Tuning Lattice Oxygen of Fe-OMS-2 Oxygen Carriers for Chemical Looping Oxidative Dehydrogenation of Ethylbenzene

This study investigated the regulation mechanism of hydrogen reduction pretreatment on the catalytic performance of Fe-OMS-2 oxygen carriers at 350 ℃. Combined with multi-dimensional characterization and activity tests, the structure-activity relationship was clarified.

The results showed that hydrogen reduction could stepwise regulate the Mn valence state (Mn⁴⁺→Mn³⁺→Mn²⁺), among which Mn³⁺ was the core active species, and its lattice oxygen could efficiently activate the C-H bond of ethylbenzene and inhibit deep oxidation. Fe³⁺ stabilized the carrier by forming a Mn-O-Fe structure and promoted the directional reduction of Mn⁴⁺ to Mn³⁺. The Fe-OMS-2 reduced for 30 min exhibited the optimal performance: the ethylbenzene conversion rate was 71.7% and the styrene selectivity was 93.5% at 350 ℃, and it maintained stable performance in 40 redox cycles with a carbon deposition amount of only 1.5 wt%.