Characterization and catalytic activity of Co/Mo-modified activated carbons derived from orange peels in limonene oxidation

The possibility of using orange peels for the preparation of porous activated carbons by the chemical activation with H₃PO₄ and the application of the obtained carbonaceous materials as the metal catalyst supports was investigated. Activated carbon and carbon-metal materials were used as the limonene oxidation catalysts. The materials were characterized by the following instrumental methods: the sorption of N2 at-196 °C, XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy) and SEM (Scanning Electron Microscope), XPS (The X-ray photoelectron spectroscopy). XRF (X-ray Fluorescence) analyses were applied to determine the elemental (Co, Mo) content in the studied samples activated carbons. The activity of the obtained catalysts was tested in the oxidation of limonene to limonene oxide (the main product), carveol, carvone and perillyl alcohol. Oxygen was used as the oxidant in the oxidation processes. The results presented in this work showed that by the modification of the activated carbon with metal compounds, i.e. cobalt and molybdenum, it is possible to obtain more active catalysts for limonene oxidation compared to activated carbon not enriched with these metal compounds. The molybdenum catalyst (AC_OP_Mo) proved to be the most active catalyst. It allowed to obtain the high selectivity of limonene oxide (37 mol%) at the high conversion of limonene (58 mol%).