The Preparation And Performance Study Of New Denitrification Catalysts Derived From Zinc Oxide Nano Arrays

Low-temperature SCR technology is a denitration technology with research value and application prospect.Many researchers have been working on the development of SCR catalysts with high activity under low temperature conditions.In this paper,the excellent physical and chemical properties of zinc oxide?ZnO?nanoarrays are used as catalyst carriers for the following studies:Diameter-adjustable ZnO nanorod arrays were grown on different substrate?cordierite ceramic and titanium sheet?via hydrothermal method.It was found that the precursor concentration,seed concentration and surfactant amount could affect the length,density and diameter of the zinc oxide nanorod array.The MnO_x-ZnO nanocomposite structure SCR denitration catalyst was prepared supported on cordierite ceramic via hydrothermal impregnation.When the Mn?NO₃?₂ concentration is0.06mol/L,the MnO_x-ZnO catalyst could get the best NO_x conversion efficiency of 96.8%under the condition at 200oC and GHSV=10,000 h^-1.MnO_x-ZnO exhibits excellent SCR activities at low-temperature range of 100-250oC as compared to its analogue MnO_x-TiO₂,physicochemical properties presented MnO_x-ZnO composite has more active sites and a larger specific surface area,possesses high content of Mn⁴⁺,proper ratio of surface-adsorbed oxygen?O??and the sample has good redox capacity.Further mechanism is systematically examined via in situ DRIFTS,the results of which demonstrates that the low-temperature SCR reactions on the MnO_x-ZnO/CC catalyst generally occur between NO_x and NH₃ species in adsorption status,following the Langmuir-Hinshelwood?L-H?pathway.Thermal solvent method was successfully conducted for the preparation of composite catalyst with ZnO nanorod array core and zeolitic imidazole skeleton shell?ZnO@ZIF-8?.We found that the solvent composition and the amount of organic ligands act together on the growth of ZnO@ZIF-8.At the same time,the thickness of ZnO@ZIF-8 shell could be gradually increased and finally stabilized over time and the shell would be very compact and the thickness which was greater than 120 nm after 32 h reaction.Because of the large specific surface area and pore volume,good thermal stability at low temperature and the excellent denitration efficiency?43.3%?at 250oC and GHSV=10,000 h^-1,We could deduce that the ZnO@ZIF-8catalyst could exhibit a certain low temperature activity and that result could a good foundation for further research and exploration.