Alpha-pinene isomerization over Ti-SBA-15 catalysts obtained by the direct method: The influence of titanium content, temperature, catalyst amount and reaction time

Abstract

This work presents the studies on the isomerization of alpha-pinene in the presence of Ti-SBA-15 catalysts with different titanium contents: 0.75, 0.90, 1.10, and 3.10 wt%, as established by the EDX method, and 0.60, 0.76, 1.08, and 2.53 wt%, as measured by the ICP-AES method. These catalysts were prepared by the hydrothermal method and were characterized by the followed instrumental techniques: XRD, UV-Vis, FT-IR, SEM, ICP-AES, EDX, TEM, and AFM. Additionally, textural parameters were determined by N2 adsorption/desorption. Preliminary studies showed that the most active catalyst was the material prepared from the crystallization gel with the molar ratio of Si:Ti = 20:1. This catalyst was further used for the detailed studies on α-pinene isomerization according to the following parameters: temperature range of 20–200 °C, 0.5–20 wt% catalyst content, and reaction times from 15 min to 24 h. The optimal conditions for α-pinene isomerization were determined on the basis of its conversion and the selectivity of the produced camphene. This study also showed that the process of α-pinene isomerization is complex because subsequent reactions occurred during the process.