Experimental and modelling-based evaluation of novel CO2 adsorbents for direct air capture

Direct air capture (DAC) has shown high potential for climate change mitigation by removing CO2 from the atmosphere and then either storing it into geological storages to generate negative emissions or utilizing it as a feedstock in various applications. The DAC technology based on amine-functionalized adsorbents has proven to be a particularly promising method for CO2 capture. However, the costs of DAC are still too high for large-scale deployment due to the technical challenges related to adsorbents and high specific energy requirement (SER) of the process. Improving the performance of the adsorbents is the most important way to reduce the costs.

In this thesis, experiments and modelling were used to evaluate how different operating conditions and adsorbent parameters affect the performance of the amine-functionalized adsorbents. The experiments investigated the CO2 adsorption and desorption capacities of the adsorbent, while the modelling utilized a dynamic CO2 adsorption model to simulate CO2 productivity and SER in a fixed adsorbent bed.

It was noticed that humidity may even double the CO2 adsorption capacity, but the co-adsorbed H2O increased the SER in regeneration. Increasing the regeneration temperature, on the other hand, accelerated the regeneration and thus improved CO2 productivity. Both CO2 productivity and SER could also be improved by optimizing the cycle duration. Among the adsorbent properties, the most significant in terms of CO2 productivity and SER were cyclic stability, maximum capacity and kinetic parameters.