Chemoselective isomerization of α-Pinene oxide to trans-Carveol by robust and mild Brønsted acidic zirconium phosphate catalyst

Abstract

The current study focuses on the synthesis of an inexpensive, efficient, and cost-effective zirconium phosphate (ZrP) and its application in the one-step catalytic valorization of biomass-derived α-Pinene oxide (APO) into trans-Carveol (TC), which is used in the fragrance industry to produce essence oil. Amorphous zirconium phosphate (ZrP) with different P/Zr molar ratios (0.6–2.4) were synthesized using a simple (refluxing) method by controlling the concentration of dopant. The presence of phosphate groups was confirmed by FTIR and XPS analysis. The phosphate functionality provides the Brønsted acidic nature, and the acidity of the catalyst (ZrP3) is 0.9 mmol/g as measured by NH3-TPD analysis. Under optimized reaction conditions, the synthesized Brønsted acid catalyst (ZrP3) was used to valorize APO, resulting in complete conversion with 76% selectivity towards TC. The catalyst was recovered, activated, and reused numerous times with slight loss of activity or selectivity.