Mass transfer limited reactions can create problems for applications like the synthesis of chemical products or the manufacture of active pharmaceutical ingredients. Poor yields, high side-product formation or impractically long reactions are potential issues. Efficient reactor design can greatly improve the mass transfer and remove the limitation to a minimum.
Classical batch reactors have been equipped with stirrers in different shapes for centuries. The principle has been the same, and although the stirrers themselves have been specialized for different applications, they suffer from inherent limitations for heterogeneous process. Solid-supported catalysts or adsorbents tend to follow the streamlines in the liquid, which means that the exchange of substrate or adsorbate between the bulk liquid and the particles is less than optimal.
The rotating bed reactor (RBR) instead keeps the adsorbent, ion exchange resin or catalyst fixed in a rotating cylinder with filters. Centrifugal force causes the liquid to pass the solid phase at high flow rate. The large velocity of the liquid in relation to the solid in turn yields efficient mass transfer.
This video demonstrates the improved mass transfer compared to a stirred tank reactor for an application where ion exchange resin is used to neutralize a base. Also note that the product in the case of the rotating bed reactor is perfectly clean, and needs no separation after the process.
An RBR enables very fast reactions, without risk of damaging the solid phase. For more examples, see the links below.
Further reading:
Industries Pharmaceuticals and Cosmetics , Food and Beverage, Environmental, Nuclear, Flavour and Fragrances
Topics Decolorization, Reactor Engineering, Downstream Processing
Products SpinChem® RBR S3, SpinChem® Vessel V3
Details
Conditions: Neutralization of sodium hydroxide (1 M, 200 µL) by cation exchanger Amberlite IRN99 (20 mL) placed either in a SpinChem® S311 rotating bed reactor (RBR) or distributed in solution agitated by a 5 cm impeller, both operated at 800 rpm within a SpinChem® V311 flower-baffled reaction vessel containing 800 mL water with phenolphthalein (20 mg/L). The reaction with RBR finished after 23 s versus 33s for the stirred tank reactor with impeller.
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