Zinc-exchanged phosphotungstic acid as catalysts for the addition-esterification of 1-hexene

The addition-esterification reaction of fatty acids and alkenes is an important method for replacing the FischerSpeier esterification due to its 100 % atomic utilization. In this study, sec-hexyl acetate was synthesized through the addition-esterification of 1-hexene. At the same time, five different zinc -exchanged phosphotungstic acid catalysts were prepared using the ion exchange method, and their catalytic activities in the additionesterification were tested and compared. Results indicate that the Zn0.5H2.0PW-I catalyst exhibits the best performance in six different catalysts, which is attributed to the synergistic effect of Bro center dot nsted and Lewis acids. The activity of catalysts is determined by the equilibrium relationship between Bro center dot nsted and Lewis acidity. In the addition-esterification of alkenes, the main activity center is the Bro center dot nsted acid site, while the Lewis acid site can improve the adsorption capacity of the catalyst for acetic acid molecules. Moreover, the preparation methods have a significant impact on the activity of catalysts. In addition, the in -situ FT-IR spectrum experiment confirms that the reaction rate of alkene isomerization is greater than that of addition-esterification, and a higher temperature is not conducive to the generation of acetate.