Fuel and related compositions – Liquid fuels – Heterocyclic carbon compound containing a hetero ring having...
Reexamination Certificate
1993-06-30
2001-10-09
Medley, Margaret (Department: 1714)
Fuel and related compositions
Liquid fuels
Heterocyclic carbon compound containing a hetero ring having...
C044S418000, C044S419000
Reexamination Certificate
active
06299655
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to diesel fuel compositions containing high molecular weight, high base number, substantially ash-free dispersants.
BACKGROUND OF THE INVENTION
Diesel engines are compression-ignition engines. That is, compression of air within the cylinder generates the heat required to ignite the fuel as it is injected. Compression ratios of 12:1 to 23:1 are common. Other factors affecting combustion in the diesel engine are combustion chamber design and fuel injection characteristics. Each of these factors is provided by the design of the various mechanical components of the engine. Fuel quantity is another factor affecting combustion in the diesel engine.
Fuel additives are employed to improve diesel engine performance. A wide variety of additives are known, including cetane number improvers which improve the ignition quality of the fuel, stabilizers, smoke reducing additives, corrosion inhibitors and detergents/dispersants.
In the diesel combustion process fuel vaporization and efficient mixing with available air are essential in insuring efficient combustion. The fuel injection equipment provides the mechanical means of achieving this and its performance is critical in controlling rate of fuel injection and fuel atomization. Optimum performance is only achieved when the fuel injection system is free from deposits and adjusted in accordance with the manufacturer's recommendations. There is, however, a tendency for diesel fuels to form deposits during distribution and combustion and these can markedly affect the combustion process.
Critical deposits can form in two basic areas. A buildup of gum or resinous degradation products can occur in the injection system. In severe cases this can result in sticking of pump plungers and injector pintles or needles. Problems often only occur on isolated cylinders, with the resultant misfire causing loss of power and increased exhaust smoke. Carbon deposits build up on the parts of the injector exposed to hot combustion gases, which can affect both fuel flow and fuel atomization characteristics of the injector. Again, loss in power, increased exhaust smoke and poor starting are the noticeable engine performance problems.
Deposit buildup in fuel pumps and injectors is not a new problem, but in recent years it is becoming more apparent, particularly in areas where fuels containing increased proportions of cracked components are being used.
Deposit buildup has been evident in both direct and indirect injection engines. Chemical additives have been used in attempts to control formation of deposits. Generally, the additives have been various nitrogen-containing compounds.
As mentioned hereinabove, deposits can operating and non-operating parts of injectors. It been found that of the many types of additives available in the art, those having the particular characteristics described in greater detail hereinafter provide exemplary cleanliness for both operating and non-operating parts of diesel fuel injectors.
SUMMARY OF THE INVENTION
The present invention relates to a composition comprising a major amount of a diesel fuel oil meeting ASTM standard specification D-975 and a minor amount, sufficient to minimize deposit formation on diesel engine fuel injectors and to maintain design flow rates and spray patterns of said injectors, of a nitrogen-containing dispersant wherein the product obtained by multiplying the oil- and diluent free percent nitrogen of said dispersant by the weight average molecular weight (Mw) of said dispersant ranges from about 45,000 to about 100,000.
DETAILED DESCRIPTION OF THE INVENTION
As stated hereinabove, the present invention is directed to diesel fuel oil compositions containing certain nitrogen-containing additives. The nitrogen-containing additives are high molecular weight, high base number dispersants. The high base number of the dispersant is derived from the nitrogen content of the dispersant. The number obtained by multiplying the weight average molecular weight (Mw) of the dispersant by the oil- and diluent free percent nitrogen is a number ranging between about 45,000 to about 100,000. For purposes of this calculation, the percent nitrogen is that of the dispersant free of oil and other diluent. It is preferred that the molecular weight of the dispersant is at least about 2,000. The preferred minimum base number of the dispersant is about 30 as determined by ASTM Procedure D-974.
Examples of useful nitrogen-containing dispersant are carboxylic dispersants, including, imides, amides, imidazolines, amine-treated ester dispersants, etc., amine dispersants, Mannich dispersants and dispersant viscosity improvers.
In one embodiment, the dispersants may be post-treated with such reagents as urea, aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinic anhydrides, nitriles, epoxides, etc.
The nitrogen-containing carboxylic dispersants include reaction products of hydrocarbyl-substituted carboxylic acylating agents such as substituted carboxylic acids or functionally equivalent derivatives thereof with an amine.
The hydrocarbyl-substituted acylating agent may be derived from a monocarboxylic acid or a polycarboxylic acid. Polycarboxylic acids generally are preferred. The acylating agent may be a carboxylic acid or functionally equivalent derivative of the carboxylic acid such as the halides, lactones, esters, anhydrides, etc., preferably acid, esters or anhydrides, more preferably anhydrides. Preferably the carboxylic acylating agent is a succinic acylating agent. The hydrocarbyl-substituted carboxylic acylating agent includes agents which have a hydrocarbyl group derived from polyalkenes.
A number of acylated, nitrogen-containing compounds having a substituent of at least 10 aliphatic carbon atoms and made by reacting a carboxylic acid acylating agent with an amino compound are known to those skilled in the art. In such compositions the acylating agent is linked to the amino compound through an amido, amido, amidine or acyloxy ammonium linkage. The substituent of at least 10 aliphatic carbon atoms may be in either the carboxylic acid acylating agent derived portion of the molecule or in the amino compound derived portion of the molecule. Preferably, however, it is in the acylating agent portion. The acylating agent can vary from formic acid and its acylating derivatives to acylating agents having high molecular weight aliphatic substituents of up to 5,000, 10,000 or 20,000 carbon atoms.
A typical class of acylated amino compounds useful in making the compositions of this invention are those made by reacting an acylating agent having an aliphatic substituent of at least 10 carbon atoms and a nitrogen compound characterized by the presence of at least one
group. Typically, the acylating agent will be a mono- or poly-carboxylic acid (or reactive equivalent thereof) such as a substituted succinic or propionic acid. The aliphatic substituent in such acylating agents is often of at least about 50 and up to about 400 carbon atoms.
In another embodiment, the hydrocarbyl groups are derived from polyalkenes having a number average molecular weight ({overscore (M)}n) value of at least about 1300 up to about 5000, and the {overscore (M)}w/{overscore (M)}n value is from about 1.5 to about 4, preferably from about 1.8 to about 3.6, more preferably about 2.5 to about 3.2. The preparation and use of substituted succinic acylating agents wherein the substituent is derived from such polyalkenes are described in U.S. Pat. No. 4,234,435, the disclosure of which is hereby incorporated by reference.
{overscore (M)}n and {overscore (M)}w referred to herein are determined using well-known methods described in the literature. Examples of procedures for determining molecular weights are gel permeation chromatography (also known as size-exclusion chromatography) and vapor phase osmometry. For simpler materials, the values are calculated. These and other procedures Are described in numerous publications including:
P. J. Flory, “Principles of Polymer Chemistry”, Cornell University Press (1953
Daly Daniel T.
Steckel Thomas F.
Fischer Joseph P.
Medley Margaret
The Lubrizol Corporation
Toomer Cephia D.
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