The push toward decarbonization is driving an increased interest in electrochemical processes. Here, the authors share their experience in industrializing these processes
The field of electrochemistry offers a disruptive methodology to revolutionize the chemical process industries (CPI) by electrifying processes. However, scaling up and implementing a new electrochemical synthesis poses challenges that can best be overcome through a combination of academic research and industrial expertise. This article discusses the potential of electrochemistry as a tool to revolutionize and decarbonize the CPI, while also examining the obstacles and unique considerations involved when implementing it in an industrial setting. Examples are given to demonstrate the versatility and exceptional performance of electrosynthesis. Having collaborated for many years between academia and industry, the authors share experiences gained from industrializing such timely methods, and aim to eliminate any concerns readers may have about scaling new electrochemical processes.
Within the CPI, lowering the carbon footprint and increasing efficiency, in line with so-called “green” processes, is becoming progressively important. Topics such as the circular economy, recycling and upcycling of raw materials and the energy transition are in focus. Processes must be redesigned in a resource-friendly and sustainable manner to circumvent the ongoing climate crisis. Disruptive technologies will play a major role in these activities to develop and establish more efficient processes.
Synthetic conversions
The use of electricity instead of chemical reagents has applications in organic syntheses, purification processes and downstream technology. By application of electricity, electrons can participate directly as reagents. An example of how a classical organic oxidative coupling could be made not only greener but also more economically efficient, by saving several synthetic steps, is the synthesis of non-symmetrical derivatives of 2,2′-biphenol shown in Figure 1.
FIGURE 1. The reaction pathway for the synthesis of biphenol is an example of an industrially relevant electro-organic synthesis. The HCH upcycling reaction pathway is an example for an electro-organic driven circular economy [3, 4, 10, 11]
Thus, a ligand backbone for a catalyst applied in a major chemical process in the production of oil additives, the hydroformylation reaction, was developed by the author’s laboratory [1–4]. The electrochemical reaction pathway saves five synthesis steps compared to the classical route and doesn’t require leaving groups in order to form the C(sp2)–C(sp2) bond.
A noteworthy illustration of electrochemical synthesis applied to inorganic components is the anodic periodate synthesis. This is a common platform oxidizer in the chemical industry, which has already been scaled-up to generate several kilograms of product. Outstandingly, this method uses only electricity to synthesize periodate, without the need for external oxidizing agents. Moreover, iodo waste can be fed in, and the complete mineralization of organics results in periodination [5]. This approach exemplifies the resource- and chemical-efficient nature of electrochemical syntheses [5–7].
A method for the oxidative ring opening of cyclic hydrocarbons was also developed to eliminate the need for an oxidizer. By utilizing nickel oxide hydroxide anodes, a process was established for synthesizing substituted adipic acid derivatives from lignin-derived feedstock and was successfully scaled up to over 10 liters [8–9]. These examples epitomize the potential of electrosynthesis to enable conversions that are not only mild, resource-efficient, and sustainable, but also capable of being scaled up to meet industrial requirements.
Downstream processing
On top of classical synthesis, electrochemistry is also used for downstream processing. Applied electrochemical downstream methods are electrodialysis, wastewater treatment and electrostatic purification. An interesting example in electrochemical waste utilization is the upcycling of chlorinated persistent pesticides. This waste is not readily decomposed by nature and has been put into landfills on a multi-million-ton scale. In order to tackle this problem, researchers developed an electrosynthesis (e-shuttle) for upcycling this waste, which generated benzene and chlorine equivalents — both base chemicals that are highly relevant for the industry [10]. This example highlights the versatility of electrochemical processes in the search of a sustainable future.
Challenges
The innovation of electrosynthesis can lead to many approaches for optimizing chemical processes, but also poses challenges. Modern approaches do not focus on electrochemical stand-alone systems, but integrate electrochemical sub-steps as a part of a longer process chain. This enables the gradual implementation of electrochemical innovations in the industrial environment.
One of the biggest challenges when using electrochemistry in the chemical industry is the technical implementation. Unlike chlor-alkali electrolysis, which has been used on a technical scale for decades, most electrochemical syntheses and processes are completely new and have to be designed from scratch. There are almost no commercially available pilot systems for the examples mentioned above, and to the current authors’ knowledge, there are no plants on an industrial scale that are commercially available. The lack of availability of these plants requires technical implementation within every company and their workshops, or highly individualized plants from the few available manufacturers (for electrodialysis, for example, Eurodia, MEGA, Fumatec).
It is even more difficult to find suppliers for large-scale plants in the field of organic electrosynthesis. Both options require knowledge of the hurdles and peculiarities of an electrochemical pilot plant and the ability to fix them internally. To dispel fears of implementing electrochemical processes, this article aims to avoid prejudices and typical mistakes from the outset [12–13].
Specific considerations
So let’s dive into the possibilities of electrochemical processes and share with you our experience in scaling up these processes. The next sections discuss the most important aspects that differ the most from classical chemical processes. These include: safety, material stability, impurities, suppliers and economics.
Safety. The safety of every reaction is of utmost importance in the chemical industry. The same applies to electro-organic reactions, where some peculiarities come into play. In scaling up an electrochemical reaction, several aspects must be considered, which can often be neglected in the laboratory on a screening scale, since working under standard laboratory conditions is sufficient for the safety concept (Figure 2).
FIGURE 2. Consider safety aspects in the scaling process of an electro-organic synthesis process
The first aspect that distinguishes the electrochemical reaction from standard organic reactions is the most obvious one, namely the use of electricity. On the one hand, this aspect offers the advantage that ending unpredictable reactions is easily ensured by switching off the electricity. However, the use of electricity brings some challenges, especially on the pilot scale. The choice of materials can prevent some problems. For example, the use of stainless-steel pipes should be avoided due to so-called stray current. In addition, it should be ensured that safety signs with warnings of electrical risks, such as “caution electricity,” are visibly displayed.
Another peculiarity in electrochemistry is the emission of gases. Typical gases formed in an aqueous solution are hydrogen at the cathode and oxygen at the anode. Since these gases can create an explosive atmosphere, especially in a mixture and when enriched, normal safety concepts, such as working in a fume hood and keeping all ignition sources away, are not sufficient at a larger scale. When working at the pilot scale, these gases must be diluted to lower than an explosive level. This can be achieved through complete inertization of the system or flushing concepts. To complete the safety concept and enable operation of the system without continuous monitoring of the flow, so-called flow-indication switch (FIS) shutdowns are used. These ensure that the power is shut off when the air flow decreases. If such a system is not sufficient, so-called explosive zones must be defined in plants. In addition to hydrogen and oxygen, toxic gases such as chlorine can also be emitted. Diluting the gas is not sufficient in this case, and neutralizing the gas is necessary.
Especially in organic electrochemistry, attention is also paid to the use of organic solvents and the use of alkylammonium salts as a supporting electrolyte, which are used in non-polar solvents. Therefore, the chemicals used should be safe in terms of their use in larger quantities (keywords are toxicity and flammability). The use of alkylammonium salts must also be considered from a process engineering and economic perspective. These chemicals are not only expensive, but are also often toxic. Therefore, a recycling process must be implemented when using them.
Material stability and impurities. To ensure safety and prevent contamination in wastewater or products, attention must also be paid to the long-term stability of materials, such as electrodes. Electrode materials should also be carefully chosen to avoid toxic metals and contamination. A certain amount of instability must be expected, therefore toxic metals, such as mercury, lead or cadmium, are to be avoided. To design an economical process, long-term stability tests for materials like electrodes, sealings and membranes are crucial prior to scaling up. Membranes should be tested for at least 1,000 hours, with a focus on their stability towards organic media. The availability of robust membranes in the market is limited, so it is important to consider material stability and availability early on, especially in organic electrochemistry.
Laboratory-scale experiments often use high-grade chemicals, but in pilot- or industrial-scale plants, lower-purity grades are used. This can lead to issues not observed in the laboratory, such as particle blockages or damage of coated electrodes. Contamination can also result in gas emissions that need to be quenched to provide safety.
Process systems and economics. In addition to differences in the chemicals used and the stability of the materials employed, the general availability of pilot systems must also be considered. Electrochemical process systems require highly customized designs, making standardized package units impractical. This results in a complex and costly scaling process, even on pilot-plant scales. Developing custom concepts with manufacturers can slow down or prevent piloting. To ensure a smooth scaling process, it is important to consider pilot system design early on. For example, persulfate electrolysis requires individually developed and optimized cell types and electrode materials, with more than five unique installations worldwide. To establish electrochemistry as a competitive technology, economic competitiveness with optimized standard processes is crucial.
In addition to comparing operating costs (OPEX), carbon emission costs must also be considered. Long-term stability tests for electrode materials and membranes are important to control irregular operational costs. Regional differences in the cost of base chemicals, such as caustic soda, and restrictive wastewater guidelines can also affect economic efficiency.
Downstream processing and simplifying organic synthesis steps are also important factors to consider. Chemical parameters and environmental influences are not the only decisive factors in the industrial environment. One of the most important factors is the scalability and technical feasibility of processes. There are different examples of electrochemical processes that have been implemented on an industrial scale in the chemical industry. The production of Lysmeral by BASF is an example of organic electrochemistry on an industrial scale with about several tens of thousands of tons per year, in addition to chlor-alkali electrolysis [14].
Scaling up: step-by-step guide
FIGURE 3. A proof of concept is typically started on the laboratory scale
This section illustrates the process of going from an initial idea to the development of a commercial process. Starting a proof of concept on a laboratory scale will likely result in a small scaleup with laboratory utensils (Figure 3). The next step is a mini plant or pilot-scale plant requiring a technical center (Figure 4). In this step, the scalability of the process is investigated and the influences of larger cells and requirements are unmasked. An industrial-scale plant is the last step of scaleup. The plant will be designed for the desired process, with larger equipment and numbering-up of electrochemical cells.
FIGURE 4. After proving a concept in the laboratory, the next step in scaleup involves a mini plant like this electrosynthesis pilot plant
Technology readiness levels.Today, the process development steps are often expressed by technology readiness levels (TRLs). This is a scale for assessing the state of development of new technologies on the basis of a systematic analysis. On a scale of 1 to 9, it indicates how advanced a technology is. In Figure 5, the four phases of process development from feasibility to technical installation are depicted. The TRLs and the decisive properties of the phases are shown.
FIGURE 5. Technology readiness levels define the four phases of scaling an electro-organic reaction
But how do you move from the current level into the next phase? When do you take the step out of the laboratory? What are the most crucial parameters to consider in each step? To answer these questions, you must first determine what you want to achieve in each of the scaling steps.
TRL 1–4. In the TRL 1–2 phase, a theoretical proof of concept is executed. Typically, you perform a literature study to represent the current state of the art and consider the feasibility of your idea. After the theoretical study, the next step includes performing experiments and evaluating the feasibility of the chemistry behind your idea. After proving the chemical viability and therefore reaching a TRL of 3–4, the next step is scaling.
Beyond TRL 4. To take the step toward a demonstration facility and thus prove the industrial feasibility, some parameters must first be precisely evaluated before reaching a TRL up to 6. The parameters mentioned in the earlier section, such as safety, long-term stability, chemical purity, supply source and economic viability for the process should be discussed. As part of the safety assessment, any potentially released gases should be examined and a plan must be developed for handling them. In addition, the scalability of the chemicals used in organic electrochemistry should be considered with regard to safety. Furthermore, the organic reaction should have been sufficiently studied so that any undesired reactions are known.
In the scaled-up process, the long-term stability of the selected materials is also an important safety consideration. In the laboratory, stable materials should have been identified for all components, such as pumps, hoses, seals, and similar items. In terms of scaling up, the same qualities of chemicals used in the pilot-scale should have been used in the laboratory. This results in circumventing unplanned events such as instabilities and leakage from the outset.
Suppliers. Once everything is ready to start scaling up, the search for suppliers starts. A pilot plant is often like a tailor-made suit that is precisely designed for the organic electrochemical reaction. It is important to pay attention to the commercial availability of materials, such as solvents, electrode materials, seals and more, and to clarify the question of in-house or outsourced engineering. Besides process and chemical parameters, the economic efficiency is decisive for scaleup.
Data generation. If the pilot plant phase is successful and you are able to transfer a laboratory reaction into a technical center, you have to start generating resilient data. These data will be the basis for calculations of operational and capital expenditures costs. Last but not least, you have to decide whether your process is not only chemically feasible, but also suitable for industrial implementation. ■
Edited by Dorothy Lozowski
Acknowledgements
Figures 1, 2 and 3 are courtesy of the Max Planck Institute for Chemical Energy Conversion and the authors. Figures 4 and 5 are courtesy of Evonik and the authors.
The authors acknowledge support by BMBF – Federal Ministry for Education and Research of Germany as part of the Cluster4Future ETOS (Electrifying Technical Organic Electrosynthesis) and the projects Outreach4ETOS (03ZU1205TB), Training4ETOS (03ZU1205QC).
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Authors
Laura Lennartz (Email: [email protected]) is engaged in an industrial Ph.D. program focused on scaling organic electrosynthesis. This work is a collaboration between Patrik Stenner’s group at Evonik and Siegfried R. Waldvogel’s group. In her research, she bridges newly developed academic electrochemical methods with the necessities of industrial processes. Lennartz studied biomedical chemistry at the University of Mainz, Germany, and earned her M.S. degree in 2022.
Patrik Stenner is the head of Electrochemical Processes and Exploration, as well as the respective Technology Platform at Evonik (Email:[email protected]; Website: www.evonik.com). Stenner studied process engineering at the Frankfurt/Main University of Applied Sciences. In 1996, he began his industrial career at Degussa’s Central Research Facilities in the Department of Physical Chemistry as a project engineer. After holding various functions at the Evonik sites in Rheinfelden, Wesseling, and Marl, Stenner took over a research lab at Process Technology in 2004 and developed the innovation field of electrochemical processes. Today, the application of electrochemical processes is a major game changer in Evonik’s sustainability transformation.
Sebastian B. Beil is a research group leader at the Max Planck Institute for Chemical Energy Conversion (Email: [email protected]). He studied chemistry in Kiel and received his Ph.D. in Mainz under the supervision of Siegfried R. Waldvogel on electro-organic transformations. Beil conducted an internship in the Baran Lab at Scripps Research in La Jolla, California and he performed postdoctoral stays in the group of Max von Delius in Ulm and in the group of David MacMillan. From 2021 to 2024, he was an assistant professor at the University of Groningen before he accepted a permanent research group leader position at the Max Planck Institute for Chemical Energy Conversion.
Siegfried R. Waldvogel is the director of the Max Planck Institute for Chemical Energy Conversion (Email: [email protected]; Website: www.mpg.de/151194/chemical-energy-conversion), where he heads large research clusters, such as ETOS (Electrifying Technical Organic Synthesis). Waldvogel studied chemistry in Konstanz and received his Ph.D. in 1996 from the University of Bochum/Max Planck Institute for Coal Research. After postdoctoral research in La Jolla, California, he started his own research at the Universities of Münster, Bonn and Mainz. In 2018, he cofounded ESy-Labs GmbH, which provides custom electrosynthesis and contract R&D. His research interests are novel electro-organic transformations, including bio-based feedstock.