Structure and Impact of Spatiotemporal Catalytic Systems

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Abstract - Luss - 9529393 Many industrial chemical reactions are carried out using heterogeneous catalysts. The phenomena of bistability, oscillatory motion and excitability, which induce a plethora of spatiotemporal motions in homogeneous liquid-phase reactions, exist also in heterogeneous catalytic reactions. Recent experimental results indicate that periodic temperature patterns, such as rotating pulses, may be found on catalytic pellets during exothermic reactions. The goal of this project is to explore and exploit such oscillatory thermal phenomena to enhance the yield and selectivity of desired products. The PI plans to conduct a combined experimental-theoretical study with the goal of finding and classifying all the possible temperature patterns that may exist on either full or hollow cylindrical catalytic pellets kept in a continuously stirred tank reactor (CSTR) and in a radial-flow packed-bed reactor. In the single-pellet experiments, the temperature patterns on the surface and sides of the catalysts will be measured by an infrared thermal imager. The test reactions will be the oxidation of hydrogen on a nickel-on-alumina catalyst and the oxidation of carbon monoxide on a platinum-on-alumina catalyst. The study will determine the conditions leading to the evolution of different patterns; the influence of intra- and interparticle transport limitations; the impact of the patterns on the performance of the catalyst; and the influence of inherent nonuniform catalytic activity on the patterns. The main dynamic features of each motion, such as characteristic length, period, velocity, and shape, will be determined. These periodic temperature motions are likely to stimulate attempts to benefit from them, especially when they induce corresponding periodic changes in the catalyst activity.