CH4–CO2 reforming over Ni-substituted barium hexaaluminate catalysts

[Display omitted] ► The used catalyst shows contraction of the unit cell, the result of NiO reduction. ► Graphitic carbon is confirmed after catalyst use. ► Catalyst light-off temperature correlates with Ni substitution into the lattice. ► Carbon deposition on the used catalysts correlates with Ni substitution. A series of Ni-substituted barium hexaaluminate catalysts, Ba0.75NiyAl12−yO19−δ (y=0.4, 0.6 and 1.0), were tested for CO2 reforming of CH4 at temperatures between 200 and 900°C. Temperature programmed surface reaction results show that the reaction lights-off in a temperature range between 448 and 503°C with a consistent decrease in light-off temperature with increasing Ni substitution. Isothermal runs performed at 900°C show near equilibrium conversion and stable product concentrations for 18h on all catalysts. Temperature programmed oxidation of the used catalysts show that the amount of carbon deposited on the catalyst increases with Ni substitution. High resolution XRD of the used Ba0.75Ni0.4Al11.6O19−δ catalyst shows a statistically significant contraction of the unit cell which is the result of NiO reduction from the lattice. XRD of the used catalyst also confirms the presence of graphitic carbon. XPS and ICP measurements of the as prepared catalysts show that lower levels of Ni substitution result in an increasing proportion of Ba at the surface.