The studies on the limonene oxidation over the microporous TS-1 catalyst

•Studies on the oxidation of limonene were performed.•In the oxidation hydrogen peroxide, methanol as a solvent and TS-1 were used.•The most beneficial conditions 1,2-epoxylimonene obtaining were determined.•The main reactions proceed during the process were established.•The proposed method is ecologically friendly and it needs mild conditions.

The studies on the oxidation of limonene with 60 wt% hydrogen peroxide over the titanium silicalite TS-1 catalyst were carried out. The influence of the following parameters was examined: the temperature 0–120 °C, the molar ratio of limonene/H2O2 = 1:2–5:1, methanol concentration 60–95 wt%, TS-1 content 0.25–8 wt% and the reaction time 15 min to 11 days. The studies showed that the most beneficial conditions for the obtaining of high selectivity of 1,2-epoxylimonene, at simultaneously high values of the conversion of reactants and the efficiency of hydrogen peroxide, are as follows: the temperature 80 °C, the molar ratio of limonene/H2O2 = 1:1, the methanol concentration 80 wt%, the TS-1 content 3 wt% and the reaction time 10 days. Moreover, the research showed that the process of limonene oxidation is very complicated, because during this process also other very useful oxygenated derivatives of limonene can be obtained, for example: perillyl alcohol, carveol, carvone and 1,2-epoxylimonene diol. The studies on the reuse of the TS-1 catalyst showed that it is very stable catalyst at the studied conditions and it can be recycled to the oxidation process at least three times.

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