“CO2 uptakes were determined by TGA in 15% CO2 balanced by N2 at 75 °C simulating PCC conditions from coal-fired power plant, within the temperature range found to be optimum for PEI by other researchers [[18], [19], [20], [21], [22], [23], [35], [42]]. Fig. 8 presents the uptake profiles for the commercial and PFA-1-derived samples. CO2 uptakes and with the times taken to reach 30 with 60 and 90% of the final uptakes after an hour are listed in Table 6.”
“Fig. 8. CO2 adsorption profiles for MCM-41 PFA-1 with 50 and 60 Wt.% PEI and MCM-41 Sigma 60% as a comparison.”
“Table 6. CO2 uptakes and times to achieve 30, 60 and 90% uptakes in 15% CO2 at 75 °C for MCM-41 series of samples.”
“The CO2 uptake profiles are dominated by the rapid initial uptake that occurs in less than 4 min, followed by a much slower uptake that typically accounts for less than 20% of the final uptake reached after an hour. At the higher PEI loadings (50 and 60 Wt.%) for the commercial MCM-41, it is noticeable that the slower component tails more and does not appear to quite reach the limiting or equilibrium capacity within one hour (Fig. 8).
As is well established [[24], [25], [35]], CO2 uptakes increase with PEI loading, as can be seen for the commercial MCM-41 going from 6.4 to 11.2 Wt.% as the PEI loading increases from 40 to 60 Wt.% (Fig. 8 and Table 6). However, the results clearly indicate that the ash derived MCM-41 samples have considerably higher maximum CO2 adsorption capacities at both 50 and 60 Wt.% PEI loading, probably attributable to the larger mesopore volumes (Table 4), 1.13, 0.96 and 0.92 cm3 g−1 for PFA-1 and 2, RHA-1, respectively compared to 0.88 cm3 g−1 for the commercial sample. As already indicated, increasing the loading further to 65 and 70 Wt.% gave samples that were adhesive and largely agglomerated with CO2 uptakes falling to well below 10 Wt.%.”