Effect of water content on the characteristics of CO2 capture processes in absorbents of 2-ethylhexan-1-amine + diglyme

Highlights: • The proposed water-free sorbent achieved 99% of CO₂ desorption efficiency at 373 K • The sorbent was highly water-tolerant and performed well at water content of 10 wt%. • Heat capacity was studied taking full account of sensible, latent and reaction heat. • Energy consumption of proposed sorbents was below 20% of that of aqueous 30 wt% MEA. • Products in water-free or lean sorbent were only carbamated EHA and protonated EHA. In our recent study (Fu et al., 2021), 70 wt% 2-ethylhexan-1-amine (EHA) + 30 wt% diglyme was proven to be a promising system for carbon dioxide (CO₂) absorption. In this work, the capture performance of 15 kPa CO₂ in 70 wt% EHA + (30 or 25 or 20) wt% diglyme solution was investigated. The evolution of solution composition during the capture process was identified. The time-dependent absorption and desorption capacities were accurately correlated by using the modified Avrami model. After 90 min of absorption, the proposed sorbents maintained relatively low viscosities (≤32.07 mPa s) and had much lower heat capacities than the aqueous 30 wt% ethanolamine (MEA). The CO₂ desorption capacities of the sorbents containing 0 wt%, 5 wt% and 10 wt% water were higher than that of the aqueous 30 wt% MEA by 134.1%, 123.6% and 91.7%, respectively. The regeneration efficiency of the sorbents containing 0 wt%, 5 wt% and 10 wt% water was 92.1%, 87.9% and 83.8%, respectively, in the 5th absorption (313 K) - desorption (373 K) cycle. Furthermore, it is encouraging to note that the energy consumption for CO₂ desorption of proposed sorbents was below 20% of that of the aqueous 30 wt% MEA.