Removal of low concentration CO2 at ambient temperature using several potassium-based sorbents

• Several potassium-based sorbents were applied to low concentration CO2 removal at ambient temperature.
• K2CO3/AC shows high carbonation conversion efficiency and CO2 sorption capacity.
• K2CO3/5A, K2CO3/13X, and K2CO3/SG show low CO2 sorption capacities.
• K2CO3/Al2O3 shows low carbonation conversion efficiency and needs high temperature of 350 °C to be regenerated.
• K2CO3/AC is a more efficacious choice for CO2 removal in confined space.

The requirement for long-duration human operation in a confined space has made removal of low concentration CO2 a critical technology. The incorporation of organic amines into a porous support is thought to be a promising approach, but the low amine utilization ratio and the loss of amine components due to evaporation in regeneration process make it necessary to try new sorbents. As K2CO3 are more difficult to be decomposed than organic amine compound, potassium-based sorbents may be more effective for CO2 removal in confined spaces. In this work, activated carbon (AC), Al2O3, zeolite 5A, zeolite 13X, and silica aerogels (SG) were chosen as the supports and K2CO3 was provided as the active component. An experimental demonstration of the CO2 sorption performances of these sorbents was present in detail in the condition of ambient temperature and the CO2 concentration of 5000 ppm. The CO2 sorption capacities are calculated as 0.87, 1.18, 0.34, 0.53, and 0.15 mmol CO2/g for K2CO3/AC, K2CO3/Al2O3, K2CO3/5A, K2CO3/13X, and K2CO3/SG, respectively. The reacted products are completely regenerated in the temperature range of 100–200 °C for K2CO3/AC and K2CO3/SG. Other sorbents, however, require a higher temperature of 350 °C in order to be regenerated. K2CO3/Al2O3 shows the highest CO2 sorption capacity, while K2CO3/AC shows the highest bi-carbonation conversion efficiency. The CO2 sorption capacities of K2CO3/5A, K2CO3/13X, and K2CO3/SG do not reach the expected values. Among these sorbents, K2CO3/AC is a new, more efficacious choice for CO2 removal in confined space at ambient temperature.

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