Redox behavior of CuZSM-5 catalysts: FTIR investigations of reactions of adsorbed NO and CO

The redox behavior of CuZSM-5 was investigated by flow microbalance and FTIR measurements using CO and NO as probe molecules. The weight change resulting from switching the now of 10% O-2 in He to pure He corresponded to the removal of extralattice oxygen and approximately 20% autoreduction of total copper ion by one electron. FTIR absorption spectra of CO over CuZSM-5 showed that the concentration of the Cu+ sites changed reversibly upon switching the pretreatment gas from He to O-2. The combined experiments (flow microbalance and CO adsorption) proved that CuZSM-5 has a redox function at 500 degrees C. Continuous measurement of NO adsorption spectra using the same wafer, following a pretreatment in flowing He at 500 degrees C, also demonstrated the redox properties of CuZSM-5. During the early stage of NO adsorption, a sharp band at 2295 cm(-1) appeared that could be assigned in several different ways. Changes occurring as NO underwent reaction on the surface were recorded.