Interactions between Ni and La2O3in Ni/La2O3Catalysts Prepared Using Different Ni Precursors

Abstract

The role of the anion (NO3−or Cl−), used in the preparation via impregnation of unreduced Ni/La2O3catalysts, in the interactions between Ni and La2O3was investigated using XRD, TPR, and ESCA experiments. The following results have been obtained: In the 20 wt% Ni/La2O3prepared using Ni(NO3)2as precursor, LaNiO3and La(OH)3were the only compounds identified by XRD in the sample calcined in O2, and La2NiO4and La(OH)3were the only compounds identified in the sample calcined in He. At lower Ni contents, the La2O3phase was additionally identified. For the 20 wt% Ni/La2O3prepared using Ni chloride as precursor, LaOCl was the only compound detected by XRD; no phase containing Ni was identified by XRD in the samples calcined in O2or He. At lower Ni chloride contents, LaNiO3was additionally detected in the sample calcined in O2and La2NiO4in that calcined in He. A comparison between the XRD spectra and the TPR curves suggested the presence of amorphous NiO in the samples based on Ni chloride. It is also shown that the Ni precursor employed in the preparation of the catalyst plays a role in the CO2reforming of CH4. During the CO2reforming of methane, the unreduced Ni/La2O3catalysts, based on Ni nitrate, had a high initial CO yield but a low time stability; in contrast, the unreduced Ni/La2O3catalysts, based on chloride, had a high stability. A possible explanation of this behavior, based on ESCA analysis and on the reaction between CH4and catalysts, is provided.