| Abstract
| - The hydrophobicity of the mesoporous FSM-16 surface was studied by measurements of adsorptionisotherms and heats of adsorption of water at 298 K. The hydrophobic−hydrophilic change on the surfacederived by water adsorption was also studied. The water adsorption isotherm of freshly prepared FSM-16was of type V and the initial heat of adsorption of water was ca. 20 kJ/mol, which is indicative of weakadsorbent−adsorbate interactions of a hydrophobic character. However, once water was adsorbed thewater adsorptivity increased at a lower relative pressure region and the initial heat of adsorption increasedto 75 kJ/mol. The surface became hydrophilic to a small extent, and the original hydrophobic behavior wasnever restored even after evacuation at high temperatures, 573 and 823 K. An in situ IR analysis revealedthat silanol groups were formed and some of them remained after reevacuation at high temperatures oncewater had been adsorbed on the freshly calcined FSM-16.
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