Several factors affecting Al-MCM-41 synthesis

Abstract

Several mesoporous aluminosilicate molecular sieves with the MCM-41 structure (Si/Al=24) have been synthesized using different aluminum and silica sources and varying several synthesis parameters during the preparation process such as the use of an anti-foaming agent, prior aging of the gel mixture or pH adjustment of the gel mixture under basic conditions followed by autoclaving three times. All samples were characterized by X-ray diffraction (XRD), N 2 physisorption, TGA, 27 Al MAS NMR and elemental analysis. There is a significant improvement in the structure by using an anti-foaming agent before adding the surfactant, by aging the mixture of silica and aluminum source prior to synthesis, and by using δ-alumina instead of PHF alumina. Also, when the sample is synthesized, alternating the pH adjustment and autoclaving three times in sequence, well-resolved XRD peaks are obtained. These Al-MCM-41 materials have BET areas around 1000 m 2/g but the amount of tetrahedral coordinated Al, on the whole, is low.