Catalytic Promotion of Activated carbon by Treatment with Some Transition Metal Cations

Abstract

A commercial activated carbon sample was treated with 1% dilute nitric acid followed by impregnation with 5 wt% and 10 wt% cobalt, nickel, or copper nitrates, which were dissolved in the minimum amounts of distilled water sufficient to cover the surfaces of activated carbon granules followed by drying at 100°C till weights became constant. The transition metal ions-treated samples were heated at 400°C in a flow of argon for 3 h. The analytical tools for characterization of different solids were X-ray diffraction, nitrogen adsorption at −196°C, infrared spectroscopy, catalytic conversion of isopropanol, and catalytic decomposition of H2O2 at 25–45°C. The results revealed that the activated carbon treated with 5 wt% and 10 wt% transition metal oxides heated at 400°C in a argon flow consisted of a mixture of very poor crystalline CoO, Co3O4, NiO, Cu2O, and CuO phases of nano-crystalline nature. The treatment of activated carbon with cobalt, copper, or nickel oxide led to a small increase in its BET surface area. All solids investigated acted mainly as dehydrogenation catalysts with selectivities above 90%. The percentage increase in the catalytic activity, measured at 225°C, due to the treatment with 5% transition metal oxide attained 6%, 24.6%, and 40.6% for cobalt, nickel, and copper oxides, respectively. The observed measurable increase in the catalytic activity of the commercial activated carbon system treated with small amounts of CoO in the catalysis of H2O2 decomposition can be considered as a consequence of the significant increase in the concentration of catalytically active sites taking part in the catalysis of H2O2 decomposition, but it did not modify the mechanism of the catalytic decomposition.