Diesel soot oxidation

In this paper we will summarize the results and idiow that chloride and copper containing compounds are the active species. In order to find de gn rules for an active catalyst in soot oxidation, the catafytic activity of several otho- metal chlorides is evaluated with respect to their melting point, as well as to the necessity of a chloride ion firr the activation of oxygen. Finally the applicability of this em as a catalyst for diesel soot oxidation is discussed. 

An exploratory study was carried out with respect to the performance of molten salts as diesel soot oxidation catalyst. The activity of two binary eutectic salts, with a low melting point, was measured and compared with the activity of two very active solid single oxides. Also the influence of NO on the oxidation rate was investigated. 

In diesel soot oxidation, the situation can be similar, but more complex. Migration of the catalyst over the soot surface can easily lead to loss of catalyst in the exhaust gas stream. Ideally the wetting of soot should occur without the loss of contact between the salt and the material by which the liquid catalyst is supported. 

Liang Q, Wu X, Weng D, Xu H (2008) Oxygen activation on Cu/Mn-Ce mixed oxides and the role in diesel soot oxidation. Catal. Today 139 113-118. 

Kalogirou M, Katsaounis D, Koltsakis G, Samaras Z (2007) Measurements of diesel soot oxidation kinetics in an isothermal flow reaetor-eatalytie effects using Pt based coatings. 

Kandylas I, Haralampous O, Koltsakis G (2002) Diesel Soot Oxidation with NO2 Engine Experiments and Simulations. Industrial Engineering Chemistry Research 41 5372-5384... 

Teraoka, Y., and Labhsetwar, N. (2013) Bench scale experiments of diesel soot oxidation using Pro,7Sro.2Ko.iMn03 perovskite type catalyst coated on ceramic foam filters. Top. Catal, 56 (18), 457-461. 

The general formula of perovskites is ABO3, and soot combustion perovskite catalysts with many different cations have been reported for both A and B positions [7]. For instance, DoggaU et al. [8] prepared BaRuOs perovskites by coprecipitation method and its catalytic activity was tested for diesel soot oxidation with O2. The catalytic activity was attributed to the dissociative adsorption of oxygen on the catalyst surface, and was postulated that the 120 planes of BaRuOs can have abundant Ru atoms that can facilitate the O2 dissociation. The advantage of using this perovskite with regard to pure ruthenium oxide was attributed to the thermal stability of Ru within the BaRuOs matrix as well as basicity offered by Ba. 

Studies on catalytic and structural properties of BaRuOs type perovskite material for diesel soot oxidation. 

Liu, J., Zhao, Z., Xu, C., et al. (2005). Diesel Soot Oxidation over Supported Vanadium Oxide and K-promoted Vanadium Oxide Catalysts, Appl. Catal. B Environmental, 61, pp. 36-46. 

Ishihara, T., Oishi, T. and Hamamoto, S. (2009). Praseodymium Oxide Doped with Bi for Diesel Soot Oxidation at Low Temperature, Catal. Commun., 10, pp. 1722-1724. 

Kustov, A. and Makkee, M. (2009). Application of NOx Storage/Release Materials Based on Alkali-earth Oxides Supported on AI2O3 for High-temperature Diesel Soot Oxidation, Appl. Catal. B Environment, 88, pp. 263-271. 

Liu S, Obuchi A, Uchisawa J, Nanba T, Kushiyama S. An exploratory study of diesel soot oxidation with NO2 and O2 on supported metal oxide catalysts. Appl Catal B. 2002 37 309. 

Catalytic removal of diesel soot particulates over LaMnOs perovskite-type oxides... 

Catalytic combustion of diesel soot particulates over LaMnOs perovskite-type oxides prepared by malic acid method has been studied. In the LaMn03 catalyst, the partial substitution of alkali metal ions into A site enhanced the catalytic activity in the combustion of diesel soot particulates and the activity was shown in following order Cs>K>Na. In the LarxCs MnOj catalyst, the catalytic activity increased with an increase of X value and showed constant activity at the substitution of x>0.3... 

The physical and chemical complexity of primary combustion-generated POM is illustrated in Fig. 10.1 (Johnson et al., 1994), a schematic diagram of a diesel exhaust particle and associated copollutants. The gas-phase regime contains volatile (2-ring) PAHs and a fraction of the semivolatile (3- and 4-ring) PAHs. The particle-phase contains the remainder of the semivolatile PAHs ( particle-associated ) along with the 5- and 6-ring heavy PAHs adsorbed/absorbed to the surface of the elemental carbon spheres that constitute the backbone of the overall diesel soot particle. Also present is sulfate formed from oxidation of sulfur present in the diesel fuel and gas- and particle-phase PACs. 

We discuss in this section four key aspects of heterogeneous reactions (1) theoretical and experimental structure and reactivity relationships (2) held measurements of relative and absolute PAH decay rates in near-source ambient air and during downwind transport (3) laboratory studies of the photolysis/photo-oxidation and gas-particle interactions with 03 and NOz of key 4- and 6-ring PAHs adsorbed on model substrates or ambient aerosols and (4) environmental chamber studies of the reactions of such PAHs associated with several physically and chemically different kinds of combustion-generated aerosols (e.g., diesel soot, wood smoke, and coal fly ash). Where such data are available, we also briefly consider some toxicological ramifications of these reactions. 

Konstandopoulos, A. G., and Kostoglou, M. Microstructural aspects of soot oxidation in diesel particulate filters. SAE Technical Paper No. 2004-01-0693 (SP-1861) (2004). 

The influence of the inlet concentration of NO was studied with four soot samples mixed with a supported platinum catalyst (I wt% Pi on ASA) at 650 K. The oxidation rate at 50% soot conversion is plotted as a function of the NO inlet concentration in Figure 12.2.a. From this figure it is clear that the influence of the NO concentration on the oxidation rate of the synthetic Printex-U and the diesel soots activated with copper or iron is comparable. There is a first order relation between the NO inlet concentration and the oxidation rate. For cerium activated soot, there is also a first order relation between the NO inlet concentration and the oxidation rate. In this case, however, the effect of NO is approximately twice as large as is the case with Printex-U, Phntex-U with a physical mixture of a cerium catalyst (not shown), and copper- or iron-activated soot. 

In spite of this, we believe that there is a real potential in ceria as an anode for conversion of hydrocarbon fuels, because ceria can tolerate carbon precipitation and is able to oxidise the carbon. In this context it should be remembered that one of the oldest applications of ceria has been as a carbon oxidation catalyst, and still today it is used as a catalyst in self cleaning ovens and for the oxidation of diesel soot in automobiles. ... 

The use of CeOs-based materials in catalysis has attracted considerable attention in recent years, particularly in applications like environmental catalysis, where ceria has shown great potential. This book critically reviews the most recent advances in the field, with the focus on both fundamental and applied issues. The first few chapters cover structural and chemical properties of ceria and related materials, i.e. phase stability, reduction behaviour, synthesis, interaction with probe molecules (CO. O2, NO), and metal-support interaction — all presented from the viewpoint of catalytic applications. The use of computational techniques and ceria surfaces and films for model catalytic studies are also reviewed. The second part of the book provides a critical evaluation of the role of ceria in the most important catalytic processes three-way catalysis, catalytic wet oxidation and fluid catalytic cracking. Other topics include oxidation-combustion catalysts, electrocatalysis and the use of cerium catalysts/additives in diesel soot abatement technology. 

Filtration techniques have been widely explored to remove particulates from diesel exhaust, but, until recently, removing the collected material from, for example, a ceramic wall filter has caused problems associated with the high ignition temperature of soot (about 6(X) C). In some situations the additional temperature rise due to soot oxidation can be sufficient to actually melt the ceramic ... 

The removal of soot from diesel exhaust gas is preferably done catalytically. Fuel additives and supported molten salts are promising catalyst for this application. NO in the exhaust gas can be used to increase the soot oxidation rate. 

Investigation of copper-cerium oxide catalysts in the combustion of diesel soot... 

The combustion of diesel soot has been studied in presence of copper-cerium oxide catalysts. These catalysts were prepared by impregnation of copper nitrate on ceria and calcination under air up to 1073 K. The solids were widely characterised by electron paramagnetic resonance (EPR) technique. For an atomic ratio Cu/Ce=l and a calcination temperature of 673 K, the catalyst seems to be t e most active in the combustion of diesel soot, when compared to other catalysts. The Cu monomers are more concerned than the dimers in this combustion. 

The purpose of this work is to study the catalytic properties of different copper-cerium oxides in the combustion of diesel soot and to correlate their activities with the nature of copper species present in the catalyst. 

---