Core–Shell Catalyst Pellets for Reaction Heat Release Control in Fixed-Bed Reactors

Core-shell catalyst pellets are an opportunity for fixed-bed reactor operation, where heat management is a challenge. Core-shell catalyst pellets consist of a catalytically active core surrounded by an inert, porous shell. The shell enables controllable heat release rates at high temperatures by limiting mass transport to the active material in the pellet core and, thus, effectively prevents thermal runaways. In addition, the inert shell influences the selectivity of the reaction system. This paper investigates the applicability of core-shell catalyst pellets in a general chemical system involving one or two equilibrium reactions, by deriving catalyst effectiveness factors, the selectivity, and a mean apparent activation energy for predicting parametrically sensitive conditions with the "practical design criterion". Experimental results are presented, which confirm the mathematical predictions and demonstrate the effectiveness of core-shell pellets for CO2 methanation. The results highlight the role of the catalyst pellet design in ensuring safe and efficient reactor operation. The results are readily applicable to other chemical processes and provide valuable insights into the opportunities of catalyst pellet design for efficient reactor operation.