Modeling adsorption of CO2 on amine-functionalized mesoporous silica. 2: Kinetics and breakthrough curves

The adsorption kinetics of CO2 on amine-functionalized mesoporous silica at low concentrations was investigated. Experimental data of CO2 uptake as a function of time at temperatures between 25 and 70 °C were fit to a series of kinetic models, namely Lagergen's pseudo-first and pseudo-second order and Avrami's kinetic models. The best fit was obtained using Avrami's model, as it provided a fractional reaction order (ca. 1.4), which has been associated with the occurrence of multiple adsorption pathways. In addition, simulations of CO2 adsorption in a column packed with amine-grafted mesoporous silica using computational fluid dynamics were carried out to predict breakthrough curves. The simulation results were compared to experimental data produced at various flow rates of a stream containing 5% CO2 balance nitrogen. In all cases, the predicted breakthrough time and the corresponding CO2 uptake were in close agreement with the experimental data.