Cetane improver

Cetane Improvers. Compared to dedicated alcohol engines, fewer hardware changes need to be made to heavy-duty engines using cetane... 

Auckland Regional Authority converted two M.A.N. buses to use a cetane improver and methanol and South Africa investigated the use of methanol with a proprietary cetane improver. Eour Renault buses were converted in Tours, Erance to operate on ethanol and a cetane improver, Avocet, manufactured by Imperial Chemical Industries (ICI). The results of these demonstrations were also technically successfiil slightly better fuel economy was obtained on an energy basis and durabiUty issues were much less than the earlier tests using dedicated engines. 

The biggest potential use of the cetane-improver approach may be in vehicle retrofits where for environmental reasons bus and tmck fleets may be requked to convert to cleaner burning fuels. 

C. M. Urban, T. J. Timbario, and R. L. Bechtold, "Performance and Emissions of a DDC 8V-71 Engine Pueled with Cetane Improved Methanol," SyPE Paper 892064, SyPE Int. Fuels and Eubricants Meeting and Expo. (Baltimore, Md., Sept. 25—28,1989) Society of Automotive Engineers, Warrendale, Pa. 

Lubricants, Fuels, and Petroleum. The adipate and azelate diesters of through alcohols, as weU as those of tridecyl alcohol, are used as synthetic lubricants, hydrauHc fluids, and brake fluids. Phosphate esters are utilized as industrial and aviation functional fluids and to a smaH extent as additives in other lubricants. A number of alcohols, particularly the Cg materials, are employed to produce zinc dialkyldithiophosphates as lubricant antiwear additives. A smaH amount is used to make viscosity index improvers for lubricating oils. 2-Ethylhexyl nitrate [24247-96-7] serves as a cetane improver for diesel fuels and hexanol is used as an additive to fuel oil or other fuels (57). Various enhanced oil recovery processes utilize formulations containing hexanol or heptanol to displace oil from underground reservoirs (58) the alcohols and derivatives are also used as defoamers in oil production. 

Lee, S. L., de Wind, M., Desal, P. H., Johnson, C., and Asim, M, Y., Aromatics Reduction and Cetane Improvement of Diesel Fuels," Catalyst Chemical Seminar, Dallas, Texas, October 12, 1993. 

The kind of reactions needed for cetane improvement would partially comply with the specifications, since aromatics and particularly polyaromatics have to be saturated... 

On sulfided metallic phases the hydrotreatment reactions also takes place. Noble metal catalysts usually include a zeolitic support. They are particularly used for fulfilling two different objectives, in the case of a gasoline oriented HCK their cracking and isomerization activity is the most important (increasing high octane and conversion yield). In a diesel HCK unit, the noble metal catalyst is mainly oriented to aromatic saturation and cetane improvement. However, in this latter case, also sulfided metal catalysts are used, especially NiW. 

Throughout the world, the most commonly utilized and available cetane improver is based on isooctylnitrate chemistry. Although other compounds have been shown to provide better performance, their cost, availability, and potential safety hazards make them undesirable. 

Isooctylnitrate cetane improvers effectively boost the cetane number by aiding in the autoignition of fuel, thus controlling ignition delay. Some typical guidelines which can be used to anticipate cetane improver performance are listed below ... 

Low-base cetane fuel will not respond to cetane improver treatment as effectively as higher-base cetane number fuel. This is demonstrated in FIGURE 4-9. 

FIGURE 4-9. Cetane Improver Response in a Base 32 Cetane and a Base 42 Cetane Fuel... 

An increase of one to two cetane numbers is typically achieved for every 250 ppm of cetane improver added to diesel fuel. On rare occasions, a boost of three cetane numbers is obtained for each 250 ppm, but this should not be expected. 

Cetane improver addition will not change the calculated cetane index only the engine cetane number will change. 

In federal diesel fuel oil DF-A, cetane improver concentration cannot exceed 0.25 wt%, and in DF-1 and DF-2, cetane improver concentration cannot exceed 0.5 wt%. 

Diesel Fuel Contains Alkyl Nitrate Cetane Improver... 

Diesel fuel containing cetane improver generates higher levels of residual carbon than untreated fuel. This is probably due to the fact that the cetane improver decomposes to catalyze fuel polymerization and gum formation during fuel pyrolysis. 

The effect of increased levels of cetane improver on the Conradson Carbon value of a typical low-sulfur diesel fuel is illustrated in FIGURE 5-6. 

FIGURE 5-6. Effect of Octylnitrate Cetane Improver on the Conradson Carbon Number of a Typical Low Sulfur Diesel Fuel... 

Recent developments and concern over the control of fuel exhaust emissions have led to the increased use of combustion system detergents, oxygenates and cetane improvers in fuel. Oxygenated blend components such as ethanol, methyl t-butyl ether (MTBE), ethyl t-butyl ether (ETBE), and /-amylmethyl ether (TAME) are also used to help limit the exhaust emissions from fuel. 

The federal diesel fuel oil specification VV-F-800D lists the following compounds as acceptable cetane improvers ... 

A thorough discussion of cetane improver performance and applications can be found in CHAPTER 4. 

Cetane improvers can interact with fuel at the 300°F (148.9°C) test temperature. The products of this interaction initiate the formation of dark, insoluble, higher-molecular-weight compounds. The result is fuel which is much darker in color than test fuel which does not contain cetane improver. This problem does not occur in all fuel containing cetane improver. 

Under the conditions of this test, the presence of cetane improver may give higher-than-normal carbon residue values. 

Octyl nitrate cetane improvers are not compatible with a number of different elastomers used in additive storage and injection systems. The information in TABLE 6-6 demonstrates that Teflon has the best compatibility with octyl nitrate cetane improver. 

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