Construction Of Nb-based Composite Catalysts And Their Applications On Organic Sulfur Pollutants Removal

The excess organic sulfur pollutants have serious adverse effects for the sustainable development of energy and the environment.In this study,the build mechanism and structure-activity of inorganic composite catalytic materials,the adsorption model for ethyl mercaptan（EM）and the photocatalytic oxidation mechanism of EM are investigated.The adsorption and catalytic remove of ethyl mercaptan in methane gas is used as the ultimate goal,the successful building of the Nb-based composites is the research premise,the continuous online adsorption and photocatalytic reaction device made by ourselves is the guarantee research conditions.This article mainly includes the following aspects:The crystal structure,band structure,density of states,front orbital,Fukui function and XRD pattern of LiNbMoO₆ are calculated via the density functional theory（DFT）.That laid a theoretical foundation for subsequent analysis the building mechanism of the composite material and the adsorption mechanism for ethyl mercaptan.The prepared LiNbMoO₆ has the same structure with the calculated.The adsorption and the photocatalytic performance for EM are studied using the gas-solid adsorption and photocatalytic device.The adsorption for ethyl mercaptan over LiNbMoO₆ is owed to the interaction of O...H-S hydrogen bond.While the adsorption ability is very weak and the ethyl mercaptan is moved out from the surface of LiNbMoO₆ easily.Under the visible light irradiation,the ethyl mercaptan could by oxided to diethyl diethyl sulfide partly over LiNbMoO₆.Fe³⁺ and Ce³⁺ are introduced to the interlamination of LiNbMoO₆ and the desulfurization performances over them are researched.Results show that the introduction of Fe³⁺ and Ce³⁺ changes the charge distribution in the interlamination and improves the adsorption and photocatalytic performance for ethyl mercaptan.The removal reaction mechanism of ethyl mercaptan on the surface of the modified materials is studied through dynamic adsorption-dynamic reaction for online detection and dynamic adsorption-static reaction offline detection methods under different lights.Results show that the different lights and different catalysts have impact on the depth of photocatalytic oxidation removal of ethyl mercaptan significantly.A series of two component Nb-based composites are built by intercalation pillaring and exfoliation recombination methods and their desulfurization performances are studied.The research results reveal that the desulfurization efficiency is improved observably.The adsorption capacity is increased to 109.1 from 45.3μmol/g and the EM is converted into diethyl diethyl sulfide completely.In the adsorption process,the ethyl mercaptan could be oxidized to sulfoxide and sulfone due to the oxidizability of precursor HNbMoO₆.The catalytic activity over TiO₂@e-HNbMoO₆ and the oxidation depth over Fe2O3@e-HNbMoO₆ are the best,respectively.The three-component composite Ag@MnO₂@e-HNbMoO₆ owns the maximum adsorption capacity at 222.7 μmol/g,and it is about 6.5 times of the original material LiNbMoO₆ and 2-4 times of that of other modification.It owe to the introduction of Ag.The addition of MnO₂ effectively enhances the oxidation properties of the composite for ethyl mercaptan.The existence of the e-HNbMoO₆ makes Ag@MnO₂@e-HNb-MoO₆ has better catalytic depth than Ag@MnO₂@e-HNbWO6 and Ag@MnO₂@e-H-TiNbO5,and the ethyl mercaptan can be oxided into sulfate and S ions.Among the three methods,the ions could directly replace the interlayer ions for ion-exchange method,the hydrogen bonds are the major interactions in the intercalation-pillaring and exfoliation-recombination methods.The adsorption of the composite for ethyl mercaptan is influenced by hydrogen bond and hard soft acid-base（HSAB）theory.Photocatalytic oxidation reaction mechanism of ethyl mercaptan on the catalyst surface is beginning with the producing of diethyl diethyl and then sulfoxide,sulfone,sulfonate and sulfate are gradually generated via the strong oxidizing species OH·The above three kinds of modified method effectively enhance the adsorption ability of the Nb-based compound catalytic materials for EM,improve the catalytic activity of the catalyst and control the depth of desulfurization.Combined with density functional theory and the experimental results,the building mechanism and the adsorption mode of the compound catalytic materials for EM,and the reaction mechanism of EM had be detailed investigated.