Diesel fuel stabilizer

A diesel fuel stabilizer containing a blend of amines, polyamines, and alkyl ammonium alkyl phosphate as specified under MIL-S-53021 is recommended for federal diesel fuel oil. This stabilizer is to be used at a treat rate of 25 lb/1,000 barrels. It is not intended for use in routine applications, but for situations where increased stability protection is required. Typical applications include fueled equipment undergoing long-term storage in a warehouse or depot, prepositioned equipment or equipment maintained in a high-temperature environment. 

Hydrocracking makes very good quality diesel fuels concerning the cetane number, cold behavior, stability, and sulfur content. However this type of stock is only available in limited quantities since the process is still not widely used owing essentially to its high cost. 

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. 

Stability. Diesel fuel can undergo unwanted oxidation reactions leading to insoluble gums and also to highly colored by-products. Discoloration is beheved to be caused by oxidation of pyrroles, phenols, and thiophenols to form quiaoid stmctures (75). Eventually, these colored bodies may increase in molecular weight to form insoluble sludge. 

Detergent Additives. Diesel engine deposits ate most troublesome in the fuel dehvery system, ie, the fuel pump and both fuel side and combustion side of the injectors. Small clearances and high pressures mean that even small amounts of deposits have the potential to cause maldistribution and poor atomization in the combustion chamber. The same types of additives used in gasoline ate used in diesel fuel. Low molecular weight amines can also provide some corrosion inhibition as well as some color stabilization. Whereas detergents have been shown to be effective in certain tests, the benefit in widespread use is not fully agreed upon (77). 

There has been a recent revival in interest in the use of ethanol-diesel fuel blends (E-diesel) in heavy-duty vehicles as a means to reduce petroleum dependency, increase renewable fuels use, and reduce vehicle emissions [27]. E-diesel blends containing 10-15% ethanol could be prepared via the use of additives. However, several fuel properties that are essential to the proper operation of a diesel engine are affected by the addition of ethanol to diesel fuel - in particular, blend stability, viscosity and lubricity, energy content and cetane number (increasing concentrations of ethanol in diesel lower the cetane number proportionately) [28]. Materials compatibility and corrosiveness are also important factors that need to be considered. 

A common method used to evaluate the stability of diesel fuel is to heat the fuel at a temperature of 300°F (148.9°C) for 90 minutes. After that time period, the fuel is analyzed for color change and deposit formation. 

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 ... 

Biodiesel methyl esters blend quite easily into petroleum based conventional diesel fuel. Biodiesel esters typically have better lubricity properties and higher cetane number ratings than conventional diesel fuel, but have poorer water demulsibility and color stability properties. At sub-zero temperatures, the handling characteristics of biodiesel becomes more difficult to control than conventional diesel fuel. 

Very poor biodiesel and biodiesel blends do not shed water as effectively as conventional diesel fuel fuel haze, gelling, and low-temperature handling problems can develop if biodiesel is contaminated with water in storage and transport. Poor double bonds present in the methyl ester compounds are active sites for oxidation and condensation reactions peroxide values can increase fuel darkening and deposit formation in storage systems can occur the addition of oxidation inhibitors to biodiesel helps improve storage stability. 

Fischer-Tropsch synthesis making use of cobalt-based catalysts is a hotly persued scientific topic in the catalysis community since it offers an interesting and economically viable route for the conversion of e.g. natural gas to sulphur-free diesel fuels. As a result, major oil companies have recently announced to implement this technology and major investments are under way to build large Fischer-Tropsch plants based on cobalt-based catalysts in e.g. Qatar. Promoters have shown to be crucial to alter the catalytic properties of these catalyst systems in a positive way. For this reason, almost every chemical element of the periodic table has been evaluated in the open literature for its potential beneficial effects on the activity, selectivity and stability of supported cobalt nanoparticles. 

In recent years, the middle distillates have been in growing demand as fuel oils and Diesel fuel. As mentioned under the discussion on Diesel-fuel additives, it has been possible to meet this demand only by the inclusion of distillates from catalytic cracking operations. These have higher volumetric heat contents and lower pour and cloud points, but their use has caused problems of stability and compatibility in storage, necessitating use of anti-screen-clogging agents (14, 41, 4 )-... 

Diesel fuel and heating fuels should pass both oxidation and thermal stability tests. As shown in Table XII, the raw Wyodak H-Coal syncrude has a very poor oxidation stability but the hydrotreated Wyodak H-Coal syncrude has an excellent oxidation stability. The oxidation stability of hydrotreated Illinois H-Coal products is also excellent, even without additives. 

Once the synthetic crude oils from coal and oil shale have been upgraded and the heavy ends converted to lighter distillates, further refining by existing processes need not be covered in detail except to note the essential character of the products. The paraffinic syncrude from oil shale yields middle distillates which are excellent jet and diesel fuel stocks. The principal requirements are removal of nitrogen to the extent necessary for good thermal stability of the fuels and adjustment of cut points to meet required pour or freeze points, limited by the presence of waxy straight-chain paraffins. The heavy naphtha from shale oil can be further hydrotreated and catalytically reformed to acceptable octane number, but with considerable loss of volume because of the only moderate content of cyclic hydrocarbons, typically 45-50%. On the other... 

Du Plessis, L. M., and de Villiers, J. B.M. 1983. Stability Studies on Methyl and Ethyl Esters of Sunflower Seed Oil. In Bagby, M. O., and Pryde, E. H. (Eds.), Proc., Vegetable Oil as Diesel Fuel Seminar III (pp. 57-62). Peoria IL USDA Northern Regional Research Center. 

Though FAME has limited oxidation stability, they remain a valid alternative for diesel. Conventional diesel fuel has a boiling range of 180-340 °C, with a composition of n-alkanes, cycloalkanes, alkyl benzenes, and polyaromatic compounds. Fossil diesels have a CN in the range 40-100. FAME has properties that are close to all these basic diesel properties. FAME can also easily blend with fossil diesel at any level due to their similar solvent behavior the viscosity of fossil diesel and biodiesel are also in the same range. 

Resistance to the Solvent Action of Fuels. Sulfur—asphalt concretes were less affected by the solvent action of fuels than was normal asphaltic concrete. The solvent action of three fuels—gasoline, JP-4 jet fuel, and No. 2 diesel fuel—was tested on samples of normal asphaltic concrete and on 15-, 25-, and 35-vol % sulfur-asphalt concretes. Two test methods developed by McBee (15) were used to determine loss in weight and loss of stability on drip and total immersion testing of Marshall compaction samples. 

Marshall stability of asphalt concrete dropped 72% after immersion testing in gasoline compared with only a 21% loss with 35-vol % sulfur-asphalt concrete. Jet and diesel fuels had a lesser effect on the Marshall stabilities than did gasoline. The solvent effect on sulfur-asphalt concrete materials decreased with increasing sulfur content in the asphaltic binder in the O-35-vol % substitution range. The greater resistance of sulfur-... 

The diesel needs to be stabilized with diesel fuel additives that will inhibit diesel polymerization and inhibit oxidation, darkening and agglomeration of certain components of the diesel. One such effective stabilizing additive is Octel FOA-6. Octel FOA-6 and FOA-3 are amine-based antioxidants that are recommended for antioxidant protection of distillate fuels such as diesel. FOA-3 and FOA-6 together with AO-22, generally give then-best performance when added hot and early to the fuel, usually to a cracked component in the run-down from the cracker. 

STORAGE STABILITY OF PLASTIC-DERIVED DIESEL FUEL... 

The expected life of a diesel fuel is indicated by the oxidation stability test (ASTM D-2276). The test measures how much gum and sediment will be deposited after conditioning the fuel at 120°C in the presence of oxygen for 16 h. It roughly corresponds to a years storage at 25°C. A result of less than 20 mg/L of sediment and gum after the test is considered acceptable for normal diesel. 

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. 

---