Copper Oxide With Embedded Ce On Surface For NH₃ Selective Catalytic Reduction Of Nitrogen Oxides

To control the toxic effects of large amounts of nitrogen oxides emitted during production and life,selective catalytic reduction and removal are highly effective approaches.Designing low-cost,durable,inexpensive catalysts for this pathway is an important issue in the study of heterogeneous catalysis.In this dissertation,CuO-based catalysts were selected to combine with rare earth elements Ce to synthesize and characterize surface-composite catalysts.Different from the traditional preparation methods,this study used the redox reaction between the Ce（IV）precursor compound and the Cu₂O matrix surface to etch and embed a small amount of Ce species on the Cu₂O surface.By varying the Ce content,a uniform dispersion surface was prepared for the Ce-Cu.The samples of compact composite layers were heat-treated to obtain a structurally stable catalyst for the selective reduction of NO with NH₃（NH₃-SCR-NO）.The catalytic activity,resistance to water and sulfur,and catalytic stability were investigated.The XRD,Raman,SEM,XPS,H₂-TPR,NH₃-TPD and other characterization methods indicate that a small amount of Ce embedded（0.83-2.3 wt.%）can obtain Cu（I）-Cu（II）and Ce（III）-Ce（IV）multi-oxidized species coexisting and compositionally adjustable composite interface on the surface of CuO.The corresponding redox properties and surface acid center properties can also be effectively regulated.resulting in an excellent performance of the NH₃-SCR-NO catalyst.Such as（CeO_x）1.6wt.%^CuO sample in the GHSV=100,000 h^-1,200^oC-220^oC range of NO conversion rate up to 95%.NO conversion can reach 90%in the temperature range of 280^oC-320^oC after adding 200 ppm SO₂.And to maintain the performance in the 48 hour stability test.This sulfur-resistant catalytic performance shows that the prepared catalyst has a good application prospect.On this basis,Ce-Cu-Mn ternary composite catalyst was also obtained by doping Ce with Cu-Mn composite oxide prepared by co-precipitation method.The results show that the NO conversion can reach 100%under the conditions of GHSV=40,000 h^-1 and 100°C-240°C.In particular,the Cu（0.3）-MnOx-Ce（12.5%）catalyst has a wider active temperature window,and its water-and sulfur-resistant ability is significantly improved compared to the Cu-Mn binary catalyst.