Lubricity additives for fuel oil compositions

Fuel and related compositions – Liquid fuels – Containing organic -c

Reexamination Certificate

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C044S391000, C044S400000

Reexamination Certificate

active

06258135

ABSTRACT:

This invention relates to additives for improving the lubricity of fuel oils such as diesel fuel oil. Diesel fuel oil compositions including the additives of this invention exhibit improved lubricity and reduced engine wear.
Concern for the environment has resulted in moves to significantly reduce the noxious components in emissions when fuel oils are burnt, particularly in engines such as diesel engines. Attempts are being made, for example, to minimise sulphur dioxide emissions. As a consequence attempts are being made to minimise the sulphur content of fuel oils. For example, although typical diesel fuel oils have in the past contained 1% by weight or more of sulphur (expressed as elemental sulphur) it is now considered desirable to reduce the level to 0.2% by weight, preferably to 0.05% by weight and, advantageously, to less than 0.01% by weight, particularly less than 0.001% by weight.
Additional refining of fuel oils, necessary to achieve these low sulphur levels, often results in reductions in the level of polar components. In addition, refinery processes can reduce the level of polynuclear aromatic compounds present in such fuel oils.
Reducing the level of one or more of the sulphur, polynuclear aromatic or polar components of diesel fuel oil can reduce the ability of the oil to lubricate the injection system of the engine so that, for example, the fuel injection pump of the engine fails relatively early in the life of an engine. Failure may occur in fuel injection systems such as high pressure rotary distributors, in-line pumps and injectors. The problem of poor lubricity in diesel fuel oils is likely to be exacerbated by the future engine developments aimed at further reducing emissions, which will have more exacting lubricity requirements than present engines. For example, the advent of high pressure unit injectors is anticipated to increase the fuel oil lubricity requirement.
Similarly, poor lubricity can lead to wear problems in other mechanical devices dependent for lubrication on the natural lubricity of fuel oil.
Lubricity additives for fuel oils have been described in the art. WO 94/17160 describes an additive which comprises an ester of a carboxylic acid and an alcohol wherein the acid has from 2 to 50 carbon atoms and the alcohol has one or more carbon atoms. Glycerol monooleate is specifically disclosed as an example. Acids of the formula “R
1
(COOH)”, wherein R
1
is an aromatic hydrocarbyl group are generically disclosed but not exemplified.
U.S. Pat. No. 3,273,981 discloses a lubricity additive being a mixture of A+B wherein A is a polybasic acid, or a polybasic acid ester made by reacting the acid with C1-C5 monohydric alcohols: while B is a partial ester of a polyhydric alcohol and a fatty acid, for example glycerol monooleate, sorbitan monooleate or pentaerythritol monooleate. The mixture finds application in jet fuels.
GB-A-1,505,302 describes ester combinations including, for example, glycerol monoesters and glycerol diesters as diesel fuel additives, the combinations being described as leading to advantages including less wear of the fuel-injection equipment, piston rings and cylinder liners. GB-A-1,505,302 is, however, concerned with overcoming the operational disadvantages of corrosion and wear by acidic combustion products, residues in the combustion chamber and in the exhaust system. The document states that these disadvantages are due to incomplete combustion under certain operating conditions. Typical diesel fuels available at the date of the document contained, for example, from 0.5 to 1% by weight of sulphur, as elemental sulphur, based on the weight of the fuel.
U.S. Pat. No.3,287,273 describes lubricity additives which are reaction products of a dicarboxylic acid and an oil-insoluble glycol. The acid is typically predominantly a dimer of unsaturated fatty acids such as linoleic or oleic acid, although minor proportions of the monomer acid may also be present. Only alkane diols or oxa-alkane diols are specifically suggested as the glycol reactant.
U.S. Pat. No. 4,090,971 describes amides of substituted hydoxyaromatic carboxylic acids in which at least one substituent is a hydrocarbon-based radical containing at least about 10 carbon atoms, these materials being described as useful as dispersant additives. The amides can be prepared via reaction of an ester intermediate with the corresponding amine; vic-hydroxylalkyl esters of the acids are disclosed as suitable intermediates.
U.S. Pat. No. 5,089,158 describes derivatives of amides of an aromatic carboxylic acid having an ortho-hydroxy group in the form of a salt with a multivalent metal ion. The amide precursors for such materials may be prepared via an ester intermediate formed by the reaction of the requisite carboxylic acid and a C1 to C6 alkanol, this ester then being amidated by reaction with an amine.
U.S. Pat. No. 4,551,152 discloses that alcohol-containing fuels may exhibit poor corrosion and wear, caused by the presence of alcohol substances. This alcohol-related problem is said to be inhibited by the presence of an ester condensate. prepared from the reaction of a carboxy phenol with a polyol of the formula:
wherein a+c is 1-20 and b is 5-50, and subsequent reaction with an aldehyde and ethylene diamine to form the condensate product.
U.S. Pat. No. 5,462,567 discloses poly(oxyalkylene) hydroxyaromatic esters according to a certain formula, wherein the ester group links a polyoxyalkylene substituent containing at least 5 oxyalkylene units with the hydroxyaromatic ring. These compounds are described as deposit-controlling additives for, inter alia, diesel fuels, when used in combination with certain aliphatic amines.
U.S. Pat. No. 4,098,708 (filed in 1975 and published in 1978) describes esters of substituted hydroxyaromatic carboxylic acids in which at least one substituent is a hydrocarbon-based radical containing at least about 10 carbon atoms, with salicylic acid esters being preferred. The acids are reacted with mono- or polyhydric hydrocarbon-based alcohols such as glycerol, pentaerythritol and a variety of glycols. The esters are described as useful dispersant additives for lubricants and normally—liquid fuels, such as diesel fuel or fuel oil according to ASTM Specification D-395.
Such fuels typically contained much higher sulphur levels than those with which the present invention is concerned, as illustrated by the referenced ASTM Specification which recites, for 1975, maximum sulphur limits of as high as 0.5%. The corresponding ASTM Specification for diesel fuel (D-975) recites limits of between 0.5 and 2.0% sulphur, depending on the intended end use of the fuel.
There exists in the art a continual need for lubricity additives showing enhanced performance over existing materials, due not only to the development of engines with more exacting requirements, but also to the general demand from consumers and fuel producers for higher quality fuels.
In addition, there is a desire for additives to be handleable without the need for special operating measures. The extent to which an additive solidifies at lower ambient temperatures (e.g. via crystallisation) determines the extent to which an additive may be handled in the absence of heating and mixing procedures. Many conventional additives require substantial mixing and heating prior to addition to the fuel, and such operations can cause processing delays and may make the use of such additives uneconomic in spite of their performance-enhancing effects.
Furthermore, there is an increasing need in the art for ‘multifunctional’ additive compositions. Such compositions provide a range of performance-enhancing functions, typically through the incorporation therein of a number of individual additives each having its own function. The resulting complex mixtures often require addition to the fuel in relatively large amounts, and may also suffer from problems of physical and chemical interaction between individual additives which can impair their subsequent performance in the fuel. The provision of an individual additive with

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