Hydrodynamics of Trickle Bed Reactors with Catalyst Support Particle Size Distributions

Abstract

Characterization of the hydrodynamics enables operation of trickle bed reactors within the desired flow regime and under conditions for uniform distribution of gas and liquid, resulting in an essentially plug flow contacting pattern. Studies reported in the literature are typically restricted to systems of beds packed with catalyst supports of a uniform size. This work addresses the impact of supports with particle size distributions on reactor hydrodynamics. An experimental database of pressure drop and liquid holdup was developed and, by careful definition of the particle diameter, literature models were adapted to account for the particle size distribution. The resulting models give improved predictions for packing media with a particle size distribution while maintaining applicability to uniform systems.

Fixed Bed Continuous Hydrogenations in Trickle Flow Mode: A Pharmaceutical Industry Perspective

“…164 The pressure drop across the reactor is highly dependent on the catalyst particle size (D p ), and therefore, a trade-off is required in order to achieve the desired rate of reaction while remaining within a feasible pressure drop range for the equipment. 163 Smaller particle diameters result in a larger pressure drop due to increased frictional losses.…”

“…reactor versus keeping the D t / D p ratio of 15 constant in 3 mm reactor with a 200 μm particle; in a 2.5 in. reactor, it is a 4233 μm particle) limiting the pressure drop for pilot or manufacturing scale operation. , Companies’ scale up strategies from laboratory scale to manufacturing scale are based on defining the D t / D p ratio and either by keeping the D t / D p ratio constant or variable. Keeping the D t / D p ratio constant may require the redevelopment of the catalyst at a larger particle size for manufacturing scale reactors, which in turn may require the redevelopment of the process with the new catalyst, whereas using a variable D t / D p ratio allows laboratory scale particles to be used in manufacturing, thereby reducing development time (see Table and section ), the latter strategy favoring the speed to market pharmaceutical operating model.…”

“…A publication from Dow “Fundamental principles of laboratory fixed bed reactor design” offers advice on bed-scale phenomena and a web-based tool () for estimating the effects of these phenomena and the authors comment on a rule of thumb that the pressure drop should not exceed 20% of the inlet pressure . The pressure drop across the reactor is highly dependent on the catalyst particle size ( D p ), and therefore, a trade-off is required in order to achieve the desired rate of reaction while remaining within a feasible pressure drop range for the equipment . Smaller particle diameters result in a larger pressure drop due to increased frictional losses.…”

Another Critical Look at Three-Phase Catalysis

“…A trickle bed reactor is a variant of packed bed where the liquid solvent is showered down from the top, thus increasing the surface area of the liquid, and gas can go either co-currently or counter-currently with the liquid. Hydrodynamics of trickle bed reactors were studied 15,16 using transport modeling, 17 computational fluid dynamics (CFD) modeling, 18 electrical resistance tomography, 19 as well as by high pressures. 20 Due to the reliability of their operation, trickle bed reactors have won a great use in oil industry, and also found applications in SO 2 oxidation, 21 glucose hydrogenation over ruthenium catalyst, 22 hydro-treating atmospheric residue, 23 hydro-purification, 24 catalytic hydro-treatment of vegetable oils, 25 fuel production via Fischer-Tropsch synthesis, 26 hydrogen production by aqueous-phase reforming of xylitol, 27 hydrogenolysis, 28,29 continuous thermal oxidation of alkenes with nitrous oxide, 30 liquid-phase selective hydrogenation of methylacetylene and propadiene, 31 hydrogen peroxide, 32 as well as continuous operation.…”