Unveiling the Role of Active Oxygen Species in Oxidative Dehydrogenation of Ethane with CO2 over NiFe/CeO2

• Published in: ChemCatChem Vol. 13; no. 13; pp. 3119 - 3131
• Main Authors: Guo, Man, Feng, Kai, Wang, Yaning, Yan, Binhang
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 07.07.2021
• Subjects: Carbon dioxide; Catalysts; Cerium oxides; Chemical synthesis; Dehydrogenation; Ethane; Intermetallic compounds; Iron compounds; Nickel compounds; oxidative dehydrogenation; Oxygen; Reforming; Selectivity; support effect; surface oxygen; Surface reactions; Transient response
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.202100333

The oxidative dehydrogenation of ethane (ODH) assisted by CO2 to produce ethylene is inevitably accompanied by the side reaction of dry reforming (DRE) to produce carbon monoxide. However, the key factor determining the dehydrogenation selectivity is still ambiguous. In this paper, four different NiFe/CeO2 catalysts were synthesized via an impregnation method over four types of CeO2. The dehydrogenation selectivity of the four catalysts ranged from 40 % to 83 %. Temperature‐programmed surface reaction and transient response experiments reveal the existence of two types of oxygen species over NiFe/CeO2 catalysts. FeOx layers exist as an oxygen species supply buffer over CeO2 supports. Weakly electrophilic oxygen species supplied by FeOx overlayers could participate in producing C2H4 while strong electrophilic oxygen species supplied by CeO2 supports could participate in producing CO. The content of weakly electrophilic oxygen species is identified to be a rational descriptor of C2H4 selectivity. Support effect: Two types of oxygen species on the surface of NiFe/CeO2 were confirmed by a combination of temperature‐programmed surface reaction and transient response experiments. Weakly electrophilic oxygen species (OODH) supplied by FeOx overlayers functionally break the C−H bonds of ethane to generate ethylene while strong electrophilic oxygen species (ODR) supplied by CeO2 supports could break both the C−C and C−H bonds to produce carbon monoxide. The ratio of OODH/(OODH+ODR) was identified as a rational descriptor of ethylene selectivity.