Carbon Dioxide Adsorption on Amine-Impregnated Mesoporous SBA-15 Sorbents: Experimental and Kinetics Study

Abstract

In this work, an experimental and theoretical investigation was conducted on the adsorptive removal of CO2 onto tetraethylenepentamine (TEPA) functionalized mesoporous SBA-15. The functionalization of SBA-15 silica with TEPA was achieved using a conventional wet impregnation technique. The structural properties of the mesoporous silica sorbents were characterized by nitrogen adsorption/desorption, SAXS, SEM, TEM, and FTIR techniques. The adsorption of CO2 on the amine-impregnated sorbent was measured by thermogravimetric method over a CO2 partial pressure range of 10–100 kPa and a temperature range of 30–100 °C under atmospheric pressure. The effects on CO2 adsorption capacity of temperature, partial pressure of CO2, amine loading, and moisture were evaluated. All the impregnated SBA-15 sorbents showed reversible CO2 adsorption behaviors with fast adsorption kinetics. The CO2 adsorption capacity measured at different temperatures suggests that the optimal adsorption temperature is 75 °C. The CO2 uptake of the amine-impregnated sorbent increased significantly in the presence of moisture. SBA-15 containing 60 wt % TEPA showed the highest CO2 adsorption capacity of 5.22 mmol/g in pure and humid CO2 at 75 °C. Temperature swing adsorption/desorption cycles were also explored using simulated flue gas in both dry and humid conditions, and it was found that CO2 uptake after ten cycles was within 90% of CO2 uptake of the first cycle. Different adsorption kinetic models have also been investigated to analyze the experimental data of CO2 uptake. The model was validated with the experimental results of isothermal adsorption measurements of CO2 on SBA-15/TEPA. It has been found that Fractional Order kinetic model (Chem. Eng. J.2011, 173, 72) is very good over the entire adsorption region of the study with a maximum average absolute deviation between experimental CO2 uptake and that calculated from the model of about 2.42%.