Template-free synthesis and boosting catalytic activity in styrene epoxidation of mesoporous rod-like MnCo₂O₄

Mesoporous rod-like MnCo₂O₄ was fabricated via a facile template-free hydrothermal method and subsequent calcination. The crystal structure, surface morphology, pore structure and surface chemical composition were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption and X-ray photoelectron spectra (XPS). Characterization results revealed that, in the target MnCo₂O₄ sample, the mesoporous structure was well-formed, and the pore size distribution was defined in 6 nm. Also, the particular rod-like morphology was obtained in MnCo₂O₄ with diameters of 100~200 nm and a length of 2~3 μm. Based on these, the MnCo₂O₄ sample was firstly used as a heterogeneous catalyst in the epoxidation of styrene. Compared with other Co-based and Mn-based catalysts, it exhibited relatively high catalytic activity, the conversion rate of styrene was 95.8%, and the selectivity of styrene oxide was 58.2%. Moreover, after five cycles, the catalytic activity did not change significantly, further confirming the stability of MnCo₂O₄. Meanwhile, the effects of main reaction parameters (reaction time, reaction temperature, the molar ratio of styrene to tert-butyl hydroperoxide (TBHP)) on the catalytic activity of mesoporous rod-like MnCo₂O₄ were systematically investigated.