Feature ArticleLiquid phase oxidation of cinnamyl alcohol to cinnamaldehyde using multiwall carbon nanotubes decorated with zinc-manganese oxide nanoparticles

•MWCNTs was functionalized and decorated with Zn-Mn oxide nanoparticles.•Zn-Mn oxide and Zn-Mn oxide/FMWCNTs were utilized as catalysts.•Cinnamyl alcohol was oxidized to cinnamaldehyde in presence of oxygen.•Both catalysts showed high activity in green solvent (water).•The catalysts were recyclable and can be used multiple times.

Zinc-manganese (Zn-Mn) oxide nanoparticles were prepared and loaded on functionalized multiwall carbon nanotubes (FMWCNTs) (Zn-Mn oxide/FMWCNT) using co-precipitation and developing condensation methods, respectively. The Zn-Mn oxide and Zn-Mn oxide/FMWCNTs were characterized using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), x-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR). The catalytic efficiencies of the prepared catalysts were tested for liquid phase oxidation of cinnamyl alcohol (CnOH) to cinnamaldehyde (CnHO) in a modified batch reactor. The reaction parameters were optimized and compared in green (water and heptane), blue (toluene, acetonitrile, and cyclohexane), and red (benzene) solvents and molecular oxygen. The maximum CnOH-to-CnHO conversion of 97.2 and 99.9% with productivity of 63.2 and 65 mmol g−1 h−1 was achieved with 0.1 g of each Zn-Mn oxide and Zn-Mn oxide/FMWCNT, respectively in water at 60 °C and time = 120 min. Both catalysts showed high conversion, high productivity, low cost, recyclability, and true heterogeneous behavior and therefore, can be used effectively for the conversion of CnOH-to-CnHO.

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