SPATIOTEMPORAL PATTERNS IN CATALYTIC REACTORS

The study of spatial structures in heterogeneous reactors is a challen ging academic topic, revealing patterns that differ from those known t o exist in reaction-diffusion systems exposed to uniform conditions as well as a practical problem that should affect design and operation p rocedures of commercial reactors like the catalytic convertor. Experim ental observations and mathematical models of spatiotemporal patterns in high-pressure catalytic reactors are reviewed. Patterns in high-pre ssure reactors, in which thermal effects provide the positive feedback , as well as the long-range communication, usually emerge due to globa l interaction. Patterns are classified comprehensively by considering reactors of increasing degree of complexity. a wire or ribbon exposed to uniform conditions, a globally coupled catalyst in a mixed reactor or in a control loop, and a fixed bed in which interaction by convecti on occurs only in one direction. Catalytic wires are not expected to e xhibit sustained patterns in the absence of global interaction. Global interactions by external control or gas-phase coupling are shown expe rimentally and analytically to induce a rich plethora of patterns. Com plex motions were simulated to occur due to the interaction of convect ion, conduction and reaction in a fixed-bed; only a few of these patte rns were experimentally observed Directions for future research are su ggested.