Hot Zone Formation during Hydrogenation of Ethylene and Acetylene Mixtures in a Shallow Packed Bed Reactor

Abstract

Localized hot spots have been observed in industrial reactors during the catalytic hydrogenation of acetylene present in ethylene-rich mixtures used as feed to polymerization reactors. It is important to determine the cause of these hot spots. Infrared imaging revealed that the transversal temperature on top of a shallow packed bed was not uniform during the hydrogenation of mixtures of ethylene and acetylene. Temperature patterns were observed only under relatively high conversion of ethylene, which is rather different from the operation of commercial acetylene purification reactors. Two qualitatively different nonuniform temperature patterns were observed: (a) antiphase oscillatory patterns and (b) nonuniform stationary hot zones. The periodic antiphase behavior, observed in approximately 60% of the experiments, consisted of a long period (35−50 min) during which the catalyst temperature was essentially at a pseudostationary state. Then, during a rather short period (3−5 min), the hot region moved from...