Diesel degradation

The tendency of the color to become darker with time is often indicative of chemical degradation. The test is conducted with the aid of a colorimeter (NF T 60-104 and ASTM D 1500) and by comparison with colored glass standards. The scale varies from 0.5 to 8. The French specifications stipulate that diesel fuel color should be less than 5, which corresponds to an orange-brown tint. Generally, commercial products are light yellow with indices from 1 to 2. 

Bregnard TP-A, P Hohener, A Haner, J Zeyer (1996) Degradation of weathered diesel fuel by microorganisms from a contaminated aquifer in aerobic and anaerobic conditions. Environ Toxicol Chem 15 299-307. 

Hess A, B Zarda, D Hahn, A Haner, D Stax, P Hohener, J Zeyer (1997) In situ analysis of denitrifying toluene-and m-xylene-degrading bacteria in a diesel fuel-contaminated laboratory aquifer column. Appl Environ Microbiol 63 2136-2141. 

Riis, V., Babel, W., and Pucci, O., Influence of heavy metals on the microbial degradation of diesel fuel, Chemosphere, 49 (6), 559-568, 2002. 

For some heavy hydrocarbon fuels, typical values range from as low as 870°C for catalytic POX upwards to 1,400°C for non-catalytic POX. For sulfur-bearing diesel fuel, a catalytic POX reactor will usually operate at approximately 925°C. This relatively elevated temperature is needed to overcome catalyst degradation due to the presence of sulfur. Non-catalytic POX reactors operating at around 1,175°C on diesel fuel. 

Acetone was detected in diesel fuel at a concentration of 22,000 pg/g (Schauer et al., 1999). Identified as an oxidative degradation product in the headspace of a used engine oil (10-30W) after 4,080 miles (Levermore et al., 2001). Acetone also was detected in automobile exhaust at concentrations ranging from 0.09 to 4.50 mg/m (Grimaldi et al, 1996) and in cigarette smoke at concentrations ranging from 498 to 869 mg/m (Euler et al., 1996). 

The Oil Snapper product is based on Serengeti s Enhanced Urea Technology and contains the minerals and chemical compounds needed by microbes to degrade petroleum hydrocarbons. This product is applicable to soils contaminated with most petroleum hydrocarbons, including diesel, No. 6 fuel oil, hydraulic oil, and crude oil. 

Although hydroprocessing will remove most of the naturally occurring antioxidants contained in fuel, other less stable, more reactive components will also be reduced. As a whole, ultra-low sulfur diesel fuel will be much less prone to color degradation and deposit formation than earlier-era diesel fuels. 

Degradation of diesel fuel color and accumulation of insoluble deposits... 

Phenylenediamine (PDA) type antioxidants are naturally very dark in color. If used in water white fuels such as kerosene, 1 diesel, or even certain hydrocarbon solvents, the color can be degraded to failing Saybolt color values. 

Fuel degradation by oxidation is a common cause of fuel stability problems. Gasoline, jet fuel, diesel fuel, and heating oil are all susceptible to oxidative degradation. The following methods can be used to help determine the oxidative stability of fuels ... 

McDow, Kamens, and co-workers also conducted laboratory experiments on the effects of common organic constituents (e.g., methoxyphenols) on the rates, mechanisms, and products of the solution-phase photodegradation of PAHs associated with wood smoke and diesel soot (see, for example, Odum et al. (1994a), and McDow et al. (1994, 1995, 1996)). Figure 10.28, for example, shows the degradation of the reactive BaP (Class II reactivity) compared to BeP (Class V reactivity) in two solvents, hexadecane, taken as representative of aliphatics in diesel soot, or a mixture of 11 methoxyphenols found in particulate matter (McDow et al., 1994). As expected, BaP decays much more rapidly than BeP. In addition, the decay in the mixture of methoxyphenols is much faster than that in hexadecane. 

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