Study On Photocatalytic Oxidation Desulfurization Catalyst Of Nb₂O₅supported On Activated Carbon

In this paper,activated carbon loaded Nb₂O₅photocatalytic oxidation desulfurization catalyst was prepared with Nb₂O₅as the active component and activated carbon as the carrier.The effects of acidification,calcination temperature,calcination time and loading amounts of Nb₂O₅on the structure,properties and photocatalytic activity of the catalyst were studied by XRD,N₂adsorption desorption,XPS,TG-DGT,FTIR and the experiments of PODS.The characterization results show that compared with the non acidified Nb₂O₅/AC catalyst,the ordered degree of graphite layer,pore volume,pore size and specific surface area of the acidified Nb₂O₅/AAC catalyst are obviously increased,and the surface oxygen groups are increased,which are conducive to improving the dispersion of active components and reducing the diffusion resistance of larger molecules in the reaction system.And the formation of oxygen vacancy on the surface of the catalyst after acidification improves the photocatalytic activity of the catalyst.The photocatalytic activity of Nb₂O₅/AAC supported on acid treated activated carbon is better than that of Nb₂O₅/AC and Nb₂O₅catalysts without acid treatment.It was found that the reaction rate of Nb₂O₅/AAC was 1.42 times of Nb₂O₅/AC catalyst and 16.9 times of Nb₂O₅catalyst.The effect of calcination temperature on Nb₂O₅/AAC catalyst was studied.The thermal decomposition process of ammonium niobium oxalate was characterized by TG-DGT,FTIR and XRD.It was found that ammonium niobate oxalate can be completely decomposed into Nb₂O₅at350?which is mainly amorphous,Nb₂O₅was evenly distributed in the pores of activated carbon,and there was no obvious characteristic peak.The results of PODS showed that the desulfurization rate of the catalyst increased first and then decreased with the increase of calcination temperature.When the calcination temperature is 350?,Nb₂O₅/AAC catalyst has the highest photocatalytic activity.The effects of calcination time and loading amount on Nb₂O₅/AAC catalyst were studied.The results showed that the suitable calcination time was 30 min,the suitable concentration of impregnating solution was 5 g/L,and the desulfurization rate was 86.65%.The effect of PODS reaction conditions on the catalytic effect of Nb₂O₅/AAC catalyst was studied.It was found that the catalyst had the highest desulfurization rate when the amount of catalyst was 1 wt%,the O/S molar ratio was 15,and the catalyst oil ratio was 1:1?volume ratio?.The desulfurization rate reached 97.77%.Its reusability was investigated,which found that the removal rate of DBT was 71.41%after the catalyst was used for 4 times.In the PODS experiment,the catalyst and H₂O₂jointly photocatalytic oxidation DBT to produce DBTO₂.The DBTO₂is polar,and is extracted and separated by methanol in time,which promotes the reaction to continue.The results showed that H⁺was the most active species in PODS.It is suggested that H⁺can capture the lone pair electrons on DBT to generate DBT⁺and then be further oxidized by·O₂^-or OH^-to generate DBTO₂.The impurity level is introduced into the oxygen vacancy,which reduces the band gap of the catalyst.