Current industrial oxidation processes that convert ethylene and propylene to value-added products (e.g., ethylene oxide (EO), ethylene glycol (EG), propylene oxide (PO), and propylene glycol (PG)) are cost, energy, and emissions-intensive. An alternative that would alleviate these issues is electrochemically oxidizing alkenes, which can be powered by renewable electricity and operated at ambient conditions.<br/><br/>Industrially, conventional production of EO (25 million metric tons (MMT) in 2016, 30 MMT in 2021) uses direct oxidation of ethylene with air or oxygen over a silver-promoted catalyst at high temperatures. This process accounted for 9 MMT of CO2 emissions in 2016 due to energy requirements and the coproduction of CO2 as a byproduct. PO (11.2 MMT in 2020) is produced from propylene with varied byproducts through one of five methods including oxidation by ethylbenzene or tert-butyl hydroperoxide (27% and 15% globally in 2015), the chlorohydrin route (41%), and oxygen atom transfer from either hydrogen peroxide or cumyl hydroperoxide (15% and 2%). EO and PO are hydrolyzed in excess water at high temperatures and pressures to form EG and PG, respectively.<br/><br/>Here we utilize process modeling, techno-economic analyses (TEA) and life cycle assessments (LCA) to compare traditional EO, EG, PO, and PG production methods to the proposed electrochemical epoxidation process. We utilize direct electrochemical alkene (ethylene, propylene, C5+ alkenes) oxidation literature data including catalyst used, potential applied, bulk electrolysis current density, and electron and carbon selectivity and apply a scaling factor to simulate electrochemical oxidation and assess the TEA and LCA performance possibilities at U.S. EO, EG, PO, and PG production facilities using geospatially variant production data. The LCA component utilizes data from openLCA software. We assess integration with distributed renewable energy generation and the projected emissions factor reduction of the U.S. electric grid over time. TEA-LCA sensitivity analysis includes considerations of a potential future carbon tax. The results provide economic and environmental insight into the substitutability of traditional industrial processes with electrochemical oxidation, supporting expanded electrification and sustainability of the chemical sector.

Reducing Cost, Energy, and Emissions of Ethylene and Propylene Oxidation via Electrochemical Routes: A Techno-economic Analysis and Life Cycle Assessment Approach

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