Conversion of limonene to limonene diol over activated carbon supported Ti catalyst

Abstract

A series of activated carbon supported Ti-3,3′-ethylen bis(3,4-dihydro-2H-1,3-benzoxazine) complex catalysts (denoted Ti-Bz (0.25)/AC, Ti-Bz(0.37)/AC, and Ti-Bz (0.5)/AC) was evaluated in the conversion of limonene to limonene diol using H2O2 as oxidant. The opening of oxazine ring as a step to the titanium complex formation was highlighted, as far as we are aware, for the first time, by NMR analysis. A range of characterization methods, including SEM–EDS, nitrogen physisorption, ATR-FTIR, and XRD, showed that the procedure used in the preparation of these materials was reproducible. Parameters affecting the catalytic performances in the production of limonene diol, such as reaction temperature, amount of catalyst tested, and its catalytic stability, were studied. Ti-Bz (0.5)/AC was the most performant catalyst leading to limonene diol yield of 36.7%. The recyclability of the catalyst was evaluated along three catalytic consecutive tests that showed no significant difference of performance compared with that of fresh catalyst.