RenewCO2, a US cleantech company founded in 2018, has developed an innovative electrolyzer technology that efficiently transforms CO₂ and water into ethylene glycol, a key component in polyester production. This approach not only contributes to carbon footprint reduction but also advances the concept of carbon recycling, playing a vital role in global efforts to achieve net-zero emissions.
(This article contains 8 diagrams and 1376 words.)
Challenges: CO₂ emissions of ethylene glycol production
Today, around 90% or more of ethylene glycol (EG) is produced from hydrocarbons via a multi-step path: first, ethylene is obtained; next, ethylene is catalytically oxidized into ethylene oxide; and finally, ethylene oxide undergoes hydration to yield monoethylene glycol (MEG).
This method faces significant economic and environmental challenges. The initial step of ethylene production, particularly through high-temperature steam cracking of hydrocarbons, is extremely energy-intensive. While the United States primarily uses natural gas liquids as feedstock, Europe and Japan still rely heavily on heavier hydrocarbons. This not only results in higher energy consumption but also generates numerous unwanted byproducts, necessitating additional energy and capital for separation processes.
A more recent alternative, often linked to Shell OMEGA technology, involves a two-step process: first, ethylene oxide (EO) reacts with CO₂ to form ethylene carbonate, which is then hydrolyzed to produce MEG. This method achieves nearly 100% selectivity to MEG.
In regions with abundant coal resources and less strict environmental regulations, ethylene glycol can be produced from coal-derived carbon monoxide (CO) through methanol intermediates. This process is sometimes referred to as the "coal-to-ethylene-glycol" route.
Conventional ethylene glycol production methods significantly contribute to global CO₂ emissions, releasing over 46 million tons annually. The process emits approximately 1 to 3 tons of CO₂ per ton of ethylene glycol produced from fossil fuels. This highlights the critical need for developing more sustainable production methods to reduce the carbon footprint associated with ethylene glycol manufacturing.
RenewCO2 Technology
Recent research has made substantial progress in the electrosynthesis of ethylene glycol, with a focus on sustainable methods powered by renewable energy. A notable advancement is the one-step electrochemical oxidation of ethylene to ethylene glycol using cobalt phthalocyanine supported on carbon nanotube (CoPc/CNT) catalysts. This innovative approach streamlines the synthesis process and demonstrates high conversion efficiency. Operating at room temperature and ambient pressure, this method shows promise for industrial applications.
Another significant development is the paired electrocatalytic technique, which employs a two-step redox process. At the anode, methanol undergoes partial oxidation to formaldehyde (CH₂O) using platinum-based catalysts. Simultaneously, at the cathode, carbon black catalysts reduce formaldehyde to ethylene glycol. This method, implemented in a membrane electrode assembly-based electrolyzer, demonstrates high efficiency at current densities relevant to industrial applications.
RenewCO2 has developed Electrocatalytic Carbon Utilization Technology (eCUT) to produce ethylene glycol from CO₂ and water (H₂O). This innovative process employs a proton exchange membrane (PEM) electrolyzer with a novel cathode design, enabling a single-step, low-temperature conversion of CO₂ to ethylene glycol with high efficiency and selectivity.
How RenewCO2 converts CO₂ into ethylene glycol
The diagram below illustrates RenewCO2’s system, which processes CO₂ and H₂O inputs to produce ethylene glycol via the advanced PEM electrolyzer. The system also features reactants recycling cycles and cathode product purification units.