Investigation of the state of copper in supported copper-titanium oxide catalysts

Supported copper-titanium oxide catalysts have been studied by IR spectrosc opy, XRD, UV-VIS diffuse reflectance spectroscopy, ESR, TPR with hydrogen a nd EXAFS. Different states of Cu2+ ions have been found on the surface of T iO2. The ratio between these states depends on the copper concentration and catalyst preparation method. Chain structures are formed due to the intera ction of Cu2+ ions with TiO2. Their concentration and geometry of their nea rest oxygen environment are determined by the structure of anatase faces. S ome of these surface-stabilized Cu2+ ions are nucleation centers of oxide c lusters. A noticeable growth of bulk CuO phase is observed after the comple tion of the formation of chain structures and oxide clusters. A quantitativ e estimation of the concentration of these copper forms in the catalysts is reported. For supported copper-titanium oxide catalysts, chain forms of Cu 2+ ions are shown to be the most active forms of copper in NO SCR with ammo nia and methane oxidation. (C) 2000 Elsevier Science B.V. All rights reserv ed.