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

SUMMARY

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.