IR and XPS study of NO and CO interaction with palladium catalysts supported on aluminosilicates

Adsorption of CO and NO individually and as a mixture of both on palladium catalysts has been investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The effect of sodium ion s has been considered by comparing Pd/SiO2 catalyst, sodium-doped Pdl SiO2, and Pd on natural and synthetic silicoaluminates containing sodium in thei r bulk structure but differing in the surface area of the support. The pres ence of sodium induces a different adsorption behavior depending on its loc ation, either at the surface of the catalysts or inside the support structu re. As a consequence, different species are formed from the reaction betwee n NO and CO at room temperature and at high temperature. Modification of th e metal surface of the Various catalysts is observed upon the gas treatment s. Palladium is oxidized to a certain extent depending on the type of the c atalyst support. Moreover, different chemical states of the adsorbed nitrog en species are found.