The application of TS-1 materials with different titanium contents as catalysts for the autoxidation of α-pinene

Titanium-silicalite TS-1 catalysts with different titanium contents were synthesized by the hydrothermal method and characterized by means of the FTIR, UV-Vis, XRD, XRF, and SEM techniques. The studies showed that in the tested reaction system the process of isomerization of alpha-pinene over these TS-1 catalysts did not occur; however, the self-oxidation of alpha-pinene did proceed. The main directions of autoxidation of alpha-pinene were the double-bond oxidation and the oxidations at allylic positions 2 and 10. This work presents the explanation of the mechanism of the alpha-pinene self-oxidation process. In addition, isomerization and hydration products of alpha-pinene oxide were formed. It was found that the optimal condition for the production of the oxide is to perform the autoxidation process at the temperature of 80 degrees C for the TS-1 20:1 catalyst (content 1 wt%), and at the reaction time of 24 h. Under these conditions, the selectivity of alpha-pinene oxide was 30.25 mol%, and the conversion of alpha-pinene reached 41.81 mol%. In addition to the production of alpha-pinene oxide, verbenol, verbenone, and campholenic aldehyde can also be obtained, which are products that can find valuable applications in the cosmetics industry, in medicine, and in the production of various polymers.