Application 1044

Simple scale-up using flexible reactors

Research and development quickly takes new directions, and the requirements on a laboratory may vary with every new project. Limiting yourself to equipment with a narrow scope of conditions and applications may become expensive, since new equipment must be acquired for anything out of scope. With budgets quickly consumed by other projects, the need for new equipment may mean significant delays and a reduced capability to take on emerging opportunities.

Many heterogeneous processes (e.g., adsorption or catalysis) are made faster by increasing the solid-to-liquid ratio. Studying scale-up effects can also help to predict full-scale performance. For these reasons, it is advisable to invest in equipment that can handle variations in operating conditions such as liquid volume, solids loading, pH, and temperature.

The RBR S3 Plus is the most modular rotating bed reactor for laboratory use. Made from two stacked rotating bed reactors, the S3 Plus quickly converts to a single RBR S3 for use with smaller solid loadings. When used in the dedicated glass reactor system, this yields an operating range of 250 - 1500 mL of liquid and 0 - 140 mL of solids.

This application note investigates the effect of solids loading on the reaction rate of two applications:

dye adsorption
biocatalytic esterification

These two reactions are mass-transport limited and relatively fast.

In the first case, an RBR S3 and an RBR S3 Plus were filled with 50 mL and 100 mL of the ion-exchange resin Purolite® NRW1160, respectively. Methylene blue was dissolved in water and the solution was decolorized by spinning an RBR at 600 RPM (reaction conditions in the details below). The results were clear: Each case followed 1st order kinetics with a rate constant for the RBR S3 Plus that was twice that of the RBR S3. Note that the solid-to-liquid ratio for the RBR S3 Plus was also twice that of the RBR S3.

Reaction rates for the RBR S3 and RBR S3 Plus for an decolorization process.

For the enzymatic esterification, the same rotating bed reactors (RBR S3 and RBR S3 Plus) were filled with 40 mL and 80 mL respectively of the biocatalyst Purolite® immo PS. The rotating bed reactors were used in separate reactions in mixtures of lauric acid, 1-propanol and water. Also in this case the reaction rate was proportional to the solid-to-liquid ratio, yielding twice the productivity with the RBR S3 Plus compared to the RBR S3.

Reaction rates for the RBR S3 and RBR S3 Plus for an enzymatic esterification reaction.

The conclusion is that with a rotating bed reactor you are making the most out of the solid-phase. Doubling the amount of catalyst or adsorbent will generally double the reaction rate constant, which makes scaling up straightforward.

Decolorization: dH20 (16 L) was filled in a rectangular container. The RBR S3 was filled with 50 mL of NRW1160. Methylene blue solution was added to the water with a resulting concentration of 3 mg/L. The RBR was lowered into the container and started spinning at 600 rpm while the spectrometer measurement was started. For the second reaction a RBR S3 Plus was filled with 100 mL of NRW1160 and used instead of the RBR S3. The procedure was otherwise identical. Enzymatic reaction: Lauric acid (681 g), 1-propanol (255 ml), and water (27.2 ml) was heated and mixed in a 2 L bottle at 60°C (sous vide bath). For the first reaction an RBR S3 was filled with immo PS enzyme (40 ml). The substrate mix at 60°C was poured into a V3 vessel at 60°C. The RBR was lowered into the solution and stirred at 500 rpm. Samples were collected at 0, 1, 3, 5, 10, 15, 20, 30, 45, 60, and 90 min. For the second reaction a RBR S3 Plus was filled with 80 mL immo PS enzyme and used instead of the RBR S3. The procedure was otherwise identical.

Simple scale-up using flexible reactors

Further reading