Cycling study of LDH based CO2 capture

https://doi.org/10.1039/C9DT03913A

“The high temperature CO₂ cycling performance of the resultant nanocomposite was determined between 600 (carbonation) and 700 °C (regeneration) for 60 cycles (86% CO₂), as described in the Experimental section. The results of the cycling study are presented in Fig. 4. The sample shows remarkable cyclic stability with nearly 100% regeneration of the sorbent within 30 min of regeneration time. The sample shows an overall working capacity of 5.10 mmol g⁻¹ compared to the adsorption capacity of 6.18 mmol g⁻¹ in the first cycle. A few cycling data are given in the inset of Fig. 4 to show the stability of the carbonation/regeneration of the sample. The carbonation of the resultant nanocomposite is very rapid and close to 90% of carbonation happens within the first 5 min of the cycle (Fig. S8†). However, the complete regeneration is achieved in less than 5 min, as is evident in Fig. S8.† To check the effect of cycling on the sample and its morphology, as well as the role of the carbon support, SEM was carried out on the cycled nanocomposite (60 cycles). After 60 cycles, the resultant nanocomposite practically retains its original morphology, having its porosity intact, as shown in Fig. 6. The observations of better cycling and retention of the morphology are very interesting results. The presence of carbon in between the MMOs in the nanocomposite has prevented agglomeration/sintering of the particles during the cycling and has hence helped in retaining its capture capacity over long cycles. To employ these sorbents on an industrial scale, it is important to check their activity and cycling stability under flue gas CO₂ concentration. The resultant nanocomposite was tested for capture and cycling stability for 40 carbonation/regeneration cycles under flue gas CO₂ concentration (gas composition of 14% CO₂ and 86% N₂) whilst keeping all other experimental conditions identical to those described in the Experimental section. The results of the cycling performance under flue gas conditions are shown in Fig. 5. The developed nanocomposite shows similar cycling stability to the case of 86% CO₂, except that the cycling capacity has decreased from 5.10 to 4.10 mmol g⁻¹. This decrease in capture capacity under 14% CO₂ compared to 86% is expected, as the partial pressure of the CO₂ is known to affect the capture capacity. Overall, the resultant organic–inorganic nanocomposite shows excellent CO₂ capture and cycling stability under both CO₂ rich and lean (flue gas) conditions.”

“Fig. 4 60 carbonation and regeneration (600 and 700 °C, respectively) cycles of the organic–inorganic hybrid MMOs generated from Ca–Al-adamantanecarboxylate LDHs under 86% CO₂ and 14% N₂. The inset shows the shape and the kinetics of the carbonation/regeneration of the organic–inorganic hybrid MMOs.”

“Fig. 5 40 carbonation and regeneration (600 and 700 °C, respectively) cycles of the organic–inorganic hybrid MMOs generated from Ca–Al-adamantanecarboxylate LDHs under 14% CO₂ and 86% N₂.”

“Fig. 6 SEM images after 60 carbonation/regeneration cycles of the organic–inorganic hybrid MMOs generated from Ca–Al-adamantanecarboxylate LDHs.”