Acetoxylation and hydration of limonene and α-pinene using cation-exchanged zeolite beta

Hydration and acetoxylation of limonene and α-pinene into terpineol and terpinyl acetate in the liquid phase have been studied using transition metal and rare earth ion-exchanged beta zeolite. These catalysts under optimized reaction conditions showed higher activity and selectivity compared to conventionally used acid catalysts such as H2SO4 and amberlyst-15. Conversions of 9–26% and 58–82% were obtained for limonene the in presence of glacial and aqueous acetic acid, respectively, and the selectivity for major products α-terpinyl acetate and terpineol were up to 54% and 65%, respectively. Conversion values in the range of 62–100% and 72–100% were obtained for α-pinene in the presence of glacial and aqueous acetic acid, respectively. Virtually no oligomerisation of monoterpenes occurred under studied conditions. From the measured acidity data of these zeolites, it is observed that both hydration and acetoxylation are Brönsted acid-catalysed reactions.

Graphical abstractHydration and acetoxylation of limonene and α-pinene into terpineol and terpinyl acetate in the liquid phase have been studied using transition metal and rare earth ion-exchanged beta zeolite. Conversions of 9–26% and 58–82% were obtained for limonene in presence of glacial and aqueous acetic acid, respectively, and the selectivity for major products α-terpinyl acetate and terpineol were up to 54% and 65%, respectively. Conversion values in the range of 62–100% and 72–100% were obtained for α-pinene in the presence of glacial and aqueous acetic acid, respectively. Figure optionsDownload full-size imageDownload as PowerPoint slide