Changes in Ni-NiO equilibrium due to LaFeO3 and the effect on dry reforming of CH4

Abstract

The interactions between Ni and LaFeO3 were studied on catalysts prepared by Atomic Layer Deposition (ALD) of 0.5-nm films of LaFeO3 on MgAl2O4. Scanning Transmission Electron Microscopy showed that the films covered the support uniformly, even after 5 redox cycles at 1073 K, and X-Ray Diffraction showed that the films had the perovskite structure. Equilibrium between Ni and NiO was studied using coulometric-titration and flow-titration measurements on 5-wt% Ni catalysts, with and without LaFeO3. While equilibrium constants for Ni/MgAl2O4 were similar to that expected for bulk Ni, equilibrium PO2 were shifted to significantly lower values in the presence of LaFeO3. In studies of Methane Dry Reforming, the shift in equilibrium resulted in catalyst deactivation due to Ni oxidation at low CO:CO2 ratios, even though Ni/LaFeO3/MgAl2O4 otherwise showed a high reaction rate and excellent tolerance against coking.