Modeling CO2 adsorption dynamics within solid amine sorbent based on the fundamental diffusion-reaction processes.

Graphical abstract Highlights • An adsorption model based on realistic diffusion-reaction processes was proposed. • The model consists of three fundamental adsorption steps at different length scales. • The bulk of the sorbent captured CO 2 simultaneously without adsorption front. • Chemical reaction step dominates the whole adsorption process. • This work provides a benchmark to evaluate the simplified adsorption models. Abstract A rigorous dynamic adsorption model, considering the realistic diffusion-reaction processes of CO 2 adsorption onto the amine functionalized mesoporous silica, was proposed in this work. Three fundamental adsorption steps at different length scales were took into account in model development and a numerical algorithm was developed to solve the coupled partial differential equations of the multi-scale model. TGA (Thermal Gravity Analysis) experiments at different temperatures and CO 2 partial pressures were conducted to acquire the dynamic adsorption curves for model fitting and validation. The simulation results based on the proposed model agreed well with the experimental data under all conditions. Through the developed model, the species distribution, mass transfer phenomena and reaction mechanisms at different scales within the sorbent were quantitatively predicted. The results indicated that the bulk of the sorbent captured CO 2 simultaneously, and no adsorption front was observed. After the very early stage, the whole sorbent reacted with CO 2 uniformly. Further mass transfer resistance analysis showed that chemical reaction was the rate-limiting step, and CO 2 diffusion in the amine layer would play an important role in the later stage of adsorption, especially at high temperatures or high CO 2 partial pressures. These findings provided a quantitative insight into dynamic evolution of CO 2 adsorption within the sorbent particle, which would guide the design of sorbents with optimal pore features and amine loadings. [ABSTRACT FROM AUTHOR]