DE69805225T2 - Lubricant additive to reduce foam in fuels - Google Patents

Description

Foam control is an extremely important aspect in the development of additive compositions for fuels in the middle distillate boiling range such as gas oils, diesel fuels, gas turbine fuels, burner fuels and similar products. If a fuel foams when being pumped between tanks, it is difficult to control flow rates and volumes. Foam formation also causes numerous problems when filling fuel tanks, such as dispensing too little fuel or fuel overflowing at the filling station.

To address the problem of foaming, a variety of antifoaming agents such as polyacrylates and polysiloxanes have been proposed for use in diesel fuels and additive packages for producing ready-to-use diesel fuels.

In the production of certain additive concentrates to improve the properties of mid-distillate range fuels, it has been found that a significant amount of antifoaming agent must be added to the concentrate in order to effectively suppress or prevent foaming in the finished fuel during the above operations. In general, a minimum of 0.5% by weight of antifoaming agent is required in the additive concentrate. In fact, however, for certain additive concentrates the amount of antifoaming agent may be as high as 10% by weight or more in order to be used effectively.

It has been shown that a high proportion of a silicone foam inhibitor and an overbased detergent can lead to a serious incompatibility. This problem manifests itself in several ways. Firstly, insoluble sediments or suspended solids can form in the additive concentrate, especially during storage. In addition, experimental results indicate that even if the interaction between the overbased detergent and the silicone foam inhibitor does not lead to visually perceptible amounts of solids, the foam inhibitor performance in the resulting finished fuel is significantly reduced. Both undesirable consequences can also occur together. However, this incompatibility does not always exist in combinations of antifoams and overbased detergents. Some products do not show the incompatibility described above when combined with an overbased calcium sulfonate detergent. Examples of this are the fuel additive HiTEC® 4043L from Ethyl Corporation, which contains a polyether-polysiloxane antifoam that is water-soluble at 25ºC, and the silicone surfactant TEGOPREN® 5851 from TH Goldschmidt AG. The present invention does not relate to such products.

European Patent Application 0 681 023 discloses a fuel additive containing an overbased alkali or alkaline earth metal detergent and a water-soluble polyether-polysiloxane copolymer as an antifoam agent. The additive may further comprise a corrosion inhibitor, a hydrocarbon-soluble ashless dispersant, diluents and other conventional additives.

European Patent Application 0 476 196 deals with fuel and additive compositions that have improved combustion properties and result in products with reduced acidity. The additives may include metal-containing basic detergent salts, fuel-soluble manganese carbonyl compounds, ashless dispersants and other conventional additive components.

This creates the need to effectively address the problem of additive incompatibility between overbased metal detergents and siloxane antifoam agents, especially when the latter are present in relatively high concentrations in additive packages and the corresponding finished fuel compositions.

It has now been discovered that the foaming behavior of fuels containing colloidally dispersed metal-containing substances, such as overbased metal detergents or metal-based emission-improving additives, can be significantly improved in the presence of a variety of antifoaming agents by adding a lubricity additive.

Summary of the invention

According to the invention, a fuel additive composition is provided which comprises (i) a lubricity additive, (ii) at least one overbased metal detergent and (iii) a siloxane antifoam agent which is insoluble in water at 25°C. The components (i), (ii) and (iii) are present in such quantities that the following ratio results when the composition is diluted with a base oil:

Component (i) 10 to 400 ppm

Component (ii) 1 to 100 ppm of the metal component

Component (iii) 1 to 30 ppm

In one embodiment of the present invention, a fuel additive composition is provided which comprises (iv) a dispersant or (v) a metal-based emission improving additive. The weight ratio of (iv) to (iii) by active ingredients is normally in the range of about 0.25 to about 300 parts by weight of (iv) per part by weight of (iii).

Other components that can and should be added to the above-mentioned concentrates are a liquid hydrocarbon-based diluent (preferably a highly aromatic one), a liquid alcoholic diluent, a demulsifier or a corrosion inhibitor, or any mixture of these substances.

Still other embodiments include liquid fuel compositions, such as mid-boiling distillate fuels, containing the components of the above additive concentrates.

In another embodiment of the present invention, a process for foam inhibition in fuel compositions with an overbased metal detergent and a silicone foam inhibitor that is insoluble in water at 25°C is presented. The fuel compositions are combined with a lubricity additive.

The above and other embodiments and advantages of this invention are explained in detail in the following description and the appended claims.

Detailed description of the preferred embodiments of the invention Component (i)

In the present invention, carboxylic acids are preferably used as lubricity additives, optionally substituted with at least one hydroxyl group or their derivatives. Preferred carboxylic acid derivatives are carboxylic acid amides and carboxylic acid esters.

The hydroxyl-substituted carboxylic acid or derivative can be used alone or in combination with any other hydroxyl-substituted acid or derivative. The hydroxyl-substituted carboxylic acid used in the present invention typically contains up to 60 carbon atoms. The hydroxyl-substituted acid can be a mono- or polycarboxylic acid or a dimerized acid. When hydroxyl-substituted monocarboxylic acids are used, they typically contain 10 to 40 carbon atoms, more usually 10 to 30 and especially 12 to 24 carbon atoms. The preferred acid of this type is a fatty acid, ricinoleic acid. When hydroxyl-substituted polycarboxylic acids such as di- or tricarboxylic acids are used, they contain 3 to 40 carbon atoms, more usually 3 to 30 and especially 3 to 24 carbon atoms. Examples of this type of hydroxyl-substituted polycarboxylic acid are ricinoleic, malic, tartaric and citric acids. Dimerized acids can also be used as hydroxyl-substituted acids. In this description, such compounds are referred to as dimer and trimer acids. When a dimerized acid is used, it typically contains 10 to 60, preferably 20 to 60 and ideally 30 to 60 carbon atoms. Such acids are prepared by dimerizing unsaturated acids and inserting a hydroxyl functionality. Such acids typically consist of a mixture of monomer, dimer and trimer. According to one embodiment of the invention, the acid is a hydroxyl-substituted dimerized fatty acid, for example from oleic and linoleic acid. Typically, the dimer is present in a mixture of 2 wt.% monomer, 83 wt.% dimer, 15 wt.% trimer and possibly higher acids. The preferred dimer acid as well as the other The acids described above are commercially available or can be prepared by application or adaptation of known techniques.

As described above, the lubricity additive compounds used can be in the form of a carboxylic acid derivative. One possible derivative is an ester of the acid and an alcohol with multiple hydroxyl groups. The polyhydric alcohol typically contains 2 to 7 carbon atoms. Examples of suitable alcohols are alkene glycols such as ethylene glycol, diethylene glycol, triethylene glycol and dipropylene glycol, glycerol, arabitol, sorbitol, mannitol, pentaerythritol, sorbitan, 1,2-butanediol, 2,3-hexanediol, 2,4-hexanediol, pinacol and 1,2-cyclohexanediol. These alcohols are generally available. Of the alcohols mentioned, glycerol and sorbitan are most suitable. In a preferred embodiment, the ester has at least one free hydroxyl group in the alcoholic portion, i.e. not all hydroxyl groups of the polyhydric alcohol are esterified. The use of glycerol monoricinoleate is particularly recommended.

Another possible carboxylic acid derivative is the ester of the hydroxyl-substituted acid and an alkanolamine of the formula:

R¹[N(R¹)(CH₂)P]qY

wherein p ranges from 2 to 10, q ranges from 0 to 10, Y is -N(R¹)₂, 4-morpholinyl- or 1-piperazinyl, N-substituted with a group R¹ or a group -[(CH₂)pN(R¹)]qR¹, in which p and q are as defined above and each substituent R¹ is independently selected from alkyl groups having 1 to 6 carbon atoms and a group of the following formula:

-(R²O)rR³

Here, r is in the range 0 to 10, R² is an alkylene group with 2 to 6 carbon atoms and R³ is a hydroxyalkyl group with 2 to 6 carbon atoms, provided that at least one R¹ group is -(R²O)rR³. The alkanolamine therefore contains no hydrogen-bearing nitrogen atoms. If free hydrogen atoms are present, it would be expected that amides would form by reaction with the acid. The alkanolamines that can be used are commercially available or can be prepared by applying or adapting known techniques.

According to a preferred embodiment, the alkanolamine Y in the above formula is -N(R¹)₂, p is 2 and q is in the range from 0 to 3. Furthermore, R¹ should preferably be C₂₋₄-hydroxyalkyl groups, in particular C₂ or C₃-hydroxyalkyl. Specific examples of such compounds are triethanolamine, triisopropylamine and ethylenediamine as well as diethylenetriamine in which all nitrogen atoms are substituted by hydroxyethyl or hydroxypropyl groups.

In another preferred embodiment, the alkanolamine Y is 4-morpholinyl or substituted 1-piperazinyl, q is 0 or 1, and p ranges from 2 to 6. Examples of such alkanolamines are aminoethylpiperazine, bis-(aminoethyl)piperazine and morpholine N-substituted with a hydroxypropyl group.

The alkanolamines are commercially available or can be prepared by applying or adapting known techniques

An amide can also be used as a carboxylic acid derivative, which is formed by reaction of a hydroxyl-substituted carboxylic acid with ammonia or a nitrogen-containing compound of the following formula:

R¹[N(R¹)(CH₂)p]qY

Where p is in the range of 2 to 10, q is in the range of 6 to 10, Y is -N(R¹)₂, 4- morpholinyl or 1-piperazinyl, optionally N-substituted with a group R¹ or a group -[(CH₂)pN(R¹)]qR¹, in which p and q are as defined above and each substituent R¹ is independently selected from hydrogen and alkyl groups having 1 to 6 carbon atoms and a group of the following formula:

-(R²O)rR³

Here, r is in the range 0 to 15, R² is an alkylene group having 2 to 6 carbon atoms, and R³ is a hydroxyalkyl group having 2 to 6 carbon atoms, provided that at least one R¹ group is hydrogen.

In a preferred embodiment, the nitrogen-containing compound Y has the form -N(R¹)₂, p is 2, and q is in the range from 0 to 3. Examples of such compounds are diethanolamine, tris(hydroxymethyl)aminomethane, triethylenetetramine or diethylenetriamine, optionally N-substituted with two hydroxypropyl groups.

In another embodiment, the nitrogen-containing compound Y is 4-morpholinyl or optionally N-substituted 1-piperazinyl, p is between 2 and 6, q is 0 or 1, and all R¹ are hydrogen. Examples of such compounds are aminoethylpiperazine, bis(aminoethyl)piperazine or morpholine.

The compounds required to produce the acid amides are commercially available or can be prepared by applying or adapting known techniques .

The alkanolamines and nitrogen-containing compounds in the above formulas with r equal to 1 or greater, i.e. those with an ether or polyether chain, can be prepared by reacting a suitable amine, morpholine or piperazine compound with a molar excess of one or more alkylene oxides. If the same type of alkylene oxide is used, R² and R³ contain the same proportion of alkylene. If different alkylene oxides are used, R² and R³ can contain the same or different alkylene groups.

In the formulas for the alkanolamine compound, p is in the range of 2 to 10, preferably 2 or 3, q is in the range of 0 to 10, preferably 0 to 5, and r is in the range of 0 to 15, preferably 0 to 10. When R¹ is alkyl, the moiety contains between 1 and 6 carbon atoms, preferably 2 to 4. R² is an alkylene group having 2 to 6 carbon atoms, preferably 2 to 4. R³ is a hydroxyalkyl group having 2 to 6 carbon atoms, preferably 2 to 4. The hydroxyalkyl group typically contains 1 to 3 hydroxyl groups. When r is greater than zero, R³ is typically a monohydroxyalkyl group, for example hydroxyethyl or hydroxypropyl. When r is zero, R³ is typically a mono- or polyhydroxyalkyl group with up to 4 hydroxyl groups, for example hydroxyethyl, hydroxypropyl or a 1-hydroxy-2,2-bis-(hydroxymethyl)ethyl group. The values p, q and r are chosen independently. This means, for example, for q greater than zero that p in each repeat unit can take on a different value. Similarly, if r is greater than zero, R² can be the same or different in each repeating unit.

The preferred carboxylic acid amides are oleylethanolamide and oleyldiethanolamide.

The acid used in the present invention without hydroxyl substitution in the main chain typically contains up to 60 carbon atoms. It can be a mono- or polycarboxylic acid or a dimerized acid. When monocarboxylic acids are used, these typically contain 10 to 40 carbon atoms, more usually 10 to 30 and especially 12 to 24. Examples of these are aliphatic fatty acids such as lauric, myristic, heptadecanoic, palmitic, stearic, oleic, linoleic, linolenic, nonadecanoic, arachidic and behenic acid. Of these, oleic and linoleic acid or a mixture thereof is preferably recommended. When using polycarboxylic acids such as di- or tricarboxylic acids, these contain 3 to 40 carbon atoms, more usually 3 to 30 and especially 3 to 24. Examples of this type of polycarboxylic acids are dicarboxylic acids such as succinic, glutaric, adipic, suberic, azelaic and sebacic acid as well as tricarboxylic acids such as 1,3,5-cyclohexanetricarboxylic acid and tetracarboxylic acids such as 1,2,3,4-butanetetracarboxylic acid.

Dimerized acids can also be used as acids without hydroxyl substitution in the main chain. Such compounds are referred to in this description as dimer and trimer acids. When using dimerized acid, it typically contains 10 to 60 carbon atoms, preferably 20 to 60 and ideally 30 to 60. Such acids are prepared by dimerizing unsaturated acids and typically contain a mixture of monomer, dimer and trimer. According to a preferred embodiment of the invention, the acid is a dimerized fatty acid, for example from oleic and linoleic acids. Typically, the dimer is present in a mixture of 2 wt.% monomer, 83 wt.% dimer, 15 wt.% trimer and possibly higher acids. The preferred dimer acid as well as the other acids described above are commercially available or can be prepared by applying or adapting known techniques.

The carboxylic acids without hydroxyl substitution can be derivatized by reaction with an alkanolamine. The alkanolamine typically has the following formula:

R¹[N(R¹)(CH₂)p]qY

Here, p is in the range of 2 to 10, preferably 2 or 3, q is in the range of 0 to 10, preferably 0 to 5, Y is -N(R¹)₂, 4-morpholinyl or 1-piperazinyl, N-substituted with a group R¹ or a group -[(CH₂)pN(R¹)]qR¹, where p and q are as defined above and each substituent R¹ is independently selected from alkyl groups having 1 to 6 carbon atoms, preferably 2 to 4, and a group of the following formula:

(R²O)rR³

Here, r is in the range from 0 to 15, preferably from 0 to 10, R² is an alkylene group with 2 to 6 carbon atoms, preferably 2 to 4, R³ is a hydroxyalkyl group with 2 to 6 carbon atoms, preferably 2 to 4, provided that at least one group R¹ is (R²O)rR³. The hydroxyalkyl group typically contains 1 to 3 hydroxyl groups. If r is greater than zero, R³ is typically a monohydroxyalkyl group, for example hydroxyethyl or hydroxypropyl. If r is zero, R³ is typically a mono- or polyhydroxyalkyl group with up to 4 hydroxyl groups, for example hydroxyethyl, hydroxypropyl or a 1-hydroxy-2,2-bis-(hydroxymethyl)ethyl group. The values p, q and r are chosen independently. This means, for example, that for q greater than zero, p can take on a different value in each repeating unit. Similarly, if r is greater than zero, R² can be the same or different in each repeating unit. Thus, the alkanolamine does not contain any nitrogen atoms carrying hydrogen. If such free hydrogen atoms were present on the nitrogen, it would be expected that amides would form by reaction with the fatty acid.

The alkanolamines suitable for the formation of the ester are commercially available or can be prepared by applying or adapting known techniques. For example, the alkanolamines with r equal to 1 or greater, i.e. those with an ether or polyether chain, can be prepared by reacting a suitable amine, morpholine or piperazine compound with a molar excess of one or more alkylene oxides. If the same type of alkylene oxide is used, R² and R³ contain the same proportion of alkylene.

When using different alkylene oxides, R² and R³ can contain the same or different alkylene groups.

According to a preferred embodiment, alkanolamines are used in which Y is -N(R¹)₂ according to the above formula, p is 2 and q is in the range from 0 to 3. The alkanolamine is preferably triethanolamine, triisopropylamine, ethylenediamine or diethylenetriamine, where all nitrogen atoms are substituted with hydroxyethyl or hydroxypropyl groups.

According to an alternative preferred embodiment, Y in the above formula is 4-morpholinyl or substituted 1-piperazinyl, p is in the range of 2 to 6, and q is 0 or 1. Examples of such alkanolamines are aminoethylpiperazine, bis(aminoethyl)piperazine and morpholine N-substituted with a hydroxypropyl group.

The described esters can be prepared by application or adaptation of known techniques or are commercially available.

In one aspect of the present invention, the lubricity-enhancing additive compound is a derivative of the hydroxyl-substituted acid and contains at least one free carboxyl group in the acid moiety. The hydroxyl-substituted acid used for this type of compound can be a polycarboxylic acid, such as a dicarboxylic acid or a dimer or trimer acid. The molarity of the acid and the compound used to form the acid derivative should be controlled so that the resulting compound contains at least one free functional carboxyl group in the acid moiety. For example, for an acid with two carboxyl groups, such as a dicarboxylic or dimer acid, the molar ratio should be 1:1.

In another aspect of the present invention, the ester contains at least one free carboxyl group in the acid moiety and no hydroxyl substitution in the acid backbone. This type of compound can be a polycarboxylic acid, such as a dicarboxylic acid or a dimer or trimer acid. The molarity of the acid and the alkanolamine should be controlled during the reaction so that the resulting ester contains at least one free functional carboxyl group in the acid moiety. For example, in the case of an acid with two carboxyl groups, such as a dicarboxylic or dimer acid, the molar ratio should be 1:1.

If the acid derivative contains at least one free carboxyl group in the acid moiety, it can be used as is or further derivatized to improve its properties. The type of compound used for this purpose normally depends on the starting acid and on the properties of the acid derivative to be modified. For example, the fuel solubility of the acid derivative can be increased by introducing a corresponding component into the molecule. A long-chain alkyl or alkenyl would be suitable for this purpose. For this purpose, the acid derivative can be reacted with an alcohol ROH or an amine RNH₂, where R is an alkyl or alkenyl with up to 30 carbon atoms, for example 4 to 30. The number of carbon atoms in the alkyl or alkenyl group can depend on the number of carbon atoms in the acid derivative itself. These compounds react with the free functional carboxyl group(s) of the acid derivative and form another ester or amide chain. Examples of suitable alcohols and amides are oleyl alcohols and oleyl amines. Alternatively, one or more polar head groups can be introduced into the molecule of the acid derivative. This further increases the lubricity-improving effect of the acid derivative. This effect is probably due to the increased affinity of the acid derivative to metallic surfaces due to the polar head. Examples of compounds for introducing one or more polar head groups are polyamines (e.g. ethylenediamine and diethylenetriamine), monohydric alcohols (e.g. ethanol and propanol) as well as alkanolamines and polyhydric alcohols, such as those already described above.

The carboxylic acid derivative is typically supplemented with a component to improve fuel solubility, unless it is a derivative of a dimer or trimer acid. Dimer and trimer acid derivatives usually contain alkyl or alkenyl moieties in the main acid chain, which ensure sufficient fuel solubility.

In the above description, it was assumed that the acid derivative is used as the starting material for further treatment. However, the same end product can also be obtained if one or more free functional carboxyl groups of a polycarboxylic acid are first converted into polar or fuel solubility-enhancing Groups are added and only then converted into the acid derivative. For this procedure, the product of the initial reaction must of course have at least one free carboxyl group in the acid part so that the acid derivative can be formed at all.

Component (ii)

Examples of metal-containing detergents include oil-soluble overbased salts of alkali or alkaline earth metals and one or more of the following acidic substances (or mixtures thereof): (1) sulfonic acids, (2) carboxylic acids, (3) alkylphenols, (4) sulfurized alkylphenols, and (5) organic phosphoric acids having at least one direct carbon-phosphorus bond. Such organic phosphoric acids can be prepared by treating an olefin polymer (e.g., polyisobutylene) with a phosphorizing agent such as phosphorus trichloride, phosphorus heptasulfide, phosphorus pentasulfide, phosphorus trichloride and sulfur, white phosphorus, and a sulfur halide or phosphorus thiochloride. The most commonly used salts of the above acids are those of sodium, potassium, lithium, calcium, magnesium, strontium, and barium.

The metal additives are preferably oil-soluble overbased salts of alkali or alkaline earth metals. Overbased salts are preferred because they allow metals to be added in a concentrated and thus cost-effective manner, but other forms are also possible. The term "overbased" describes metal salts in which the metal is present in stoichiometrically larger amounts than the organic acid radical. This includes both low-base detergents, i.e. those with a total base number (TBN) of about 6 to 40, and highly basic substances, i.e. those with a total base number of about 250 to 500. In the usual methods for preparing overbased salts, acid dissolved in mineral oil is heated with a stoichiometric excess of a metallic neutralizing agent such as metal oxide, hydroxide, carbonate, bicarbonate or sulfide, the mixture is carbonated in the presence of a promoter and then filtered. Suitable promoters include phenolic substances such as phenol, naphthol, alkylphenol, thiophenol, sulfurized alkylphenol and condensation products of formaldehyde with a phenolic substance. Other suitable promoters include alcohols such as methanol, 2-propanol, octyl alcohol, cellosolve, carbitol, ethylene glycol, stearyl alcohol and cyclohexyl alcohol as well as amines such as aniline, phenylenediamine, phenothiazine, phenyl- β-naphthylamine and dodecylamine. A particularly effective method for preparing overbased salts is to mix acid with an excess of a basic alkaline earth neutralizing agent and at least one suitable promoter and to carbonize the mixture at an elevated temperature of about 60 to 200°C.

Examples of overbased sulfonates are overbased lithium, sodium, potassium, calcium and magnesium sulfonates. The sulfonate moieties are bound to an aromatic core, which in turn usually has one or more aliphatic substituents that ensure hydrocarbon solubility.

The metal carboxylates can be derived from any organic carboxylic acid. Preferably, a monocarboxylic acid with about 4 to 30 carbon atoms should be used as the starting point. These can be aliphatic, alicyclic or aromatic carboxylic acids. Monocarboxylic acids such as aliphatic acids with about 4 to 18 carbon atoms are preferred, especially those with an alkyl group of about 6 to 18 carbon atoms. The alicyclic acids can generally contain between 4 and 12 carbon atoms. The aromatic acids can generally have one or two condensed rings and contain between 7 and 14 carbon atoms, where the carboxyl group can be attached to the ring, but does not have to be. The carboxylic acid can be a saturated or unsaturated fatty acid with about 4 to 18 carbon atoms. Examples of carboxylic acids for the preparation of metal carboxylates are: butyric acid, valeric acid, hexanoic acid, heptanoic acid, cyclohexanecarboxylic acid, cyclodecanoic acid, naphthenic acid, phenylacetic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, suberic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, linolenic acid, heptadecanoic acid, stearic acid, oleic acid, nonadecanoic acid, eicosanoic acid, heneicosanoic acid, docosanoic acid and erucic acid.

The carboxylic acids most suitable for preparing the oil-soluble salts of the present invention are salicylic acids. Examples of overbased salicylates include lithium salicylates, sodium salicylates, potassium salicylates, calcium salicylates and magnesium salicylates, with the aromatic moiety normally being substituted by one or more aliphatic moieties which provide hydrocarbon solubility.

Examples of suitable overbased metal-containing phenolate detergents include, but are not limited to, substances such as overbased lithium phenolates, sodium phenolates, potassium phenolates, calcium phenolates, magnesium phenolates, sulfurized lithium phenolates, sulfurized sodium phenolates, sulfurized potassium phenolates, sulfurized calcium phenolates, and sulfurized magnesium phenolates. Each aromatic group has one or more aliphatic groups which provide hydrocarbon solubility. The above overbased metal detergents are often referred to as "overbased phenolates" or "overbased sulfurized phenolates."

Also suitable, although less preferred, are (a) the overbased lithium, sodium, potassium, calcium and magnesium salts of hydrolyzed phospho-sulfurized olefins having 10 to 2000 carbon atoms or of hydrolyzed phospho-sulfurized alcohols or aliphatic-substituted phenolic compounds having 10 to 2000 carbon atoms. Other similar overbased alkali and alkaline earth metal salts of oil-soluble organic acids are also suitable, such as the overbased aliphatic sulfonate salts, often referred to as "petroleum sulfonates." In addition, mixtures of salts of two or more different overbased alkali or alkaline earth metals can be used. Salt mixtures of two or more different acids or two or more different types of acids (e.g. one or more overbased calcium phenolates with one or more calcium sulfonates) can also be used. Rubidium, caesium and strontium salts are suitable, but too expensive for most applications. Barium salts are also effective, but from a toxicological point of view the use of the heavy metal barium is difficult to justify at present.

The metal-containing detergent may be low-base or high-base or a mixture of these types. Low-base detergents have a total base number of greater than about 8 but less than about 200. Preferred metal-containing detergents are high-base calcium and magnesium sulfonates, sulfurized phenates and salicylates having a total base number (TBN) according to ASTM D 2896-88 of at least 200, preferably greater than 250.

Component (iii)

The present invention uses antifoam additives that are conventional in fuel compositions, such as silicone antifoams. The advantages of the present invention are most apparent when the antifoam used exhibits severe incompatibility with the overbased metal detergents. Incompatibility with the overbased metal detergents is manifested by violent foaming when the antifoam and detergent are brought together. This behavior is often encountered when the antifoam is essentially insoluble in water at 25°C. This problem is solved by adding a lubricity additive of the type described above. Preferred antifoams are polyether-polysiloxane copolymers of the formula:

Here, R can be independently selected from the group of H, OH, C₁₋₃-alkyl, polyalkoxy, poly-(alkoxy)-X (X is OH, methyl or an ester) and polyalkoxy derivatives, where aromatic, phenolic or phenol derivatives of the alkoxy or polyether chain are polymerized on. Polyalkoxy chains typically contain ethoxy or propoxy units or mixtures thereof. The polyether-polysiloxane copolymers can be organosilicone terpolymers, such as those with alkylphenol or modified alkylphenol derivatives and polyethers, which are polymerized on a polysiloxane copolymer. Preference is given to antifoam agents which are essentially insoluble in water at 25°C.

Suitable polyether-polysiloxane copolymers for use in the present invention include the foam inhibitor S911, a polyether-polydimethylsiloxane from Wacker Chemie GmbH, the foam inhibitor Dow Corning® Q2- 2600, a polyether-polysiloxane copolymer from Dow Corning and the antifoam TP325, an organosilicone terpolymer from OSi Specialties Inc.

This invention does not relate to polyether-polysiloxane copolymer foam inhibitors which are water soluble at 25°C and do not exhibit severe incompatibility with overbased metal detergents. An example of such copolymers is the silicone surfactant TEGOPREN® 5851 from T.H. Goldschmidt AG of Essen, Germany. Foam inhibitors of this particular class do not exhibit the foam stabilizing effect which the lubricity additives of the present invention serve to control.

Component (iv)

In the preferred embodiments of this invention, the compositions comprise at least one hydrocarbon-soluble dispersant. Suitable dispersants include long-chain succinimides, long-chain succinic esters, long-chain succinic ester amides, long-chain polyamines, and long-chain Mannich bases. The long chain of these dispersants contains an average of at least 20 carbon atoms, for example an average of 30 to 200 or more. Such long-chain substituents are typically derivatized from polyolefin oligomers or from polymers having a suitable average molecular weight of about 800, 950, 1200, 1350, 1500, 1700, 2100, or 2300. These in turn are prepared by polymerizing or copolymerizing olefin monomers such as propylene, butylenes, isobutylene, amylenes, mixtures of ethylene and propylene and the like.

Methods for preparing such dispersing detergents, which are suitable, among other things, as additives for fuel compositions, are well known and discussed in the literature. For example, typical suitable succinimides have been described in the published PCT patent application WO 93/06194 and the published European patent application No. 0 441 014 (14 August 1991). Succinesters and succinesteramides were disclosed, for example, in US-A-3,184,474, 3,331,776, 3,381,022, 3,522,179, 3,576,743, 3,632,511, 3,804,763, 3,836,471, 3,862,981, 3,936,480, 3,948,800, 3,950,341, 3,957,854, 3,957,855, 3,991,098, 4,071,548 and 4,173,540. Long-chain polyamine dispersing detergents are described, for example, in US-A-3,275,5 54, 3,394,576, 3,438,757, 3,454,555, 3,565,804, 3,671,511, 3,821,302 and European Patent Publication 0 382 405. Suitable fuel-soluble Mannich base dispersing detergents are described, for example, in US-A-3,948,619, 3,994,698 and especially 4,231,759.

A preferred group of dispersing detergents for this invention are succinimides formed by the reaction of a polyisobutenyl succinic anhydride and a polyamine, particularly an ethylene polyamine having an average of 2 to 6 nitrogen atoms per molecule such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine and N-(2-hydroxyethyl)ethylenediamine. In these dispersants, the polyisobutenyl group preferably has a GPC average molecular weight in the range of 750 to 2300, more preferably 800 to 1350.

Further preferred are Mannich base dispersants formed by reaction of the following components: (i) an alkylphenol in which the alkyl group is derivatized from an olefin polymer having a molecular weight in the range 750 to 2300, preferably 800 to 1350 and more preferably from 800 to 1100, (ii) a polyalkylenepolyamine and (iii) formaldehyde or a precursor of formaldehyde. Ideally the alkyl group of the alkylphenol is derivatized from polypropene having an average molecular weight in the range 800 to 1100 and the polyalkylenepolyamine is diethylenetriamine. Other useful dispersants are mentioned in EP 0 476 196 B1.

Component (v)

Other possible substances for the compositions of this invention are metal-based emission-improving additives such as cyclopentadienylmanganese tricarbonyl compounds. Such compounds can contribute to the reduction of exhaust emissions, in particular of particles and smoke, in ready-to-use fuels. In addition, cyclopentadienylmanganese tricarbonyl compounds in the compositions of this invention have a positive influence on the cleanliness of the intake system, especially the intake valves. The cyclopentadienylmanganese tricarbonyl compounds suitable for the implementation of this invention include cyclopentadienylmanganese tricarbonyl, methylcyclopentadienylmanganese tricarbonyl, dimethylcyclopentadienylmanganese tricarbonyl, trimethylcyclopentadienylmanganese tricarbonyl, tetramethylcyclopentadienylmanganese tricarbonyl, pentamethylcyclopentadienylmanganese tricarbonyl, ethylcyclopentadienylmanganese tricarbonyl, Diethylcyclopentadienylmanganesetricarbonyl, propylcyclopentadienylmanganesetricarbonyl, isopropylcyclopentadienylmanganesetricarbonyl, tert-butylcyclopentadienylmanganesetricarbonyl, octylcyclopentadienylmanganesetricarbonyl, dodecylcyclopentadienylmanganesetricarbonyl, ethylmethylcyclopentadienylmanganesetricarbonyl, indenylmanganesetricarbonyl and the like, including mixtures of two or more such compounds. Preference is given to cyclopentadienylmanganese tricarbonyls which are liquid at room temperature, such as methylcyclopentadienylmanganese tricarbonyl, ethylcyclopentadienylmanganese tricarbonyl, liquid mixtures of cyclopentadienylmanganese tricarbonyl and methylcyclopentadienylmanganese tricarbonyl, mixtures of methylcyclopentadienylmanganese tricarbonyl and ethylcyclopentadienylmanganese tricarbonyl, etc. The preparation of such compounds is described in the literature, for example in US-A-2,818,417.

Although less preferred, other fuel-soluble or dispersible manganese compounds may also be added to the compositions of this invention. These include, for example, manganese oleates, manganese naphthenates, manganese octylacetoacetates, and manganese ethylenediamine tetraacetates.

In principle, the advantages of this invention can be used for any fuel derived from petroleum, biomass, coal, shale or tar sands. Under current conditions, the base fuels are usually derived primarily, if not exclusively, from petroleum.

The invention is thus applicable to fuels such as kerosene, jet fuel, aviation gasoline, diesel fuel, domestic heating oil, light cycle oil, heavy cycle oil, light gas oil, heavy gas oil, bunker oil, residual fuel oils, ultra-heavy fuel oils and generally to any liquid (or flowable) product suitable for combustion in an engine (e.g. diesel fuel, gas turbine fuels, etc.) or in a burner. Other suitable fuels include liquid fuels derived from biomass such as vegetable oils (e.g. rapeseed oil, jojoba oil, cottonseed oil, etc.) or liquid waste fuels derived from, for example, municipal or industrial waste.

In general, the components of the additive compositions are added in small amounts sufficient to improve the combustion and other properties of the existing base fuel. The respective Quantities therefore depend on the type of base fuel and the application conditions of the finished fuel. In general, however, the following concentrations (ppm) of the components (active ingredients) in the base fuels can be given as guide values:

For fuels that additionally contain one or more of components (iv) and (v), the following concentrations (ppm) of the active ingredients are typical:

The fact that the individual components (i), (ii) and (iii) and optionally also (iv) or (v) can be added to the fuel separately or in various sub-combinations is advantageous. Normally, the exact mixing sequence is not important. Furthermore, the components can be added in the form of a solution or dilution. Preferably, however, the components used in this invention should be introduced in the form of an additive concentrate, as this makes the mixing processes simpler and reduces the likelihood of mixing errors. Apart from This makes use of the advantages of the compatibility and solubility properties of the overall concentrate. Such a concentrate is part of the present invention and typically contains between 99 and 1% by weight of additive and between 1 and 99% by weight of solvent or diluent. The solvent or diluent must be miscible or soluble in the fuel intended for the concentrate. The solvent or diluent can of course be identical to the fuel. Examples of other solvents or diluents include white spirit, kerosene, alcohols (e.g. 2-ethylhexanol, isopropanol and isodecanol), aromatic solvents (e.g. toluene and xylene) and ignition accelerators (e.g. 2-ethylhexyl nitrate). These substances can be used individually or as a mixture.

The compositions of the present invention may further contain optional components that are conventional in fuel compositions, such as fuel stabilizers, ignition promoters, anti-icing additives, combustion moderating additives, cold flow improvers, antistatic additives, biocides, antioxidants, corrosion inhibitors, wax inhibitors and metal deactivators.

The various optional components contemplated for fuel compositions are added in conventional amounts. The amounts of such optional components are not critical to the practice of the present invention. The amounts used in the particular case are sufficient to impart the desired properties to the fuel composition and are well known to those skilled in the art.

The invention is illustrated by the following examples.

Examples

The basic formulation for Examples 1 and 2 and Comparative Examples 1-4, excluding the antifoam and lubricity additives listed in Table 2, is broken down below. The amounts are given in ml of additive per 1000 ml of fuel. Table 1

¹ 2-Ethylhexanol

² Demulsifier OFRIC® D5021, commercially available from Baker Performance Chemical

³ Corrosion inhibitor HiTEC® 536, low molecular weight polyalkylene polyamine succinimide/amide, commercially available from Ethyl Corporation

&sup4; Detergent HiTEC® 611, an overbased calcium alkylbenzene sulfonate with a nominal total base number of approximately 300, commercially available from Ethyl Corporation

&sup5; Ashless polyisobutylene succinimide dispersant based on polyisobutylene, succinic anhydride and tetraethylene pentamine with a number average molecular weight of 950

&sup6; Cyclopentadienylmanganese tricarbonyl compound in xylene/heptane solvent mixture

The additive was added to all treated fuels in such a way that this base formulation is present in an amount of approximately 0.44 ml per 1000 ml of fuel.

To evaluate the various additives and their effect on fuel compositions, the foam volume and the time until the first foam-free spot on the fuel surface were measured. The lower the foam volume and the shorter the time until the first foam-free spot, the better the foaming behavior. The base fuel used in these examples is a low-sulfur diesel fuel (< 0.05 wt.% sulfur content).

Several portions of the base formulation were each added with certain amounts of the lubricity additive and various antifoam agents, and the additive concentrates thus obtained were mixed into the base fuel. These fuel compositions thus contained approximately 0.44 ml of the base formulation to 1000 ml of fuel with an appropriate amount of antifoam and lubricity additive. Each fuel was then immediately shaken under controlled conditions and the time until the foam dissipated was measured. These measurements were made using glass measuring cylinders in accordance with ASTM D 1094 which were first cleaned in chromic acid for at least one hour, rinsed with water, then rinsed with acetone and dried. The cylinders were filled with fuel to the 100 ml mark. They were then stoppered and shaken for 1 minute at a rate of 2-3 movements per second, covering 15 to 30 cm in a vertical plane. The shaken cylinders were then placed on a horizontal, vibration-free surface and the maximum foam volume (ml of foam) and the times until the first smooth spot on the fuel surface (in seconds) were recorded.

As the results in Table 2 show, for fuel compositions containing the additive compositions of the present invention (Examples 1 and 2), the foam volume and the time to the first foam-free spot are significantly reduced compared to compositions containing only the base fuel (Comparative Example 5) or additive mixtures whose composition does not correspond to the present invention (Comparative Examples 1-4). This is demonstrated by the significantly lower values for the foam volume and the time to the first foam-free spot in Examples 1 and 2. Table 2

7 HiTEC®2658 lubricity additive, oleyldiethanolamide, commercially available from Ethyl Corporation

8 Foam inhibitor S911, a silicone foam inhibitor, commercially available from Wacker Chemie GmbH

9 Antifoam Q2-2600, a silicone antifoam, commercially available from Dow Corning

Table 3 shows the improved foaming behavior of a system with a foam inhibitor and an overbased detergent by adding a fatty acid lubricity additive.

The results in Table 3 show that for fuel compositions containing the additive blends of the present invention (Example 3), the foam volume and the time to the first foam free spot are significantly reduced compared to compositions containing additive blends not in accordance with the present invention (Comparative Example 6). This is demonstrated by the significantly lower values for the foam volume and the time to the first foam free spot in Example 3. Table 3

¹⁰ Oleic acid from Aldrich Chemical Company

This invention is susceptible to considerable variation in its practice. Accordingly, this invention is not limited to the specific examples presented.

Claims (14)

1. A fuel additive composition comprising (i) a lubricity additive, (ii) an overbased metal detergent and (iii) a siloxane antifoam agent insoluble in water at 25ºC, wherein components (i), (ii) and (iii) are present in amounts such that when the composition is diluted with a base oil, the following amount of each component is present: Component (i) 10 to 400 ppm Component (ii) 1 to 100 ppm of the metal component Component (iii) 1 to 30 ppm 2. A fuel additive composition according to claim 1, in which the lubricity additive is a carboxylic acid, a carboxylic acid amide or a carboxylic acid ester. 3. A fuel additive composition according to claim 1 or 2, wherein the lubricity additive is selected from the group consisting of oleylethanolamide and oleyldiethanolamide. 4. A fuel additive composition according to any preceding claim, wherein the overbased metal detergent is selected from the group consisting of calcium sulfonates, magnesium sulfonates, sulfurized calcium phenates, sulfurized magnesium phenates, calcium salicylates and magnesium salicylates, wherein the detergent has a total base number (TBN) according to ASTM D 2898-88 of at least 200. 5. A fuel additive composition according to any preceding claim, in which the antifoam agent is a silicone antifoam agent. 6. A fuel additive composition according to claim 5, wherein silicone foam inhibitor is a polyether polysiloxane copolymer. 7. A fuel additive composition according to any preceding claim, further comprising at least one component selected from the group consisting of dispersants, metal-based emission improvers, demulsifiers and corrosion inhibitors. 8. A fuel additive composition according to claim 7, wherein the dispersant is a hydrocarbon soluble dispersant selected from the group consisting of long chain succinimides, long chain succinic esters, long chain succinic ester amides, long chain polyamines and long chain Mannich bases. 9. A fuel additive composition according to claim 7, wherein the metal-based emission improver is a cyclopentadienyl manganese tricarbonyl compound. 10. Additive concentrate comprising 99 to 1% by weight of the additive according to any one of the preceding claims and 1 to 99% by weight of a solvent or diluent for the additive, wherein the solvent or diluent is miscible with or can dissolve in the fuel in which the concentrate is to be used. 11. A fuel composition comprising (a) a major proportion of a base fuel and (b) a minor amount of the fuel additive according to any of claims 1 to 9, wherein the fuel additive is present in sufficient amount to improve the foaming behavior of the fuel. 12. A method for reducing foam in a fuel composition containing an overbased metal detergent and an antifoam agent insoluble in water at 25°C, comprising combining a lubricity additive with the fuel composition. 13. The method of claim 12, wherein the lubricity additive is a carboxylic acid, a carboxylic acid amide or a carboxylic acid ester. 14. The method of claim 12, wherein the siloxane antifoam agent is a polyetherpolysiloxane copolymer.