Mass transfer limitations in a trickle‐bed reactor

The hydrogenation of alpha‐methylstyrene to cumene at 20 to 50°C. was studied experimentally with a trickle‐bed reactor comprising a single vertical column of spherical porous palladium‐on‐alumina catalyst pellets. Other studies with powdered catalyst and studies in which catalyst pellets were swirled in a reactor allowed the intrinsic kinetics and effectiveness factor of the catalyst pellets to be determined. At 50°C. the reaction rate in the trickle‐bed was about one‐half of that in the absence of mass transfer limitations in the outside liquid film. The effectiveness factor of the pellets alone at 50°C. was 0.0057, and the tortuosity factor was 7.5. Experimental results are compared with four theoretical models for tricklebed reactors and criteria are presented for estimating whether mass transfer through the outside film is a significant resistance in an industrial trickle‐bed reactor.