CO 2 emission is generally regarded as the major contributor to global climate change, and polyethylenimine (PEI)-based CO 2 adsorbents are promising materials for the capture of low concentration CO 2 . This paper deals with the deactivation kinetics of PEI-based CO 2 adsorbents used for the capture of low concentration CO 2 . EA and TG analyses demonstrated that thermal degradation and O 2 -induced deactivation of the adsorbents occurred simultaneously under air exposure conditions. It was found by N 2 exposure experiments at the temperature of 50–80 °C that the thermal degradation of PEI-based adsorbents followed a first-order reaction model with an activation energy of 80.98 kJ/mol and a pre-exponential factor of 6.055 × 10 8 (h –1 ). The parallel reaction model was employed to distinguish the O 2 -induced deactivation from the thermal degradation of the adsorbents through air exposure experiments within 50–80 °C. The O 2 -induced deactivation exhibited a second-order reaction with an activation energy of 74.47 kJ/mol and a pre-exponential factor of 6.321 × 10 6 (% –1 ·h –1 ). The results of simulating the overall deactivation of the adsorbents by the parallel reaction kinetic model were well consistent with those of the experiments, proving that the parallel reaction model was feasible for the description of the deactivation of PEI-based adsorbents.

The kinetics and mechanism of low-concentration CO 2 adsorption on a solid-supported polyethylenimine (PEI) adsorbent in a humid confined space were investigated, where the content of CO 2 was about 0.4 % (v). A flow system, equipped with a dew point meter and IR gas analyzer connected in series for online measurement, was developed and the co-adsorption performance of CO 2 and H 2 O was analyzed. It was found that the H 2 O adsorption capacity and activation energy were not significantly changed when 0.4 % (v) CO 2 was applied in the co-adsorption process, indicating that the effect of dilute CO 2 could be neglected. However, the CO 2 adsorption capacity increased with the assistance of H 2 O, and then it decreased slightly when the H 2 O content in air flow was above 1.56 % (v). This implied that the adsorption activation energy of CO 2 could be significantly reduced due to the existence of H 2 O in air flow. The direct formation of bicarbonate on the supported PEI adsorbent was favoured for the co-adsorption process of CO 2 and H 2 O.