Building Electrochemical Roadmaps for Decarbonization in the Specialty Chemical Sector

Abstract

Greenhouse gas emissions from the chemical manufacturing industry are enormous, by some estimates they amount to 5% percent of the global total.1,2 Moreover, chemical manufacturing is widely considered as a “difficult-to-decarbonize” sector due to the deeply entrenched reliance on crude-based hydrocarbons as fuels and feedstocks.3 The ultimate goal of eliminating anthropogenic greenhouse gas emissions, clearly demands a wholesale reconsideration of energy and material flows in chemical manufacturing.One area of research that has gained momentum in the past decade is the use of electrochemistry to perform organic redox reactions. These types of electrosynthetic transformations provide a straightforward means to electrify chemical manufacturing, thereby decreasing the global warming impact as the carbon intensity of grid electricity diminishes with continued adoption of low-carbon power sources. Further improvements are achievable through decarbonization of material inputs, e.g., by replacing problematic redox reagents like methane-derived hydrogen or fuming nitric acid with reactive hydrogen and oxygen intermediates generated at electrodes via water electrolysis.Despite these promising advances, interest in organic electrosynthesis to date has mainly focused on the production of commodity chemicals (e.g., CO2 reuse, ammonia electrosynthesis) at the expense of specialty chemical synthesis. This focus is well justified based on the possible impact of major breakthroughs on global emissions, but it constitutes missed opportunities to drive broad adoption of electrosynthesis across the chemical industry. To address this knowledge gap, our lab has undertaken a collaborative research effort with a global specialty chemical manufacturer to explore opportunities to decarbonize through electrification strategies involving electrosynthetic reaction schemes.This presentation will detail our recent work on a holistic “scoping study” to estimate the potential for reducing the global warming emissions profiles for a representative set of specialty chemicals through the adoption of electrosynthetic methods. First, we mapped the supply chain for 12 specific chemicals (chosen for their relevance to the specialty industry and significant global warming potential from current production methods) in terms of all reactive processes required to generate these compounds from petrochemical feedstocks. Next, we searched for literature reports detailing electrosynthetic pathways to generate each intermediate species along the manufacturing supply chain. The relevant electrochemical reactions were broadly classifiable as (a) generating alternatives to petrochemical feedstocks; (b) direct replacement of an existing chemical redox reaction with an electrochemical reaction; or (c) intensified approaches that use electrochemistry to reduce the total number of reactive process steps required. Finally, we benchmarked the potential for reduced greenhouse gas emissions for electrosynthetic schemes compared to the incumbent technologies based on a set of simplifying assumptions that involve calculating baseline emissions intensities as a function of the thermodynamic minimum energy input and the carbon intensity of the electric power supply, and further applying generic “efficiency factors” to account for all emissions in excess of this thermodynamic minimum. The results of this analysis suggest remarkable opportunities to develop electrosynthetic schemes for a handful of reactions for which global warming emissions could be reduced even in the most conservative scenarios of low process efficiency and high carbon intensity of the input power.This presentation will also cover the hurdles we have identified in the development of modular and continuously operated electrosynthetic reactors, as well as what we have learned in addressing these challenges.References(1) Saygin, D.; Gielen, D. Zero-Emission Pathway for the Global Chemical and Petrochemical Sector. Energies 2021, 14 (13), 3772. https://doi.org/10.3390/en14133772.(2) 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.(3) Gross, S. The Challenge of Decarbonizing Heavy Industry, 2021. https://www.brookings.edu/wp-content/uploads/2021/06/FP_20210623_industrial_gross_v2.pdf.