Dynamic Intermediate-Temperature CO Adsorption Performance of KCO-Promoted Layered Double Hydroxide-Derived Adsorbents.

The dynamic adsorption characteristics of KCO-promoted layered double hydroxides (LDHs)-based adsorbent, with organic and inorganic anion intercalation, were studied. MgAl-LDH, KCO/MgAl-LDH, and KCO/MgAl-LDH(C16) with varying KCO loads were prepared and used for intermediate-temperature CO 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 KCO promotion. Thermogravimetric CO adsorption tests on the constructed adsorbent materials showed that the 12.5 wt% KCO/MgAl-LDH(C16) adsorbent with organic anion intercalation exhibited optimal adsorption activity, achieving an adsorption capacity of 1.12 mmol/g at 100% CO and 350 °C. However, fixed-bed dynamic adsorption tests yielded different results; the 25 wt% KCO/MgAl-LDH prepared through inorganic anion intercalation exhibited the best adsorption performance in low-concentration CO 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% KCO/MgAl-LDH adsorbent during the early stages of adsorption, thereby facilitating efficient CO capture in low-concentration CO streams. This is a conclusion that differs from previous reports. Earlier reports indicated that LDHs with organic anion intercalation exhibited higher CO adsorption activity in thermogravimetric analyzer tests. However, this study found that for the fixed-bed dynamic adsorption process, KCO-modified inorganic anion-intercalated LDHs perform better, indicating their greater potential in practical applications.