced.The kinetic reaction behavior of oxidative desulfurization of 320.0 ppmw model oil respective prepared by DBT,4-MDBT and 4,6-DMDBT and 320.0 ppmw mixed model oil prepared by three sulfur-containing compounds with the same concentration over Mo-NH2-SiO2 catalyst.It was found that the oxidation rate constants k of DBT,4-MDBT and 4,6-DMDBT in the mixed model oil close to diesel component were all smaller than that of 320.0 ppmw model oil prepared by DBT,4-MDBT and 4,6-DMDBT,and activation energy Ea is high than 320.0 ppmw model oil prepared by DBT,4-MDBT and 4,6-DMDBT.Based on the research of the model oil,the catalytic performance of the Mo-NH2-SiO2 catalyst was evaluated in marine diesel oil.These results implied that most of the sulfur compounds in diesel oil were converted into the corresponding sulfones after the oxidation treatment.The extraction of sulfone by acetonitrile,the content of sulfur in marine diesel oil decreased from 16032.9 ppmw(1.6 wt%)to 3206.1 ppmw(0.3 wt%),and the sulfur removal was 80.1%.Meanwhile,there was almost no decrease on catalytic activity after 10 times recycle of the Mo-NH2-SiO2 catalyst.Therefore.Mo-NH2-SiO2 catalyst has excellent stability in marine diesel oxidative desulfurization.