Shadowing Effect in Catalyst Activity: Experimental Observation

The influence of the spatial distribution of catalyst particles in a fixed bed reactor on the observed reaction rates has historically been of central interest in catalysis and chemical physics. Results from both fields suggest that the apparent catalyst activity is determined by the distance between active particles and transport phenomena, although a universal understanding of their combined influence remains incomplete. In this study, pulse experiments under contrasting transport regimes show that a given amount of catalyst particles exhibits higher activity with increasing degrees of separation. This is attributed to a shadowing effect induced by the competition between closely neighboring active particles, which limits their combined apparent activity. Experimental results also suggest the dependence of this effect on mass transport phenomena within the reactor space.