Influence of the titanium content in the Ti-MCM-41 catalyst on the course of the α-pinene isomerization process

Abstract

Titanium-containing mesoporous silica catalysts with different Ti contents were prepared by the sol–gel method, whereby the molar ratios of silicon to titanium in the crystallization gel amounted to, respectively, 40:1, 30:1, 20:1 and 10:1. The produced Ti-MCM-41 materials were characterized by the following instrumental methods: XRD, UV-Vis, FT-IR, SEM, and XRF. Textural parameters were also determined for these materials by means of the N2 adsorption/desorption method. The activities of these catalysts were investigated in the α-pinene isomerization process. The most active catalyst was found to be the material with the molar ratio of Si:Ti equal to 10:1, which contained 12.09 wt% Ti. This catalyst was used in the extended studies on the α-pinene isomerization process, and the most favorable conditions for this reaction were found to be temperature of 160 °C, reaction time of 7 h, with the catalyst composition of 7.5 wt% relative to α-pinene. These studies showed that the most active catalyst, at the best reaction conditions, allowed for the attainment of 100% conversion of α-pinene over a period of 7 h. After this time the selectivities (in mol%) of the main products were as follows: Camphene (35.45) and limonene (21.32). Moreover, other products with lower selectivities were formed: γ-terpinene (4.38), α-terpinene (8.12), terpinolene (11.16), p-cymene (6.61), and α-phellandrene (1.58).