The results of an investigation are reported concerning the NO reduction activity of 10 different carbons and activated carbons, covering a wide range of surface areas and pore size distributions.These samples were subjected to temperature-programmed reaction (TPR) and isothermal reaction (at 600 °C) studies in a flow microreactor at a constant feed NO partial pressure of 0.404 kPa. It was found that, even though these carbons exhibited a wide range of reactivity, their qualitative behavior in the TPR experiments was quite similar, with the exception of samples that contained significant levels of potassium. However, even these samples assumed behavior similar to the uncatalyzed samples after undergoing a second acid wash. The TPR behavior of all the uncatalyzed carbons was consistent with the two temperature regime behavior observed by other workers for the NO-carbon reaction. However, the mechanism of the potassium-catalyzed reaction is still not completely understood and will be the subject of a forthcoming study. The most striking result of the current work, however, was that the only correlation found between NO reduction activity and carbon properties, over a very wide range of reactivities, was the total surface area as determined by N2 adsorption. From this behavior, it was concluded that, under the experimental conditions used in the current work, all the available surface area of the carbons seems to be effective for the reaction and that, apparently, accessibility problems due to diffusional limitations are not important.
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