CO2 reduction from amine solutions

CO2 reduction from amine solutions

01/10/2021 - 30/09/2025

Anthropogenic CO2 emissions have substantially increased the CO2 concentration in the atmosphere, aggravating the effects of global warming. To achieve the goal of 1.5°C above pre-industrial levels – set up in the Paris agreement of the COP 21 and reiterated in the COP 26 in Glasgow –, 45% of carbon dioxide emissions (relative to 2010) must be reduced by 2030. An approach to decrease the CO2 concentration is to capture the gas from the atmosphere, more effectively from source points (flue gases). A well-established technology for carbon capture (CC) is the amine scrubbing. However, this process has high operational costs, due to the large energy consumption of the solvent regeneration: the solution must be heated to release CO2 in the gas form (which is then compressed and stored) and to regenerate the amine, which is reused as capturing agent. Avoid the heating of the capture solution is a way to reduce the costs of the amine scrubbing process and it can be achieved by the direct use of the capture solution for the production of value-added chemicals. The electrochemical CO2 reduction (eCO2R) can be used as a technique to make the amine scrubbing more economically feasible. When based on renewable sources (such as solar and wind power plants), the direct reduction of the capture solution can promote the generation of chemicals (such as formic acid or CO) and the recycling of the amine without the energetic penalty or additional CO2 emissions. The eCO2R products can be further utilized, substituting oil-based chemicals, and leading to a broad circular carbon economy.

The goal of this PhD is to develop a capture and utilization process where CO2 is directly converted from the amine capture solution to valuable products, simultaneously to the amine recycling. Primary and secondary amines react with CO2 generating carbamates, as the example of monoethanolamine (MEA) in the following reaction:

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Breaking the C-N bond is responsible for the high energy demand in the recycling of the capture solution. The target is to promote the eCO2R directly from the carbamate and avoid the heating requirement. For that, tin (Sn) catalysts will be used in first instance, as these are known as proper catalysts for the production of formic acid from CO2. The catalyst optimization is within the scope of this PhD. Once the direct eCO2R is well stablished, new types of Sn will be prepared, as well as blends with different metals, aiming for an improved conversion performance and higher energy efficiency. Formic acid was chosen as benchmark product because it is easily produced from the eCO2R and it is a valuable chemical, widely used in the industry, with a high energy storage capacity, besides from being a promising reagent for fuel cells, as well as platform chemical.