Investigating the enhancement of the rate of CO2 capture of CaO in the presence of steam through 18O Isotope labeling: Pitfalls and findings

Data that was used to produce Figures 2-6 in the article. Figure 2: Results from the TGA experiments over five cycles of CO2 sorption and release using a limestone-based sorbent. (a) CO2 sorption in a dry CO2-containing atmosphere. (b) CO2 sorption in a humid CO2-containing atmosphere using deionized water. (c) and (d) show the MS signals corresponding to the TGA measurements shown in (a) and (b) for the fifth carbonation cycle. (e) and (f) show the MS signals that correspond to the same cycling experiment shown in (b), but using steam derived from labeled water (H218O) instead of deionized water; in (e) both N2 and CO2 flowed through the saturator, whereas in (f) only N2 flowed through the saturator. Figure 3: (a)-(d) Raman spectroscopy measurements of partially carbonated sorbents after five reaction cycles plus an extended carbonation for 4 h. The order of the plots is the same as in Figure 2c-f, corresponding to the different atmospheres during the carbonation stage (dry, humid (H216O), humid (H218O) with N2 and CO2 flowing through the saturator, and humid (H218O) with only N2 flowing through the saturator). (e) XRD measurement of a partially carbonated sorbent (using labeled water H218O). (f) Example of a TGA experiment (here using deionized water H216O) to produce the samples for the subsequent analyses shown in (a)-(e). Figure 4: Results from TGA experiments of CO2 sorption and release using a limestone-based sorbent. (a) CO2 sorption in a humid CO2-containing atmosphere using steam derived labeled water (H218O) with both N2 and CO2 flowing through the saturator. (b) CO2 sorption in a humid CO2-containing atmosphere using labeled water (H218O) with only N2 flowing through the saturator, two cycles only. (c) Long CO2 sorption under dry conditions at 650 °C; after 10 h CO2 sorption continued using steam derived from labeled water (H218O), showing an increase in the rate of CO2 uptake. (d) Raman spectroscopy measurements of the sample shown in (c). Figure 5: Blank measurements (empty crucible) using the TGA-MS. (a) and (b) show the MS signals corresponding to the experimental conditions in Figure 2; in (a) both N2 and CO2 flowed through the saturator filled with labeled water (H218O), whereas in (b) only N2 flowed through the saturator. (c) and (d) MS signals showing the influence of temperature on the exchange of oxygen between H2O and CO2 when feeding a mixture of steam derived from labeled water (H218O) and CO2; in (c) the MS signals are plotted on a linear scale, whereas in (d) the MS signals are plotted on a logarithmic scale. (e) Influence of temperature on the stability of the MS signals due to water (m/z 18 and m/z 20) in the absence of CO2; here, pure N2 flowed through the saturator filled with a mixture of deionized water and labeled water (H218O). Figure 6: Raman spectroscopy measurements of partially carbonated sorbents following a temperature-programmed (TP) treatment in a larger TGA under different conditions. (a) The partially carbonated sorbent was prepared by calcining CaCO3 powder at 900 °C, followed by exposure to 5 vol.% CO2 and 2 vol.% steam derived from labeled water (H218O) at 700 °C for 12 h. The CO2 uptake was 0.75 g CO2 per g sorbent. (b) The material prepared in (a) was heated from room temperature to 600 °C in 5 vol.% CO2 and 2 vol.% steam derived from deionized water. (c) The material prepared in (a) was heated from room temperature to 600 °C in 5 vol.% CO2. (d) The material prepared in (a) was heated from room temperature to 600 °C in 2 vol.% steam derived from deionized water. Ratio of peak areas (CaC16O3 at 1090 cm-1 and CaC18O16O2 at 1069 cm-1): 1.4 (a), 1.3 (b), 1.3 (c) and 1.3 (d).