Fossil fuel derived carbon dioxide (CO<sub>2</sub>) emissions have continuously increased over the past century and their impact on climate change is self-evident. The chemical industry is an important contributor to this increase, accounting for more than 5.5% of the global emissions. Implementing electrochemical routes for the production of large volume chemicals can allow for the direct integration of renewable energy sources into chemical manufacturing. In this way, solar-powered electrochemical processes could greatly contribute to the reduction of the carbon footprint of the chemical industry. Although inorganic electrosynthetic processes have been successfully implemented in industry at scale (e.g. chloro-alkali and Aluminum production), the implementation of electrochemical methods for the production of organic chemicals has been limited, even if their potential impact is significantly larger.<br/><br/>Organic electrosynthetic processes face common challenges such as limited reactant concentrations in electrolyte, a complex array of possible organic side reactions, and the narrow electrochemical stability window of the often required aqueous electrolytes. Furthermore, the direct coupling of these electrosynthetic processes with intermittent renewable power sources requires a thorough understanding of the dynamic operation of electrochemical reactors to obtain high selectivity and efficiency. As a case study, this work addresses the feasibility of solar-driven electrohydrodimerization of acrylonitrile (AN) to adiponitrile (ADN), a precursor to Nylon 6,6. Although this model reaction is the largest and most successful organic electrosynthesis implemented in industry, it faces many challenges owing to its limited energy conversion and selectivity. Through a combination of experimental electroanalytical characterization and technoeconomic modeling, we elucidate guidelines for the optimal design and operation of photovoltaic-driven (PV) ADN electrosynthetic reactors. Our results provide insights into mass transport limitations that affect the selectivity of ADN electrosynthesis and on how to control electrode processes to mitigate them. Furthermore, we demonstrate that by rationally designing PV-driven ADN reactors, the effects of fluctuating solar irradiation on selectivity can be minimized, enabling practical solar-electrosynthetic processes for the manufacture of polymer precursors.

Design considerations of sunlight-driven organic electrosynthetic processes

2019 Spring National Meeting

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