Heteropolyacid-based Nanocomposite Materials:Syntheses And Desulfurization Performance

The development and utilization of energy has made great progress in recent years,and with it,environmental problems have become increasingly prominent.Fuel oil produces large amounts of sulfur oxides during the combustion process,which not only cause environmental pollution such as smog and acid rain,but also seriously affect human health conditions.The production of ultra-clean fuels with very low sulfur content is extremely important to meet the strict regulatory requirements,as the European Union has strictly enforced a<10 ppm sulfur content in fuels for environmental and healthcare reasons.Currently,hydrodesulfurization is a conventional process for the removal of organic sulfides in industry,with high removal efficiency for sulfides,disulfides and other sulfur-containing compounds,but low desulfurization efficiency for some sulfides with spatial site resistance.Therefore,the development of various alternative methods has received a lot of attention in clean fuel production.In this paper,nanocomposite catalytic materials were designed based on heteropolyacids by different methods.Heteropolyacids show great potential for applications in desulfurization,and they were loaded onto carriers to prepare composite catalysts with high catalytic activity and stability using their catalytic active sites.The structural characteristics of the catalysts were characterized by X-ray powder diffraction,infrared spectroscopy,scanning electron microscopy,transmission electron microscopy,etc.The effects of different process parameters on the catalyst performance were investigated in detail,and the reaction mechanism of the catalysts was also explored,the experimental results were as follows:1.Representative Zr-based organic framework materials（MOF）Ui O-67 and Keggin-type heteropolyacid H₃PMo₆W₆O₄₀·n H₂O（PMo W）were selected for the preparation of PMo W-Ui O-67（Zr）composite catalysts by a solvothermal synthesis method.Ui O-67（Zr）is a typical MOF material consisting of zirconium ions and 4-4’-biphenyl dicarboxylic acid with a large specific surface area and excellent chemical stability,as well as the ability to optimize its catalytic performance by loading multiple acids.The two types of cages contained in Ui O-67（Zr）allow a uniform dispersion of PMo W inside and also prevent leaching of the active site.The PMo W-Ui O-67（Zr）catalytic material with matched dimensions was synthesized,and the effect of complete desulfurization could be achieved in 30 min at 60°C,oxygen-sulfur ratio equal to 6,and catalyst dosage 0.015 g.The catalyst could be recycled five times by washing,and had certain removal effect on different sulfides,which has good application prospects.2.Zr O₂ nanofibers with large specific surface area were prepared by electrostatic spinning technique,and PMo W-Zr O₂ nanocatalysts were successfully prepared by combining ion exchange method to load PMo W onto the surface of Zr O₂ nanofibers.In the process of extractive catalytic oxidation desulfurization,we found that the crystalline phase of Zr O₂nanofibers,calcination temperature,reaction temperature,hydrogen peroxide dosage,and catalyst dosage all have an effect on the desulfurization efficiency.For different sulfur-containing compounds,the removal efficiency is in the following order:dibenzothiophene（DBT）>4,6-dimethyldibenzothiophene（4,6-DMDBT）>benzothiophene（BT）.The catalyst was cycled six times with only a slight decrease for DBT removal efficiency,and filtration experiments,free radical capture experiments were performed in the desulfurization process,and the reaction mechanism was similarly investigated.