Fluid-mediated interactions among particles in a catalytic reactor

Pedro Edgardo Arce, Purdue University

Abstract

The role of catalyst particles in the analysis and design of chemical reactors has been largely attributed only to provide the surface area for the reaction. However, previous experimental and theoretical studies have shown that local reaction kinetics and spatial transport processes can interact to yield a variety of intriguing spatially non-uniform steady states--in short, collaborative or cooperative phenomena between reaction centers communicated for a given kind of transport process. Virtually all the work done in this area has been motivated by the Rashevsky-Turing ideas of symmetry-breaking in uniform states because of diffusion interactions between the neighbors. A broader class of collaborative phenomena can be displayed by assemblies of catalyst particles showing only interactions mediated by the fluid medium. The present work focusses on the analysis of fluid-mediated interactions in assemblies of catalyst particles exposed to a well-mixed environment--in essence a CSTR. This situation is of relevance for the investigation of such interactions in, for example, packed-bed reactors where it is possible to envisage a collection of particles locally exposed to a well-mixed environment. This dissertation has shown that catalyst particles in assemblies can behave very differently with respect to particles in "isolation". Many collaborative phenomena have been introduced and the nature of its origin as well as the implications to the catalytic reactor have been analyzed in great detail. Examples of these findings are the following: uniform steady states can show collaborative multiplicity and collaborative reversal of instability before breaking the symmetry. This mechanism allows the particle to preserve partially, the stability inside the reactor. Pattern formation is displayed when the assembly of catalyst particles breaks the symmetry of the uniform steady state. Collaborative multiplicity and collaborative reversal of stability can be observed in patterns; however it is impossible for the assembly to show collaborative reversal of instability. The mathematical analysis is based on a theory that exploits the complete understanding of the isolated particle in an operator-theoretic framework. The investigation is carried on further by the use of singularity theory and group-theoretic methods. Finally, the implications (to catalytic reactors) of collaborative phenomena with respect to selectivity, productivity and parametric sensitivity are discussed. Several possible extensions to the investigation performed in this thesis are outlined at the end of this dissertation.

Degree

Ph.D.

Advisors

Ramkrishna, Purdue University.

Subject Area

Chemical engineering

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