Promoting effect of Pt, Pd and Rh noble metals to the Ni_0.03Mg_0.97O solid solution catalysts for the reforming of CH₄ with CO₂

Reforming of CH₄ with CO₂ to produce synthesis gas was studied over Ni_0.03Mg_0.97O solid solution catalyst and its bimetallic derivative catalysts which contained small amounts of Pt, Pd and Rh, respectively (the atomic ratio of M/(Ni+Mg) was varied from 0.007 to 0.032%, M=Pt, Pd or Rh). It was found that there was a significant promotion in both activity and stability due to the addition of noble metals. The optimum loadings of these noble metals were observed at the atomic ratio of M/(Ni+Mg)≈0.021%. Temperature programmed hydrogenation (TPH) of carbonaceous species formed during the catalytic reaction indicated that the good resistance of Ni_0.03Mg_0.97O solid solution to carbon deposition was retained on the bimetallic catalysts. Furthermore, we obtained a clear evidence showing the formation of Pt-Ni alloy particles by means of TEM and EDS observation. The kinetic study and temperature programmed reaction (TPR) of CH₄ suggest that CH₄ decomposition as the rate-determining step on the Ni_0.03Mg_0.97O is accelerated by the alloy formation. The improved stability was attributed to the promotion in catalyst reducibility.