Equilibrium and kinetics analysis of carbon dioxide capture using immobilized amine on a mesoporous silica

Thermogravimetric analysis is used to study the adsorption kinetics, equilibrium, and thermodynamics of CO2 on immobilized polyethylenimine sorbent impregnated on a mesoporous silica over the range of 300-390 K and 5-100% CO2 concentration. Adsorption isotherm models were fitted to the experimental data indicating that a change in adsorption mechanism occurred near 70 degrees C. Below this temperature, the adsorption data followed the heterogeneous isotherms, while data taken at higher-temperatures followed isotherms for homogeneous surfaces. Heat of sorption was estimated to be 130 kJ/mole for the low-temperature regime, but this decreased to 48 kJ/mole above 70 degrees C. The rate of CO2 fractional uptake decreased as temperature increased. A phenomenological kinetic model was derived from the Weibull distribution function using a nucleation growth theory to describe the two-step process. The kinetic model was used to predict the uptake at different operating conditions and resulted in good agreement with experimental data. Published 2012 American Institute of Chemical Engineers AIChE J, 59: 923-935, 2013