Developing effective iron-incorporated zeolites and determining their active centers for the direct oxidation of CH

4

to oxygenates have remained challenging topics so far. In this paper

we successfully prepare the highly-dispersed iron supported Y zeolites by a facile solid-state ion-exchange method with ferrocene

which was conducted under water-free conditions followed by a series of calcination. Moreover

extra-framework dinuclear Fe

2+

complexes are identified as so-called active α-iron sites on zeolites. ICP-OES

N

2

adsorption-desorption test

X-ray diffraction

solid-state

27

Al NMR

N

2

O titration

TEM

EPR and

57

Fe Mössbauer spectra were carried out to characterize properties of sample structure

acid sites

as well as the supported iron species. Characterization results indicate that high-temperature treatments have no effect on the typical structure feature of zeolites. Compared with catalysts synthesized by conventional impregnation

the samples prepared by the facile approach possess abundant dinuclear Fe

2+

complexes but no Fe

2

O

3

bulks and show weak

acidity. These lead to a higher oxygenate selectivity in CH

4

oxidation to oxygenates. Remarkably

the oxygenate (HCHO and CH

3

OH) selectivity of 6.5% at 375℃ can be eventually obtained.