https://doi.org/10.1002/ente.201402211
“In addition to the adsorption capacities, the study of the regeneration of the materials at a low temperature is also important. A high energy requirement for regenerating the liquid amine absorbent (for example, 10–30 % monoethanolamine in water is regenerated at T=140 °C) in conventional carbon capture systems presents a major obstacle for a wider application. During the regeneration of these liquid-phase systems, much of the energy was spent on the evaporation of water, which is the “non-adsorptive” component of the adsorbent. To circumvent this obstacle, water-free solid-state adsorbents with a low regeneration temperature (T<100 °C) are preferred.”
“In our regeneration study, four adsorption–regeneration cycles were carried out with the chitosan/MCF-3 sample, as shown in Figure 6. The overall adsorption for each cycle retained a minimum of 88 % of the capacity from the previous cycle and the overall drop in capacity is less than 15 % over 4 cycles. Therefore, this adsorbent can be regenerated at a low temperature (T=75 °C) with little loss in adsorption capacity. A higher retention of capacity, up to 98 %, can be achieved by regeneration at T=100 °C but this would lead to higher energy consumption. In comparison with solid state CaO adsorbent, which has been suggested for large-scale carbon capture but requires a high-temperature regeneration at T=700 °C,31 our chitosan/MCF-3 adsorbent represents a significant advancement in terms of reducing the energy consumption for regeneration, saving operational costs and, more importantly, reducing the overall carbon footprint. One interesting feature in this study was that there was a “step-wise” weight loss after every regeneration cycle without effect on the adsorption. This may be as a result of the displacement of strongly bound water or acetic acid from the adsorbent by adsorbed CO2. During regeneration, these molecules (water and acetic acid) left the system as the CO2 was desorbed at T=75 °C. Nonetheless, this feature has no impact on the overall performance of the adsorbent.”
“Figure 6 Gravimetric adsorption of CO2 by chitosan/MCF-3. Four regeneration cycles are shown with a t=90 min adsorption at T=25 °C and a t=30 min desorption at T=75 °C. The adsorption capacity measured for each cycle is shown above the corresponding adsorption peak.”