Role of Electronic Factor in Soot Oxidation Process Over Tunnelled and Layered Potassium Iron Oxide Catalysts

Abstract

This paper describes the investigations of the catalytic activity in soot oxidation over well-defined iron oxide based materials. The nanostructuration of iron oxide by potassium into tunnelled (KFeO 2 ) and layered (K 2 Fe 22 O 34 ) ferrites and the surface promotion with CeO 2 results in the marked increase in the catalytic activity (decrease of the ignition temperature down to 210°C and T 10 % to 310°C). The measurements of the catalysts work function showed that both nanostructuration and surface promotion with ceria of the best KFeO 2 phase led to increase of the electron availability (decrease of the work function). Strong correlation of the catalytic activity in soot combustion of the Ce-K-Fe-O systems with the work function value was revealed for the first time in the model studies, and can be used as a guideline for optimisation of the real catalytic filters.

How to Efficiently Promote Transition Metal Oxides by Alkali Towards Catalytic Soot Oxidation

“…The pellet was then ground for 15 min, repressed and heated. The temperature of 800°C was maintained for 20 h. The sample was then removed once the furnace had cooled [21].…”

“…Enhancing the catalytic activity of such materials by alkali addition has been frequently reported [20][21][22][23][24]. Doping occurs mainly in one of two ways: alkali cations can be dispersed on the surface [25,26] or intercalated into the structure [20].…”

“…Secondly, the formation of low melting point compounds or superficial carbonate intermediates may improve soot-catalyst contact [9]. Intercalation very often leads to layered or tunneled structures (nanostructuration) enabling very high potassium cation mobility [20,21] but can also change the catalytic activity leaving the structure unaffected, i.e. intercalation in glass [27] or substitution of other metals [28].…”

“…Previous research in this area revealed, that the calcination of a spinel wet impregnated with alkali can lead to promotion of both natures [20,21]. The aim of this work was to perform systematic research concerning surface and bulk promotion in order to compare their effect for manganese, iron and cobalt spinels.…”

Strong Enhancement of deSoot Activity of Transition Metal Oxides by Alkali Doping: Additive Effects of Potassium and Nitric Oxide

“…More comprehensive studies on the surface alkali promotion of d-and f-electron metal oxides such as cobalt, lanthanum, iron, chromium, manganese, niobium, vanadium, and cerium are presented in [14]. Examples of the use of mixed oxides (potassium bulk promotion) as catalysts include K 6 [17] or KVO 3 and K 4 V 2 O 7 [18]. Potassium containing glasses [19,20] have also been found recently as a component of the most active soot combustion catalysts [21].…”