Thermal stability and hydrophobicity of mesoporous silica FSM-16

Thermal stability and hydrophobic property of mesoporous silica, FSM-16, has been studied. The mesoporous structure of FSM-16 was stable against calcination up to 1073 K in vacuo, but collapsed at 1273 K. Adsorption isotherm and differential heat of adsorption measurements showed that the calcination temperature affected the hydrophobic nature of FSM-16, and that the surface changed to hydrophilic by hydroxylation of surface siloxane during water adsorption. Once the surface became hydrophilic, the hydrophobic character was never restored even after evacuation at 823 K.