Studies on adsorption of NO on Cu-ZSM-5/cordierite and mechanism of NO decomposition by IR spectroscopy

The adsorption of NO on in-situ synthesized Cu-ZSM-5/cordierite monolithic catalyst samples with different Si/Al ratios is studied by diffuse reflectance Fourier transform infrared spectroscopy at different NO partial pressure from omega =5 x 10(-4) to 2 x 10(-3) and temperatures from 298 K to 773 K. The Cu exists mainly in Cu2+ state even at room temperature. No Cu+-NO is found under the conditions. Several N2O species are observed on the catalyst surface as well as on the Cu/cordierite sample. It is supposed that there exists a copper-zeolite-substrate interaction on the in-situ synthesized monolithic catalyst. The band at 2133 cm(-1) is attributed to NO+-O-lattice and only related to the zeolite matrix. A possible mechanism of NO decomposition over the Cu-ZSM-5/cordierite monolithic catalyst is drawn.