Self-sustained oscillations of temperature and conversion in a packed bed microreactor during 2-methylpropene (isobutene) hydrogenation

• A kinetic study of 2-methylpropene hydrogenation was examined in a flow microreactor.
• Dimensionless criteria analysis has shown the presence of heat and mass transfer limitations.
• Self-sustained and reproducible oscillations of 2-methylpropene conversion appeared.
• The decrease of space velocity by half extended the oscillation period from 11 to 22 h.
• The mechanism responsible for oscillations is proposed.

Hydrogenation of 2-methylpropene over commercial platinum catalyst has been studied in a packed bed microreactor. Using common dimensionless criteria and experimental diagnostic the presence of heat and mass transfer limitations has been detected. Analysis of experimental results has pointed to the presence of heat and mass transfer control. Consequently, only a limited set of data under the kinetic control regime could be collected. Self-sustained spontaneous and reproducible oscillations of 2-methylpropene conversion have been observed experimentally under certain conditions. The temperature of the catalyst bed well reflected the oscillatory course of 2-methylpropene conversion. The observed oscillations exhibited exceptionally long periods ranging from 11 to 22 h depending on the prevailing space velocity. The appearance of oscillations of the conversion has been ascribed to the complex interaction between the exothermic reaction, heat transfer and a reversible decrease in the catalyst activity. Possible mechanisms of temporary catalyst activity decrease have been proposed.

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