(401a) Reaction Networks in Multi-Scale Modelling Frameworks for Sustainable Process and Product Design

While a large amount of sustainability research is focused towards green chemistry, efficiency and process optimization, it does not adequately capture interactions between multiple scales such as chemical reaction modeling, life-cycle processes and economic activities. These interactions are critical in identifying novel reaction pathways and product substitutes which can lead to environmental sustainability and economic prosperity. An integrated model capable of obtaining optimal reaction pathways in terms of more holistic objectives and large system boundaries can therefore drive the reductionist research in a more promising direction. Our work extends the process-to-planet multiple scale modelling framework to accommodate molecular pathways, process flowsheets, supply chain activities and economic scale activities, integrated via inter-scale cut-off flows and disaggregation. The resulting framework contains an optimization formulation with decision variables may comprise of any/all amongst process variables, reaction pathway/product formulation and value chain pathways. Various economic, environmental and social objectives are considered to build pareto surfaces.

The system expansion approach of including Environmentally Extended Input Output (EEIO) and Life Cycle Assessment (LCA) methods into Sustainable Process Design (SPD) is directly inspired from previous work in our group, the Process to Planet (P2P) framework [1]. The novelty in this work, however, is vested in linking reaction pathways and associated decision variables in the optimization scheme. We use models such as Reaction Network Flux Analysis (RNFA) [2] and Process Network Flux analysis [3], to model these reaction networks into reactor-separator modules whose conversions are constrained by either yield restrictions or kinetic/thermodynamic models if available. These modules are used as basis for development of the process scale mass and energy flows, which are then linked to the value chain and economic activities using the P2P framework [1]. This results in a framework capable of finding an optimal pathway for production of a commodity from a holistic viewpoint while considering environmental impacts and natural resource use.

In this work, we present the formulation of the framework that combines the aforementioned multiple scales to facilitate sustainable process and product design. We will also highlight the benefits of such an approach to capture holistic effects on reaction pathway selection, alongside various other advantages such as being able to use group contribution theory to fill in data voids in value chain activities and eliminating non-promising novel pathways based on holistic considerations. We will demonstrate the framework for the reaction network of converting Itaconic acid (obtained from corn) to 3 MTHF [2]. Voll and Marquardt [2] have studied the same and found optimal reaction steps for highest product yield, CO₂ emissions and other objectives. We will compare the optimal reaction pathways obtained by the framework while considering the larger system boundary with the results in [2]. Further, we will attempt to find the optimal pathways and product in a polymer production industry for the circularity and sustainability of plastic use in the economy.

References

1. Hanes, Rebecca J., and Bhavik R. Bakshi. "Sustainable process design by the process to planet framework." AIChE Journal 61, no. 10 (2015): 3320-3331.
2. Voll, Anna, and Wolfgang Marquardt. "Reaction network flux analysis: optimization‐based evaluation of reaction pathways for biorenewables processing." AIChE Journal 58, no. 6 (2012): 1788-1801.
3. Ulonska, Kirsten, Mirko Skiborowski, Alexander Mitsos, and Jörn Viell. "Early‐stage evaluation of biorefinery processing pathways using process network flux analysis." AIChE Journal62, no. 9 (2016): 3096-3108.