STEADY-STATE MULTIPLICITY IN CARBON-MONOXIDE OXIDATION OVER LAMNO3

Multiple steady states have been observed during catalytic carbon monoxide oxidation over polycrystalline LaMnO3. The bistability was noted only at a carbon monoxide partial pressure P(co) greater-than-or-equal-to 46 kPa. The transition to the more reactive state sets in at 220-degrees-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.