Physicochemical, surface and catalytic properties of Co3O4/Mn2O3 and Mn2O3/Co3O4 systems

ABSTRACT

The two catalytic systems were prepared using equimolar proportions of cobalt nitrate and manganese carbonate [Co3O4/Mn2O3] and manganese carbonate and cobalt nitrate Mn2O3/Co3O4]. The mixed solids were subjected to heating at 500, 700, and 900°C. The solid - solid interactions taking place in the two catalytic systems were followed up using XRD investigation. Their specific surface areas were determined from nitrogen - adsorption isotherms carried out at - 196°C. Their catalytic activities were studied via following up the kinetics of CO oxidation by O2 at 125-400°C using a static method. The results obtained revealed that solid - solid interaction took place between cobalt and manganese oxides at 500 - 900°C yielding cobalt manganite and manganese cobaltite. In Co3O4/Mn2O3 system, a complete conversion of cobalt and manganese oxides took place at 900°C to yield cobalt manganite. In the other system, however, a partial conversion of Mn2O3/Co3O4 took place at 900°C. The specific surface areas of the two investigated systems are close to each other and decrease by increasing their calcinations temperature within 500 - 900°C.The decrease was, however, more pronounced by increasing the calcinations temperature from 700 to 900°C. The catalytic activity of Mn2O3/Co3O4 is smaller than that measured for the other system calcined at 500 °C. Opposite results were observed for the solids calcined at 700°C and 900°C. The catalytic reaction proceeds via almost the same mechanism in contact with different solids