Influence of calcination temperature on CO2 capture using tubular MgO and stability analysis

https://doi.org/10.1039/D2NA00213B

“The CO₂ capture performance of the MgO sample was examined again, applying a higher calcination reaction temperature of 450 °C to obtain complete regeneration (referred to as MgO_HT). As shown in Fig. 3(a), the MgO_HT sample exhibited stable carbonation and complete regeneration compared to the MgO sample. However, the degree of carbonation decreased continuously for the given cycles. Note that MgO/CNT_Air stably maintained its carbonation–calcination reactivity for the given period, even at the lower calcination temperature of 400 °C.

The weight change profiles of the above sample were converted to the MgO conversion (X_N) to MgCO₃, as shown in Fig. 3(b). MgO conversion of MgO/CNT_Air abruptly decreased from 0.68 (X₁) to 0.32 (X₃), then gradually increased to 0.39 (X₄) and 0.45 (X₁₁). After that, the conversion was stabilized at ∼0.44 for the remaining cycles. The MgO sample similarly exhibited a steep decrement from 0.77 (X₁) to 0.12 (X₁₃). Then, the pattern stabilized with a low value of MgO conversion. On the other hand, MgO_HT exhibited a gradual decrease in MgO conversion from 0.58 (X₂) to 0.32 (X₃₀). Note that, starting from X₁₅, MgO/CNT_Air showed MgO conversion higher than that of MgO_HT. The recyclability of MgO/CNT_Air was further examined for 100 cycles of carbonation–calcination (Fig. 4). The MgO conversion of MgO/CNT_Air steadily decreased from 0.32 (X₆₆) to 0.26 (X₁₀₀). The decaying patterns of both MgO/CNT_Air and MgO_HT were analyzed. The slopes were −0.0023 (X_N/cycle) and −0.0095 (X_N/cycle) for MgO/CNT_Air and MgO_HT, respectively. These results indicate that the inactivation tendency of MgO_HT was four times faster than in the case of MgO/CNT_Air, which implies that MgO/CNT_Air can achieve better durability even under mild regeneration conditions.”

“Fig. 3 CO₂ capture performance of MgO-based sorbents for 30 cycles of carbonation–dissociation measured by TG-DSC. (a) Normalized weight (wt%) profiles and (b) MgO conversion (X_N). Weight profiles are normalized according to each weight of pristine MgO-based sorbents.”

“Fig. 4 CO₂ capture performance of MgO_HT (30 cycles) and MgO/CNT_Air (100 cycles) in MgO conversion (X_N) by TG-DSC. Linear regressions of performance decay are given.”