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CO2-based Electrosynthesis of ethylene oXIDE

Periodic Reporting for period 1 - CO2EXIDE (CO2-based Electrosynthesis of ethylene oXIDE)

Reporting period: 2018-01-01 to 2019-06-30

The substitution of fossil based production routes with new and innovative synthesis strategies for bulk chemicals, fuels and fuel additives is a strategic goal within the next decade. Following the Paris agreement, the European Union’s strategy pursues a climate neutral Europe by 2050. Thus, the CO2 utilization (CCU) and storage (CCS) are important goals for scientists, government and society.
The CO2EXIDE project proposes a substitution of a fossil based chemical process for ethylene oxide (EO) production. The proposed technology consists on the combination of cathodic and anodic electrochemical processes (“simultaneous electrochemical factories”) driven by renewable energy from wind mills or solar panels, water and CO2 as a carbon source. This will direct the chemical production of bulk chemicals and fuels into a new circular industrial age (Figure 1). These processes will entail: (i) the reduction of greenhouse gas emissions, (ii) the reduction of environmental impacts of crude oil production, (iii) a product oriented use of energy, and (iv) parallel substitution of fossil based chemicals with renewable ones.

The CO2EXIDE proposal focus on the CO2-based Electrosynthesis of ethylene oXIDE and derived products. The development, from TRL4 to TRL6, aims at a) simultaneous synthesis of value added products at the cathode and anode; b) modular nature for integrated electrochemical and chemical conversion technologies; c) feasibility at larger scales for a decentralized application; d) high energy and material efficiency/yield, e) low operating conditions (pressure and temperature), f) low invest and maintenance costs and g) the substitution of the fossil based production of EO with a CO2-neutral and renewable process.
In accordance with the global challenge of replacing polluting chemical reactions with more environmentally friendly electrochemical processes, the use of CO2 as singular carbon source for the cathodic production of ethylene and the parallel anodic production of hydrogen peroxide (H2O2) opens a direct access to high volume bulk chemicals as ethylene, H2O2 and especially ethylene oxide (EO) in an efficient way (Figure 2). The subsequent combination of ethylene and H2O2 in a catalytic chemical reaction provides the bulk chemical EO, which can be the basis for e.g. polyethylene glycol, ethanol, 1,3-propane diol, acetaldehyde, etc. In summary, ethylene, H2O2 and EO are amongst the chemicals with the largest energy consumption due to their high annual production volumes. The combination of new technologies and production of large volume chemicals could also act as stabilizer for the national and transnational European electricity grid infrastructure in the future as it is currently being discussed and demonstrated for the power to gas technology.
Biogenic CO2 capture and purification
CO2EXIDE partners have performed a detailed research of the potential CO2 sources for the EO synthesis. Green CO2 sources like biogas, bioethanol, biomass as also fossil sources from heat and power generation, iron industry, chemical industry, pulp and paper, cement and refinery industry have been included in the investigation. Besides the available CO2 amounts, other key factors like CO2 concentrations, typical impurities and also centralisation/decentralisation of the CO2 sources have been systematically evaluated. This results and outstanding findings will be soon published as a review.
Biogenic CO2 has been successfully captured from a biogas plant in Bruck an der Leitha (Figures 3a and 3b). The biogas off-stream was harnessed, upgraded with a special multistep process and analysed for their impurities. 99 %(v/v) biogenic CO2 gas cylinders were filled and shipped to partners and will be used as feedstock for the synthesis of ethylene oxide in the demonstrator.

Catalyst development
Catalyst development for CO2 reduction to ethylene and water oxidation to H2O2 has been the main focus in the first half of the project. The selectivity achieved up to now for ethylene production, at current densities between 100 to 200 mA cm-2, is comparable to the state of the art. Otherwise, higher currents up to 350 mA cm-2 can be achieved but at the expense of selectivity. As for the anodic production of H2O2, CO2EXIDE has reached current densities and product concentrations way beyond the state of the art. An overview of the concept definition and design guidelines for the electrochemical synthesis of H2O2 was published at:
Perry,S., Pangotra,D., Vieira,L., Csepei,L-I, Sieber,V., Wang,L. Ponce de León,C. & Walsh, F.. Electrochemical synthesis of hydrogen peroxide from water and oxygen. Nature Reviews Chemistry 3, 442–458 (2019).
Outperforming catalysts will be up-scaled to a larger electrolyser for the process integration and demonstration in a relevant environment.

Chemical conversion, assembly and tests
The electrolyser and the chemical reactor have been so far developed in parallel. The coupling of the two reactors will take place in the second half of the project.
As one of the most versatile chemical intermediates, the industrial production of EO is mainly carried out by the direct oxidation of fossil-based ethylene. Ethylene is the most-produced petrochemical building block with a global demand in 2015 is estimated at 143 million tons. By far, the predominant manufacturing route to ethylene is steam cracking gaseous (ethane, propane, or butane) or liquid feedstocks (naphtha or gas oil). This noncatalytic cracking process is run at very high temperatures (up to 850 °C), with significant greenhouse gas emissions and energy demand. Hence, it is assumed that the CO2-based, renewable intermediates ethylene and H2O2 and the product EO will provide the vital option to substitute the fossil-based routes.

The first project period focused on the definition and study of the benchmark systems for the analysis of potential impacts of a CO2EXIDE technology roll-out in Europe. In the second half of the project, the integration of electrolyser, ethylene enrichment unit and chemical reactor for epoxidation will take place as demonstration plant located in Krakow. This will be the first plant for non-fossil EO produced directly from CO2, water and electricity, promising a radical innovation in the chemicals production sector.

The impact related studies will evaluate the environmental & socio-economic performances of the process along the whole value chain. It will include a detailed Life Cycle Assessment (LCA) according to the ISO guidelines 14040/14044 with special focus on the supply of renewable electricity and CO2 to the electrochemical conversion and further chemical processing. LCA for the green production of EO will be performed also regarding new process concepts and value supply chains for renewable chemicals. This will result in an “Environmental Product Performance” profile encompassing a wide range of environmental impact categories for the production of the fossil and bio-based benchmarks.

The economic analysis of the CO2EXIDE technology approach will derive CAPEX and OPEX estimation for assessing specific production costs. This analysis will provide a picture of the business perspective for the proposed electrocatalytic „simultaneous-factories”, and will identify potential fields of application and market uptake as the ‘green value’ of the produced bulk chemicals.
Figure 1: CO2EXIDE vision
Figure 3b: Commissioning of the in-situ gas chromatograph for the analysis of the off-gas stream
Figure 2: Concept of CO2EXIDE
Figure 3a: Substrate delivery to biogas plant in Bruck an der Leitha (Lower Austria)