Kinetic study of α-pinene allylic oxidation over FePcCl16-NH2-SiO2 catalyst

The kinetic of alpha-pinene oxidation over an iron hexadecachlorinated phthalocyanine immobilized on modified silica (FePcCl16-NH2-SiO2) with t-butyl hydroperoxide (TBHP) as oxidant is proposed. Reaction rates were calculated by the initial reaction rate method from the data obtained in a batch reactor, and compared with kinetic expressions proposed from mechanisms based on Langmuir Hinshelwood Hougen Watson (LHHW) and power-rate law models. The kinetic parameters were estimated from the experimental data by optimization using the Genetic Algorithm. A kinetic expression based on LHHW model with the adsorption of alpha-pinene, TBHP and the main reaction products (verbenone, alpha-pinene epoxide and verbenol) on the surface of the catalyst predicted the experimental data with good accuracy (R-2 =0.986). The apparent activation energy of alpha-pinene allylic oxidation over FePcCl16-NH2-SiO2/TBHP was 40.08 kJ/mol. alpha-Pinene conversion of 83.7% was obtained after 23 h with a selectivity to verbenone of 23%. Under the reaction conditions leaching of the active species was not observed; however, the effect of radicals in the bulk liquid phase was demonstrated, confirming that the reaction involves a combination of both heterogeneous and homogeneous pathways. The catalyst can be used at least in seven cycles without loss of alpha-pinene conversion nor verbenone selectivity. (C) 2016 Elsevier B.V. All rights reserved.