Ethylbenzene dehydrogenation with CO2 over Fe-doped MgAl2O4 spinel catalysts: Synergy effect between Fe2+ and Fe3+

Fe-doped MgAl2O4 spinel catalyst of MgFe0.1Al1.9O4 and supported catalyst of Fe2O3–MgO/γ-Al2O3 for ethylbenzene dehydrogenation in the presence of CO2 were studied by Mössbauer spectroscopy (MS) combining with the partial reduction method in the presence of H2, and the catalytic activity of the ferrous iron species was discussed. The results showed that the catalytic performance of Fe3+ existing in spinel is superior to α-Fe2O3, and the synergistic effect between Fe2+ and Fe3+ might indeed increase the catalytic activity since Fe2+–O2− formed in the process of reduction has moderate basicity, which was more favorable for desorption of CO2 compared with Mg2+–O2−. The reduced MgFe0.1Al1.9O4 containing Fe2+ of around 25% exhibits much higher catalytic activity than unreduced catalyst, with improved styrene yield nearly 2 times to 45.0%. MgxFe1−xO as another ferrous iron species formed in the reduction process of Fe2O3–MgO/γ-Al2O3 showed inconspicuously catalytic activity.

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► The catalysts were studied by Mössbauer spectroscopy combining with the partial reduction method.
► The synergy effect between Fe2+ and Fe3+ contributed to the good catalytic performance.
► A possible mechanism of EB dehydrogenation with CO2 over Fe-doped spinel was proposed.