Metal ion-exchanged zeolites as solid acid catalysts for the green synthesis of nopol from Prins reaction

Abstract

The application of metal ion-exchanged zeolites as highly active and selective catalysts for the synthesis of nopol from the Prins reaction of β-pinene is reported. The catalysts were prepared by an ion-exchange method and characterized by XRD, pyridine-FT-IR, AAS, NH₃-TPD and SEM. The Zn-beta catalyst showed the best performance among the different types of zeolites. The acidity of the Zn-beta zeolite was correlated with the amount of zinc and activity of the reaction. For different metal ion-exchanged beta catalysts, the yield of nopol increased with a decrease in Brönsted to Lewis acidity (B/L) ratio. The influence of solvent on the Prins reaction in terms of acceptor and donor number was investigated. The degree of Zn loading, amount of solvent, temperature, catalyst amount, mole ratio and recyclability of the catalyst were investigated.