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, SBET = 910 m2/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, Km, 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 H2 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 Km 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.

Graphical abstractThe 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, SBET = 910 m2/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, Km, 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 H2 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 Km 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.