Layered Double Hydroxides/Multiwalled Carbon Nanotubes-Based Composite for High-Temperature CO2 Adsorption

Layered double hydroxides (LDH)-derived mixed metal oxides (MMO) are considered as promising solid sorbents for CO 2 capture in the temperature range of 350–500 °C. Accordingly, they find potential applications in the sorption enhanced water–gas shift process and in removal of CO 2 from hot flue gas/syngas. Numerous strategies have been explored to improve the CO 2 capture property of LDH-derived MMO under the conditions of intended applications. These strategies include novel sorbents by replacement of cations and intercalation of organic anions on Mg–Al LDH, development of LDH-based hybrid/composite materials, optimization of synthesis conditions to control particle size, and method development for different types of alkali impregnation. The present work involves synthesis of a Mg–Al LDH/multiwalled carbon nanotubes (MWNTs) composite and explores its applicability for CO 2 capture under dry conditions. Additionally, K 2 CO 3 is impregnated onto the composite to study the effect of alkali promotion. The K 2 CO 3 -promoted Mg–Al LDH/MWNT composite exhibited a fresh adsorption capacity of 1.12 mmol g –1 at 300 °C under a total pressure of 1 bar. The enhanced CO 2 sorption capacity of composites in comparison with their pristine counterparts can be attributed to improved particle dispersion. Further, the K 2 CO 3 -promoted Mg–Al LDH/MWNT composite shows an average working capacity of 0.81 mmol g –1 over 10 cycles in the temperature range of 300–400 °C. The deactivation model provides excellent predictions of the experimental CO 2 breakthrough curves obtained with various sorbents. The values of model parameters are comparable with those reported in the literature.