Temperature patterns on a hollow cylindrical catalytic pellet

The atmospheric oxidation of a mixture containing 6 vol % carbon monoxide was carried out on a hollow cylindrical catalytic pellet. The catalyst was held in a conical reactor which enabled simultaneous measurement of the temperature patterns on the top and side of the pellet by an IR imager. Upon a decrease in the reactor temperature the fully ignited, high temperature state of the pellet is transformed to a nonuniform one with temperature fronts separating high and low temperature regions. The transition and the resulting states are rather intricate and are strongly influenced by the nonuniformity of the catalyst and the transport to and from it, as well as the global coupling, which stabilizes temperature fronts and patterns, which would not exist in its absence. Intricate pulse splitting and extinction were observed both on the top and the side of the pellet. Highly irregular motions and conversions were obtained following a decrease in the reactor temperature. (C) 1999 American Institute of Physics. [S1054-1500(99)00901-5].