Enhancement of ethylbenzene dehydrogenation of perovskite-type BaZrO3 catalyst by a small amount of Fe substitution in the B-site

•Co-feeding steam lead to severe loss of catalytic activity over BaZrO3.•BaM0.02Zr0.98O3 (M:Fe, Mn) catalyst presented high activity for EBDH with steam.•Ratio from 2%- to 4%-Fe substitution drastically improved catalytic performance.•Defect–dipole (Fe3+–Vox) in BaFe0.02Zr0.98O3 catalyst was present after reaction.•The presence of defect–dipole might bring high activity for EBDH with steam.

The purpose of this study was to clarify the effect of a transition metal (Mn, Fe, Co) substitution in the BaZrO3 catalyst on the performance of ethylbenzene dehydrogenation (EBDH) with steam. The BaZrO3 catalyst showed a high performance for the EBDH without steam, however the co-feeding of steam produced a significant decrease in the EBDH activity. By partially substituting the Zr site in the BaZrO3 catalyst with Mn or Fe, the dehydrogenation activity was dramatically improved, while the Co-substituted catalyst showed a significantly low activity. In particular, the Fe substitution of a small percentage from 2 to 4% was effective for the drastic enhancement of the EBDH performance with steam. Comparing the styrene yield over the BaFe0.02Zr0.98O3 catalyst with that over the industrial potassium-promoted iron oxide (Fe–K) catalyst, the BaFe0.02Zr0.98O3 catalyst produced a higher styrene yield than the Fe–K catalyst. From the ESR measurement, we found that the Fe-substituted BZO catalyst had the defect–dipole (Fe3+–Vox) in its structure after EBDH with steam. Highly-active BaFe0.02Zr0.98O3 catalyst had a large amount of the defect–dipole and therefore an increase of the oxygen mobility. On the other hand, although low-active catalyst had a large amount of the defect–dipole, but the non-uniformity in the environment of the defect–dipole was increased. Such differences might cause a redox property and a performance for EBDH with steam. The drastic change in activity and environment around the oxygen defect by a small amount of Fe substitution is reported for the first time in the field of perovskite catalysts.

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