The performance of structured packings in trickle-bed reactors

An experimental study was carried out to investigate whether the use of structured packings might improve the mass transfer characteristics and the catalyst effectiveness of a trickle-bed reactor. Therefore, the performances of a structured packing, consisting of KATAPAK elements, and a dumped packing, consisting of small diameter spherical particles, have been compared for both a chemisorption process and a process where a heterogeneously catalysed chemical reaction is carried out. The chemisorption of CO2 in aqueous amine solutions and the hydrogenation of a-methylstyrene catalysed by palladium on ¿-alumina were chosen as model reactions, respectively. The performance of the trickle-bed reactor was quantified by measuring the specific gas-liquid contact area and the volumetric liquid-side mass transfer coefficient in the case of the chemisorption process and the conversion rate in the case of the heterogeneously catalysed chemical reaction. These parameters were measured for both packing types as a function of a number of process parameters. In this paper, the experimental results are presented and a comparison is made of the performances of the two packing types for both types of processes. Both packing types showed similar mass transfer characteristics as well as volumetric conversion rates. However, the structured packing showed a much higher contact efficiency as well as a much higher catalyst effectiveness. A significant improvement is therefore expected when a structured packing is used with a higher specific geometrical area than that applied in this study. Furthermore, the structured packing is favoured in the case of fast exothermic liquid-phase reactions