Abstract:
Silatrane synthesized from inexpensive precursors, silica and TEA, was used as the precursor for MCM-41 synthesis at low temperature because of its stability in aqueous solutions. Using cationic surfactant cetyltimethyl ammonium bromide (CTAB) as a template, the resulting meso-structure mimics the liquid crystal phase. Varying the surfactant concentration, ion concentration and temperature of the system, changes the structure of the liquid crystal phase, resulting in different pore structures and surface area. After heat treatment, very high surface area mesoporous silica was obtained and characterized using XRD, BET and TEM. XRD and TEM results show a clear picture of hexagonal structure. The surface area is extraordinarily high, up to more than 2400 m²/g while the pore volume is as high as 1.72 cc/g. A series of mesoporous vanadosilicate B-MCM-41 molecular sieves with various vanadium concentrations was investigated by XRD, DR-UV and TPR. XRD and DR-UV show that the solid products have the MCM-41 structure and dispersed on the wall of MCM-41 in the state of monomeric tetrahedral coordination. TPR profiles of V-MCM exhibit only a single reduction peak at temperature range 500 ̊-570℃. It is suggested that the reduction peak is due to the reduction of surface vanadia, which has been ascribed to the tetrahedral coordination of the V ions.
