Comparison of catalyst pellet shapes for CO2 methanation in a single pellet string reactor

The influence of the shape of catalyst pellets on their catalytic performance was investigated for the exothermic CO 2 methanation reaction using single pellet string reactors (SPSRs). A novel laboratory-scale manufacturing method was developed to produce catalyst pellets with defined shapes (cylinders, trilobes, and quadrilobes) from a co-precipitated Ni–Al catalyst precursor. Catalytic testing at a gas hourly space velocity, G H S V , of 20 000 h −1 and 400 °C revealed that among the tested pellet shapes, quadrilobes exhibited the highest CO 2 conversions, followed by trilobes and cylinders. A correlation was found between the CO 2 conversion and the geometric lateral surface area of the pellets, indicating that the reaction predominantly occurs near the external surface due to pronounced internal mass transfer limitations. Thermal imaging of the SPSRs revealed comparable temperature distributions for all investigated pellet shapes, with localized hotspots forming near the reactor inlet and outlet temperatures approaching the set oven temperature. Therefore, heat transfer effects contributed only marginally to the observed differences in catalytic performance. Overall, this study demonstrates that the SPSR is a powerful tool for investigating the apparent kinetic behavior of shaped catalyst pellets. • Investigation of different catalyst pellet shapes in SPSRs for exothermic reactions. • Novel method to produce extrudable catalyst pellets in small batches. • Thermal imaging for investigating heat propagation within the reactor. • Correlation of catalytic activity with lateral surface area across pellet shapes.