| This thesis contains three research papers. The first paper is about the model development and validation. An isothermal three phase catalytic model, named CatReac™, is developed at Michigan Technological University for analysis and optimization of fixed-bed catalytic reactor processes. CatReac™ provides a comprehensive performance calculation of a fixed-bed catalytic reactor that includes important mass transfer mechanisms and reaction pathways. The mass transfer mechanisms include: advective flow, gas-to-liquid and liquid-to-solid mass transport, intraparticle transport by pore and surface diffusion for each contaminant and their by-product pathways. Unlike present models used to describe fixed-bed catalytic reactors, CatReac is capable of describing reaction pathway networks and both steady and unsteady state flow conditions.; The second paper is mainly concerned with the model application. CatReac™ was primarily developed to describe the performance of Volatile Reactor Assembly (VRA) which is a three-phase catalytic wet oxidation reactor used on International Space Station (ISS) to oxidize polar, low molecular-weight organic components not otherwise efficiently treated via adsorption or ion exchange. The VRA oxidizes these components into mineral and/or organic acids that are subsequently removed by ion exchange. The major objective of this paper is to validate the CatReac™ model for describing the VRA under both gravity and micro-gravity conditions. For this purpose, single feed fixed-bed experiments were used to determine the equilibrium and kinetic rate parameters; multifeed experiments were used to validate the model predictions using determined parameters. The last paper studied the temperature effect on the equilibrium and kinetic rate parameters. A method, originated from group contribution theory, was used to estimate the model parameters for other compounds based on molecular structure. Experiments were used to validate the model and model parameter estimation techniques, proposed in this work, for both steady- and unsteady-state fixed-bed operations.; Some basic information is included repeatedly in the introduction parts of these papers for future publication. |
