Prospects of hydrogen cogeneration and carbon dioxide utilization in electrochemical refineries for ethylene production via oxidative coupling of methane: A techno-economic assessment

Ethylene is recognized as one of the most significant chemicals globally.¹ The projected ethylene production for 2023 stands at 227.6 million tonnes, with expectations of continued demand growth. The primary use of ethylene, accounting for over 76%, lies in the production of plastics such as polyethylene, polyvinyl chloride, and polystyrene.² Despite the enduring carbon retention potential of plastics themselves, traditional ethylene feedstock production from fossil resources contributes substantially to greenhouse gas emissions, ranging from 0.29 to 2.29 kg_CO2/kg_Ethylene depending on various factors like feedstock and process design.^3–5 Various decarbonization strategies, including the utilization of hydrogen as a primary heat source, have been proposed to reduce the carbon footprint of ethylene production,⁶ but their efficacy remains limited, offering at best a 0–30% reduction in on-site CO₂ emissions.⁵

Looking ahead to a future abundant in renewable energy, there's potential for refineries to transition from conventional thermochemical methods to electrochemical synthesis routes. Proton-conducting high-temperature membranes to produce ethylene from ethane,⁷ and the oxidative coupling of methane (OCM) in solid oxide cells have emerged as promising alternatives. OCM presents a particularly groundbreaking opportunity as it allows for the upgrading of simple organic molecules like methane; and as such, the utilization of methane from biogenic sources, thereby reducing reliance on fossil resources and mitigating emissions from ethane feedstock production. However, despite these promising developments, there's a significant gap in our understanding of the performance, costs, and competitive advantages associated with practical electrochemical system implementations.

Recent advancements in electrochemical OCM,^8,9 including demonstrations with metal-supported cells¹⁰, indicate progress towards enhancing flexibility in operating conditions and system integration. To accelerate and better guide solid oxide OCM cell development, a comprehensive system-level analysis is conducted to evaluate the potential implications of operating conditions on both performance and economics in prospective OCM-based ethylene refineries. This work builds upon previous work by the authors¹¹ and further investigates possibilities of H₂ co-production and CO₂ utilization.