Deactivation Avalanches through the Interaction of Locally Deactivated Catalyst with Traveling Hot Spots

摘要

Packed-bed reactors with exothermic reactions tend to amplify transient perturbations of input parameters such as feed temperatue, composition, flow rate, etc. These can grow into large-amlitude temperature (and concentration)_ wave-traveling hot spots (THS)- with peak temperatures well above the adiabatic temperautre rise. Thus, THS accelerate thermal degradation of the catalyst. If the deactivation is localized (i.e. inactive pellest are surrounded by active catlyst) the THS develop much higher temperatures than they would in a uniformly active bed. The dynamics responsible for this secondary temperature overshoot and further accelerated deactivation is related to "wrong-way behavior". This sequence constitutes a new dynamical mechanism of catalyst deactivation in which a low-activity domain acts as nucleating cener for self-accelerated, avalanchelike, catalyst deactivation.