Syngas Production by Chemical Looping Dry Reforming of Methane over Ni-modified MoO/ZrO.

We investigated supported-MoO materials effective for the chemical looping dry reforming of methane (CL-DRM) to decrease the reaction temperature. Ni-modified molybdenum zirconia (Ni/MoO/ZrO) showed CL-DRM activity under isothermal reaction conditions of 650 °C, which was 100-200 °C lower than the previously reported oxide-based materials. Ni/MoO/ZrO activity strongly depends on the MoO loading amount. The optimal loading amount was 9.0 wt.% (Ni/MoO(9.0)/ZrO), wherein two-dimensional polymolybdate species were dominantly formed. Increasing the loading amount to more than 12.0 wt.% resulted in a loss of activity owing to the formation of bulk Zr(MoO) and/or MoO. In situ Mo K-edge XANES studies revealed that the surface polymolybdate species serve as oxygen storage sites. The Mo species were reduced to Mo species by CH to produce CO and H. The reduced Mo species reoxidized by CO with the concomitant formation of CO. The developed Ni/MoO(9.0)/ZrO was applied to the long-term CL-DRM under high concentration conditions (20 % CH and 20 % CO) at 650 °C, with two pathways possible for converting CH and CO to CO and H via the redox reaction of the Mo species and coke formation.