Spatiotemporal patterns in a model of heterogeneous reaction in a porous catalyst particle

The mathematical model of the heterogeneous reaction of CO oxidation on the Pd catalyst embedded in zeolite matrix is numerically studied. The reaction system comprises two phases: the gas phase in the pore space and the adsorbate layer on the catalyst surface. The model involves surface reaction and diffusion of adsorbates, diffusion in the gas phase, and interphase mass exchange. In a spherical zeolite particle on a stationary reaction regime the self-imposed radial gradient of reagent concentration arises in both phases. When the reaction proceeds in an oscillatory regime, the reaction rate waves moving in radial direction are observed in the model. The velocity of wave propagation depends on the radial coordinate, so the waves arrange a specific type of wave pattern. The patterns become more complicated with the external CO pressure increasing and turn in chaotic picture near the upper boundary of oscillatory domain. The radial distribution of the local average frequency of oscillations calculated with the help of the analytical signal is applied for description of the wave patterns.