Preparation And Properties Of Nb₂O₅/SBA-16 Photocatalytic Oxidation Desulfurization

In this paper,the niobium ammonium oxalate was used as raw material to prepare Nb₂O₅ photocatalyst by the process of calcining under the protection of N₂.The crystal phase structure,surface functional groups,thermal decomposition process and light absorption performance of Nb₂O₅photocatalyst prepared at different temperatures were characterized by XRD,XRD、FTIR、TG、UV-vis DRS.Results showed that the catalyst particle size and crystallinity of Nb₂O₅ are raised with the increasing temperature and when the calcination temperature was 550℃,the crystal phase changed from the chemical stability of the worst hexagonal system（H-Nb₂O₅）into orthogonal crystal system（O-Nb₂O₅）which has high stability and catalytic activity;The absorption ability towards incident light is strong.A one-step impregnation method was used to load Nb₂O₅ onto the mesoporous SBA-16 molecular sieve.The photocatalyst supported by Nb₂O₅/SBA-16 was characterized by XRD,FTIR,BET,uv-vis DRS,SEM,TEM and EDS.The result indicated that Nb₂O₅ was distributed on the mesoporous molecular sieve SBA-16 uniformly and when the loading of Nb₂O₅ is 20 wt%,the effect on surface pore and adsorption capacity of SBA-16 was the lowest,so the 20 wt%is the most suitable load.At the same time,EDS element analysis results showed that Nb,O and Si elements in Nb₂O₅/SBA-16 were all reflected in the spectrogram,the content of Nb element was the highest and the distribution of Nb element was uniform,which proved the viewpoint that Nb₂O₅ is fully and uniformly loaded on mesoporous SBA-16.The mixed solution of dibenzothiophene（DBT）and dodecane was used as the simulated diesel oil,and the photocatalytic oxidation desulfurization（PODS）reaction was used as the measuring probes to detect the photocatalyst activity.The influence of the content of H₂O₂（O/S mole ratio）,the amount of catalyst and the amount of extraction agent（CH₃OH）added in the reaction on the simulated oil desulfurization effect was investigated,meanwhile,the recycling operation was employed to investigate its reusing performance and explore the PODS reaction principle.The results showed that:（1）the Nb₂O₅photocatalyst prepared by calcining ammonium oxalate niobium under N₂protection to 550℃has high desulfurization activity,and when the O/S mole ratio of 15,the volume ratio of CH₃OH and reaction fluid is 1:1,catalyst dosage is 1 wt%in the desulfurization system,the desulfurization rate is highest,at 93.65%.Moreover,the desulfurization rate of the photocatalyst was still as high as 90.34%after repeated use for 5 times,indicating that the photocatalyst was recyclable.（2）Compared with Nb₂O₅,Nb₂O₅/SBA-16catalyst has a higher desulfurization rate,and when Nb₂O₅ load is 20 wt%,Nb₂O₅/SBA-16 has the best desulfurization effect.In reaction condition,when the O/S molar ratio of 10:1,the volume ratio of CH₃OH and reaction fluid volume ratio is 1:1,catalyst dosage is 1 wt%,the PODS reaction system shows the best desulfurization effect with a desulfurization rate as high as98.06%.And the desulfurization rate of 95.85%can still be achieved after the Nb₂O₅/SBA-16 photocatalyst was used for 5 times,which can be used as an effective and green and recyclable photocatalyst.