Quantification of temperature-dependent CO2 adsorption kinetics in Lewatit VP OC 1065, Purolite A110, and TIFSIX-3-Ni for direct air capture

Abstract

One of the critical factors affecting the performance of an adsorption-based direct air capture (DAC) process is the CO₂ adsorption kinetics. Yet, this data is not currently available in the literature for many DAC adsorbents, particularly at the relevant conditions for DAC (i.e. ∼ 0.04 %_vol or 400 ppm). In this study, we report temperature-dependent linear driving force constants (k_LDF(T)) measured at 400 ppm CO₂ between 20 °C and 70 °C for three promising DAC adsorbents: Lewatit VP OC 1065, Purolite A110, and TIFSIX-3-Ni. The experimental data was fitted using maximum likelihood estimation (MLE) to determine the k_LDF(T) constants with the experimental standard deviation also presented as a fitted parameter, as it was not possible to fully characterise the experimental uncertainty otherwise. TIFSIX-3-Ni exhibits the fastest adsorption kinetics across the whole temperature range, while Purolite A110 has faster adsorption kinetics compared to Lewatit VP OC 1065 at temperatures greater than 40 °C. Overall, the k_LDF(T) values determined in this work can be used for initial process scale modelling to assess the process performance of these adsorbents for DAC, while future work is required to ascertain the controlling diffusion mechanisms, and reaction kinetics, over a wide range of conditions.