Non-ionic surfactant (C13EOm, m = 6, 12 and 18) for large pore mesoporous molecular sieves preparation

Polyoxyethylene tridecylethers (C13EOm, m = 6, 12 and 18) have been used as templating agents for synthesis of large pore mesoporous materials. The effect of surfactant/silicium molar ratio, heating time, and temperature, and the number of oxpethylene units on the mesoporous material syntheses has been studied in detail. Final compounds were characterized by different techniques such as SEM, TEM and nitrogen adsorption-desorption analysis. The present work shows that the surfactant/tetramethoxysilane molar ratio has a strong effect on the pore diameter for a given surfactant. It is evidenced that both tetramethoxysilane (TMOS) and surfactant can play a role of swelling agent depending on the surfactant/TMOS molar ratio. It is also shown that the pore diameter depends strongly on the heating time and temperature, oxyethylene unit number and surfactant/TMOS molar ratio. All these factors can affect jointly or separately the pore diameter of obtained materials. It is revealed that the surfactant conformation can be changed with the heating temperature. At higher temperature, a more extended molecular conformation can be obtained, which leads to materials with larger pore size. (C) 2001 Elsevier Science B.V. All rights reserved.