Integrated capture and conversion of CO2 towards formate and CO

12-06-2021 | P2Chemicals | Research result

In a paper in Industrial Engineering Chemical Research (IECR), VoltaChem/TNO researchers led by Prof. Earl Goetheer present a novel methodology for integrated capture and conversion of CO2. They efficiently convert CO2 into formate and CO in an electrochemical flow reactor, using a mixture of chemical and physical absorption solvents both for CO2 capture and as electrolyte for electrochemical conversion. "Now that we have demonstrated the technical feasibility of the concept, we are confident that integrated capture and conversion will enable us to create value from CO2", says first author Dr Elena Pérez-Gallent, electrochemical research scientist.

Integrated capture and conversion of CO₂ has a high potential for reducing capital and operational cost when compared to traditional methodologies that employ capture, desorption, and utilization as independent, subsequent processes. It thus provides a far better outlook to create value from CO₂ as a building block for commodity chemicals. However, carbon capture and utilization technologies have been studied mostly independently. The research performed at the VoltaChem/TNO laboratories in Delft now provides an outlook on the merits of integrating the two. 

Elevated temperatures

In their IECR paper, the researchers report how a mixture of chemical and physical absorption solvents allowed for the captured CO₂ to be converted to formate with faradaic efficiencies of up to 50% and with carbon conversion of ca. 30%. The methodology is based on the liberation of the captured CO2 inside the electrochemical reactor at elevated temperatures. These are an inherent trait of an electrochemical system, since the Ohmic losses associated to the process lead to an increase of temperature. 

The researchers investigated the effects of temperature, composition, and concentration of the solvent/electrolyte on the faradaic efficiency, the rate of the conversion reaction and its selectivity. Among others, they established that the reaction rate of the integrated process significantly improved when increasing the temperature from 15 to 75 °C. They attribute this to the preponderant liberation of CO₂ at elevated temperatures, being 8 times higher at 75 °C than at 15 °C. They also conclude that the nature of the amine-based electrolyte and its relative composition play a significant role in the product distribution of the CO₂ reduction reaction. As an example, using an aqueous electrolyte decreases formate production due to the higher production of hydrogen. 

Scaling-up

The proposed methodology was brought a step forward towards scaling-up and validation of the electrochemical conversion in a semicontinuous laboratory system using an flow reactor. According to Dr Elena Pérez-Gallent, the study provides a positive perspective towards implementation of technology for integrated capture and utilization of CO₂. Now that the technical feasibility of using carbon capture media as the electrolyte in producing chemicals has been demonstrated, the team really believes in the technology and expects to expand the concept to other products. Further research will focus on improving the performance towards higher efficiency and selectivity, and on scaling up to larger electrode areas. "Given the potential economic merits of integrated processes in comparison to conventional systems, we are confident we are on the right track towards creating value from CO₂."

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Paper

Elena Pérez-Gallent, Chirag Vankani, Carlos Sánchez-Martínez, Anca Anastasopol, and Earl Goetheer: Integrating CO₂ Capture with Electrochemical Conversion Using Amine-Based Capture Solvents as Electrolytes. Ind. Eng. Chem. Res. 2021, 60, 11, 4269–4278 DOI: 10.1021/acs.iecr.0c05848

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VoltaChem is currently developing a Flagship Program on Integrated CO₂ capture and conversion. More information on this Flagship Program can be found here. 

More information about the TNO lab in Delft and other research facilities can be found here. 

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