Predictive Modeling and Rational Catalyst Design

The role of kinetic and reactor modeling is crucial in the continued advancement of these catalysts as they are optimized for specific applications. We have described different mechanisms for SCR for feed compositions spanning the standard to fast to NO2 types. Convergence to the correct mechanisms is essential if predictive mechanistic-based kinetic models are to be developed. To date the kinetic models have been of the global variety. While these are usefiil for reactor optimization, microkinetic models are needed to guide rational catalyst design and the discovery of new catalyst formulations. 

As the above examples illustrate, the kinetics of surface-catalytic events depend on complex structural and electronic considerations that, thus far, have not been understood at the level of detail that would permit predictive mathematical modeling and therefore rational design. For this reason, the molecular-level engineering of catalytic surfaces harbors perhaps the greatest future potential for chemical reaction engineering, at least from the standpoint of the design of catalysts. 

This chapter is devoted entirely to performance models of conventional catalyst layers (type I electrodes), which rely on reactant supply by gas diffusion. It introduces the general modeling framework and employs it to discuss the basic principles of catalyst layer operation. Structure-based models of CCL rationalize distinct regimes of performance, which are discernible in polarization curves. If provided with basic input data on structure and properties, catalyst layer models reproduce PEFC polarization curves. Consistency between model predictions and experimental data will be evaluated. Beyond polarization curves, performance models provide detailed maps or shapes of reaction rate distributions. In this way, the model-based analysis allows vital conclusions about an optimal design of catalyst layers with maximal catalyst utilization and minimal transport losses to be drawn. 

---