Aqueous H2O2 as an oxidant for CO over Pt- and Au-NaY catalysts

The oxidation of carbon monoxide with aqueous hydrogen peroxide was carried out over Pt- and Au-NaY catalysts, that were prepared by the impregnation of NaY zeolite (Si/Al = 5.6, S-BET = 910 m(2)/g) with aqueous solutions of tetramine platinum(II) nitrate and hydrogen tetrachloroaurate trihydrate, respectively. The Pt- and Au-NaY catalysts exhibited high activity at relatively low temperatures as low as 303 K in the CO-H2O2 reaction. Pt-NaY was compared favorably with Au-NaY at similar reaction conditions, where the specific reaction rate constant, K-m, over Pt-NaY was five times of magnitude higher than that of Au-NaY at 323 K. These data were confirmed by the values of activation energy evaluated from Arrhenius plots. The Pt-NaY was reduced in flowing H-2 at 623 K for 2 h. The catalytic activity of reduced Pt-NaY was about 44 times more active than that of analogous unreduced catalyst at 303 K. The catalytic activity of Au-NaY was greatly affected by thermal treatment. A higher K. value was obtained at 353 K over Au-NaY, exceeding this temperature led to a decrease in activity due to sintering of Au particles. It is proposed that a dual Au(0)/Au(I) site is necessary to catalyze the reaction, where, Au(0) accelerates the H2O2 decomposition and the CO adsorption capability was enhanced on Au(I) site. (c) 2006 Elsevier B.V. All rights reserved.