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Cobalt-containing catalysts supported on ZSM-5 zeolite and mesoporous siliceous SBA-15 were prepared and characterized by nitrogen sorption, X-ray diffraction, scanning electron and transmission electron microscopies, energydispersive X-ray, Fourier transform infrared, ultraviolet−visible diffuse reflectance, X-ray photoelectron spectroscopies, and temperature-programmed desorption of ammonia measurement. The effect of cobalt loading ratio on the selective catalytic reduction (SCR) of nitrogen oxides (NO x ) with ammonia was investigated. The existing Brønsted acid sites contributed to the cobalt species finely dispersed within the ZSM-5 zeolite, either as isolated cobalt ions anchored at α, β, and γ sites, or as amorphous cobalt oxides enriched on the ZSM-5 surface. NO x conversion profiles of Co/ZSM-5 exhibited two peaks. The low-temperature peak (<300 °C) was induced by cobalt ions at β and γ sites, while the high-temperature peak (>300 °C) was assigned to the amorphous and crystalline cobalt oxides. With increasing cobalt content, the intensity of lowtemperature peak was enhanced monotonously, and the peak position remained constant. Increasing cobalt content promoted the high-temperature peak to shift toward lower temperatures. NO x conversion profiles of Co/SBA-15 only exhibited a hightemperature peak. For Co/SBA-15, the poor dispersion of cobalt species was derived from the absence of Brønsted acid sites. The activity of Co/SBA-15 catalysts was lower than that of the Co/ZSM-5 catalysts due to inactive cobalt ions anchored on isolated Si−OH groups, and agglomerated cobalt oxides within the SBA-15 channels blocking the reactant pathway to active sites.

The performance of the conventional engine-cooling system has always been constrained by the passive nature of the system and the need to provide the required heat-rejection capability at high-power conditions. This leads to considerable losses in the cooling system at part-load conditions where vehicles operate most of the time. A set of design and operating features from advanced enginecooling systems is reviewed and evaluated for their potential to provide improved engine protection while improving fuel efficiency and emissions output. Although these features demonstrate significant potential to improve engine performance, their full potential is limited by the need to balance between satisfying the engine-cooling requirement under all operating ambient conditions and the system effectiveness, as with any conventional engine-cooling system. The introduction of controllable elements allows limits to be placed on the operating envelope of the cooling system without restricting the benefits offered by adopting these features. The integration of split cooling and precision cooling with controllable elements has been identified as the most promising set of concepts to be adopted in a modern engine-cooling system.

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