Adsorption of CO2 on FSM-type mesoporous silicas

Abstract

FSM-type mesoporous silicas with different pore sizes (FSM-10 with 1.7 nm, FSM-12 with 2.1 nm, FSM-14 with 2.3 nm and FSM-16 with 2.8 nm) were prepared and studied to use as adsorbents for CO₂. The amount of adsorbed CO₂ and the IR spectra of surface silanol groups of FSM after CO₂ adsorption were measured. The results of isosteric heat of adsorption of CO₂ indicated that both FSM-10 and FSM-12 were energetically homogeneous adsorbents for adsorption of CO₂. On the other hand, both FSM-14 and FSM-16 had energetically different adsorption sites. The number of energetically higher adsorption sites of FSM-14 was fewer than that of FSM-16. The results of the IR spectra for free silanol groups of FSM-14 and FSM-16 were compatible with the results for isosteric heat of adsorption. The amount of CO₂ adsorbed on FSM-14 and FSM-16, except for FSM-12, from CO₂–N₂ gas mixtures (CO₂/N₂=20.1/79.9) as capillary condensation increased rapidly with an increase in the total pressure from 0.4 to 0.5 MPa.