Abstract
To modify the adsorption characteristics of the mesoporous silica FSM-16, Al-incorporated FSM-16 (Al-FSM-16) and trimethylsilylated FSM-16 (TMS-FSM-16) were prepared. The pore structureand the adsorption characteristics of these modified mesoporous materials were examined by usingprobe molecules of N2 and CO2. BET surface area of Al-FSM-16 was reduced to 470 m2·g-1, about one-half of the surface area of FSM-16. However, the separation factor for CO2 from CO2-N2 gas mixtures (CO2/N2=20.1/79.9) on Al-FSM-16 was higher than on FSM-16 in the total pressure range from 0.2 to 0.3 MPa. This implies that CO2 is adsorbed selectively to Na+, which is present to compensate for thenegative charge generated by incorporating Al in the framework of the mesoporous silicas. By trimethyl-silylation of FSM-16, 82% of the surface area was covered with trimethylsilyl (TMS) groups, and thepore size decreased to 2.3 nm from the 2.8 nm of FSM-16. Much less CO2 was adsorbed on TMS-FSM-16 than that on FSM-16, possibly due to the smaller amount of free SiOH groups of TMS-FSM-16.
