Bi- and trimetallic Ni catalysts over Al2O3 and Al2O3-MOx (M = Ce or Mg) oxides for methane dry reforming: Au and Pt additive effects

The effects of Au and Pt addition (in very low concentrations, 0.2 wt%) on the catalytic performances of4 wt% Ni catalysts supported over Al2O3and Al2O3-10 wt%MOx(M = Ce or Mg) oxides were studied in thedry reforming of methane (DRM). The properties of the catalysts, before and after long-run tests, wereinvestigated employing N2adsorption-desorption isotherms, XRD, H2-TPR, XPS, TEM, EDX microanalysisand O2-TPO. It was shown that addition of a small amount of Au and Pt (0.2 wt%) to Ni catalyst leads toformation of a synergistic interaction, which induces easy reduction of NiO species and decrease of particlesize. It was also found that the small amount of Au and Pt addition plays an important role on catalyticperformance of bi-/trimetallic catalysts and carbon poisoning. The improvement of catalytic activity andstability obtained for the trimetallic NiAuPt/Al2O3catalyst was attributed to the formation of high activeNi-Au-Pt nanoparticles, synergistically interacting, where growth of small amount of bamboo-like carbonnanotubes occurs. Conversely, abundant amorphous carbon and both, amorphous and carbon nanotubes,were detected in the bimetallic, NiAu and NiPt, and monometallic Ni alumina supported catalysts.The effect of Al2O3doping with MgO or CeO2also significantly improves the catalytic performance ofmonometallic Ni catalyst and the nature and amount of carbon deposits as well. However, the supporteffect was weakened in both Mg and Ce doped trimetallic catalysts due to the dominant role of Ni-Au-Ptinteraction responsible of the enhanced activity for DRM.