The purpose of this study was to clarify the effect of a transition metal (Mn, Fe, Co) substitution in the BaZrO<inf>3</inf> catalyst on the performance of ethylbenzene dehydrogenation (EBDH) with steam. The BaZrO<inf>3</inf> 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 BaZrO<inf>3</inf> 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 BaFe<inf>0.02</inf>Zr<inf>0.98</inf>O<inf>3</inf> catalyst with that over the industrial potassium-promoted iron oxide (Fe-K) catalyst, the BaFe<inf>0.02</inf>Zr<inf>0.98</inf>O<inf>3</inf> 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 (Fe<sup>3+</sup>-V<inf>ox</inf>) in its structure after EBDH with steam. Highly-active BaFe<inf>0.02</inf>Zr<inf>0.98</inf>O<inf>3</inf> 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.
- Dehydrogenation of ethylbenzene
- Perovskite oxide catalyst
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Process Chemistry and Technology