Study On The Surface Regulation Process And Mechanism Of Cerium-based Catalysts For Low Temperature Selective Catalytic Reduction

According to the characteristics of the flue gas of cement kilns in China,the development of low-temperature denitration catalysts with water and sulfur resistance has broad application prospects.A series of Mn-Ce/GO and Mn-Ce/ODA-GO catalysts with different supports were prepared by hydrothermal method and then characterized by X-ray diffraction（XRD）,super depth of field microscope,contact angle tester,scanning electron microscope（SEM）,transmission electron microscope（TEM）,N₂-adsorption-desorption test（N₂ adsorption-desorption）,hydrogen programmed temperature reduction（H₂-TPR）,X-ray photoelectron spectroscopy（XPS）,in situ diffuse reflectance infrared fourier transform spectroscopy（in-situ DRIFT）and denitrification activity tests to characterize the crystal structure,micro-morphology,redox properties,hydrophobic properties and surface element content of the composites,and further explored the denitrification mechanism and water and sulfur resistance mechanism of the composites.In this paper,the hydrophobic modification of graphene oxide was studied with different amounts of octadecylamine（ODA）.It was found that after ODA modification,micro-nano-level sheet-like structures appeared on the surface of the ODA-GO sheet,with obvious morphological changes and increased powder roughness.When 200 mg ODA was added,the maximum contact angle of ODA-GO reached 148.9°,and it had quite excellent hydrophobic properties.In order to improve the anti-poisoning performance of composite catalytic materials,the effects of GO and ODA-GO carriers on the SCR activity,water and sulfur resistance of cerium-based denitration catalysts were investigated.It was found that the Mn-Ce/200ODA-GO catalyst has excellent low-temperature denitration activity,and the NO_X conversion rate reached 100%at 155°C.After 100 ppm SO₂ and 10 vol.%H₂O were passed at 160°C,the denitration of the composite catalytic material activity can still be maintained above 90%.In addition,the Mn-Ce/200ODA-GO catalyst has the largest contact angle,which is 140.1°,has fairly excellent hydrophobic properties,and protects the active site from poisoning by sulfate.The catalytic mechanism research found that the two catalysts follow the Eley-Rideal（E-R）mechanism.Compared with the Mn-Ce/GO catalyst,the Mn-Ce/ODA-GO catalyst adsorbs on the Lewis acid site（L acid site）.Both NH₃ species and NH₄⁺species adsorbed on the Bronsted acid site（B acid site）can react with NO+O₂;the reaction forms at different temperatures are different.At low temperatures,the L acid complexes NH₃ and Gaseous NO reactions are predominant.At high temperatures,the coordination of NH₄⁺at the B acid site with activated bidentate nitrate and bridging nitrate is predominant.In addition,the Mn-Ce/ODA-GO catalyst has better inhibition of sulfation and prevents sulfate species adsorbed on the catalyst surface from occupying the active site of the catalytic reaction,so that the SCR reaction can proceed smoothly.