https://doi.org/10.1039/D1RA09250B
“A certain proportion of nano-CaCO3 powder (>95% purity, 70 nm, Hu Zhou Ling Hua Ltd China) and dopant BeO (>99% purity, Aladdin) were added into 50 vol% ethanol aqueous solution under ultrasonic dispersion. Then the aluminum sol (10 wt%, Zibo Longao Ltd) was added to this slurry and stirred at 80 °C. The weight fraction of carrier Al2O3 was set as 15 wt% in the nano-CaO-based adsorbent. The slurry was allowed to dry overnight at 110 °C. Finally, the resulting sample went through calcination at 500 °C for 3 h under N2 atmosphere for dehydration. All adsorbent powders were ground to be 60–80 μm sized particles before being tested further.
The designation and composition of adsorbents are listed in Table 1. Ca/Al represented the nano-CaO/Al2O3 adsorbent without any dopants. CaBeα/Al (α = 0.125–4) represented nano-CaO-BeO/Al2O3 adsorbent doped with BeO and molar ratio of CaO to BeO was α.”
Table 1 Nano-CaO-based adsorbents’ composition and designation
| No. | Sample | Molar ratio of CaO to BeO dopants | CaO content (wt%) | BeO dopant content (wt%) |
|---|---|---|---|---|
| 1 | Ca/Al | — | 85.0 | 0 |
| 2 | CaBe4/Al | 4 : 1 | 76.2 | 8.8 |
| 3 | CaBe2/Al | 2 : 1 | 69.4 | 15.6 |
| 4 | CaBe1/Al | 1 : 1 | 58.8 | 26.2 |
| 5 | CaBe0.5/Al | 1 : 2 | 44.8 | 40.2 |
| 6 | CaBe0.25/Al | 1 : 4 | 30.5 | 54.5 |
| 7 | CaBe0.125/Al | 1 : 8 | 18.6 | 66.4 |
As shown in Figure 5, the increase of BeO loading promoted the decomposition of CaCO2 by shifting the temperature to a low value. However, this might be ascribed to the changes of CaO morphologies due to the largely reduced content of CaO.
“Fig. 5 Comparison of decomposition rates of CaCO3 in nano-CaO-based adsorbents with different BeO doping contents during continuous heating process.”
It is clear that the capacity of CO2 capture is reduced with the increase of BeO loading (Table 4). The authors suggested that the enhancemen of CaCO3 decomposition might be due to the improved heat transfer from BeO addition. This is difficult to justify.
Table 4 The sorption capacity and carbonation conversion of adsorbents with different BeO doping contents
| Sample | Sorption capacity (mol kg−1) | XN |
|---|---|---|
| CaBe4/Al | 11.7 | 0.859 |
| CaBe2/Al | 9.9 | 0.803 |
| CaBe1/Al | 8.1 | 0.773 |
| CaBe0.5/Al | 5.9 | 0.736 |
| CaBe0.25/Al | 4.3 | 0.796 |
| CaBe0.125/Al | 2.8 | 0.844 |