Publication

Poisoning of Mn-Ce/AC catalysts for low-temperature NH3-SCR of NO by K+ and its counter-ions (Cl- /NO3- /SO42- )

Abstract

Mn-Ce/AC catalysts for low-temperature NH3-SCR of NOx were deliberately loaded with various potassium salts (KCl, KNO3, and K2SO4) to investigate the influence of the counter-ions on the poisoning impact. Whereas K salts poisoning had only marginal impact on the textural properties of the catalysts, but it altered the chemical properties of the catalysts significantly. Potassium addition lowered the relative surface concentration of Mn4+ and M-O in Mn-Ce/AC catalyst, suggesting that K might occupy the oxygen vacancies around Mn atoms, thereby weakening the NH3 adsorption. The extent of inhibition strongly depended on the anion, with Cl- causing a higher degree of poisoning than that of either NO3- or SO42- . While K+ could hinder NH3 adsorption, both NO3and SO42- provided new acid sites that could offset the deactivation.

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Related concepts (38)
Potassium
Potassium is the chemical element with the symbol K (from Neo-Latin kalium) and atomic number 19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure. It was first isolated from potash, the ashes of plants, from which its name derives. In the periodic table, potassium is one of the alkali metals, all of which have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge (which combines with anions to form salts).
Metal
A metal (from Ancient Greek μέταλλον métallon 'mine, quarry, metal') is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typically ductile (can be drawn into wires) and malleable (they can be hammered into thin sheets). These properties are the result of the metallic bond between the atoms or molecules of the metal. A metal may be a chemical element such as iron; an alloy such as stainless steel; or a molecular compound such as polymeric sulfur nitride.
Heavy metals
Heavy metals are generally defined as metals with relatively high densities, atomic weights, or atomic numbers. The criteria used, and whether metalloids are included, vary depending on the author and context. In metallurgy, for example, a heavy metal may be defined on the basis of density, whereas in physics the distinguishing criterion might be atomic number, while a chemist would likely be more concerned with chemical behaviour. More specific definitions have been published, none of which have been widely accepted.
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