Supported Co-Based Catalytic Systems for the Epoxidation of Terpenes Using O2 as Oxidant

We synthesized and characterized a range of cobalt-based catalyts supported on mesoporous silica (SBA-15 and SBA-16), commercial silica and functionalized carbon nanotubes (CNT), investigated their efficiency in the aerobic epoxidation of terpenes, specifically limonene and α-pinene. Cobalt deposition was achieved by impregnation with cobalt(II) acetylacetonate and the resulting systems were characterized by XPS, ICP-OES, N₂ adsorption-desorption, TEM, STEM-HAADF and EDX. Variations in pore structure, cobalt dispersion, and oxidation states depending on the support used were observed. Catalytic tests demonstrated that Co/SBA-15 (1.6 % Co) exhibited superior catalytic activity in the oxidation of limonene compared to Co/SBA-16, Co/SiO₂c, and Co/CNT, achieving 90 % conversion with a 68 % selectivity towards 1,2-limonene oxide. In contrast, for α-pinene oxidation, Co/SBA-15 showed lower activity, while other catalysts achieved full conversion. The study also explored the effect of cobalt loading on catalytic performance, indicating that higher loadings generally led to rapid catalyst deactivation due to the formation of larger cobalt oxide particles. The findings underscore the critical role of support structure and cobalt dispersion in enhancing catalytic efficiency for terpene epoxidation. Additionally, we demonstrated the potential for 3 recycling and scale up to the gram level while maintaining high activity and selectivity.