(20a) Rigorous Modeling and Multicriteria Optimization of a Multiphasic Enzymatic Hydrolysis Process

Zitzewitz, P., Hamburg University of Technology
Fieg, G., Hamburg University of Technology

The development of efficient production processes for complex reaction systems poses one of the major challenges in chemical industry. Enzymatically catalyzed reactions offer a great opportunity to replace conventional processes by more efficient and environmentally friendly green ones. On the other hand, they are often accompanied by a very complex phase and reaction behavior. A widely-spread and particularly industrially relevant example of application is the hydrolysis via carrier-fixed enzymes. The development of modeling approaches as well as methods and tools for the model-based optimization of such processes are distinguished both by their practical relevance and their great potential for saving resources and costs.

Hence, the hydrolysis of a short-chain fatty acid methyl ester via immobilized lipase (Novozym® 435) is closely studied as a reference system within a research project in close consultation with industrial companies, e.g. BASF Personal Care and Nutrition GmbH and Evonik Industries AG. The high complexity of this three-phasic reaction system is especially characterized by the mutual interaction of multiple mechanisms such as enzymatic kinetics, liquid-liquid equilibrium, reaction equilibrium and mass transfer phenomena.

For the first time in this field of research a holistic approach was chosen which covers the investigation in an innovative experimental plant, the development and validation of a rigorous model of the reaction process and finally the application of this model for a process design with superimposed multicriteria optimization. This optimization ultimately provides a powerful tool to drastically reduce both resource and energy consumption and thus operation costs for industrial processes containing three-phasic reaction systems.

Through many years of research the reaction system was thoroughly investigated experimentally in preceding research projects. In particular, a sophisticated concept to experimentally decompose the reaction progress was developed and implemented in the form of an experimental plant with a continuous liquid-liquid phase separation. Combining these experimental methods and results with theoretical methods, a rigorous model of the reaction process was developed and validated.

In the first part of the presentation the concept for the model-based optimization will be described in detail. Here, the chosen exemplary hydrolysis process for this purpose is depicted and discussed. This process consists of two major parts: A reactor and a distillation part. In the reactor, a multistage extractive reaction process is conducted in a countercurrent arrangement and two separate product streams are obtained. These are further purified via conventional distillation to gain high purity products for sale as well as educts for recycle. Different modeling approaches for the reaction process are presented and finally the concepts and methods to combine the process simulation with the practice-oriented cost-driven multicriteria optimization using evolutionary algorithms are shown. In the second part of the presentation optimization results will be presented and discussed in detail.