The Migration Of Cu Species Over Cu/SAPO-34and Its Effect On NH₃Oxidation At High Temperature

Cu/SAPO-34catalyst, as the NH3selective catalytic reduction (NH3-SCR) catalyst,has become the research focus because of its broad activity widow, N2selectivity andgood hydrothermal stability. In this research, we prepared a series of Cu/SAPO-34with various CuO/Cu2+ratio by hydrothermally treating the impregnatedCu/SAPO-34catalyst. Morover, the the influence of Cu species migration on NH3oxidation mechanism and its inhibition on NH3-SCR activity over Cu-SAPO-34catalysts were studied.The XRD, SEM, EDS, BET were conducted to analysis the physical property, andthe ICP-AES, H2-TPR and CO-DRIFTS were conducted to estimate the Cu speciesdistribution. The NH3oxidation activity test was performed to research the effect ofCu species migration on the NH3oxidation activity and mechanism.The results revealed that the CuO species initially existed on the external surfaceof the fresh impregnated Cu/SAPO-34catalyst, and converted to the isolated Cu2+andnanosized CuO in the cavity of the SAPO-34support during the hydrothermaltreatment. The NH3-SCR activity over the hydrothermally treated Cu/SAPO-34catalysts improved due to the increase of the isolated Cu2+amount, while the NH3oxidation activity declined. In conclusion, the Cu species migration caused thedecrease of the NH3oxidation activity and the great variation of the generated NOamount. Furthermore, it was proposed that the NH3oxidation mechanism over theCu/SAPO-34catalysts contained two steps: firstly, molecular NH3reacted with O2atCuO sites; secondly, the generated NO was reduced by NH3to N2at isolated Cu2+.