Dynamic Intermediate-Temperature CO 2 Adsorption Performance of K 2 CO 3 -Promoted Layered Double Hydroxide-Derived Adsorbents.

The dynamic adsorption characteristics of K 2 CO 3 -promoted layered double hydroxides (LDHs)-based adsorbent, with organic and inorganic anion intercalation, were studied. MgAl-LDH, K 2 CO 3 /MgAl-LDH, and K 2 CO 3 /MgAl-LDH(C16) with varying K 2 CO 3 loads were prepared and used for intermediate-temperature CO 2 sequestration. The adsorbent was thoroughly characterized using X-ray diffraction, Brunauer-Emmett-Teller, scanning electron microscopy, and Fourier Transform Infrared Spectroscopy techniques, which revealed enhanced adsorption properties of MgAl-LDH, due to K 2 CO 3 promotion. Thermogravimetric CO 2 adsorption tests on the constructed adsorbent materials showed that the 12.5 wt% K 2 CO 3 /MgAl-LDH(C16) adsorbent with organic anion intercalation exhibited optimal adsorption activity, achieving an adsorption capacity of 1.12 mmol/g at 100% CO 2 and 350 °C. However, fixed-bed dynamic adsorption tests yielded different results; the 25 wt% K 2 CO 3 /MgAl-LDH prepared through inorganic anion intercalation exhibited the best adsorption performance in low-concentration CO 2 penetration tests. The recorded penetration time was 93.1 s, accompanied by an adsorption capacity of 0.722 mmol/g. This can be attributed to the faster adsorption kinetics exhibited by the 25 wt% K 2 CO 3 /MgAl-LDH adsorbent during the early stages of adsorption, thereby facilitating efficient CO 2 capture in low-concentration CO 2 streams. This is a conclusion that differs from previous reports. Earlier reports indicated that LDHs with organic anion intercalation exhibited higher CO 2 adsorption activity in thermogravimetric analyzer tests. However, this study found that for the fixed-bed dynamic adsorption process, K 2 CO 3 -modified inorganic anion-intercalated LDHs perform better, indicating their greater potential in practical applications.