https://doi.org/10.1016/j.cej.2014.04.063
“TGA experiments have been conducted to determine the CO2 uptake at different adsorption temperatures with 15% CO2 in N2. The results shown in Fig. 10 indicate that CO2 uptake is sensitive to the adsorption temperature, increasing as the temperature increases from 50 to 70 °C, reaching its peak value at around 70 °C, then decreasing as the temperature increases further to 80 °C. This observed trend does not agree with the thermodynamic behaviour implied by Langmuir Eqs. (3), (4). Similarly, Yue et al. [36] found that the maximum adsorption capacity appeared at 100 °C for their 50 wt% TEPA-impregnated SBA-15 adsorbent. Xu et al. [37] found the maximum capacity at 75 °C for the molecular basket adsorbent and Son et al. [15] also observed a maximum capacity at 75 °C for their 50 wt% PEI-impregnated KIT-6 adsorbent. As suggested by Yue et al. [36], the appearance of the “optimal” adsorption temperature may be resulted from the compromise between diffusion-controlled effects at lower temperature and thermodynamics-controlled effects at higher temperature.”
“Fig. 10. TGA results of CO2 uptake at different adsorption temperatures.”
“The temperature dependence on the capacities for the PEI–silica adsorbent was further investigated in the fluidized bed tests. Fig. 11 compares the adsorption capacities when the Initial Bed Temperature (IBT) was set to 50 °C and 70 °C for Batch I PEI–silica adsorbent. Due to the exothermal heat released during adsorption process, the fluidized bed temperature increased from the IBT of 50 °C and 70 °C up to about 65 °C and 80 °C respectively. Because the reactor is properly insulated and there is no cooling heat exchanger installed inside the reactor, the bed temperature would remain at the higher temperature for several hours once it was increased from the IBT. Therefore, the bed temperature with the IBT of 50 °C is closer to the optimal adsorption temperature as indicated by TGA results. The noticeable difference in capacities with two IBTs can be clearly identified from Fig. 11. For this reason, most of the adsorption tests with the BFB reactor were conducted at an IBT of 50 °C. The details of the bed temperature increase and heat of adsorption will be further discussed in Section 3.7.”
“Fig. 11. Effect of initial bed temperature (IBT) on capacities (Batch I, cycles ID: I56–I68, with moisture and oxygen).”