Suchergebnisse

H– and Na–saponite supports have been prepared by several synthesis approaches. 5% Cu/saponite catalysts have been prepared and tested for soot combustion in a NOx + O2 + N2 gas flow and with soot and catalyst mixed in loose contact mode. XRD, FT-IR, N2 adsorption and TEM characterization results revealed that the use of either surfactant or microwaves during the synthesis led to delamination of the saponite support, yielding high surface area and small crystallite size materials. The degree of delamination affected further copper oxide dispersion and soot combustion capacity of the Cu/saponite catalysts. All Cu/saponite catalysts were active for soot combustion, and the NO2-assisted mechanism seemed to prevail. The best activity was achieved with copper oxide supported on a Na–saponite prepared at pH 13 and with surfactant. This best activity was attributed to the efficient copper oxide dispersion on the high surface area delaminated saponite (603 m2 g−1) and to the presence of Na. Copper oxide reduction in H2-TPR experiments occurred at lower temperature for the Na-containing catalysts than for the H-containing counterparts, and all Cu/Na–saponite catalysts were more active for soot combustion than the corresponding Cu/H–saponite catalysts. ; The financial support of Generalitat Valenciana (Project PROMETEOII/2014/010), Catalan Government (2014SGR1146), Spanish Ministry of Economy and Competitiveness (Projects CTQ2012-30703 and CTQ2011-24610) and UE (FEDER funding) is acknowledged.

Copper and cobalt oxides supported on ceria-yttria-stabilized zirconia (Ce-YSZ) have been studied as an alternative to noble metals for the removal of soot from diesel engines. The Ce-YSZ support was activated in order to obtain a catalyst with a high redox performance. The resulting catalysts were characterised by N2 physisorption, ICP, XRD, TPR-H2, TPR-CO, HAADF-STEM and XEDS. The catalytic performance of the materials was evaluated in the oxidation of NO to NO2 and in the combustion of soot in the presence/absence of NOx. The Co/Ce-YSZ catalyst showed a maximum NO2 production activity higher than 70%, i.e., very close to that obtained with a commercial Pt catalyst used as a reference and significantly better than that of Cu/Ce-YSZ. A similar trend was observed in the combustion of soot in the presence of NOx, thus indicating the prevalence of the NO2-assisted mechanism for the oxidation of soot when NO2 is present. Results obtained with unsupported Co3O4 and CuO oxides suggest that a Co-containing catalyst is not only a better NO2 generator but also utilises NOx more efficiently. Co3O4 entities would act as a pseudo-platinum phase that would provide a fresh supply of NO2 along the catalytic bed, thus accelerating the soot combustion reaction. However, if NOx is absent, the order of the soot combustion rate matches the performance in reducibility ('active oxygen' mechanism), with the Cu catalyst being more active than Co or Pt. Under these conditions the Ce-YSZ supported catalysts benefit from the excellent oxygen-exchange properties of surface Ce-Y-Zr oxide nanostructures. ; The authors thank the Spanish Government (Ministerio de Economía y Competitividad): Projects MINECO/FEDER MAT2017-87579-R, CTQ2015-64801-R, FPU grant FPU17/00603 (Ministerio de Economía, Educación, Cultura y Deporte (Spain)); the Junta Andalucía (FQM-110 group) and Generalitat Valenciana (PROMETEO/2018/076) for financial support.