Fuel and related compositions – Liquid fuels – Organic nitrogen compound containing
Reexamination Certificate
1997-06-26
2003-05-13
Medley, Margaret (Department: 1714)
Fuel and related compositions
Liquid fuels
Organic nitrogen compound containing
C044S419000
Reexamination Certificate
active
06562086
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvement of lubricity of fuels, and more particularly to chemical treatment of low sulfur diesel fuels and spark ignition fuels for improvement of lubricity.
2. Description of the Prior Art
Low sulfur diesel fuels were developed in the early 1990s in response to environmental concerns. Such fuels are prepared by severely hydrotreating diesel components to produce a low sulfur, olefin and aromatic content fuel. Standards have been set for such low sulfur content fuels. According to ASTM Standard Specification for Diesel Fuel Oils D-975-96a low sulfur diesel fuel has a maximum sulfur content of 0.05% based on mass, versus levels as high as 0.5% or more for equivalent standard diesel fuels. As used herein, the phrase “low sulfur diesel fuels” refers to such hydrotreated fuels of maximum sulfur content of 0.05% based on mass.
While such fuels are desirable from an environmental standpoint, they suffer from a serious problem of substantially reduced lubricity. “Lubricity” refers to the lower friction, wear or scuffing that a liquid may give compared to another liquid of the same viscosity. See, for example, “The Lubricity of Diesel Fuels,” Wei, D. et al., Wear, 111 (1986), pp. 217-235.
Many articles have discussed low sulfur diesel fuels and their poor lubricity characteristics. For example, see “Lubricity Additives—Performance and No-Harm Effects in Low Sulfur Fuels,” Batt, R. J., et al., SAE Publication 961943 (1996); “Development of Laboratory Tests to Predict the Lubricity Properties of Diesel Fuels and the Application to the Development of Highly Refined Diesel Fuels,” Bovington, C. et al., Tribotest Journal 2—2, December 1995, (2) 93 1354-4063; and PCT patent application, International Publication No. WO 94/17160 (Exxon Chemical Patents, Inc.); all of which are incorporated herein by reference. The cited PCT patent publication (p. 1), notes that the poor lubricity of the low sulfur diesel fuel creates a serious problem because “the ability of the fuel to lubricate the injection system of the engine is reduced such that, for example, the fuel injection pump of the engine can fail relatively early in the life of an engine . . .”
This concept of lubricity and lubricity additives, to which the present invention is directed, is distinct from wear-reducing additives as used in lubricants and in lubricity additives. Moreover, although mainly boundary lubrication, where the additive forms a layer between the two metal surfaces, is thought to be operative, mechanisms of providing good lubricity varying from boundary lubrication to hydrodynamic (hydraulic lubrication) have been suggested as the role of lubricity additives.
Thus, U.S. Pat. No. 4,204,481 (Malec) appears to be directed to wear in injectors in conjunction with standard relatively high sulfur content fuel. For instance, in the “Background of the Invention,” Malec reports that certain alcohols have been substituted for conventional petroleum-derived diesel fuels and that while such alcohols (with the addition of certain accelerators) may be used as fuels, they are “notably deficient in lubricity or lubricating properties with the result that engine wear from the use of these fuels in internal combustion reciprocating diesel engines is a serious problem . . .” and of “particular concern are wear problems associated with the fuel injector mechanisms used in such engines.” By contrast, the subject invention is directed to lubricity at fuel pumps, in particular, rotary/distributer pumps, where the lubricant is the fuel itself, and which as a result are the cite of most wear problems as opposed to in-line fuel pumps which are lubricated by engine oil. See, for instance, “Severe Hydrotreating of Diesel Can Cause Fuel-Injector Pump Failure,” Booth, M. et al., Oil and Gas Journal, Aug. 16, 1993, pp. 71-76.
As reported in the cited Tribotest Journal article and elsewhere, temperature and wear mechanisms present are critical in determining whether a pump will fail. These considerations of temperature and wear mechanisms emphasize the distinctive nature of the lubricity problem as opposed to the problem of injector wear, to which the cited Malec patent is directed. Injectors, are subjected not only to very high cylinder temperatures (and so operate at much higher temperatures than do fuel pumps), but also to a substantially different wear mechanism than are fuel pumps. In particular, injectors experience linear (up and down) type of wear, while fuel pump wear is the result of sliding and rotary components from the action of the pump. And it has been noted that adhesion, sliding wear, oxidative and fatigue wear are all found in fuel pumps using poor lubricity fuel.
Some lubricity aids have been developed for low sulfur diesel fuels, but each suffers from one or more drawbacks when applied to such fuels. For example, many additives are fatty acids or modified fatty acids and so are acidic in character, which is undesirable due to concerns that they will react or otherwise interfere with the effectiveness of other additives, such as amine surfactants. Other additives are esters, but have several free hydroxide groups on the molecules which cause the additive to exhibit poor water tolerance and high dose rates may be required. Likewise, imidazolines have been found to have poor water tolerance and/or poor hydrolytic stability, resulting in precipitate formation upon extended exposure to moisture. Still other additives increase the tendency of the fuel to form an emulsion and thus to become hazy upon exposure of the fuel to moisture. Generally, however, low sulfur diesel fuels are so new that few lubricity aids have been developed for them, regardless of efficacy or drawbacks.
Moreover, although low sulfur diesel fuel is of particular concern, there is a continual search for new alternative lubricants for spark ignition fuels as well.
SUMMARY OF THE INVENTION
The present invention, therefore, is directed to a novel fuel composition of improved lubricity. The fuel composition comprises a lubricity-increasing amount of a lubricity aid dissolved in a fuel selected from the group consisting of low sulfur diesel fuel and spark ignition fuels. The lubricity aid is an alkanolamide of a fatty acid, an alkanolamide of a modified fatty acids or a mixture thereof, provided that if the lubricity aid is other than an alkanolamide of an aryl-substituted fatty acid, the composition further necessarily comprises a haze-reducing amount of a dehazer.
The present invention is also directed to a fuel lubricity additive comprising about 3 to about 20 parts by weight lubricity aid per part by weight dehazer, the lubricity aid being selected from the group consisting of alkanolamides of fatty acids, alkanolamides of modified fatty acids and mixtures thereof.
The present invention is further directed to a method for improving the lubricity of a low sulfur diesel or spark ignition fuel. According to the method, a lubricity-increasing amount of a lubricity aid is added to the fuel. The lubricity aid is selected from the group consisting of alkanolamides of fatty acids, alkanolamides of modified fatty acids and mixtures thereof. If the lubricity aid is an alkanolamide of an aryl-substituted fatty acid, it is preferred that a haze reducing amount of a dehazer is also added to the fuel. If the lubricity aid is other than an alkanolamide of an aryl-substituted fatty acid, a haze-reducing amount of a dehazer must also be added to the fuel.
Among the several advantages of this invention, may be noted the provision of a superior lubricity aid for use in low sulfur diesel fuel and spark ignition fuels; the provision of such aid that does not cause or increase hazing of the fuel when the fuel contacts water; the provision of such aid that is effective when used in relatively low dosage; the provision of such aid that has a low acid number; and the provision of a method for increasing the lubricity of such fuels with such aid.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accorda
Gentry David R.
Stehlin Mark P.
Weers Jerry J.
Baker Hughes Inc.
Medley Margaret
Thompson & Coburn LLP
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