A Simulation Framework for Understanding Transport and Kinetics in Transient Reactor Experiments

Transient experiments provide a unique vantage point for heterogeneous catalysis, where the kinetic properties of complex industrial materials can be precisely characterized in a highly controlled manner. Dynamic variation of catalyst surface states and the changing response of chemical reactions can bring great insight, but these methods require complex analysis. Temporal Analysis of Products (TAP) is one such method, used to measure kinetic properties by separating the intrinsic reaction on a catalytic surface from the mass transport in the reactor using precisely controlled reactant pulsing under low pressure conditions. However, calculating intrinsic kinetic quantities from the exit flux measured in TAP experiments requires careful data analysis and/or modeling. In this paper, we demonstrate a virtual TAP reactor model (VTAP) that connects the observed exit flux with the reactor concentration profile and catalyst surface state evolving as a function of time. A simple adsorption process (A(g) + * → A*) and catalytic reaction (A(g) + * → A*→ B* → B(g) + *) are modeled and discussed. As kinetic quantities and number of active sites are changed, the presentation of distinct rate/concentration ‘fingerprints’ emerge that form the basis of benchmarking catalyst behavior. These reaction simulations are used to interpret experimental pulse response data collected on both simple, Pt/SiO2, and complex, MoCx/ZSM5, catalysts. The strategies for interpreting the reactor exit flux data to extract intrinsic and transient kinetics quantities using the VTAP model are discussed. Transport and reaction simulations supported by the VTAP model framework provide clear visualization of the unique reactor physics and catalyst dynamics, laying the groundwork for designing more informative experiments that advance industrial catalysis.