Soluble organic fraction

The average ambient concentrations of the cyclohexane-, di-chloromethane- and acetone-soluble organic fractions from January, 1978 to August, 1979 were 2.9 yg/m, 1.0 yg/m and 4.4 yg/m. Respirable suspended particulate matter averaged 30.3 yg/m. ... 

As far as toxicology is concerned, one must distinguish between soot, which is formed by the uncontrolled combustion of coal and oil, and carbon black, which is industrially produced under precisely defined conditions. Commercial carbon blacks are characterized by an atomic ratio H C of <0.1, low ash content, and high adsorption capacity. The soluble organic fraction (extractable materials) is less than 0.5 wt%. 

Figure 6 Effect of platinum content (g ft ) in diesel oxidation catalysts on tailpipe emissions in the ECE R49 test carbon monoxide (a), hydrocarbon (b), soluble organic fraction (c), sulfur trioxide (d), and particulates (e). The fuel sulfur content was 500 ppm.

Since about 1991, diesel oxidation catalysts have been generally applied to passenger cars in the European Union and to some medium and heavy duty trucks in the USA. Their principle of operation is shown in Fig. 101. The amount of carbon monoxide, hydrocarbons and aldehydes is reduced by oxidation of these components to carbon dioxide and water. The mass of particulate matter emitted is reduced by the oxidation of the liquid hydrocarbons, which are adsorbed on the particulates. These liquid hydrocarbons originate both from the fuel and the lubricating oil, and are commonly denoted as the soluble organic fraction (SOF). The adsorbed polynuclear aromatic hydrocarbons are also removed by oxidation. 

The washcoat composition is quite different to that used for three-way catalysts. The washcoat oxides used are chosen so as to ensure a minimal adsorption both of the soluble organic fraction and of the sulfur oxides SO2 and SO3. The properties of three different oxides in these respects are shown in Figs. 103 and 104. The composition of the washcoat is, together with the choice of precious metal formulation. 

Figure 103. The amount of soluble organic fraction (SOF) adsorbed on an aged diesel oxidation catalyst, as a function of the washcoat formulation (monolith catalyst with 62cellscm", dedicated diesel washcoat formulations with platinum at a loading of l.76gl diesel engine bench aging for 50 h diesel fuel containing 0.15 wt. % sulfur). Reprinted with permission from ref. (68], C 1991 Society of Automotive Engineers, Inc.

Figure 107. Conversion of (a) gaseous hydrocarbons (b) total particulate (PT) matter and (c) the soluble organic fraction (SOF) as a function of the exhaust gas temperature, reached over diesel eatalysts based on platinum or on palladium (monolith catalyst with 62 cells cm dedicated diesel washeoat formulations with platinum and palladium both at a loading of 0.35 g 1" and 1.41 g 1" in the fresh state heavy duty diesel engine bench light-off test at an average engine speed setting and various engine load settings).

In this study, the concentrations of several kinds of nitro-PAH, such as 1-nitropyrene (1-NP), 2-nitropyrene (2-NP), 2-nitrofluoranthene (2-NF), and 2-NTP, in the soluble organic fraction of airborne particles were determined by a column switching HPLC-chemiluminescence detection system in order to clarify the occurrence and behaviour of 2-NTP in the atmosphere. 

The application of exhaust gas aftertreatment methods is currently mainly focussing on reducing the soluble organic fraction of particulates by means of oxidation catalysts. The exhaust gas aftertreatraent strategies that may be followed in the future are ... 

The main liquids present in the particulates are a combination of lighter unbumed fuel and lubricating oil, e.g. swept from the cylinder walls. Together these are the so called soluble organic fraction (SOF) or volatile organic fraction (VOF) which are in the form of discrete aerosols and/or are adsorbed on the dry carbon... 

A laboratory method simulating the adsorption and subsequent catalytic combustion of the soluble organic fraction (SOF) on these newly developed diesel oxidation catalysts, is also described in this paper. This technique, based on thermal chromatography, allows characterization of the initiation of catalytic oxidation and analysis of the products giving insight into the mechanism of operation. 

A possible exception to some of the statements made above is emphasized by the work of Van Schreven (1964), who found that grinding may decrease the rate of decay of plant materials that have been oven-dried. This treatment increases the carbon—nitrogen ratio of the water-soluble organic fraction. 

Now that many jurisdictions regulate the sulphur and biodiesel content of diesel fuel, significant variability exists in diesel fuel composition and, consequently, UFP emissions. One investigation has demonstrated a 30% decrease in PM emissions with use of 100% biodiesel fuel but the soluble organic fraction increased by 40% (Sharp 1998). The sulphur content in diesel fuel also greatly influences the observed UFP emissions. In jurisdictions that have implemented ultra-low sulphur fuel, significant reductions in ambient UFP have been observed (WShlin 2009). 

Particulate matter consists basically of three fractions, the relative amounts of which depend strongly on fuel quality and engine conditions. The first is dry soot, which is a low-hydrogen-content, polyaromatic species that, regardless of the catalyst, cannot be oxidized under normal diesel exhaust conditions. The second component is the soluble organic fraction (SOF), derived from unbumt fuel and lube oil, and consisting mostly of HCs in the C20-C28 range. The SOF... 

BSO, benzene-soluble organic fraction of particulate matter. Cyclohexane extract of particulate matter. 

---