CATALYTIC-OXIDATION OF AN AMORPHOUS-CARBON BLACK

The oxidation of an amorphous carbon black in the presence of a potass ium-copper-vanadium catalyst supported on alpha-alumina has been studi ed. Burnoff temperatures in the presence of catalyst were lowered by a bout 300 K with respect to those for uncatalyzed combustion. Cycles of temperature-programmed reduction and oxidation, along with TG-MS anal yses demonstrated that a redox mechanism is at the basis of the cataly st strong activity. A differential flow reactor was employed to perfor m kinetic tests. The progress of the catalytic combustion process was followed measuring the concentrations of carbon oxides in the product stream at the reactor outlet with on-line NDIR analyzers. The dependen ce of the reaction rate on the relevant variables was investigated. In particular, the apparent activation energy for the catalytic oxidatio n was found to be less than half that of the corresponding uncatalyzed process, while the carbon reactivity showed a linear dependence upon the amount of catalyst and a square root dependence upon the oxygen pa rtial pressure. The results allowed the formulation of a mechanism for the catalytic oxidation of carbon black and suggest that the limiting step of the overall process is that of catalyst reduction. On the bas is of such findings a kinetic equation for catalytic carbon black oxid ation is proposed.