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 prepare d 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 m easured. The results of isosteric heat of adsorption of CO2 indicated that both FSM-10 and FSM-12 were energetically homogeneous adsorbents for adsorp tion of CO2. On the other hand, both FSM-14 and FSM-16 had energetically di fferent adsorption sites. The number of energetically higher adsorption sit es of FSM-14 was fewer than that of FSM-16. The results of the IR spectra f or free silanol groups of FSM-14 and FSM-16 were compatible with the result s for isosteric heat of adsorption. The amount of CO2 adsorbed on FSM-14 an d 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 p ressure from 0.4 to 0.5 MPa.