Effect of synthesis parameters on morphology and activity of bimetallic catalysts in CO2-CH4 reforming

High surface area CeO2-ZrO2 (80/20 wt.%) mixed oxide supports with superior reducibility were synthesized by two solvothermal approaches, hydrothermal aging in NH4OH aqueous solution and glycothermal aging in ethylene glycol. The materials aged in alkaline water at elevated temperature and pressure exhibit large crystallite sizes (roughly 30-40 nm), and structural segregation of the CeO2 and ZrO2 crystal phases. The materials synthesized by reduction in ethylene glycol show properties of homogeneous solid solutions with highly developed nanocrystalline structure (an average crystallite size was estimated at about 6 nm). Bare CeO2-ZrO2 supports were selected mostly on grounds of their reducibility for the subsequent homogeneous deposition coprecipitation with nickel and cobalt (3, 6, 12, 18 wt.%) loadings. The bimetallic catalysts were thoroughly characterized and then examined in the catalytic CO2-CH4 reforming reaction. The materials which exhibited both small crystallite sizes of the employed support and small active bimetallic particles, demonstrated high catalytic activity and good resistance to carbon accumulation on the catalyst surface. Dry reforming process over catalysts bearing glycothermally aged supports revealed the simultaneous occurrence of reverse water gas shift reaction, whereas the hydrothermally prepared supports stimulate methane dehydrogenation reaction at higher temperatures; the occurrence of both reactions is influenced by the dispersion of active metal species. (c) 2012 Elsevier B.V. All rights reserved.