Pt-Ni/ZnO-rod catalysts for hydrogen production by steam reforming of methanol with oxygen.

Ni, Pt and a mixture of Ni and Pt supported on ZnO-rods were evaluated in autothermal steam reforming of methanol (ASRM) for hydrogen production as a function of the reaction temperature. The catalytic materials were characterized by SEM-EDS, XRD, TEM, HRTEM, TPR and BET. Analysis by SEM and TEM showed structural modifications on the surface of the ZnO rods after Ni impregnation. The reactivity of the catalytic materials in the range of 200-500 °C showed that the bimetallic sample had better catalytic activity among all the catalysts studied. This finding could be associated to PtZn and NiZn alloys present in this catalyst, which were identified by XRD and HRTEM analyses. Catalyst characterization by XRD after the catalytic testing showed that the intermetallic PtZn phase was stable during the reaction in the Pt/ZnO-rod sample. The cubic Ni-Zn structure identified in the Ni/ZnO-rod sample was transformed to Zn-Ni-O and metallic Ni phases, respectively. On the bimetallic PtNi/ZnO-rod sample, the cubic Ni-Zn structure remained, although the tetragonal NiZn structure is unstable and was destroyed during the ASRM reaction and then a new phase of NiPt emerged. The promotion effect of Pt and/or Ni on the ZnO-rod was clearly shown.