Follow:

CO2 capture capacity (under 86 and 14%CO2) of MMOs derived from Mg–Al-acetate LDHs

https://doi.org/10.1039/D1DT00602A

“CO2 capture studies on MgO and MMOs derived from Mg–Al LDHs are usually carried out at around 200–250 °C. The mechanism of CO2 adsorption over MMOs is not yet clear, but it is broadly assumed that it is due to chemisorption.57 The earlier studies of CO2 capture on MMOs showed the evidence for metal carbonate formation during the CO2 sorption over LDH derived MMOs.58 The MgO present in the MMOs is found to be the active phase for the formation of metal carbonates. Assuming chemisorption as the adsorption mechanism, one would expect that the formation of metal carbonates would take place based on the amount of MgO present in the MMOs. However, the amount of CO2 capture realized for LDH derived MMOs is very negligible (2–5%) when compared to the amount of MgO present.22

In this work, CO2 capture studies of the resultant MMOs are carried out as described in the Experimental section. The CO2 capture performance of the obtained MMOs was evaluated in the range from 200 to 300 °C at atmospheric pressure and under both CO2 rich (86% CO2) and more diluted (14% CO2) conditions, and it is presented in Fig. 7.”

74EHS6Tr

“MMOs derived from 4 : 1 LDH showed a CO2 capture capacity (86% CO2) of 1.19 mmol g−1 at 200 °C, which decreased to 0.87 mmol g−1 at 300 °C. This reduction in the capture capacity at 300 °C from that at 200 °C is similar to that previously reported in the literature.30

However, the CO2 capture capacity observed at 200 °C is one of the highest values reported so far for pristine/unpromoted MMOs (Table 2).20,59 The observed CO2 capture capacity represents a very significant improvement compared to the capture capacity previously reported for acetate LDH derived MMOs (0.56 mmol g−1).60 Similarly, MMOs derived from 3 : 1 LDH showed better CO2 capture capacities than the previously reported values, with capture capacities of 1.02 mmol g−1 (86% CO2) at 200 °C and 0.7 mmol g−1 at 300 °C.60 MMOs derived from 4 : 1 LDH showed better CO2 capture capacities at all temperatures than those derived from 3 : 1 LDH. The higher uptake could be due to the higher amount of Mg2+ present in the MMOs derived from 4 : 1 LDH. For comparison, the CO2 capture capacity of MMOs derived from the commercial LDH Pural MG70 (Mg/Al = 2.33) was tested at 200 °C under 86% CO2. The sample showed a CO2 capture capacity of 0.67 mmol g−1 which is much lower than the capture capacity achieved for the MMOs derived from Mg–Al-acetate LDHs synthesized by acetamide hydrolysis. The CO2 capture profiles of MMOs derived from both 3 : 1 and 4 : 1 LDHs were studied at 200, 250 and 300 °C and are given in Fig. S8. All the samples showed a very rapid initial uptake of CO2 followed by a slow and steady uptake. None of the samples reached equilibrium within 2 h of experimental time. However, the samples captured more than 80% of CO2 within the first 10–15 min compared to the overall capture capacity achieved over 2 h (the inset of Fig. S8).”

1eYSPLLJ

Leave a Comment