Characterization of CuO-Kaolin Solids Used for Co-oxidation

Abstract

Six samples of copper oxide/kaolin were prepared by impregnating

kaolin with solution containing different concentrations of Cu-nitrate. The

obtained solids were thermally treated at different temperatures. The thermal

products were characterized by XRD-analysis and were tested in the

oxidation of carbon monoxide.

The results of X-ray investigation revealed that, supported metal oxide

on the surface of kaolin appeared as crystalline oxide in the X -ray diffracto

gram. Solid-solid interaction occurred between the oxide and the decomposition

products of kaolin yielding aluminate CuAl₂O₄ and CuAl₂O₄-

Al_2O3 solids solution. The prepared solids were tested in the oxidation of

carbon monoxide. The results of the effect of calcination temperature on

the activity revealed that catalysts activated at 350ºC were more active

than those activated at 550 or 750ºC. The low activity may be attributed

to the interaction between CuO and the thermal decomposition products

of kaolin and/or sintering of the heated solid. The catalytic activity increased

with increasing the metal oxide content in the catalyst and also

with increasing the reaction temperature. The presence of oxygen (air)

prevents the appearance of monovalent copper or metallic copper. This is

because the reduced forms of copper are oxidized as fast as they formed.