G-C₃N₄-base Supported And Composite Photocatalytic Oxidative Desulfurization Catalyst

In this paper,the modification of g-C₃N₄-based supported and composite catalyst were studied.TiO₂-g-C₃N₄/BMMS supported photocatalyst were prepared with melamine as nitrogen source,butyl titanate as titanium source and bimodal mesoporous silica?BMMS?as carrier;Bi₂WO₆/Ce-g-C₃N₄composite photocatalyst was prepared with melamine as nitrogen source,ceric sulfate as cerium source and bismuth nitrate pentahydrate as bismuth source.The prepared catalyst was characterized by XRD,N₂ adsorption/desorption,TEM,SEM,EDS,FTIR and UV-vis and used for photocatalytic oxidative desulfurization?PODS?of dibenzothiophene-containing dodecane solution as the simulated diesel,so as to investigate the catalystic performance.Then the reaction conditions were optimized and the catalytic reaction mechanism was proposed.The main results and conclusions were as follows:The characterization results of TiO₂-g-C₃N₄/BMMS catalyst showed that the catalyst had highly ordered double mesoporous structure with TiO₂-g-C₃N₄was loaded onto the BMMS carrier and its specific surface area was higher than TiO₂.The active components of TiO₂-g-C₃N₄/BMMS were well dispersed and the chemical interaction obviously existed between TiO₂ and g-C₃N₄.Compared with pure TiO₂,the band gap became narrower and the optical absorbance became greater.And compared with TiO₂/g-C₃N₄,the catalytic activity of TiO₂-g-C₃N₄/BMMS was markedly improved and the desulfurization rate can reach 96.6%.After 8 times recycling,the desulfurization rate still achieved over 90%.The optimized process conditions were as follows:When O/S molar ratio as 10:1,catalyst and oil ratio?v/v?as1:1 and catalyst dosage?mass percentage?as 3wt%of simulated oil's mass,TiO₂-g-C₃N₄/BMMS catalyst got the desulfurization rate of 96.6%under 120min of visible illumination.Based on the comparison experiment of the composition of catalytic system and the capture experiment of active intermediates,the mechanism of catalytic reaction was proposed.It was considered that methanol,hydrogen peroxide and catalyst were indispensable under visible light conditions.And·O₂^-and h⁺played an important role in PODS reaction.The characterization results of Bi₂WO₆/Ce-g-C₃N₄ catalyst showed that after Ce-g-C₃N₄ and Bi₂WO₆ were complicated,the Ce-g-C₃N₄ was helpful to the growth of Bi₂WO₆ crystal to some extent.Ce doping didn't change the crystal structure of g-C₃N₄ and the chemical interaction existed between Bi₂WO₆ and Ce-g-C₃N₄.The layers of Ce-g-C₃N₄ and Bi₂WO₆ microspheres were uniformly crosslinked.Compared with pure Bi₂WO₆,the absorption edge was redshifted and the band gap became narrower.And compared with Bi₂WO₆/g-C₃N₄,the catalytic activity of Bi₂WO₆/Ce-g-C₃N₄ was markedly improved and the desulfurization rate can reach 88%.After 6 times recycling,the desulfurization rate still achieved over 83%.The optimized process conditions were as follows:When O/S molar ratio as 10:1,catalyst and oil ratio?v/v?as 1:1 and catalyst dosage?mass percentage?as 1wt%of simulated oil's mass,Bi₂WO₆/Ce-g-C₃N₄ catalyst got the desulfurization rate of 88%under120 min of visible illumination.According to the comparison experiment of the composition of catalytic system and the capture experiment of active intermediates,the mechanism of catalytic reaction was proposed.It was considered that under the visible light conditions,methanol,hydrogen peroxide and catalyst were necessary conditions for PODS reaction.And·O₂^-and h⁺played key roles in the reaction.