Esterification of octanoic acid using SiO2 doped sulfated aluminum-based solid acid as catalyst

• We reported a new solid acid of SO42 −/Al2O3-SiO2.
• SiO2 as additive improved the acid conversion and methyl octanoate yield.
• The optimal acid conversion and methyl octanoate yield were 99.11% and 99.07%.
• SAS-5 could be recycled for nine times with considerable esterification activity.

In this paper, SO42 −/Al2O3-SiO2 (SAS) was prepared and used for the esterification of octanoic acid with methanol. The effect of introduction of SiO2 was characterized by nitrogen sorption, ICP-AES, XRD, NH3-TPD, TG, FTIR and FTIR-pyridine adsorption. The results demonstrated that the doping of SiO2 resulted in the increase of BET surface areas and amount of surface sulfur species which led to an increase of acid sites especially Brönsted acid sites, which consequently boosted the catalytic esterification activity. In addition, the introduction of SiO2 can also increase the thermal stability of SO42 − and its interaction with Al2O3 support which resulted in the alleviation of catalyst deactivation.

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