Fluidic effects on kinetic parameter estimation in lab-scale catalysis testing - A critical evaluation based on computational fluid dynamics

The influence of fluidic effects on two different kinetic parameter identifications in lab-scale catalysis testing was investigated using computational fluid dynamics. Firstly, the dry reforming of methane in a stagnation flow reactor with a detailed surface mechanism was simulated fully in three-dimensional. It is shown that the 3D simulations are not advantageous over the commonly used stagnation-flow boundary-layer problem description. This reactor setting is a valuable example of how fluidic effects on kinetic parameter estimation can be suppressed. Secondly, the oxidative coupling of methane in a fixed-bed reactor with a 10-step kinetic mechanism was simulated with a porous-media model. The experimental results could not be reproduced. The underlying plug-flow model for kinetic parameter identification fails in this highly exothermic reactor, because of significant radial temperature profiles and resulting radial concentration profiles. The correct prediction of temperature profiles is of major significance. This investigation highlights the importance of well defined reactor configurations in combination with spatially resolved temperature and concentration profiles for the determination of reliable kinetic parameters for highly exothermic or endothermic reactions.