Diesel ageing

As diesel ages a fine sediment and gum forms in the fuel brought about by the reaction of diesel components with oxygen from the air. The fine sediment and gum will block fuel filters, leading to fuel starvation and engine failure. Frequent filter changes are then... 

The procedure most commonly employed (NF M 07-047 or ASTM D 2274) Is to age the diesel fuel for 16 hours while bubbling oxygen into it at 95°C. The gums and sediment obtained are recovered by filtration and weighed. There is no official French specification regarding oxidation stability however, in their own specifications, manufacturers have set a maximum value of 1.5 mg/100 ml. 

Long-chain esters of pentaerythritol have been used as pour-point depressants for lubricant products, ranging from fuel oils or diesel fuels to the high performance lubricating oils requited for demanding outiets such as aviation, power turbines, and automobiles. These materials requite superior temperature, viscosity, and aging resistance, and must be compatible with the wide variety of metallic surfaces commonly used in the outiets (79—81). 

The age of diesel oil in the subsurface soil environment can be determined by utilizing the fact that the composition of the diesel oil (the ratio between -alkanes and isoprenoids) changes due to biodegradation. In one study, the ratio of C , to pristane was highly correlated with the residence time of diesel fuel at 12 test locations (Christensen et al 1993). 

Christensen LB, Larsen TH. 1993. Method for determining the age of diesel oil spills in the soil. Ground Water Monitor Remediation 13(4) 142. 

Konstandopoulos, A. G., Kostoglou, M., Skaperdas, E., Papaioannou, E., Zarvalis, D., and Kladopoulou, E., Fundamental studies of diesel particulate filters Transient loading, regeneration and aging. SAE Technical Paper No. 2000-01-1016 (SP-1497) (2000). 

In order to improve the stability of synthetic diesels and biodiesels it is necessary to add free-radical trapping additives known as antioxidants (such as DTBHQ, lONOX 220, Vulkanox ZKF, Vulkanox BKF, and Baynox). Butylated hydroxy toluene (BHT) in particular prevents oxidation and radical polymerization reactions that can lead to diesel fuel ageing. 

Figure 14 Optimal passive NO performance (without secondary fuel injection) for fresh and aged catalysts on a 1.9-liter TDI diesel bench engine.

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