Synthesis, structure and catalytic activity of CuO/TiO2 mixed oxides obtained by alkoxo-methods in CO oxidation

Abstract

Structural, electronic and catalytic properties of CU-O/TiO 2 mixed oxide catalysts tested for CO oxidation, wich were obtained by a modified alkoxysynthesis method from Ti(O n Bu) 4 and Cu(Cu 17 H 35 COO) 2 , have been studied by X-ray diffraction, EXAFS, XPS, magnetic susceptibility techniques and kinetic measurements. Partial chelation of Ti(O n Bu) 4 by acetylacetone was shown to stabilise sols and to ensure anatase-based single phase Cu x Ti 1 − . 0,5x 0 2 (x ≤ 0.06).For x ≥ 0.06, the formation of cupric oxide and titania gives evidence of phase separation. At temperatures T < 150 °C, an overall CO conversion over the Cu x Ti 1–0,5x O 2 depends on the parameter x and on mean crystal size < d >: by increasing x and decreasing < d >, there is a marked increase in activity. It is suggested that terminal (non-bridged) oxygen of the bond Cu = O S , surface anion vacancy V S , related to the reduced Cu + 1 state and surface labile species O S participate in CO oxidation. At temperatures T > 150-200°C, the participation of lattice oxygen in the reaction mechanism is postulated.