(257d) Scale and Effects of Catalyst Deactivation in Enzymatic Catalyzed Reactive Distillation

Increasing global competition and environmental legislation require the chemical sector to produce more cost efficient and reduce emissions. Process integration reduces the energy consumption of a process as well as its investment costs. An example for an integrated process is the combination of reaction and separation in form of the reactive distillation (RD) or reactive dividing wall column (RDWC). However, many of the industrially employed catalysts also enhance the production of unwanted side products that require additional, expensive purification steps. The employment of enzymatic catalysts is a promising approach to greatly increase the selectivity and reduce the required temperatures for chemical reactions. As enzymes are often product inhibited, the in situ product removal of a reactive distillation allows fully taking advantage of the enzyme’s potential. Studies on laboratory and pilot plant scale columns have already shown the feasibility of this approach^1,2. For the next step, the industrial application in a continuous reactive distillation, the stability of the enzymes is a fundamental condition, but yet untested under operating conditions. Therefore, knowledge about the scale of deactivation, the influencing factors and how to operate a column to minimize deactivation and maximize the production time before a standstill is required, are key questions still to be answered.

Our research aims to systematically investigate the behavior of eRDWCs. The first step has been to show the general feasibility of a successful operation with a continuous eRDWC 12 m high pilot plant.¹ Focus of this work was to develop a start-up strategy and to show that the column can be operated successfully for different operating conditions. Using the acquired experimental data a comprehensive simulation model was validated. The next step is a comprehensive approach to answer the questions about enzyme stability that hinder the industrial application. To analyze the scale and driving forces of enzyme deactivation two different experimental set-ups have been built. First, the eRDWC pilot plant and additionally a fixed-bed reactor have been employed in long term studies to test enzyme deactivation. After examining the experimental results on the quantity and driving forces of deactivation the second part of the project uses the developed mathematical model to analyze the influence on deactivation. The combined results from experimental and simulation studies allow a much deeper understanding about how to minimize enzyme deactivation in reactive distillation and additionally how to achieve the required conversion and purities for reduced enzyme activities.

This presentation will give a comprehensive overview about the scale and underlying causes of enzyme deactivation. A short introduction will explain how an eRDWC works and when to employ it. The simulation model and pilot plant will be presented. Selected experimental results about enzyme activity from the eRDWC and fixed-bed reactor experiments will be shown. From this data conclusions will be drawn about scale and influencing factors. Finally, it will be explained how to limit the enzyme deactivation by employing a smart process control and how to maintain the product specifications if deactivation occurs.

References

1.Egger T, Fieg G. Enzymatic catalyzed reactive dividing wall column: Experiments and model validation. AIChE J. 2016. doi:10.1002/aic.15598 .

2.Heils R, Jensen J, Wichert S, et al. Enzymatic Reactive Distillation: Kinetic Resolution of rac -2-Pentanol with Biocatalytic Coatings on Structured Packings. Ind. Eng. Chem. Res. 2015;54(38):9458-9467. doi:10.1021/acs.iecr.5b02802 .