| An important objective in process development is optimal reactor and operating conditions design. In order to accomplish this, one needs reliable, predictive, and efficient chemistry models. Development of such chemistry models is a difficult task for complex processes; main problems include lack of kinetic parameters, reaction pathways, thermodynamic inconsistency, insufficient validation, and pressure and materials gap. Therefore, traditional modeling approaches, including microkinetic analysis, have only partially succeeded in developing predictive models. This dissertation has two main objectives: (1) to propose a novel hierarchical multiscale approach for development of predictive microkinetic models to overcome the current limitations, and (2) to apply this approach to various hydrogen generation processes.; To achieve the first objective, we propose a novel hierarchical approach with 6 important features: (1) bottom-up mechanism building for sequential mechanism development moving from simple to more complex fuels, (2) hybrid parameter estimation using semi-empirical tools, literature experiments, and first-principles techniques, (3) thermodynamic consistency that ensures correct equilibrium predictions, rates, and energy balance, (4) important parameter identification using sensitivity analysis and refinement using first-principles techniques, (5) mechanism validation and analysis to ensure agreement with multiple experimental data, to overcome the pressure gap problem, and to understand the underlying physics of a process, and (6) computer-assisted model reduction that allows development of one-step rate expressions to efficiently implement them in reactor design.; As a second objective, we apply this approach to the development of predictive microkinetic models for H2 production. H2 production from fuel processing is a crucial component in the blooming fuel cell technology. A number of catalytic processes such as, CH4 partial oxidation, steam reforming, dry reforming, autothermal reforming, etc., could be employed for H2 generation, followed by water-gas shift and preferential CO oxidation for CO cleanup. NH3 decomposition is also an attractive alternative. These processes have their own advantages and shortcomings in terms of commercialization at different scales. In this dissertation, we have developed a total of 12 microkinetic and 2 reduced models on 3 catalysts, for these H2 production processes. |
