Low-concentration CO2 capture system with liquid-like adsorbent based on monoethanolamine for low energy consumption

Abstract

Direct air capture (DAC) of atmospheric CO2 is becoming ever more important for a carbon neutral society. To achieve this, it is critical to reduce the energy consumption of DAC systems. In this work, as a solution, a liquid-like adsorbent (LLA) is used as an adsorbent for DAC of low-concentration CO2. We improve the performance of LLA with monoethanolamine (MEA), and named it as LLA-M to efficiently capture atmospheric CO2 and reduce energy consumption at DAC environment. The effective dispersion of MEA in the LLA promotes CO2 capture by overcoming their low thermal stability. When 40 wt% MEA is added, the highest performance is achieved along with a CO2 capture capacity of 2.50 mmol g−1 in 100% CO2 atmosphere and 1.01 mmol g−1 in low CO2 concentration atmosphere. The loss and deterioration of MEA is suppressed by the LLA and therefore the performance is stably maintained while repeating the CO2 capture/regeneration cycles. Consequently, the CO2 capture capacity is improved by 29.9% compared with when using only MEA. More importantly, the results indicate a record CO2 capture energy consumption of 0.89 GJ tCO2−1 at 100% CO2 condition and 2.13 GJ tCO2−1 at 400 ppm CO2 condition. Furthermore, the LLA-M can be recycled below 120 °C which makes it possible to reduce energy consumption by exploiting renewable energies such as solar heat. This study offers a promising low-carbon route for efficient atmospheric CO2 capture using an LLA incorporated with MEA.