Chemical looping offers an alternative approach to catalytic conversion that eliminates mixing fuel and oxidant by facilitating oxygen exchange between the reactant streams via an oxygen carrier material (OCM) which is cycled between them. This allows for side reaction elimination, leading to a safer process in which potentially increased conversions and higher selectivity can be achieved. However, material design for such a process remains a challenge since an OCM should tackle all problems associated with a catalytic process that also involves methane activation such as: slow kinetics, particle agglomeration and carbon deposition, while exhibiting excellent oxygen storage and exchange ability that will allow the material to perform reliably under repeated redox cycling. Here, we design an exsolved perovskite system that addresses these limitations and apply it for the first time for the conversion of methane to syngas. The exsolved nanoparticles act both as oxygen reservoirs and active sites while the system exhibits high reactivity and selectivity with perovskite host and metal particles working synergistically producing syngas with a desirable H2:CO ratio for synthetic fuel production. The methane conversion process is monitored operando via synchrotron X-ray coupled with gas analysis. This allows for the system’s structural and compositional changes to be investigated under reaction conditions, revealing the link between structure and activity as mediated by oxygen transport. Rietveld refinement analysis reveals that nanoparticles and perovskite host work in tandem which seems to mediate oxygen exchange, possibly accounting for the high selectivity observed. Long term cycling of the system for methane partial oxidation showcases its excellent redox stability and resistance to agglomeration and coking while high selectivity is maintained. These results provide valuable insight on the performance of exsolved systems and open new possibilities for the application of redox exsolution for the design of active and robust OCMs and catalysts for a plethora of applications.

Perovskites decorated with exsolved Ni nanoparticles: Operando monitoring of phase and structural changes that dictate redox methane conversion to syngas

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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