The conversion of methane into alcohols under moderate reaction conditions is a promising technology for converting stranded methane reserves into liquids that can be transported in pipelines and upgraded to value-added chemicals. We demonstrate that a catalyst consisting of small nickel oxide clusters supported on ceria-zirconia (NiO/CZ) can convert methane to methanol and ethanol in a single, steady-state process at 723 K using O as an abundantly available oxidant. The presence of steam is required to obtain alcohols rather than CO as the product of catalytic combustion. The unusual activity of this catalyst is attributed to the synergy between the small Lewis acidic NiO clusters and the redox-active CZ support, which also stabilizes the small NiO clusters.

Ceria–zirconia-supported Ni catalysts (Ni/Ce0.83Zr0.17O2 or Ni/CZ) are prepared by dry impregnation, strong electrostatic adsorption, coprecipitation (CP), and combustion synthesis (CS). The nature and abundance of Ni species in these samples are characterized by X-ray adsorption spectroscopy, temperature-programmed reduction, and CO chemisorption. The bulk synthesis methods (i.e., CP and CS) produce Ni cations that are incorporated into the CZ lattice forming mixed-metal oxides with Ni3+ species at low Ni content. The formation of mixed-metal oxides increases the reducibility of CZ and increases the abundance of active surface oxygen. All NiO/CZ catalysts are active for methane dry reforming and retain some of their activity at a steady state. The initial methane conversion correlates linearly with the fraction of accessible Ni after reduction. The predominant path of catalyst deactivation strongly depends on the structure of the catalyst and, thus, on the synthesis method used. All catalysts experience agglomeration of Ni particles under reaction conditions. Improving the Ni dispersion to isolated species embedded in a support does not improve resistance to Ni particle growth. Coke formation is inversely related to the concentration of active surface oxygen. The dominant deactivation mechanism for catalysts made by CS is the encapsulation of Ni particles by the support.

Methane is converted over nickel on ceria zirconia (Ni/CZ) into ethane, aromatics, and hydrogen at steady state up to the thermodynamic limit at temperatures of 350 to 500 °C. At 450 and 500 °C, traces of ethylene are also produced. Ni/NiO particles activate methane and couple the resulting surface species to hydrocarbon products. Large Ni particles are responsible for the formation of carbonaceous deposits. Furthermore, aromatics are formed on these sites. Smaller Ni/NiO particles are responsible for the formation of ethane and ethylene and appear to provide sustained activity. It is suggested that these Ni sites are too small to assemble aromatic deposits, and hence they remain active throughout the reaction.

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Several ceria‐zirconia supported mono and bi‐metallic transition metal oxide clusters containing Fe, Cu, and Ni are synthesized by dry impregnation. Through XRD, H2‐TPR, NH3‐TPD, pyridine adsorption followed by FTIR spectroscopy and XAS, the well‐dispersed nature of the transition metal oxide clusters is revealed, and the Lewis acidity of the catalysts is assessed. In‐situ FTIR spectroscopy is used to monitor the methane activation on catalyst surfaces. All catalysts activate methane at 250 °C forming methyl, alkyl, and methoxy species on the catalyst surface. By co‐feeding steam and oxygen together with methane, continuous direct oxidation of methane to methanol can be achieved, with the complete oxidation to CO2 as the other reaction path. Methoxy species are found to be a key intermediate for methanol production. Lowering the methane conversion improves the methanol selectivity. By extrapolation, it is estimated that methanol selectivity close to unity can be achieved below a threshold of methane conversion at about 0.002 %. The formation of CuO and NiO mixed metal oxides produces stronger Lewis acid sites and yields higher methanol selectivity.