Construction Of Hexagonal Boron Nitride Supported Platinum-based Catalysts For Catalytic Oxidative Desulfurization Of Diesel

With the continuous emission of sulfur oxide SO_x caused by the combustion of organic sulfur compounds in diesel,environmental pollution has become increasingly serious.To solve this problem,we urgently need a green and economical desulfurization technology to obtain the low-sulfur production of diesel fuel.Traditional hydrodesulfurization technology?HDS?is less active to aromatic sulfides such as dibenzothiophene?DBT?and 4,6-dimethyldibenzothiophene?4,6-DMDBT?.Moreover,the reaction conditions are more demanding and reaction need high energy consumption.Researchers are constantly looking for new desulfurization technologies to assist HDS.Because of mild conditions,a high removal of macromolecular aromatic sulfides,not affecting the cetane ratio and other characteristics,oxidative desulfurization?ODS?technology has been widely concerned by researchers.Among them,the design of high-efficiency catalysts has become the key to oxidative desulfurization technology.In this paper,a series of novel boron nitride supported platinum-based catalysts were designed and prepared for the study of the deep oxidation of desulfurization with activation of molecular oxygen in diesel fuel.Firstly,Pt nanoparticles were immobilized on the edge of h-BN by impregnation thermal reduction method using commercial h-BN as support to obtain a Pt/h-BN heterogeneous catalyst.X-ray diffraction?XRD?,transmission electron microscopy?TEM?and other characterization methods proved that Pt nanoparticles are highly dispersed at the edge of h-BN.In the ODS process,Pt/h-BN had a higher catalytic activity for DBT,4-methyldibenzothiophene?4-MDBT?and 4,6-DMDBT.The DBT removal reached 98.3%,and the TOF value is 2300 h^-1.Through cycling experiments,it was found that the Pt/h-BN catalyst could be cycled 5 times,the catalytic oxidative desulfurization activity did not drop significantly,indicated the industrial application prospects.Electron-loss energy spectroscopy?EELS?,X-ray photoelectron spectroscopy?XPS?and activity comparisons demonstrated that electrons at the edge of h-BN will transfer from Pt atoms to B atoms.The electron loss of Pt was favorable for the adsorption of sulfur compounds,which enhanced the catalytic activity.Few-layered BN nanosheets?BNNS?were prepared by a green high-yield liquid nitrogen gas phase exfoliation.The Pt particles with different size were supported on the BNNS to obtain a catalyst.The purpose is to expose more B and N defects to enhance the interaction with Pt particles.By the method of atomic force microscopy?AFM?,XRD and TEM,it was found that the layer number of h-BN was significantly reduced and successfully stripped to about 3 layers.Besides,3 nm,5 nm,and 7 nm Pt particles had been successfully synthesized and were supported on BNNS to achieve catalysts Pt-3/BNNS,Pt-5/BNNS and Pt-7/BNNS.During the ODS experiment,it was found that the smaller the Pt size is,the higher the activity is.The Pt-3/BNNS?Pt-3 represents 3 nm Pt?has the highest sulfur removal.The DBT removal reaches97.6%after a 7 h reaction and 4-MDBT and 4,6-DMDBT can also be removal effectively.The hot filtration experiment proved that the Pt particles did not fall from the support,and there is not a significant decrease in catalytic activity after 6 recycles,indicating that Pt-3/BNNS has an excellent reuse performance and stability.A PtCu/BNNS heterogeneous catalyst was obtained by hydrothermal synthesis.The few-layered BNNS was prepared via a liquid nitrogen gas phase exfoliation method.Using XRD,TEM,HRTEM and other characterization methods,it was verified that the supported metal is PtCu alloy with an octahedron shape.Through multiple experiments and analysis,it was found that the activity was greatly improved when the supported metal changed from single metal Pt to PtCu alloy,and the reaction temperature is 110^oC,lower than before.On the basis of the high catalytic activity of PtCu/BNNS,there is still a high sulfur removal while in real diesel oil.The recycling performance of catalyst is still excellent after 10 reuse..