Influence of surface composition on hydrogen peroxide decomposition catalyzed by Co(II) aminopyridine-supported compounds on amorphous silica gel

Cobalt compounds supported on 2-, 3-, and 4-aminopyridine-modified silica surfaces, named Si12Co, Si13Co, and Si14Co, respectively, were used to catalize the decomposition of hydrogen peroxide on ethanolic solutions at 293, 298, and 303 K. The calculated k values ( x 10(-4) s(-1)) for Si12Co, Si13Co, and Si14Co are 0.65, 1.24, and 4.78 (293 K); 1.23, 1.87, and 6.33 (298 K); and 1.80, 2.80, and 10.30 (303 K), respectively. All obtained results evidence that such decomposition is a first-order reaction. Zinc-, nickel-, and copper-supported compounds were also tested, but exhibited a very low catalytic activity. By using the k values at 298 and 303 K, and employing the equation In (k(1)/k(2))=E-a/R(1/T-2=1/T-1), the activation energy values for the considered reaction were Si12Co = 57.20, Sil3Co = 60.60, and Si14Co = 73.10 kJ mol(-1), respectively. The low values calculated for Ea are in agreement with a free-radical machanism. (C) 2002 Elsevier Science (USA).