Breakthrough measurements of CO2 through aminofunctionalised aerogel adsorbent at low partial pressure: Experiment and modeling

•Adsorption kinetics of CO2 and aminofunctionalised aerogels researched.•Two aminosilanes used for silica aerogel functionalisation and adsorbent generation.•Aminofunctionalised aerogels exhibit low isosteric heat of adsorption.•Description of breakthrough behavior by isothermal dispersed plug flow model.•Fast adsorption kinetics for aminofunctionalised aerogel particles.

Designing adsorbers for the CO2 removal from enclosed inhabited spaces demands the utilization of tailor made adsorbents and the determination of adsorption kinetics. As shown in previous studies aminofunctionalised aerogels are well suited for CO2 adsorption at low partial pressure due to their high CO2 adsorption capacity at low partial pressures in moist conditions and their ease of regeneration. To gain further insight into the adsorption kinetics of aminofunctionalised aerogels several breakthrough experiments were conducted in this work. An isothermal dispersed plug flow model using pore diffusion to describe the mass transport in the solid phase was applied to describe the breakthrough of the CO2 through the aerogel adsorbent. The aminofunctionalised aerogels exhibited a low heat of adsorption and consequentially a mild temperature increase during the adsorption process. Determination of bulk density was conducted by the measuring of the skeletal density and the specific pore volume of aminofunctionalised aerogel microparticles, a method showing good agreement with conventional bulk density determination for aerogel monoliths. From modeling the breakthrough experiments a pore diffusion coefficient of 3.4 × 10−6 m2/s could be established for both M-APTMS and T-APTMS functionalised aerogels. The established tortuosity was 3.8 for the M-APTMS and 3.7 for the T-APTMS functionalised aerogel. Using the pore diffusion constant the model was able to describe the breakthrough through the aerogel adsorbers of different lengths and at various flow speeds in dry and moist conditions. The established diffusion coefficient suggests that aminofunctionalised aerogels exhibit fast mass transport kinetics rendering them suitable as adsorbents for CO2 removal from enclosed inhabited environments.

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