Investigation the effects of Al-grafting and calcination temperature on acidity and physicochemical properties of silica SBA-15

Abstract

In this study, the effect of calcination temperature and Si/Al mole ratio on acidity and physicochemical properties of silica SBA-15 were investigated. Silica SBA-15 samples were calcined at 350, 450 and 550?C, and then post-synthesis, the Al-grafting method was applied to incorporate aluminum species into their framework with Si/Al mole ratio of 10 and 30. Characterizations using small angle XRD and N2 adsorption?desorption techniques indicated that the hexagonal mesoporous structure was retained after performing Al-grafting even at the high aluminum loading. Moreover, FTIR results implied that the aluminum species were incorporated into the SBA-15 framework. NH3-TPD results showed that by decreasing Si/Al mole ratio at all calcination temperatures, the number of weak acid sites increased in comparison to those of the pure SBA-15 samples. Additionally, the maximum total acidity of synthesized samples was observed at the calcination temperature of 450?C with Si/Al mole ratio of 30.