The performance of structured packings in trickle-bed reactors

An experimental study was carried out to investigate whether the use of str uctured packings might improve the mass transfer characteristics and the ca talyst effectiveness of a trickle-bed reactor. Therefore, the performances of a structured packing, consisting of KATAPAK elements, and a dumped packi ng, consisting of small diameter spherical particles, have been compared fo r both a chemisorption process and a process where a heterogeneously cataly sed chemical reaction is carried out. The chemisorption of CO2 in aqueous a mine solutions and the hydrogenation of alpha-methylstyrene catalysed by pa lladium on gamma-alumina were chosen as model reactions, respectively. The performance of the trickle-bed reactor was quantified by measuring the spec ific gas-liquid contact area and the volumetric liquid-side mass transfer c oefficient in the case of the chemisorption process and the conversion rate in the case of the heterogeneously catalysed chemical reaction. These para meters were measured for both packing types as a function of a number of pr ocess 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 charac teristics as well as volumetric conversion rates. However, the structured p acking showed a much higher contact efficiency as well as a much higher cat alyst effectiveness. A significant improvement is therefore expected when a structured packing is used with a higher specific geometrical area than th at applied in this study. Furthermore, the structured packing is favoured i n the case of fast exothermic liquid-phase reactions.