Catalytic behavior of potassium containing compounds for diesel soot combustion

An, Hongmei; McGinn, Paul J.

doi:10.1016/j.apcatb.2005.06.013

Cited by 135 publications

(62 citation statements)

References 21 publications

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“…These catalysts are among the most active for soot combustion, but in most cases they are unstable if subjected to high temperature [10,17,[32][33][34]. This is the case, for instance, of the birnessite catalyst included in Figure 3.…”

Section: -Why Ceria Catalysts For Soot Combustion?mentioning

confidence: 99%

Diesel soot combustion ceria catalysts

Bueno‐López

2014

Applied Catalysis B: Environmental

396

243

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This review article summarizes the contents of the keynote lecture with the same tittle presented at the 7 th edition of the International Conference on Environmental Catalysis hold in Lyon (France) in September 2012. Different aspects of the ceria-catalyzed Diesel soot combustion reactions have been critically discussed, such as the high catalytic activity of ceria for Diesel soot combustion in comparison to some other potential catalysts, the potential ceria-catalyzed Diesel soot combustion mechanisms (the so-called NO 2 -assisted mechanism and the active oxygen mechanism) and the effect of ceria doping with suitable cations like those of Pr, La or Zr. Ceria must be doped in order to enhance thermal stability, but ceria doping also changes different physicochemical and catalytic properties of ceria. Zr-doping, for instance, has a double role on ceria as soot combustion catalyst: enhances ceria oxidation capacity of the adsorbed NOx species (positive effect) but stabilizes NO 2 on surface (negative effect). The surface properties of a ceria catalyst are usually more important than those of bulk: high surface area/small crystal size usually has a positive effect on the catalyst performance and, in mixed oxides, the surface composition also plays a role. The optimal dopant loading depends on the foreign cation being, for instance, around 5-10%, 20-30% and 50 mole % for La 3+ , Zr 4+ , and Pr 3+ / 4+ , respectively.Keywords: DPF regeneration; soot; ceria; doped-ceria; Diesel engine contamination. 2This review article summarizes the contents of the keynote lecture with the same tittle presented at the 7 th edition of the International Conference on Environmental Catalysis hold in Lyon (France) in September 2012. 1.-The problem.Soot particles are formed as undesired by-products in combustion process, being one of the main pollutants emitted by Diesel engines together with NOx, CO and unburned hydrocarbons [1]. Typical gas exhaust composition of a Diesel car, which is summarized in Table 1, is 30-80 ppm hydrocarbons, 200-1500 ppm CO, 300-1650 ppm NO (~ 0 ppm NO 2 ), 5-18% O 2 , > 2% H 2 O and > 2% CO 2 .Soot particles consist of a carbon nucleus with some inorganic material and adsorbed hydrocarbons, SO x , and water [2]. Figure 1 shows TEM images of a real soot sample. The single particles of few nanometers present an amorphous core surrounded by a graphitic shell, and such single particles agglomerate in larger entities with size typically in the range 0.1-10 µm [3].Several adverse effects on health have been attributed to soot. A fraction of these particles (the so-called PM-10, with size smaller than 10 m) can penetrate the respiratory tract and are deposited on lungs increasing cancer risk, asthma and bronchitis. The adsorbed hydrocarbons are mutagenic substances and SO x in contact with water form strong acid compounds.Diesel particle traps with different designs can be used for soot removal from gas streams, wall-flow monoliths being the most popular [3,4]. Figure 2 shows a commercial SiC Diesel Part...

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Section: -Why Ceria Catalysts For Soot Combustion?mentioning

confidence: 99%

Diesel soot combustion ceria catalysts

Bueno‐López

2014

Applied Catalysis B: Environmental

396

243

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“…Despite of the progress made, the reaction mechanism for this process has been scarcely addressed and therefore a lot of work is still needed in order to understand and advance a rational catalyst design. The investigated catalytic systems operate satisfactory only above 500°C, but upon impregnation with alkali, among which potassium [5,8] is the most extensively investigated, their activity can be substantially enhanced [9]. Its positive role on soot combustion has been discussed in terms of: (i) an electron donor effect, increasing the oxygen reactivity; (ii) autogenic formation of low melting point compounds, or eutectics with other components of the catalyst, wetting the soot surface to increase the contact with the catalyst, (iii) the formation of a [10].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2013

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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.

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“…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].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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The effect of surface and bulk potassium promotion on the transition metal oxides (Mn, Fe, Co) catalytic activity in catalytic soot oxidation was investigated. The surface promotion was obtained via incipient wetness impregnation, whereas the bulk promotion-nanostructuration-was obtained via wet chemical synthesis or solid state reaction leading to mixed oxide materials. The introduction of potassium into the transition metal oxide matrix results in the formation of tunneled or layered structures, which enable high potassium mobility. The structure of the obtained materials was verified by powder X-ray diffraction and Raman spectroscopy and the catalytic activity in soot oxidation was determined by TPO-QMS and TGA. It was found that the surface promotion does not alter the metal oxide structure and leads to either enhancement (Mn, Fe) or deterioration (Co) of the catalytic activity. Simultaneously, the catalytic activity in soot combustion of the potassium structured oxides is strongly enhanced. The most active, cobalt oxide based catalyst significantly lowers the temperature of 50 % of soot conversion by *350°C comparing to the non-catalyzed process. The study allows for the establishment of rational guidelines for designing robust materials for DPF applications based on ternary metal oxides.

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Catalytic behavior of potassium containing compounds for diesel soot combustion

Cited by 135 publications

References 21 publications

Diesel soot combustion ceria catalysts

Diesel soot combustion ceria catalysts

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

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

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