Lattice Oxygen Regulation of Perovskites for Chemical Looping Oxidative Dehydrogenation of Ethylbenzene to Styrene

The direct dehydrogenation processproduces over 90% of globalstyrene. However, it is hampered by high energy consumption due toequilibrium limitation, a high steam/ethylbenzene feeding ratio, andcomplicated separation procedures. In this study, we propose the synthesisof a novel perovskite-structured metal oxide as the redox catalystfor chemical looping oxidative dehydrogenation (CL-ODH) of ethylbenzeneinto styrene. Lower ethylbenzene activation temperature and higheroxygen storage capacity contributing to high ethylbenzene conversionare achieved by Mn doping of the B site in SrFeO3-delta, and styrene yield is further enhanced by Ba doping of the A site.The optimized Sr0.8Ba0.2Fe0.2Mn0.8O3-delta catalyst exhibits favorabledehydrogenation activity but is deactivated in the first five redoxcycles due to the severe carbonation and perovskite structure decomposition.The decarbonization treatment on the catalyst at 950 degrees C in anO(2) atmosphere restores the perovskite structure and dehydrogenationactivity, resulting in 85% ethylbenzene conversion and 89% styreneselectivity at 550 degrees C. Ethylbenzene on the catalyst undergoesfull combustion via adsorbed oxygen, ODH of ethylbenzene into styreneand H2O using lattice oxygen, and direct dehydrogenationwithout available lattice oxygen. The proposed redox catalyst demonstratesefficient conversion of ethylbenzene into styrene, showing great potentialfor the energy conservation and process intensification of styreneproduction. Modulated Sr0.8Ba0.2Fe0.2Mn0.8O3-delta experiences combustion,partial oxidation, direct dehydrogenation of ethylbenzene, and reoxidationin a redox cycle accompanied by a renewable process.