Enhanced Microstructured Reactor Performance under Forced Temperature Oscillations

Abstract

The forced variation of reaction parameters is a known method to improve the performance of catalytic reactors leading to process intensification. The most often experimentally varied parameters so far were the reactant concentrations or pressure. Due to the high thermal inertia of conventional reactors it was almost impossible to achieve fast periodic reproducible temperature changes. However, it has been proven theoretically that fast periodic temperature variations may increase the reaction rate compared to the stationary temperature conditions.The possibility to thermally cycle microstructured stainless steel reactors in a periodic way with temperature differences of up to 60 K and a frequency as high as 0.06 Hz has been demonstrated. This gives the opportunity to study the influence of fast temperature changes on heterogeneously catalyzed gas phase reactions. The catalytic CO oxidation over Pt supported on Al2O3 was chosen as a test reaction. The concentrations of CO, O2 and CO2 were monitored online at the reactor outlet using FTIR and mass spectrometry. The experimental measurements under non-stationary temperature conditions have shown an increase in the measured CO2 concentration compared with the one under temperature stationary conditions. For a temperature oscillation frequency of 0.048 Hz with an amplitude of 38 K, the mean CO2 concentration is 1.72 times higher than the mean value obtained under quasi-stationary conditions. A possible explanation for this phenomenon is an increase of the reaction rate due to the presence of a transitional reactive species surface coverage resulting from the temperature oscillations.