Diesel additives

Other significant parameters related to the low-temperatnre characteristics are pour point (PP) and cold filter plugging point (CFPP). These parameters are coded and measured by the ASTM and DIN methods and generally vary in a mntnally coherent manner. The ponr point can be reduced by using additives, bnt these have no appreciable effect on the clond point. 

Diesel made predominantly from polyethylene has a higher proportion of paraffins and therefore a higher cloud point. The paraffins crystallize as the temperature is lowered, leading to small visible crystals forming in the diesel. It is these wax crystals that can plug filters at low temperatures. 

The addition of small amounts of cold flow improvers (also known as pour point depressants) brings the pour point of the diesel into the normal range. This can be achieved for example by addition of 1000 ppm of Callington Haven Roxdiesel Pour Point Depressant. 

It has been found that additives such as pour point depressants can lower the pom-point, but not the cloud point. It has been found empirically that styrene monomer can lower the cloud point since the paraffinic wax crystals are more soluble in the styrene than in the diesel. Styrene monomer is proposed as a suitable additive to depress the cloud point. 

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An extensive review has been conducted to identify potential oxygenates for blending into diesel fuels [55]. Over 70 molecules were identified and tested, taking into account numerous physical properties such as oxygen content, flash point, viscosity, cetane number, corrosivity, toxicity, and miscibility with diesel blends. Five key aspects were considered critical to develop commercially valuable diesel additives ... 

Biological, toxicological and environmental issues were also taken into account. Based on these aspects, bioethanol itself does not possess the necessary characteristics as diesel additives, and its conversion into ETBE suffers from limits in the availability of isobutene. There is thus the need to develop alternative oxygenated fuel additives. 

Herbstman, Sheldon. 1990. Diesel Additives to Improve Fuel Quality. Lubrication. vol. 76, no. 2. White Plains, N.Y. Texaco, Inc. 

Component Function European gasoline + diesel additive package (mass%)... 

Biodiesel is a renewable energy produced from sustainable animal fat and vegetable oil feedstocks, such as soy, rapeseed, sunflowers, palm oil, hemp, and algae, and can be used as a vehicle or transportation fuel. As with ethanol, however, biodiesel is more often used as a diesel additive to reduce the levels of pollution emitted by traditional diesel engines. It is primarily produced through a process known as transesterification, which is the exchange or conversion of an organic acid ester into another ester. 

The foaming of diesel fuel has drawn a certain attention in the last decade. Antifoams are usually one component of a package of diesel additive, which is used to adjust and improve the properties of the distillate from the refinery [44]. Antifoams prevent foam formation of the treated diesel fuel during pumping at refineries and service stations at treat rates between 5 and 15 ppm. They help to shorten substantially the filling time of fuel tanks and avoid splashing over. 

Texaco/NYSERDA/BIOFINE ethyl levulinate D-975 Diesel Additive Test Program, Glenham, NY, June, 2000. 

Issariyakul, T., Dalai, A.K. and Desai, P. 2011. Evaluating esters derived from mustard oil (Sinapis alba) as potential diesel additives. J. Amer. Oil Chem. Soc. 88 391 02. 

The differences between the measured cetane numbers and the cetane indices calculated by the above formula are relatively small for cetane indices between 40 and 55. Nevertheless, for diesel fuels containing a pro-cetane additive, the CCl will be much less than the actual value (refer to paragraph d). 

Improving the cetane number by additives results in better engine behavior, as would be predicted by the combustion mechanisms in the diesel engine (noise reduction, better operating characteristics, particularly when cold). Nevertheless, concerning certain items such as pollution emissions, it may be better to obtain a higher cetane number rather by modification of the... 

The gas oil cut from catalytic cracking called Light Cycle Oil (LCO), is characterized by a very low cetane number (about 20), high contents in aromatics, sulfur and nitrogen, all of which strongly limit its addition to the diesel fuel pool to a maximum of 5 to 10%. 

The level of injector fouling is most often illustrated in terms of residual flow (RF) expressed as a percentage of the flow under new conditions for a given needle lift. An RF on the order of 20% for a lift of 0.1 mm is a good compromise. This level may not be achieved with certain aromatic or naphthenic diesel fuels. The best recourse is then detergent additive addition. 

In order to meet French manufacturers fuel quality specifications, a diesel fuel should contain a detergent additive whose effectiveness will have been demonstrated by the procedure described previously. 

Diesel engine injector fouling. Residual flow (RF) for different additive levels. ... 

Diesel fuels, like gasoline, are formulated with additives that affect the process of combustion, in this case to improve the cetane number. Diesel fuels also contain detergents for irijection systems as well as compounds for improving the fuel s low tempierature rheology. Finally, decreasing particulate emissions is a problem of increasing concern, but the mechanism of action to promote this effect is not clearly understood. 

Unlike spark-induced combustion engines requiring fuel that resists autoignition, diesel engines require motor fuels, for vhich the reference compound is cetane, that are capable of auto-igniting easily. Additives improving the cetane number will promote the oxidation of paraffins. The only compound used is ethyl-2-hexyl nitrate. 

The role of detergent additives is to maintain clean injectors so as to insure good distribution of diesel fuel in the cylinder. The structure of these compounds is similar to that of detergents for gasoline engine admission systems. Commercialized compounds are from the succinimide family (see Figure 9.1). 

Additives for Improving the Cold Behavior of Diesel Fuel (Coley, 1989)... 

The nature of these paraffins and their concentration in diesel fuel affect the three temperatures that characterize the cold behavior. The cloud point is the temperature at which crystals of paraffins appear when the temperature is lowered. The cold filter pluming point is defined as the temperature under which a suspension no ionger flows through a standard filter. Finally, the pour point is the temperature below which the diesel fuel no longer flows by simple gravity in a standard tube. These three temperatures are defined by regulations and the refiner has three types of additives to improve the quality of the diesel fuel of winter. 

The elimination of lead, the reduction of aromatics in gasoline, and the desulfurization of diesel fuels are oing to require significant reformulations of these products that will irripiy development of specific additives that allow the refiner to optimize costs while meeting the required specifications. 

Although lubricant base stocks have been subjected to dewaxing processes, they still contain large amounts of paraffins that result in a high pour point for the oil. In the paragraph on the cold behavior of diesel fuels, additives were mentioned that modify the paraffin crystalline system and oppose the precipitation of solids. 

Coley, T.R. (1989), Diesel fuel additives influencing flow and storage properties . In Gasoline and diesel fuel additives (Owen, K. Ed.). John Wiley. 

Damin, B., A. Faure, J. Denis, B. Sillion, P. Claudy and J.M. Letoffe (1986), New additives for diesel fuels cloud point depressents . SAE paper No. 86-1527, International fuels and lubricants meeting and exposition, Philadelphia, PA. 

Montagne, X., D. Merrier and J.-C. Guibet (1987), "Fouling of automotive diesel injectors. Test procedure, influence of composition of diesel oil and additives". SAE paper No. 87-2118, International fuels and lubricants meeting, Toronto, Ontario. 

Nelson, O.L., R.W. Krumm, R.S. Fein, D.D. Fuller, G.K. Rightmire and G.E, Ducker (1989), "A broad spectrum, non metallic additive for gasoline and diesel fuels performance in gasoline engines". SAE paper No. 89-0214, fnt. Congress, Detroit, MI. 

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