Absorption accompanied with chemical reaction in trickle-bed reactors

Abstract

Pergamon ('hcm~,ai f~mt.wcrl.a .gclenc(.. Vo] Abstraet---A new development in the field of internals in packed columns is the use of structured packing types. Recently, a new structured packing type coated with a thin alumina layer (KATAPAK rM) has been developed, in this report, the results of an experimental and theoretical study concerning the possible applicability of this new packing material for hydrogenation processes in a trickle-bed reactor is presented. The palladium catalyzed hydrogenation of ~-methylstyrene is used as a model reaction to study hydrodynamics and mass transfer characteristics in a trickle-bed reactor under reactive conditions. Conversions at several process conditions are measured in a pilot plant in which 3 mm spheres as well KATAPAK rM is applied as packing materials. A comparison of the results of some physical absorption experiments with the results of hydrogenation experiments showed that the resistances in series model--in which the total resistance against mass transfer is calculated from the separate resistances--is not valid in systems where heterogeneous reactions at the solid surface can enhance the mass transfer-rate at the gas-liquid interphase. With the aid of a developed trickle-bed reactor model, based on liquid diffusion, simultaneous reaction at the solid surface and zero volume mixing points, the mass transfer phenomena in trickle-bed reactors in conditions where the resistances in series model fails can be explained and described. The numerically solved model calculates the hydrogen profiles in the liquid films of the reactor and over all single pass conversions at several process conditions. These conclusions are confirmed by the results of the simulation of a model reactor, i.e. the laminar film reactor with a catalytically active wall. From the results of the measurements it could be concluded that in trickle-flow conditions, the application of KATAPAK TM does not significantly improve on the overall performance of trickle-bed reactors. The increase of the physical absorption rate due to better mass transfer characteristics of structured packings compared to dumped packing types--as reported in literature--will be eliminated to a certain extent in reactive systems due to the enhancement effect of heterogeneous reactions in trickle-tlow operation. (' 1997 Elsevier Science Lid

Recent Developments on Hydroprocessing Reactors

“…Another work of structured packing in cocurrent downward mode was reported by Nijhuis et al (2001) with monolithic catalyst. In contrast to the results of Versteeg et al (1997), they have reported better performance in terms of productivity of the monolithic catalyst for the hydrogenation of α-methylstyrene and better selectivity for the hydrogenation of benzaldehyde to benzylalchol. Though this type of reactor may be advantageous for some specific reactions, it cannot be useful, in general, considering the point of catalyst utilization per reactor volume and mass transfer driving force.…”

Systems with Structured Packing: Fluid-Dynamics and Liquid-Solid Mass Transfer

“…Studies on gas-and liquid-side mass transfer and separation efficiency [10,11,14,16,20,21,24,25] were carried out to provide design correlations and performance characteristics. Some recent papers deal with gas-liquid mass transfer in trickle-flow conditions [14,25]. Together with other research work [20±22] they give information on the behavior of a new catalytically active structured packing developed by Sulzer, the inventor of the first corrugated sheet packing.…”