CeO sub(2) and Co sub(3)O sub(4)-CeO sub(2) nanoparticles: effect of the synthesis method on the structure and catalytic properties in COPrOx and methanation reactions

• Published in: Journal of materials science Vol. 51; no. 8; pp. 3989 - 4001
• Main Authors: Peiretti, Leonardo F, Navascues, Nuria, Tiscornia, Ines S, Miro, Eduardo E
• Format: Journal Article
• Language: English
• Published: 01-04-2016
• Subjects: Catalysis; Catalysts; Cobalt; Mixed oxides; Nanoparticles; Synthesis; Synthesis (chemistry)
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-015-9717-2

CeO sub(2) and Co sub(3)O sub(4)-CeO sub(2) nanoparticles were synthesized, thoroughly characterized, and evaluated in the COPrOx reaction. The CeO sub(2) nanoparticles were synthesized by the diffusion-controlled precipitation method with ethylene glycol. A notably higher yield was obtained when H sub(2)O sub(2) was used in the synthesis procedure. For comparison, two commercial samples of CeO sub(2) nanoparticles (Nyacol super( registered ))-one calcined and the other sintered-were also studied. Catalytic results of bare CeO sub(2) calcined at 500 degree C showed a strong influence of the method of synthesis. Despite having similar BET area values, the CeO sub(2) synthesized without H sub(2)O sub(2) was the most active sample. Co sub(3)O sub(4)-CeO sub(2) catalysts with three different Co/(Co + Ce) atomic ratios, 0.1, 0.3, and 0.5, were prepared by the wet impregnation of the CeO sub(2) nanoparticles. TEM and STEM observations showed that impregnation produced mixed oxides composed of small CeO sub(2) nanoparticles located both over the surface and inside the Co sub(3)O sub(4) crystals. The mixed oxide catalysts prepared with a cobalt atomic ratio of 0.5 showed methane formation, which started at 200 degree C due to the reaction between CO sub(2) and H sub(2). However, above 250 degree C, the reaction between CO and H sub(2) became important, thus contributing to CO elimination with a small H sub(2) loss. As a result, CO could be totally eliminated in a wide temperature range, from 200 to 400 degree C. The methanation reaction was favored by the reduction of the cobalt oxide, as suggested by the TPR experiments. This result is probably originated in Ce-Co interactions, related to the method of synthesis and the surface area of the mixed oxides obtained.