Statistical fluctuations of conversion and temperature in an adiabatic fixed-bed reactor for co-oxidation

✍ Scribed by H.U. Onken; E. Wicke

• Publisher: Elsevier Science
• Year: 1986
• Tongue: English
• Weight: 50 KB
• Volume: 41
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(86)87197-4

✦ Synopsis

Nonperiodic temporal varlations of exit concentrations and temperature were observed for the co-oxidation with air in an adlabatic fixedbed reactor fllled with (\mathrm{Pt} / \gamma-\mathrm{Al}{2} \mathrm{O}{3}) catalyst pellets. These irregularities occur only in the transition region between bistable and unlque stable behaviour. They are accompanied by temperature waves which originate in the entrance region of the catalyst bed and propagate with increasing amplitudes as ignition zones towards the bed exIt (typical creeping velocity: (0.5 \mathrm{~cm} / \mathrm{min}) ). Measurements with a cluster of a few catalyst pellets exposed to the co/alr gas stream Indicate that the origin of the variations at the bed entrance are thermokinetic oscillations.

It can be shown by a computer simulation of a simple cSTR model reaction with a reversible deactivation step to generate osclllations that the perlodicity is destroyed already by very small fluctuations of the feed parameters (e.g. (\pm 0.2 \mathrm{~K}) ) within the parametric sensitive region of transition from bistable to unlque stable behaviour.