Adsorption of carbon dioxide on solid amine-functionalized sorbents: A dual kinetic model

Developing efficient technologies for carbon capture is one of the biggest challenges of the future. Therefor, adsorption-based processes are considered to be very promising methods and amine-functionalized solid sorbents emerge as the most suitable materials for this task. To judge the techno-economic viability of such new materials, the investigation of process performance is necessary. Yet accurate but simple models representing the thermodynamic and kinetic properties of these materials are still lacking. For instance, the kinetics of CO2 adsorption on amine-functionalized sorbents are still widely discussed. Common pseudo-first-order and pseudo-second-order models cannot describe the corresponding adsorption kinetics accurately. In comparison, Avrami's kinetic model and the generalized fractional-order kinetic model are more suitable to describe experimental data. Unfortunately, for these models the adsorption kinetics are a power function of the adsorption time. But, the fitted parameters of Avrami's kinetic model and the generalized fractional-order kinetic model often depend on the specific operation conditions, e.g. CO2 mole fraction or temperature, and any reasonable correlation between the operation conditions and adsorption parameters can be derived. Furthermore, the time dependence makes the models unsuitable for the simulation of dynamic and periodic processes such as temperature swing adsorption. Too overcome these severe limitations, we present a dual kinetic model (DKM). We show that the model can describe the adsorption and desorption kinetics for different amine-functionalized materials surprisingly well, even more accurately than time-dependent adsorption models. This new model can now be easily incorporated into dynamic swing adsorption simulations to investigate new carbon capture processes.