CO2 capture cycling study (under 86% CO2) of MMOs derived from Mg–Al-acetate LDHs

https://doi.org/10.1039/D1DT00602A

“To evaluate the effects of the synthesis method and starting precursors on the CO₂ capture performance of the materials, we also tested the CO₂ capture capacity of MMOs derived from anion exchanged Mg–Al-acetate LDH. They showed a CO₂ capture of 0.57 mmol g⁻¹ at 200 °C under 86% CO₂. This observed CO₂ capture capacity is similar to the reported value (0.56 mmol g⁻¹) for acetate LDH derived MMOs under similar testing conditions.⁵⁴ This clearly highlights the need for alternative strategies in developing improved LDH based MMOs for medium-to-high temperature CO₂ capture applications. The MMOs derived from Mg–Al-acetate LDHs synthesized by acetamide hydrolysis were tested for cyclic CO₂ stability and the results were compared with the CO₂ cyclic stability of MMOs derived from the commercial LDH Pural MG70. The results are presented in Fig. 8. The MMOs derived from Mg–Al-acetate LDH (Mg/Al = 4) retained 65% (0.77 mmol g⁻¹ CO₂) of their initial capture capacity after 10 adsorption/regeneration cycles. On the other hand, MMOs generated from Mg–Al-acetate LDH (Mg/Al = 3) showed a better stability as the capture capacity loss was around 28% after 10 cycles. This improved CO₂ cycling stability might be attributed to the additional aluminium present in the sample compared to the MMOs having Mg/Al = 4 (lower aluminium content).^20,70 The commercial LDH based MMO sorbents (Pural MG70) showed a 35% loss in the capture capacity after 10 cycles. The CO₂ capture capacity retained by the commercial LDH based MMOs after 10 cycles (0.43 mmol g⁻¹) was much less than the MMOs derived from the Mg–Al-acetate LDHs (0.77 mmol g⁻¹). Overall, MMOs derived from Mg–Al-acetate LDHs synthesized by modified acetamide hydrolysis showed better CO₂ capture and cycling stability than the MMOs derived from the anion exchanged and commercial LDHs.”