Co-existance of various active gold species in Au-mordenite catalyst for CO oxidation

Different structural and electronic states of gold species in H-mordenite with SiO2/Al2O3 molar ratio 206 and their transformations under redox treatments have been studied by the methods of diffuse reflectance UV–visible spectroscopy and FTIR spectroscopy of adsorbed CO. Different states of ionic and metallic gold were detected in the zeolite channels and on the external surface of the zeolite – Au+ and Au3+ ions, charged clusters Aunδ+, and neutral nanoparticles Aum. Catalytic tests of the samples revealed the co-existence of several types of active species of gold in CO oxidation – gold clusters <1.5 nm (responsible for low-temperature activity) and gold nanoparticles (responsible for high-temperature activity).