Effect of Aqueous Solution pH on the Oxidation of Methane to Methanol at Low Temperature

This study investigated the effect of different aqueous solution pH on the reactivity of the Fe/ZSM-5 zeolite in the process of selective oxidation of methane to methanol using H2O2 as oxidant at low temperature. Fe/ZSM-5 catalyst was prepared by solid ion exchange method, and its structure and physical properties were characterized by means of X-ray diffraction (XRD), inductively coupled plasma (ICP), diffuse reflectance ultraviolet/visible spectroscopy (DR UV-Vis), Raman spectroscopy (Raman), and solid-state nuclear magnetic resonance (Solid-state NMR). H2SO4 and NaOH were used to adjust the pH of the reaction solution, and the products were quantitatively analyzed by gas chromatography and liquid NMR. The influences of different aqueous solution pH on the reactivity of the reaction were systematically investigated. Besides, the effects of the aqueous solution pH on the metal leaching out of the Fe/ZSM-5 catalyst and the residual concentration of H2O2 were further investigated. It is expected that the obtained experimental results could provide guidance for further optimization of the selective oxidation of methane to methanol reaction.