Stability of using CaO-alone for ICCU-RWGS

“The excellent performance of CaO-alone in ICCU has been extended to its stability. Using TGA analysis at 600 °C under CO2 and H2 switching, we obtain a very stable ICCU performance after 154 cycles of carbonation and regeneration in relation to weight changes, reducing from 4.1 mmol/gCaO in the 1st cycle to 3.6 mmol/gCaO in the 150th cycle (Fig. 2a and fig. S13). The lower initial adsorption capacity at 600 °C is mainly caused by the slow kinetics of CaCO3 regeneration. That is, CaO can not fully return to the initial state before the 2nd carbonation cycle (fig. S13). However, such incomplete desorption has shown extremely excellent cyclic performance. In contrast, higher initial adsorption capacities are obtained at 650 °C and 700 °C (12.44 and 10.66 mmol/gCaO in the 1st cycle, respectively) due to the enhanced kinetics (fig. S14 and S15). However, the capacity of CO2 capture is significantly reduced in the initial 30 cycles, decreasing to 5 and 4 mmol/gCaO at 650 °C and 700 °C, respectively. In terms of long-term stability, the cycle performance at 600 °C is superior to 650 °C and 700 °C, corresponding to 3.72, 3.61 and 2.12 mmol/gCaO after 120 cycles, respectively. The severity of sintering under various temperatures can be clearly observed from SEM (fig. S17). The above results demonstrate both acceptable adsorption performance and the long-term stability of CaO under isothermal conditions.”


Fig. 2. Cyclic carbonation and H2-regeneration performance of CaO under isothermal (600 °C, 650 °C and 700 °C) and non-isothermal conditions (carbonate at 650 °C and regenerate at 850 °C). (a) Cyclic capacity of CO2 capture; (b) Comparison of dynamic profiles of 2nd and 50th cycles; (c) Comparison of carbonatation and regeneration rate in cycles;(d) Comparison of carbonatation and regeneration time in cycles. (carbonation rates and times were calculated from the rapid adsorption stage)


Fig. S13. Long term cycle evaluation of CaO over isothermal CaL in H2 under 600 ˚C. (154 cycles)


Fig. S14. Long term cycle evaluation of CaO over isothermal CaL in H2 under 650 ˚C. (124 cycles)


Fig. S15. Long term cycle evaluation of CaO over isothermal CaL in H2 under 700 ˚C. (123 cycles)


Fig. S17. SEM images of CaO after cycling under various condition. (a) Raw CaO (calcined CaCO3); (b) 600 ˚C isothermally cycled CaO (154 cycles); (c) 650 ˚C isothermally cycled CaO (124 cycles); (d) 700 ˚C isothermally cycled CaO (123 cycles); (e) 650 ˚C-CO2-850 ˚C-H2 cycled CaO (54 cycles) and (f) 650 ˚C-CO2-850 ˚C-CO2 cycled CaO (50 cycles).

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