Exploring the carbon-chain structure-activity relationship of CO2 and ketone-based absorbents

With regard to the physical absorbents for CO 2 removal, the alteration of carbon-chain structure may benefit the CO 2 absorption performance. However, the relationship between the carbon-chain structure of ketones absorbents and their CO 2 absorption capacity has rarely been studied, and the related mechanism is unclear. In this study, theoretical calculations and thermodynamic experiments were carried out to explore the effects of the carbon-chain length and isomerism of ketones on their CO 2 absorption performance. The density functional theory (DFT) simulations show that the F-∥ configuration is more stable than the others for the CO 2 +ketone complex in most cases. The followings are obtained according to the experimental results, which are pretty consistent with DFT calculations. The dissolution of CO 2 in the ketone is a typical physical process. As the number of carbon atom increases, the CO 2 absorption capacity of straight-chain ketones increases. Straight-chain ketones exhibit higher CO 2 absorption capacity than branched-chain ones. The effect of increasing carbon-chain length and isomerism on CO 2 absorption capacity are both stronger for the ketones with fewer carbon atoms; the influence mechanism can be attributed to different degrees of weak hydrogen-bond interaction between CO 2 and ketone molecules, suggested by the DFT simulation results. The above conclusions are beneficial for the development of potential CO 2 capture absorbents. In addition, the industrial application feasibility of surveyed ketone absorbents is also discussed.