Aqueous-phase partial oxidation of methane with H2O2 over Fe-ZSM-5 catalysts prepared from different iron precursors

Abstract

Fe-ZSM-5 is an active catalyst for the selective oxidation of methane with H2O2 in liquid water. To prepare the active Fe-ZSM-5 catalyst, the effect of the Fe precursor on the catalytic performance was examined. Additionally, two preparation methods, wet impregnation (WI) and ion-exchange (IE), were also applied. The prepared catalysts were characterized using various techniques, such as nitrogen physisorption, X-ray diffraction, UV–Vis spectroscopy, and Fourier-transform infrared (FTIR) spectroscopy after NO adsorption (NO-FTIR). Fe-ZSM-5 prepared from FeCl2 appears to be the most active among the Fe-ZSM-5 catalysts prepared from FeCl2, FeSO4, Fe(CH3CO2)2, FeCl3, Fe2(SO4)3, Fe(C5H7O2)3, and Fe(NO3)3 using the WI method. For Fe-ZSM-5 catalysts prepared using the IE method, divalent Fe precursors, such as FeSO4, FeCl2, and Fe(CH3CO2)2, are better than trivalent Fe precursors, such as Fe2(SO4)3, FeCl3, and Fe(NO3)3, in terms of catalytic activity. The active catalyst has the dominant extra-framework Fe2+ species probed with UV–Vis spectroscopy and NO-FTIR.