Lubricity additives for fuel oil compositions

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

Reexamination Certificate

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C044S403000, C044S405000

Reexamination Certificate

active

06277159

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 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 add, 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 and EP-A0 719 761 describe certain amides of substituted hydoxyaromatic carboxylic acids, these materials being described as useful as dispersant additives for lubricants and fuels, respectively. No mention is made of low sulphur middle distillate fuels or how to solve their corresponding problem of poor lubricity.
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, formed from amide precursors via an ester intermediate. The salts so formed are preferably overbased.
EP-A-0 663 898 describes certain compounds having the formula;
wherein B represents an aromatic system, A represents a hydrocarbyl group, R
1
and R
2
are the same or are different and each independently is an aliphatic hydrocarbyl group containing 10 to 40 carbon atoms, z is at least 1 and wherein the aromatic system carries at least one activating group which may be a hydroxyl group. The aromatic system may also carry a substituent of general formula:
wherein w=0 or 1 and Q represents A, Such materials are described as cold flow-improving additives for middle distillate fuels.
There exists in the art a continual need for lubricity additives showing enhanced performance, 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.
Furthernore, 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 multiple performance enhancing effects can reduce or avoid the need for such complex compositions and their associated problems.
It has now been found that certain amine salts of specific substituted aromatic carboxylic acids show lubricity performance. Some of these amine salts may also impart other performance enhancing effects to low-sulphur fuel oils.
In a first aspect, this invention provides a fuel oil composition obtainable by the addition of a minor proportion of a compound comprising one or more aromatic ring systems wherein at least one of the ring systems bears, as substituents;
(i) one or more hydrocarbon groups imparting oil solubility to the compound, and
(ii) one or more hydroxyl groups or derivatives thereof or both, and
(iii) one or more amine salt groups to a major proportion of a liquid hydrocarbon middle distillate fuel oil having a sulphur concentration of 0.2% by weight or less, based on the weight of fuel.
In a second aspect, this invention provides a fuel oil composition obtainable by the addition, to the fuel oil defined under the first aspect, of an additive composition or concentrate into which has been incorporated the compound defined under the first aspect.
In a third aspect, this invention provides a compound comprising one or more aromatic ring systems, wherein at least one of the ring systems bears, as substituents;
(i) one or more hydrocarbon groups imparting oil solubility to the compound, and
(ii) one or more hydroxyl derivatives of the formula —OR′ wherein R′ is hydrocarbyl or a group of the formula
wherein M represents an oxygen atom or an NH group and n represents a number from 1 to 50, and
(iii) one or more amine salt groups.
Further aspects of this invention include an additive composition into which has been incorporated the compound of the third aspect, and an additive concentrate obtainable by incorporating the compound or additive composition and optionally one or more additional additives, into a mutually-compatible solvent ther

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