Carbonaceous soot

Atmospheric particulates (sea salt, carbonaceous soot, and sulfuric acid aerosols) are known to provide a condensed phase for conq>lex heterogeneous chemistry to occur. Although the presence of atmospheric particulates are known to alter trace gas concentrations, details of the specific chemical mechanisms for condensed phase chemistry have not been identified. 

For example, studies of the morphology of a number of flame-generated aggregates (different carbonaceous soots, A1203 aerosols, etc.) [203] by both TEM and ALS procedures resulted in D2 = 1.7 0.15, while analysis of silhouettes of computer models of seven proteins [211] gave a value of D2 = 1.120 0.025, etc. 

The pressure drop over the filter increases continuously with time until the moment, when a critical soot load has accumulated on the filter surface. Self-ignition of the soot then occurs, which in addition depends on the exhaust gas temperature, the filter temperature, the oxygen concentration, the type and amount of the volatiles adsorbed onto the carbonaceous soot matrix, and the packing density of the soot on the filter surface. The soot-laden filter bums free, the pressure drop decreases and the loading/regeneration cycle repeats itself again, as shown in Fig. 15.4. 

Particulate matter from waste combustors includes inorganic ash present in the waste and carbonaceous soot formed in the combustion process. The inorganic-ash fraction of the PM consists of mineral matter... 

Figure 14.13 shows a TEM image of soot clusters sampled from an acetylene-in-air diffusion flame. Analysis shows these clusters are fractals with D — 1.8 and a = 23 nm (thus for X= 514.5 nm a= 0.28). This is typical of carbonaceous soot formed in a variety of flames. 

The soot containing cores were tested for conversion of CjHg, a model hydrocarbon, and the retained carbonaceous soot using an automated laboratory... 

Kayama et al evaluated soot oxidation over Ag/CeOg by TG analysis of the catalyst in contact with the carbonaceous soot. They... 

Figure 8.31 Performance of CeOj-Ag compared with conventional catalysts and in the absence of a catalyst, (a) Evaluation of carbonaceous soot oxidation, (b) Arrhenius plots. Reprinted with permission from Kayama et aZ. Copyright 2010 the American Chemical Society.

For the bare particles at high electrolyte concentration, the structural coefficient ko is very close to unity and the surface-to-surface distance between the particles contained in the aggregates is approximately zero. The expected result is in good agreement with other experiments [30,56] and simulations [57]. The obtained value is, however, significantly smaller than the values reported in [58] for carbonaceous soot aggregates formed in laminar diffusion flames. This is not surprising... 

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