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Alumina supported Co–K–Mo based mixed metal oxide type catalytic materials have been prepared by co-impregnation. These catalysts show excellent activity for carbon as well as diesel soot oxidation, which could be due to the redox properties of Mo and Co as well as to a synergistic effect of molybdenum, cobalt, and K contents. The catalyst containing 5 wt% molybdenum shows a lowering of carbon oxidation by about 190 °C under loose contact conditions as compared to the non-catalyzed reaction, as well as to bare alumina. Characterization studies suggest a composite nature of these materials, while thermal stability investigations confirm the stable nature. The selected catalyst has been studied by XPS, however, it is difficult to conclude which are the important factors contributing to the catalytic activity. It appears to be a synergistic effect of Co, K, and Mo components as these catalysts show much improved activity as compared to the individual components in supported and unsupported forms. [ABSTRACT FROM AUTHOR]

Ruthenium based catalysts show excellent catalytic activity for several oxidation reactions, however, their thermal stability has been a challenge. We have been successful in stabilizing ruthenium in perovskite structure, which results in a remarkable improvement in its thermal stability. La3.5Ru4.0O13 lanthanum ruthenate type perovskite was prepared by using various methods, including co-precipitation as well as a template method, which resulted in improved physical properties. This perovskite phase was found to be thermally very stable, possibly due to the 4+ oxidation state of ruthenium in a stable matrix. In this work, we have studied the catalytic properties of La3.5Ru4.0O13 phase for CO and hydrocarbon oxidation reactions. The lanthanum ruthenate shows active CO oxidation beyond about 150 and 170 °C for propene oxidation. The thermal and chemical stability of this material makes it suitable for various catalytic applications, while relatively insignificant poisoning by SO2 is an important observation to further explore. [ABSTRACT FROM AUTHOR]

Perovskite type catalysts with SrCoO3 and Sr0.8Ce0.2CoO3 compositions have been prepared by co-precipitation and other methods and, their catalytic activity towards diesel particulate matter (PM)/carbon oxidation has been evaluated under the loose contact condition. These catalysts show excellent catalytic activity for PM/carbon oxidation, despite their low surface area and under the loose contact condition. The synergistic effects of Ce incorporation in perovskite and presence of a small amount of potassium appears to be responsible for the high soot oxidation activity of these perovskite type materials. The Ce incorporation seems to be contributing by enhancing the redox property of the catalyst, while it appears unlikely that potassium is contributing by improving the catalyst–soot contact through its volatization. The catalysts show excellent thermal stability and stable activity under repeated cycles of use. [ABSTRACT FROM AUTHOR]

Various amounts of ruthenia–cobaltate bimetallic catalyst supported on zirconia have been prepared by co-impregnation method and their catalytic activity towards soot/carbon oxidation has been evaluated using TG technique under the loose contact condition. These catalysts show good activity for carbon/soot oxidation, which is observed to be a factor of ruthenia content. The thermal stability experiments confirmed the stability of catalytic materials in air at least up to 900 °C. In this way, ruthenia can be easily dispersed on zirconia possibly through the solid solution formation, while its thermal stability can be significantly improved by introducing a transition metal namely cobalt. Formation of Ru–Co bimetallic clusters over zirconia is probably responsible for its thermal stability, while dissociative adsorption of oxygen on catalyst surface appears to be responsible for their catalytic activity. [ABSTRACT FROM AUTHOR]

Thermal behaviour of hydrous ruthenia (RuO2·nH2O) and ruthenia containing 10% titania ((RuO2)0.9-(TiO2)01·nH2O) was characterised on heating in air by emanation thermal analysis (ETA), thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA). The anhydrous ruthenia and ruthenia containing 10% titania samples were prepared by heating their hydrous precursors at 500°C in air. The temperature intervals of the samples dehydration and crystallisation were determined. XRD, TEM and surface area measurements were also used for the characterisation of the samples. The ETA results, evaluated by a mathematical model, brought about new information about surface area and microstructure development of the intermediate products of the oxides under in situ conditions of the heating in air. A good agreement between ETA and the results of other methods was obtained. The NOx reduction by CO was used to test the catalytic properties of these samples. [ABSTRACT FROM AUTHOR]

Abstract: The reduction of NO by CO over H and Na forms of Ru exchanged mordenite has been studied with ruthenium content of 0.2, 1 and 3wt.%. The catalysts were characterized with respect to X-ray diffraction, BET surface area, temperature programmed oxidation, and temperature programmed desorption of ammonia. These catalysts have been evaluated for their activity for NO–CO reaction using a steady state gas laboratory evaluation assembly. The catalysts show high activity for NO reduction and almost 100% conversion of NO to N2 was observed below 400°C. The activity was found to be a factor of ruthenium content, however, Ru-mordenite in Na form was observed to be relatively more active than Ru-mordenite in H form, probably due to the electron donation from sodium to ruthenium sites. New zeolite phases with improved hydrothermal stability, high surface area and reasonable cation exchange properties can be potential materials for catalytic reduction of NOx. Introduction of active metal ions through ion exchange insures their high dispersion in zeolite supports, which also offer tailoring possibilities for DeNOx catalysts. [Copyright &y& Elsevier]