A Generalizable Electrochemical Platform for Batch-to-Continuous Transitions
Authors: Hacku Robert , Cormack Glenn , Petek Tyler , McKone James 
Published: December 2024

Greenhouse gas emissions from the chemical industry are massive, amounting by some estimates to ~5% of the global total.1 Chemical manufacturing is also very difficult to decarbonize due to the dual use of hydrocarbons as a fuel and feedstock.2 Hence, to eliminate anthropogenic greenhouse gas emissions the chemical industry must undergo a fundamental change in how it uses energy and materials. Organic electrosynthesis has seen a significant increase in research interest as an alternative to the traditional thermochemical approach for chemical production. Electrochemical transformations offer a direct path to electrification via driving reactions with electricity rather than heat. This means that as grid electricity decarbonizes, so too do electrochemical processes. Moreover, environmentally hazardous chemical oxidants, such as fuming acid mixtures, and reductants like methane-derived hydrogen, can be replaced by oxygen and hydrogen intermediates generated on the surface of electrodes through water electrolysis.

Despite the potential advantages for broad implementation of industrial electrosynthesis, research interest falls primarily on the production of commodity chemicals, such as CO2 valorization and nitrogen fixation. Successful implementation of these schemes could certainly drive a significant amount of global decarbonization, but this focus has also led to underdevelopment of other electrochemical reactions that could be implemented today with significant emissions reductions. The focus of this presentation is on these types of under-explored organic electrosynthetic transformations that are specifically relevant to specialty chemical manufacturing.

The electrochemical literature has many examples of batchwise electrosynthesis of specialty chemicals.3 Scaling these processes to industrially relevant levels very often benefits from the development of continuous reactor systems. Although continuous electrosynthetic reactors have made extensive progress, there does not yet exist a well- developed and standardized set of methods, reactor architectures, and design principles for these types of cells. This lack of standardization stands as a significant impediment to adoption, especially in commercial settings. To address this knowledge gap, our lab is researching and designing a generalizable, modular electrochemical reactor to aid the transition from batch to continuous processing.

This presentation will detail our recent work to determine the key differentiating characteristics of electrochemical reactions to design a modular and easily reconfigurable platform. Eight electrochemical reactions of various electrolyte composition and phase relationships were chosen as a basis to develop the reactor platform. The relevant design criteria for reactor design encompassed considerations of: (a) the composition of the electrolyte, including pH, reactant/product phase, material compatibility; (b) the electrode structure and functionalization, to be tuned to the intended reaction; and (c) the requirement of a divider, such as a porous separator or ion exchange membrane. By studying these and literature examples of successful batch-to-continuous transitions, we determined that reactors aimed at maximizing electrode-electrolyte contact converge toward a filter-press style. Next, we used these characteristics to design and fabricate a single reconfigurable filter press cell designed to accomplish each of the eight reactions of interest. Through its design and materials of construction, this cell is capable of handling a wide range of pH, any geometry of compressible or plate electrodes, and can be operated with or without a separator. Finally, we validated this platform by demonstrating the ability to generate reaction products with performance criteria that match or exceed those from an analogous batch reactor configuration. This validation also leads to several improvements to be made on this basic design, which will be incorporated into future iterations.

References

(1) Gabrielli, P.; Rosa, L.; Gazzani, M.; Meys, R.; Bardow, A.; Mazzotti, M.; Sansavini, G. Net-Zero Emissions Chemical Industry in a World of Limited Resources. One Earth
2023, 6 (6), 682–704. https://doi.org/10.1016/j.oneear.2023.05.006.

(2) Gross, S. The Challenge of Decarbonizing Heavy Industry, 2021. https://www.brookings.edu/wp-content/uploads/2021/06/FP_20210623_industrial_gross_v2.pdf.

(3) Li, Y.; Dana, S.; Ackermann, L. Recent Advances in Organic Electrochemical Functionalizations for Specialty Chemicals. Curr. Opin. Electrochem.
2023, 40, 101312. https://doi.org/10.1016/j.coelec.2023.101312.