An Integrated Multiscale Modeling Framework for Multiphase Reactive Extraction

Over the past couple of decades, process intensification has emerged as an attractive toolbox toward more sustainable capital- and energy-efficient processes via the synergistic combination of process blocks (such as unit operations, tasks, and phenomena) or the application of innovative techniques that enhance mass and heat transfer rates. Since the advent of process intensification, the combination of reaction and separation into a single process unit has found widespread interest and use in both academia and industry. Multiphase catalysis based on reactive extraction is one example of such an intensified configuration where reaction and extraction are carried out simultaneously. This offers several important advantages that include increments in yield and selectivity, breaking of thermodynamic barriers, easier separation of catalyst and/or products, and reduction in energy and material consumption. These advantages have brought about a renewed interest in the application of this technology in recent years, especially in the context of the emerging Bio-to-X and Power-to-X concepts.

A rational analysis, design, and optimization of such processes requires an intimate knowledge of kinetics and thermodynamics of mass transfer and reactions. However, there is no general model for multiphase reactive extraction, particularly if catalysts are used for reactions and/or interfacial mass transfer. Although statistical or empirical models have seen a rise in recent years and helped to an extent in this regard, they possess a limited ability to extrapolate to new systems or to derive physically interpretable causation. Therefore, creating mechanistic models that can potentially be applied to any (or many) chemical systems is an open research area of great importance.

Systematic modeling approaches have been in the mainstream of process systems engineering for over two decades now. Similarly, molecular modeling has helped computational chemists gain fundamental insights on (especially, catalytic) reactions that has led to the development of many new catalysts and/or reactions over the years. However, these two computational domains have largely remained disjunct. Due to the inherent multiscale nature of multiphase catalysis, we hypothesized that an integrated modeling framework that can bridge observations and theory both within and across the scales of computational chemistry and process systems engineering can lead to the sought-after universal model for these processes.

In this work, we applied a bottom-up approach to design such an integrated multiscale framework that is universally applicable to any physically imaginable chemical system, limited only by the available computational resources. As part of the framework, quantum chemical and statistical thermodynamic methods are used to estimate the necessary phenomenological properties of a system that are then used in mathematical equations describing the macroscopic behavior of a multiphase reactive extraction system. The applicability of the framework is demonstrated in four case studies with different levels of complexity and different objectives. The results of this work showcase that the multiscale framework fills a critical gap in the development of multiphase catalysis.