Steady-state multiplicity in carbon monoxide oxidation over LaMnO 3

Abstract

Multiple steady states have been observed during catalytic carbon monoxide oxidation over polycrystalline LaMnO 3. The bistability was noted only at a carbon monoxide partial pressure P co ≥ 46 kPa. The transition to the more reactive state sets in at 220°C. Upon cooling, the activity of the catalyst is sustained at a lower temperature than the ignition point. The width of the hysteresis loop increases with increasing carbon monoxide concentration. An oxidation/reduction mechanism is proposed whereby the high activity state is the surface-reduced form. The apparent activation energy is 16–19 kJ/mol for both steady states of the catalyst, indicating that a similar pathway for carbon monoxide oxidation is followed in the two states.