An in situ, energy-dispersive X-ray diffraction study of natural gas conversion by CO₂ reforming

The selective CO₂ reforming of methane to synthesis gas over a rare-earth iridate pyrochlore, Ln₂Ir₂O₇ (Ln = Eu), and rare-earth ruthenate pyrochlores, Ln₂Ru₂O₇ (Ln = Nd, Sm, Eu, Gd), has been studied in situ by using energy-dispersive X-ray diffraction with synchrotron radiation. Analysis of the diffraction data shows that the oxides are activated by reduction to the platinum group metal, the iridate by a second-order kinetic reaction, and the ruthenates by a first-order process. Temperature programmed reductions under carbon monoxide, hydrogen, and methane establish that the iridates proceed directly to the metal, whereas the ruthenates reduce via an oxygen deficient pyrochlore.