The integrated process setup of reaction and separation
in reactive
distillation can be favorable for enzyme-catalyzed reactions that
are often equilibrium-limited and/or inhibited by the product of the
reaction. However, until now, no appropriate way has described the
implementation of the enzymes into distillation columns. In this work,
a special type of biocatalytic coating for commercially available
structured packings was developed to enable enzymatic reactions in
reactive distillation columns. Lipase CALB was immobilized within
the silica-gel based coating and showed high long-term stability,
i.e., the coatings can be stored for at least 50 days at room temperature
without any significant loss of enzyme activity. In addition, the
silica-gel coatings were stable in organic media and at increased
temperatures. Reactive distillation experiments were carried out in
a batch reactive distillation setup comprising of structured A3-500
packings from Montz (Hilden, Germany) coated with the catalytic silica
gel. Stepwise removal of the low boiling point product from the distillate
shifted the equilibrium to the product side and increased the conversion
of the reactants from 60% to 98%, in comparison with the corresponding
setup in a standard batch reactor. The stability of the silica-gel
coating and loss of the enzyme was investigated during the distillation
runs. Overall, the integration of an enzymatic reaction into a reactive
distillation column offers new possibilities for the application of
biocatalysts in organic synthesis.