Adsorption of CO2 on FSM-type mesoporous silicas

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-N-2 gas mixtures (CO2/N-2=20.1/79.9) as capillary condensation increased rapidly with an increase in the total pressure from 0.4 to 0.5 MPa.