Dry reforming of methane on MgO–Al2O3 supported Ni–Mo alloy catalysts: insight into the role of Mo and reforming mechanism

MgO–Al 2 O 3 supported Ni and Ni–Mo bimetallic catalysts (referred as Ni/MgAl and Ni x Mo/MgAl with the Ni/Mo atomic ratio of x, respectively) were prepared by the co-precipitation method and tested for the dry reforming of methane (DRM) on an atmospheric quartz fixed-bed. The XRD, XPS, XAFS and magnetic measurement results demonstrate that the Ni–Mo alloy forms in Ni x Mo/MgAl, which inhibits the sintering of metal particles and enhances the degree of coordination unsaturation of metal sites, and subsequently Ni x Mo/MgAl expose more metal sites than Ni/MgAl. The CO 2 -TPD and TPSR reveals than the presence of Mo promotes the adsorption and dissociation of CO 2 , beneficial to DRM and suppressing carbon deposition. Particularly, compared to that on metallic Ni, the graphitic carbon is remarkably suppressed on Ni–Mo alloy own to the charge transfer from Ni to Mo and the isolated Ni ones by the Mo ones. During DRM, Ni x Mo/MgAl are more active than Ni/MgAl, especially Ni 5 Mo/MgAl, which gives the CH 4 and CO 2 conversions of 82.3% and 87.4% at 800 °C, respectively. Also, Ni 5 Mo/MgAl is more stable than Ni/MgAl, and Ni–Mo alloy structure maintains during the reaction and after the regeneration. In addition, the DRM mechanism dominatingly via the HCOO∗ intermediate species is proposed based on in situ DRIFTS and TPSR.