https://doi.org/10.1016/j.jiec.2017.05.018
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The influence of temperature on the CO2 capture process was investigated by operating adsorption experiments at 30 °C, 45 °C, 60 °C, 75 °C, 90 °C and 105 °C with a feed flow rate of 60 ml/min on the HPS-TEPA-60% adsorbent.
As shown in Fig. 8, the TEPA modified HPS showed a dependence on adsorption temperature: the amount of CO2 capture first increased with the increase of temperature to a maximum, then decreased. 4.45 mmol/g was measured at 45 °C and 4.74 mmol/g was measured at 60 °C for HPS-TEPA-60%. With increasing the temperature, the adsorption capacity of CO2 continued to grow larger and reached its maximum of 5.01 mmol/g at 75 °C. However, the CO2 capture capacity dropped to 4.72 mmol/g at 90 °C. This experiments result is similar to the previously reported results by Wang et al. [55]. They also observed the best temperature of 75 °C for CO2 adsorption from a simulated gas stream over PEI/SBA-15 via a fix-bed method.
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“Fig. 8. CO2 adsorption capacities at different adsorption temperatures.”
“The temperature-dependent adsorption results indicate that the CO2 adsorption is a kinetic control process. As the temperature rises, the expansion of TEPA loaded into different pore of the support and the decrease of CO2 diffusion resistance make a contribution to the increase of CO2 adsorption capacity [34]. At low temperature, the TEPA is loaded inside the pore as bulk nanoparticles, being only the external active sites of TEPA accessible to CO2 molecules [56]. And the diffusion of the CO2 molecules from the surface to the bulk of TEPA is dominated as the main adsorption resistance. The amount of CO2 capture is poor due to the CO2 molecular kinetic energy is not able to overcome the diffusion resistance. When the temperature increase to 75 °C, the TEPA molecule became easier to move and could disperse more uniformly occupying all the available space in the support channel [55], [57]. Thus, more active sites were exposed for CO2 to reaction and the internal diffusion resistance decreased. This leads to a remarkable improvement of CO2 capture capacity. In contrast, as the temperature rises to 90 °C, although more amine active sites are becoming accessible, CO2 desorption from adsorption sites in the pore becomes more preferential, leading to a reduce in the CO2 adsorption capacity. In summary, it is noteworthy that the CO2 adsorption capacity obtained at 75 °C is very noticeable which makes the TEPA modified HPS materials as good candidates to remove CO2 effectively by adsorption.”