The dynamics of packed bed reactors loaded with oxide catalysts

The lattice of an oxide catalyst used for oxidation reactions can act as a reservoir for oxygen, storing and releasing it for reactions at the catalyst surface under appropriate conditions. The implication of this oxygen storage property on the dynamic response characteristics of oxide catalysts has been investigated through an experimental study of 2-butene oxidation over vanadium oxide as a model reaction. Isothermal reaction rate measurements in a differential reactor and nonisothermal studies in a single pellet reactor have been carried out. Following a step increase in the feed butene concentration, isothermal reaction rate overshoot and pellet temperature overshoot were observed. These observations could be modelled in a qualitatively correct way by a very simple model accounting for the dynamic participation of lattice oxygen in the catalytic reactions. It is demonstrated through model simulations that the ignition characteristics of a catalyst pellet are significantly affected by the participation of the lattice oxygen, when steady state multiplicity is present. The initiation of dynamic runaway of a wall-cooled packed reactor, upon start-up, owing to the participation of lattice, is illustrated through simulations