Thermodynamic control of product formation during the reaction between CH4 and Pt promoted ceria-zirconia solid solutions

Abstract

The reaction between CH4 and framework oxygen of Pt promoted Ce x Zr1-x O2 (x = 0.25, 0.5, 0.75, 1) solid solutions was studied at 873 K for syngas (CO + H2) production. The homogeneity and cubic/tetragonal structure of the solid solutions were confirmed by powder X-ray diffraction. The thermodynamic properties of the solid solutions, connected with Ce4+/Ce3+ redox reactions, were measured by titrating the oxygen content of the oxides after equilibration in flowing mixtures of H2 and CO2 with 10-31 < pO2 < 10-22 atm. The transient reactions between the oxides and discrete pulses of CH4, as well as of isotopically labeled 13CH4 + 12CO mixtures (limited to the material with x = 0.25) were investigated and reactivity, conversion and selectivity were measured. A strong correlation between the thermodynamic properties of the oxides and the syngas selectivity was found. The 13C scrambling in CO and CO2 during co-feed experiments confirmed equilibration of these molecules with the oxides surfaces. © 2010 The Author(s).