Vanadium-containing nickel phosphate molecular sieves as catalysts for α-pinene oxidation with molecular oxygen: A study of the effect of vanadium content on activity and selectivity

Vanadium-containing nickel phosphate molecular sieves (V-VSB-5) were applied as heterogeneous catalysts for the liquid phase oxidation of α-pinene with molecular oxygen at 60 °C. It has been found that the vanadium content in V-VSB-5 materials affects the conversion of α-pinene and product distribution. The conversion of α-pinene increases with increasing of V content. The major products were α-pinene oxide, verbenol and verbenone. Acid-base properties of V-VSB-5 affect the distribution of by-products formed via the isomerization of α-pinene oxide over Lewis acid sites and Brönsted acid sites to campholenic aldehyde and trans-carveol. The increase in V content in V-VSB-5 leads to the increase in isomerization of α-pinene oxide to trans-carveol and decrease in that to campholenic aldehyde.