A comparative study of CO2 capture by amine grafted vs amine impregnated zeolite 4A

Abstract

Zeolite 4A was functionalized via grafting and impregnation techniques using 0.3 wt% of isopropylamine (IPA) and (3-aminopropyl) trimethoxysilane (APTMS) respectively. Physicochemical properties of zeolite 4A containing binder were changed after amine loading, as both specific surface area and pore volume was decreased by 1.52 % 18.18 % and 28.06 % 90.90 % for Z4A-IPA (IPA impregnated zeolite 4A) and Z4A-APTMS (APTMS grafted zeolite 4A) respectively. The adsorbed CO2 amount of Z4A, Z4A-IPA, and Z4A-APTMS were 1.58 mmol g-1 (6.95 wt%), 2.31 mmol g-1 (10.16 wt%) and 1.05 mmol g-1 (4.62 wt%) respectively at 1 bar and 25 °C. Noticeably, among all the studied adsorbents, Z4A-IPA displayed the highest adsorption capacity of 1.39 mmol g-1 (6.11 wt%) at 0.15 bar, which is akin to the CO2 partial pressure of post-combustion flue gas. The multilayer tethering of the bulkier APTMS on the zeolite external surface resulted in the partial blockage of the pores and hence the facile access of CO2 inside the pores of zeolite was hindered. However, Z4A-APTMS was found to be more thermal stable than Z4A-IPA. Furthermore, we observed that physisorption was playing a vital role in CO2 adsorption for pristine zeolite 4A (Z4A), whereas, after amine incorporation, the presence of amine induced the heterogeneous interaction between CO2 and sorbents.