Surface interaction and reaction of NO + CO on a supported Au catalyst

Abstract

The adsorption, dissociation and reaction of NO with CO have been investigated on supported Au catalysts. The main method was FTIR spectroscopy. Although very limited dissociation of NO was observed on reduced Au catalyst, catalytic tests showed that all the samples used effectively catalyse the NO + CO reaction above 573 K. By means of FTIR spectroscopy several new absorption bands have been detected on the Au samples, the position of which depended on the nature of the support: it was 2212 cm⁻¹ for Au/TiO₂; 2220–2230 cm⁻¹ for Au/MgO; 2256 cm⁻¹ for Au/Al₂O₃; and 2305 cm⁻¹ for Au/SiO₂. These bands were attributed to the asymmetric stretch of NCO attached to the oxides. This idea was strengthened by the results obtained following the HNCO adsorption on supports alone, which gave the same absorption bands. It was demonstrated and assumed that an NCO species is formed on Au crystallites, and then migrates from the Au onto the acceptor sites of the support where it is accumulated and stabilized. The Au-NCO species was characterized by an absorption band at 2185–2195 cm⁻¹ produced either by the low temperature reaction or by the adsorption of HNCO on Au/SiO₂.