Hybridization of Fossil‐ and CO2‐Based Routes for Ethylene Production using Renewable Energy

• Published in: ChemSusChem 2020-12, Vol.13 (23), p.6370-6380
• Main Authors: Ioannou, Iasonas, D'Angelo, Sebastiano C., Martín, Antonio J., Pérez‐Ramírez, Javier, Guillén‐Gosálbez, Gonzalo
• Format: Article
• Language: English
• Subjects: Carbon; carbon capture and utilization; Carbon dioxide; Carbon sequestration; Chemical industry; Environmental impact; Ethylene; hybridization; Pricing; renewable resources; sustainable chemistry; Water splitting
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202001312

Carbon capture and utilization (CCU) has recently gained broad interest in the chemical industry. Direct electro‐ and thermocatalytic technologies are currently the focus of intense research, where the former employs electricity directly to reduce the CO2 molecule, while the latter comprises hydrogenation of CO2 in tandem with electrocatalytic water splitting. So far, it remains unclear which of the two is superior, yet this information is considered critical. Focusing on the platform chemical ethylene, the two CCU routes were compared using state‐of‐the‐art performances with the fossil technology considering different power and CO2 sources. The thermo‐route was found to be, at present, economically and environmentally better, yet under the same electrolyzer efficiencies, the electro‐route would become superior. CCU routes could substantially improve the carbon footprint of the fossil ethylene (by 236 %) while decreasing at the same time impacts on human health, ecosystem quality, and resources (64, 140, and 80 %, respectively). However, they are economically unattractive even when considering externalities (indirect cost of environmental impacts), that is, 1.7‐ to 3.9‐fold more expensive compared to the current fossil‐based analogue. Acknowledging this limitation, the concept of hybridization was applied as a means to smooth the transition towards more sustainable chemicals. Accordingly, it was found that an optimal hybrid plant could produce carbon‐neutral (cradle‐to‐gate) ethylene with a premium of only 30 % over the current market prices by judiciously combining CCU routes with fossil technologies. A closer look: The direct electroreduction of CO2 and the “green” methanol dehydration toward ethylene (where methanol is produced via CO2 hydrogenation) are compared with the fossil‐based technology for a range of power and CO2 sources. A hybrid ethylene plant combining fossil and CCU technologies is revealed as an optimal strategy to smooth the transition toward a decarbonized chemical industry.