Highly efficient trans–cis isomerization of lycopene catalyzed by iodine-doped TiO2 nanoparticles

Abstract

Highly efficient trans–cis isomerization of lycopene was achieved in the presence of a novel iodine-doped titanium dioxide (I-TiO₂) catalyst. The catalyst was prepared via a hydrothermal route and subsequent vacuum calcination and was characterized with thermogravimetric analysis, X-ray diffraction, nitrogen adsorption–desorption isotherms, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy techniques. Factors that affected the reaction parameters, such as the reaction temperature, the concentration of substrate, the weight of the catalyst and the reaction time, were investigated in detail. Application tests showed that the catalyst was highly active in the isomerization of lycopene in a heterogeneous reaction, and the conversion of all-trans-lycopene exceeded 80% after 2 h of reaction at 75 °C in ethyl acetate. Moreover, the catalyst displayed no significant loss of activity after five cycles of reuse.