Synthesis and characterization of Mn-Silicalite-1 by the hydrothermal conversion of Mn-magadiite under the neutral condition and its catalytic performance on selective oxidation of styrene

Abstract

The incorporation of manganese into the framework of Silicalite-1 (denoted as Mn-Silicalite-1) was achieved by the hydrothermal conversion manganese ion exchanged magadiite (Mn-magadiite) under the neutral condition. The influences of the synthetic conditions (the reaction time, the reaction temperatures and the precursors) on the synthesis of Mn-Silicalite-1 were studied in detail to reveal the successful synthesis of Mn-Silicalite-1. The introduction of the manganese into the framework of Silicalite-1 was demonstrated by the means of X-ray powder diffraction (XRD), energy-dispersive X-ray spectrometer (EDS), elemental mapping, X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–Vis), field emission scanning electron microscopy (FE-SEM), N2 adsorption/desorption isotherms and temperature-programmed reduction (TPR). The BET surface area (SBET) and pore volume (Vp) of Mn-Silicalite-1 measured 323 m2/g and 0.052 cm3/g, respectively. All results confirmed that Mn atoms were successfully doped into the framework of Silicalite-1 and homogeneous solid-solutions of Mn-Silicalite-1 were synthesized. Furthermore, the catalytic properties of the as-synthesized Mn-Silicalite-1 were evaluated by the styrene oxidation reaction. Mn-Silicalite-1 significantly increased the active sites of the catalyst and improved the catalytic efficiency. Low temperature was beneficial to the formation of styrene oxide and high temperature was beneficial to the formation of benzaldehyde.