Amplification of inlet temperature disturbances in a packed-bed reactor for CO oxidation over Pt/Al2O3

The commonly used packed-bed catalytic reactor can exhibit complex dynamic features such as wrong-way behavior, differential-flow instability, different kinds of traveling waves and bifurcation behavior. Understanding these phenomena is essential for developing reliable reactor control systems. Of primary interest to the present study is the differential flow instability, which may cause amplification of small amplitude inlet perturbations of concentration, temperature, and flow rate into large temperature excursions. CO oxidation served as a model reaction to demonstrate resonance amplification of inlet temperature perturbations in a tubular reactor packed with 0.02 wt% Pt/Al2O3 catalyst. Very low-frequency inlet perturbations did not cause large temperature increases in the reactor because the separation of thermal and concentration waves becomes insignificant when the system changes slowly between steady states. High-frequency perturbations, on the other hand, were attenuated as the waves propagated through the reactor bed. However, amplification at intermediate frequencies could be considerable. Amplification could be suppressed by increasing the axial thermal conductivity of the bed or by using highly concentrated catalyst.