Epoxidation of β-pinene with a highly-active and low-cost catalyst

As β-pinene is one of the main compounds of turpentine oil, its epoxidation is of academic and industrial interest. In the present work, the activity of a low-cost calcium material and magnesium oxide was compared with that of hydrotalcites for the catalytic epoxidation of β-pinene. FTIR, XRD, nitrogen adsorption/desorption isotherms, BET and TPD-CO2 analyses were used for identifying the influence of basicity and textural properties of the materials on β-pinene epoxidation. Materials with medium-strength basic sites showed the highest activity; a complete conversion of β-pinene and 74% selectivity towards β-pinene epoxide was reached over magnesium oxide. A mechanism for this reaction over magnesium oxide is proposed based on the deprotonation and hydration of the catalyst, which favored the formation of an intermediate oxidant and the activation of the substrate. Purification of the reaction product by filtration, liquid–liquid extraction, drying and simple distillation leads to a final β-pinene epoxide concentration higher than 90% wt; the stability of the epoxide was verified by measuring its composition during 20 days.