Chemical looping oxidative dehydrogenation (CL-ODH) of ethane utilizes a transition metal oxide based oxygen carrier, also known as redox catalyst, to convert ethane into ethylene under an autothermal cyclic redox scheme. Unlike conventional ODH, CL-ODH eliminates the needs for gaseous oxygen, rendering a potentially safer and more efficient process. We reported Li-promoted La0.6Sr1.4FeO4 (LaSrFe) as an effective redox catalyst for CL-ODH. However, its oxygen capacity is relatively low (&lt;0.3 wt%). The current study investigates Na or K as a promoter and finds similar promotional effects: alkali promoter notably increases the selectivity of the pristine LaSrFe but suppresses its oxygen carrying capacity. The K-promoted LaSrFe was further characterized with Low Energy Ion Scattering (LEIS) and 18O2-exchange experiments. LEIS analysis indicates that the surface layer contained exclusively of K2O whereas 18O2-exchange experiments confirm that the oxygen surface exchange and incorporation rates are significantly lower for K-promoted LaSrFe. Meanwhile, co-promotion of Li and K achieved up to 86% ethylene selectivity and 60% ethane conversion while maintaining an oxygen capacity of 0.65 wt%. This enhanced performance was ascribed to the higher oxygen capacity of K substituted LaSrFe and the higher selectivity induced with Li promotion. In addition to LaSrFe, other oxide substrates within the same Ruddlesden-Popper structure family were also investigated to determine the general effects of A-site and B-site compositions of the oxide substrate on the ODH performance of the alkali promoted redox catalysts.

Alkali-promoted mixed oxide redox catalysts for chemical looping-oxidative dehydrogenation of ethane (CL-ODH)

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.