Soot particulates

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 combustion temperature of soot particulates can be lowered by the addition of an oxidation catalyst in the form of fuel additives[2], by spraying metal salt solution on an accumulated soot or by the impregnation of filter walls with an oxidation catalyst. For the last option, oxides of supported metals are considered to be... 

Several researchers have focused their attention on the application of oxide materials to lower the oxidation temperature of soot particulates. It was reported that active soot oxidation catalysts are PbO, C03O4, V2O5, M0O3, CuO, and perovskite type oxides[3]. 

In this paper, we prepared LaMnOa perovskite-type oxides using the malic acid method and investigated their physical properties. It has been also investigated the effect of partial substitution of metal iorrs into La and Mn sites and the reaction conditions on the activity for the combustion of soot particulates. 

Although various restrictions have been placed on carbon particulate emissions from different types of power plants, these particles can play a beneficial, as well as a detrimental, role in the overall plant process. The detrimental effects are well known. The presence of particulates in gas turbines can severely affect the lifetime of the blades soot particulates in diesel engines absorb carcinogenic materials, thereby posing a health hazard. It... 

A. Pigeaud, "Study of the Effects of Soot, Particulate and Other Contaminants on Molten Carbonate Fuel Cells Fueled by Coal Gas," Progress Report prepared by Energy Research Corporation for U.S. Department of Energy, Morgantown, WV, under Contract No. DE-AC21-84MC21154, June 1987. 

Although various restrictions have been placed on carbon particulate emissions from different types of power plants, these particles can play a beneficial, as well as a detrimental, role in the overall plant process. The detrimental effects are well known. The presence of particulates in gas turbines can severely affect the lifetime of the blades soot particulates in diesel engines absorb carcinogenic materials, thereby posing a health hazard. It has even been postulated that, after a nuclear blast, the subsequent fires would create enormous amounts of soot whose dispersal into the atmosphere would absorb enough of the sun s radiation to create a nuclear winter on Earth. Nevertheless, particulates can be useful. In many industrial furnaces, for example, the presence of carbon particulates increases the radiative power of the flame, and thus can increase appreciably the heat transfer rates. 

Howsam and Jones, 1998). For example, the pyrolysis of naphthalene can yield a range of HMW species such as perylene and benzofluoranthenes, possibly as a result of cyclodehydrogenation of the binaphthyls (Howsam and Jones, 1998). This may be particularly important for compounds that are deposited on the walls of open fireplaces along with soot particulates close to the hot zone of the flame. 

Fie. 6 shows by example the influence of the number of valves (2V -> 4V, improved breathing and more uniform fuel distribution) and the compression ratio on fuel consumption and soot particulates versus the NOx level in the ECE R49 test for a 1.5L/cyl. DI-TCI-HD diesel engine. The NOx reduction was achieved by a delayed start of injection. In this example, the advantage of the 4-valve technique primarily consists in the improved fuel consumption at the target low NOx level. 

The second technique is based on a filter to capture the soot particulates. Common filters are wall flow monoliths or ceramic foams. Cordierite wall flow monoliths are probably currently the most used particulate traps. They can capture diesel particulates with an efficiency of 99%. At normal diesel engine exhaust gas temperatures, the captured soot is not reactive enough to prevent build up on the filter, with an intolerable high pressure drop over the exhaust system as a result. The oxidation rate of the soot should, therefore, be increased which can be achieved by increasing the temperature of the filter, resulting in higher fuel consumption and thus making this solution unfavourable. The other possibility is catalytic oxidation of the collected soot. Several catalytic systems will be discussed. 

The liquid state of the catalyst might also result in higher particulate capture by materials that are normally poor soot filters, for example ceramic foams. The micro porous structure can retain the molten salt, while the surface is covered with liquid catalyst, causing the soot particulates to stick. 

Figure 2a. TEM micrograph of soot particulates om a 100 ppm fuel additive run. No individual copper particles can be observed.

B. L. Drolen and C. L. Tien, Absorption and Scattering of Agglomerated Soot Particulate, Journal of Quantitative Spectroscopy and Radiative Transfer, 37, pp. 433-448,1987. 

Boiler efficiency improvements have to be achieved by trying to reduce emissions. Emissions of air-pollutants from combustion in gas and oil utility boilers are nitrogen oxides (NOJ, carbon monoxide (CO), and methane (CH4). In oil-fired boilers we also have to consider the presence of sulfur oxides (SO ), volatile organic compounds (C Hy), and soot (particulate matter, PM). Also carbon dioxide (CO2) has to be considered an air pollutant for ifs global warning potential. 

Soot/catalvst ratio A series of experiments with different [soot/catalyst] ratios is carried out with stoicliiometric substituted Pd doped perovskite as catalyst. Results show that the combustion temperature increases when the [soot/catalyst] ratio is higher than 15 wt%. This is probably due to the lack of contact between catalyst surface and all the soot particulates beyond this point. 

Their results showed that 26% of the mass of the latex was converted to soot (particulate), 11% of which was comprised of condensed PAHs. The yields of PAHs from cotton were higher than those from coal. Along with PAHs and soot, CO, CO2 and NOx were measured at the exit of the furnace. 

Drolen BL, Tien CL Absorption and scattering of a omerated soot particulate, J Quant Spectrosc Radiat Twk 37(5) 433—448, 1987. 

NOj , CI2 and SO c cause corrosion. In addition to the above concerns, emission of pollutants such as HCl, CO2, unbumed hydrocarbons, soot, particulates, dioxins, furans, and volatile organic compounds and metals have received increased attention from many countries around the world. The concerns over pollutants, which are produced as by-products from the direct result of the combustion process [40], are common to aU combustion sources. 

It is the only direct method available to measure free radicals. ESR is used to study both the radicals and the reactions, chemical and physical, which create or modify free radicals. Examples of reactions that can create or change free radicals are electrochanical reactions, exposure to UV radiation, and exposure to ionizing radiation, among others. ESR samples can be liquid, such as oil, blood, or saliva, solid, or gaseous, such as measurement of soot particulates in air. ESR is both a qualitative and quantitative technique, measuring the type and concentration of free radicals in a sample. Qualitative information is obtained from the g value of a peak, while quantitative results are obtained by integrating the area under the peaks. 

Teraoka et al. [15] also reported that Co, Mn, and Fe perovskite-type and Cu-based I<2NiF4-type oxides (all with La partially substituted by alkaline metal or alkaline earth metal cations) catalyze the simultaneous removal of NO and diesel soot particulates and that these perovskite-related oxides are superior to transition metal simple oxides and Pt/Al203 with regard to their selectivity toward NO reduction. 

Teraoka, Y., Nakano, K., Shangguan, W.F., and Kagawa, S. (1996) Simultaneous catalytic removal of nitrogen oxides and diesel soot particulate over perovskite-related oxides. Catal Today, 27, 107-113. 

Catalytic removal of diesel soot particulates over K and Mg substituted Lai K Coi yMgy03 perovskite oxides. Catal. Commun, 49,15-19. 

Teraoka, Y., Kanada, K., and Kagawa, S. (2001) Synthesis of La-K-Mn-O perovskite-type oxides and their catalytic property for simultaneous removal of NO and diesel soot particulates. Appl. Catal. 

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