US20100205852A1

US20100205852A1 - Polyamine additives for fuels and lubricants

Info

Publication number: US20100205852A1
Application number: US12/696,213
Authority: US
Inventors: Jörn Karl; Marco Bergemann; Mirjam Herrlich-Loos; Georg Schäper
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2004-08-06
Filing date: 2010-01-29
Publication date: 2010-08-19
Also published as: NO20070929L; JP2008509236A; WO2006015818A1; EP1789520A1; CA2576014A1; CN1993449A; KR20070049178A; AU2005270367A1; MX2007000844A; BRPI0514160A; US20070214713A1

Abstract

The present invention relates to the use of polyamines having at least one terminal secondary or tertiary amine function as a detergent additive for fuels and lubricants; to additive concentrates comprising such polyamines; to fuels and lubricants additized with these polyamines and to processes for their preparation.

Description

PRIOR ART

During the operation of combustion engines, there may be formation of undesired deposits in the region of the combustion chamber and of the fuel intake system. In the case of diesel fuels, carbon deposits are to be observed in the region of the injection nozzles and holes and can impair the optimal formation of a finely divided fuel mist in direction-injection high-performance systems such as common rail, pump-nozzle or pump-line-nozzle and thus lead to increased fuel consumption and emissions. In order to minimize or entirely prevent the disruptions associated with the occurrence of such deposits, detergent additives are added to the fuels.
Examples of such detergent additives include in particular polyalkenylsuccinimides. These find manifold use in fuels and lubricants, typically in combination with other additives; cf., for example, EP-A-0264247, EP-A-0271937 and WO-A-98/42808.
For instance, WO-A-98/42808 describes the use of specific reaction products of a polyalkenyl derivative of a monoethylenically unsaturated C₄-C₁₀-dicarboxylic acid with a polyamine having terminal primary amine groups as a detergent additive for low-sulfur diesel fuels.
DE-A-101 23 553 discloses a process for preparing polyalkenylsuccinimides in which PIBSA is, for example, reacted with an oligo- or polyamine in the presence of an alcohol. The oligo- or polyamines used likewise have terminal primary amine groups.
WO 2004/024851 describes synergistically active additive mixtures for lubricants and fuels composed of an additive having detergent action and a partly or fully neutralized fatty acid. The detergent additives specified include compounds having a hydrophobic hydrocarbon radical having an Mn of from 85 to 20 000 whose polar end group is selected from moieties derived from carboxylic anhydrides and having hydroxyl and/or amino and/or amido and/or imido groups. Dicarboximides of polyalkylene polyamines having terminal secondary or tertiary amine end groups in the end product were not investigated therein.
A disadvantage of the additives and the additive mixtures described in the prior art is that relatively high dosages are required to achieve a cleaning or keep-clean effect.

BRIEF DESCRIPTION OF THE INVENTION

It is therefore an object of the present invention to provide improved detergent additives for fuel and lubricant compositions, especially diesel fuels, which are effective even at low dosages and especially effectively reduce nozzle carbonization.
It has been found that, surprisingly, the above object is achieved by providing linear polyamines having at least one terminal secondary or tertiary amine function as a detergent additive for fuels and lubricants.
The invention firstly provides the use of a compound of the general formula I
R¹R²N((CH₂)_xNH)_y(CH₂)_zNR³R⁴ (I)
where
R¹, R², R³and R⁴are each independently H or C₁-C₁₀-alkyl but neither R¹and R²nor R³and R⁴are simultaneously H; or R1 and R²together with the nitrogen atom to which they are bonded form a C₄-C₆-dicarboximide ring which is substituted by at least one polyalkenyl radical R which has a number-average molecular weight Mn of from 100 to 2500, and where R³and R⁴are preferably simultaneously C₁-C₁₀-alkyl;
y is an integer from 1 to 100, for example from 1 to 50, from 1 to 20 or from 1 to 10, for example 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 and
x and z are independently an integer from 2 to 12, for example from 2 to 10, from 2 to 8, from 2 to 6 or 2, 3 or 4,
as a detergent additive for fuels and lubricants. In particular its use for diesel fuels and in that caseits use for the purpose of reducing the carbonization of the nozzles in diesel engines should be mentioned. For example, the additives according to the present invention are suitable for reducing the carbonization of the nozzles in diesel engines with direct fuel injection, like those based on the “common rail”, “pump-nozzle” or “pump-line-nozzle” principles.
A “reduction of the carbonization of the nozzles” is understood to be a partial or complete reduction of the degree of the carbonization of the nozzles in comparison with the degree of carbonization occurring with a fuel without additives (i.e. in the absence of a compound of formula I in the fuel), as determined in a standardized test engine, in particular in accordance with the standardized test engine employed for the determination of air flow restriction described below.
A first preferred group of compounds comprises compounds of the following general formula II
where x, y, z, R, R³and R⁴are each as defined above. Such compounds are thus terminated by a secondary or tertiary amine function. Especially mentioned are compounds of formula II where R³and R⁴are the same or different and are a C₁-C₁₀-, C₁-C₈-, C₁-C₆-, C₁-C₅- or C₁-C₄-alkyl group.
Embodiments of polyalkenyl radicals R which are preferred in accordance with the invention are illustrated later in section C2). Especially preferably, R is a polyisobutenyl radical. The polyisobutenyl radical has in particular an Mn of from about 500 to 1000.
A second preferred group of compounds comprises compounds of the formula I, wherein R¹, R², R³and R⁴are each independently H or C₁-C₁₀-alkyl but neither R¹and R²nor R³and R⁴are simultaneously H, and x, y and z are each as defined above. Such compounds are thus terminated by two secondary and/or tertiary amine functions.
Preference is given in particular to those compounds of the formula I and II, wherein x and z are each independently an integer from 2, 3 or 4 and y is 1, 2 or 3.
Particular preference is further given to those compounds of the formula I and II wherein R³and R⁴are each independently H or C₁-C₈-, C₁-C₆-, C₁-C₅or C₁-C₄-alkyl but R³and R⁴may not simultaneously each be H; or wherein R³and R⁴are simultaneously C₁-C₈-, C₁-C₆-, C₁-C₅or C₁-C₄-alkyl. Preferably R³and R⁴have the same meaning.
Particular preference is also given to compounds of the formula I wherein R¹, R², R³and R⁴are simultaneously each C₁-C₄-alkyl.
In another preferred embodiment, the reaction products or mixtures, partly purified if appropriate, obtained in the preparation of compounds of the formula I are used.
It is possible in accordance with the invention to use, for example, a reaction product comprising an imide compound of the formula I, for example a compound of the formula II, the reaction product being obtainable by reacting a cyclic C₄-C₆-dicarboxylic anhydride which is substituted by at least one polyalkenyl radical R which has a number-average molecular weight Mn of from 100 to 2500 with a polyamine of the formula III
H₂N((CH₂)_xNH)_y(CH₂)_zNR³R⁴ (III)
where x, y, z, R³and R⁴are each as defined above, if appropriate followed by a removal of volatile constituents of the reaction mixture. The reaction can be effected according to the disclosure of DE-A-101 23 553.
The above-described detergent additives are used customarily in combination with at least one further conventional fuel or lubricant additive which will be described more precisely later.
The additive of the formula I is added in an amount of about 1-200 mg/kg of fuel, more preferably in a dosage of from 1 to 100, from 1 to 50, from 1 to 30, from 2 to 20 or from 2 to 16 mg/kg of fuel.
The additive of the formula I is preferably added in an amount which brings about a maximum degree of carbonization of 80%, preferably of 70%, for example from 0 to 65%, from 2 to 50% or from 5 to 40%, determined to CEC F23 A 01 (in an XUD9 test engine at 0.1 mm needle stroke) via the percentage air flow restriction.
The invention further provides fuel compositions comprising in a majority of a hydrocarbon fuel boiling in the range from 100 to 500° C., for example from 150 to 400° C. or from 160 to 360° C., in particular a middle distillate fuel, for example diesel fuel, an effective amount of at least one detergent additive of the formula I as defined above.
The invention also provides lubricant compositions comprising in a customary lubricant, at least an effective amount of at least one detergent additive of the formula I as defined above.
The invention also relates to additive concentrates comprising at least one detergent additive of the formula I as defined above in combination with at least one further customary fuel or lubricant additive. The inventive additive is present in the concentrates preferably in an amount of from 0.1 to 80% by weight, more preferably from 1 to 70% by weight and in particular from 20 to 60% by weight, based on the total weight of the concentrate.
The invention also provides a process for preparing a fuel composition having improved fuel intake system-cleaning action, wherein an effective amount of at least one compound as defined above or of an additive concentrate as defined above is added to a commercial fuel composition.
Finally, the invention provides a process for preparing a lubricant composition having improved cleaning action, wherein an effective amount of at least one compound as defined above or of an additive concentrate as defined above is added to a commercial lubricant composition.

DETAILED DESCRIPTION OF THE INVENTION

A) Preferred Embodiments of Inventive Polyamines

In the above definition of the R¹, R², R³and R⁴radicals, C₁-C₁₀-alkyl represents in particular C₁-C₄-alkyl radicals such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, and also the longer-chain pentyl, hexyl, heptyl, octyl, nonyl and decyl radicals, and also the mono- or polybranched, for example mono-, di- or tribranched, analogs thereof.
The C₄-C₆-dicarboximide ring is derived in particular from monoethylenically unsaturated C₄-C₆-dicarboxylic acids and derivatives thereof, especially anhydrides. Suitable dicarboxylic acids are the monounsaturated forms of succinic acid, glutaric acid and adipic acid.

A1) Dicarboximide Derivatives of Group 1

These compounds are obtainable, for example, by the reaction of a dicarboxylic acid substituted by a hydrophobic hydrocarbon radical or of a dicarboxylic acid derivative substituted by a hydrophobic hydrocarbon radical with an amine which has at least one NH₂group. Preference is given to reacting a carboxylic anhydride.
The molar ratio of dicarboxylic acid (derivative) groups to hydrocarbon radical is in the range of 0.8:2, or 0.9:1.5 or 0.9:1.05, as described, for example, also in EP-A-0 355 895 and 0 587 381.
The reaction of such dicarboxylic acids or derivatives thereof, especially of dicarboxylic anhydrides, with amines may result in product mixtures which comprise dicarboxylic monoamides, dicarboxylic diamides, ammonium salts of dicarboxylic monoamides, dicarboxylic monoamide monoesters, amidines and dicarboxylic mono- and diimides. Suitable as the inventive additive are both the acylation products specified individually and mixtures thereof.
However, preference is given to dicarboximides, especially dicarboxylic monoimides and mixtures which comprise them. The imide fraction is in particular in the range from 1 to 100 mol %, for example from 10 to 95 mol % or from 30 to 90 mol %.
The coupling ratio (PIBSA/AMINE) is in the range from 0.5 to 2 based on the ratio of succinic acid groups to amine, for example from 0.8 to 1.2, more preferably from 0.9 to 1.05.
Amines suitable for the reaction with the dicarboxylic acid or the dicarboxylic acid derivative are polyamines of the above formula III.
Suitable polyamines are, for example, the mono-N,N-dialkyl derivatives of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, dipropylenetriamine, tripropylenetetramine, tetrapropylenepentamine, pentapropylenehexamine, dibutylenetriamine, tributylenetetramine, tetrabutylenepentamine, pentabutylenehexamine.
Examples include: N,N-dimethyldimethylenetriamine, N,N-diethyldimethylenetriamine, N,N-dipropyldimethylenetriamine, N,N-dimethyldiethylene-1,2-triamine, N,N-diethyldiethylene-1,2-triamine, N,N-dipropyldiethylene-1,2-triamine, N,N-dimethyldipropylene-1,3-triamine (i.e. DMAPAPA), N,N-diethyldipropylene-1,3-triamine, N,N-dipropyldipropylene-1,3-triamine, N,N-dimethyldibutylene-1,4-triamine, N,N-diethyldibutylene-1,4-triamine, N,N-dipropyldibutylene-1,4-triamine, N,N-dimethyldipentylene-1,5-triamine, N,N-diethyldipentylene-1,5-triamine, N,N-dipropyldipentylene-1,5-triamine, N,N-dimethyldihexylene-1,6-triamine, N,N-diethyldihexylene-1,6-triamine and N,N-dipropyldihexylene-1,6-triamine.
A2) Polyamines of Group 2 which are Terminated by Two Secondary and/or Tertiary Amine Functions
Nonlimiting examples include:
Linear polyamines terminated by identical N,N-dialkylamino groups, such as bis[2-(N,N-dimethylamino)ethyl]amine, bis[2-(N,N-diethylamino)ethyl]amine, bis[2-(N,N-dipropylamino)ethyl]amine, bis[3-(N,N-dimethylamino)propyl]amine, bis[3-(N,N-diethylamino)propyl]amine, bis[3-(N,N-dipropylamino)propyl]amine, bis[4-(N,N-dimethylamino)butyl]amine, bis[4-(N,N-diethylamino)butyl]amine, bis[4-(N,N-dipropylamino)butyl]amine, bis[5-(N,N-dimethylamino)pentyl]amine, bis[5-(N,N-diethylamino)pentyl]amine, bis[5-(N,N-dipropylamino)pentyl]amine, bis[6-(N,N-dimethylamino)hexyl]amine, bis[6-(N,N-diethylamino)hexyl]amine, bis[6-(N,N-dipropylamino)hexyl]amine and the corresponding analogs terminated by identical monoalkylamino groups. Also usable are corresponding polyamines which are terminated by different mono- or dialkylamino groups, and mixtures of such compounds.
Polyamines of the above type are described in Kirk-Othmer “Encyclopedia of Chemical Technology”, 2nd edition, Volume 7, pages 22 to 37, Interscience Publishers, New York (1965, “Ethylenamines” chapter).

B) Preparation of Inventive Additives

B1) Dicarboximide Additives of Group 1

Processes for preparing these compounds are known to those skilled in the art. A particularly suitable process for preparing polyalkenylsuccinimides is described in the German patent application DE-A-10123553.4, which is fully incorporated herein by reference. In this process, a polyalkenylsuccinic anhydride is reacted first with an alcohol or a phenol and subsequently with an amine. Alternatively, the polyalkenylsuccinic anhydride is reacted with the amine in the presence of an alcohol or of a phenol.
Alcohols suitable for preparing polyalkenylsuccinimides are preferably monohydric; however, polyhydric alcohols are also suitable.
Preference is given to using monohydric alcohols having from 1 to 16 carbon atoms, such as methanol, ethanol, propanol, isopropanol, butanol, sec-butanol, isobutanol, tert-butanol, 2-hydroxymethylfuran, amyl alcohol, isoamyl alcohol, vinylcarbinol, cyclohexanol, n-hexanol, 6-capryl alcohol, 2-ethylhexanol, n-decanol, lauryl alcohol, isooctyl alcohol and mixtures thereof. Preferred alcohols are those having from 6 to 16 carbon atoms. Particular preference is given to 2-ethylhexanol.
Suitable phenols include phenol, naphthol, (o,p)-alkylphenols and salicylic acid.
Processes for preparing polyalkenyl-substituted dicarboxylic acids or derivatives thereof are known. For instance, the German patent application DE-A-10123553.4 describes the preparation of a polyolefin-substituted carboxylic acid or of a derivative thereof by the reaction of a polyalkene with a monounsaturated acid or derivative thereof, in the course of which the polyalkylene adds to the double bond of the acid component in an ene reaction. Other processes are described, for example, also in WO-A-98/42808, which is incorporated herein by reference.

B2) Polyamines of Group 2 Having Two Terminal Secondary or Tertiary Amine Functions

They are prepared as described in Ullmann's Encyclopedia of Industrial Chemistry, 6^thed. 2000, Electronic release, Chapt 8.2, Oligo- and Polyamines.
The polyamines of the formula III are prepared in a similar manner.

C) Different Applications of Inventive Polyamines

The inventive polyamine products can be used as additives (usually in the form of additive packages or concentrates) for fuels, especially diesel fuel, heating oil, kerosene, or middle distillates in general, and gasoline fuel, or lubricants.
When the inventive polyamines are used as diesel fuel additives, they contain an effective amount of polyamine. Appropriately, the diesel fuels contain a proportion of from about 1 to 5000 ppm, or of from about 5 to 1000 ppm, for example from about 5 to 200 or from 10 to 100 ppm, based on the total weight of the diesel fuel.
The diesel fuel additive mixtures used comprise at least one further additive selected from other customary detergents, corrosion inhibitors, dehazers, demulsifiers, antifoams, antioxidants, metal deactivators, multifunctional stabilizers, cetane number improvers, combustion improvers, dyes, markers, solubilizers, antistats, lubricity improvers.
The inventive polyamines may also be used as additives for heating oil. They are used in an effective amount, appropriately in an amount of from 10 to 1000 ppm, preferably from 50 to 500 ppm, based on the total weight of the heating oil. This may comprise at least one further additive which may be selected from corrosion inhibitors, demulsifiers, antifoams, antioxidants, metal deactivators, ferrocenes and deodorants.
The inventive polyamines may also be used as additives for gasoline fuels. These contain an effective amount of inventive polyamines, appropriately from 1 to 5000 ppm, or of from about 5 to 1000 ppm, for example from about 5 to 200 or from 10 to 100 ppm, based on the total weight of the gasoline fuel.
The gasoline fuel additive mixtures may also comprise at least one further additive selected from other customary detergent additives, carrier oils, lubricity improvers, solvents and corrosion inhibitors.
Finally, the inventive polyamines are also suitable for lubricant compositions which contain an effective amount of inventive products, appropriately from 0.1 to 10% by weight, preferably from 0.5 to 5% by weight, based on the total weight of the lubricant composition.
The lubricant compositions may also comprise further additives which are in particular selected from lubricity improvers, wear protection additives, corrosion inhibitors, VI improvers.
Some additives usable as coadditives are described hereinbelow:

C1) Detergent Additives

Additives having detergent action have at least one hydrophobic hydrocarbon radical having a number-average molecular weight (Mn) of from 85 to 20 000 and at least one polar moiety selected from:

(a) mono- or polyamino groups having up to 6 nitrogen atoms, of which at least one nitrogen atom has basic properties;
(b) nitro groups, optionally in combination with hydroxyl groups;
(c) hydroxyl groups in combination with mono- or polyamino groups, in which at least one nitrogen atom has basic properties;
(d) polyoxy-C₂-C₄-alkylene groups which are terminated by hydroxyl groups, mono- or polyamino groups, in which at least one nitrogen atom has basic properties, or by carbamate groups;
(e) carboxylic ester groups;
(f) moieties obtained by Mannich reaction of substituted phenols with aldehydes and mono- or polyamines;
(g) moieties derived from carboxylic anhydrides and having hydroxyl and/or amino and/or amido and/or imino groups,
- these imido-containing detergents not, like the inventive polyamines of the formula I, having a terminal secondary or tertiary amine group.

Additives containing mono- or polyamino groups (a) are preferably polyalkene monoamines or polyalkene polyamines based on polypropene or on reactive (i.e. having predominantly terminal double bonds, usually in the beta- and gamma-position) or conventional (i.e. having predominantly internal double bonds) polybutene or polyisobutene having M_N=from 300 to 5000. Such additives based on reactive polyisobutene, which can be prepared from the polyisobutene which may contain up to 20% by weight of n-butene units by hydroformylation and reductive amination with ammonia, monoamines or polyamines, such as dimethylaminopropylamine, ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine, are disclosed in particular in EP-A 244 616. When polybutene or polyisobutene having predominantly internal double bonds (usually in the beta and gamma position) are used as starting materials in the preparation of the additives, a possible preparative route is by chlorination and subsequent amination or by oxidation of the double bond with air or ozone to give the carbonyl or carboxyl compound and subsequent amination under reductive (hydrogenating) conditions. The amines used here for the amination may be the same as those used above for the reductive amination of the hydroformylated highly reactive polyisobutene. Corresponding additives based on polypropene are described in particular in WO-A 94/24231, which is fully incorporated herein by reference.
Further preferred additives containing monoamino groups (a) are the hydrogenation products of the reaction products of polyisobutenes having an average degree of polymerization P=from 5 to 100 with nitrogen oxides or mixtures of nitrogen oxides and oxygen, as described in particular in WO-A 97/03946, which is fully incorporated herein by reference.
Further preferred additives containing monoamino groups (a) are the compounds obtainable from polyisobutene epoxides by reaction with amines and subsequent dehydration and reduction of the amino alcohols, as described in particular in DE-A 196 20 262, which is fully incorporated herein by reference.
Additives containing nitro groups, optionally in combination with hydroxyl groups, (b) are preferably reaction products of polyisobutenes having an average degree of polymerization P=from 5 to 100 or from 10 to 100 with nitrogen oxides or mixtures of nitrogen oxides and oxygen, as described in particular in WO-A 96/03367 and WO-A 96/03479, which are fully incorporated herein by reference. These reaction products are generally mixtures of pure nitropolyisobutenes (e.g. alpha,beta-dinitropolyisobutene) and mixed hydroxynitropolyisobutenes (e.g. alpha-nitro-beta-hydroxypolyisobutene).
Additives containing hydroxyl groups, optionally in combination with mono- or polyamino groups, (c) are in particular reaction products of polyisobutene epoxides obtainable from polyisobutene having preferably predominantly terminal double bonds and M_N=from 300 to 5000, with ammonia or mono- or polyamines, as described in particular in EP-A 476 485, which is fully incorporated herein by reference.
Additives containing polyoxy-C₂- to C₄-alkylene moieties (d) are preferably polyethers or polyetheramines which are obtainable by reaction of C₂- to C₆₀-alkanols, C₆- to C₃₀-alkanediols, mono- or di-C₂-C₃₀-alkylamines, C₁-C₃₀-alkylcyclohexanols or C₁-C₃₀-alkylphenols with from 1 to 30 mol of ethylene oxide and/or propylene oxide and/or butylene oxide per hydroxyl group or amino group and, in the case of the polyetheramines, by subsequent reductive amination with ammonia, monoamines or polyamines. Such products are described in particular in EP-A 310 875, EP-A 356 725, EP-A 700 985 and U.S. Pat. No. 4,877,416, which are fully incorporated herein by reference. In the case of polyethers, such products also have carrier oil properties. Typical examples of these are tridecanol butoxylates, isotridecanol butoxylates, isononylphenol butoxylates and polyisobutenol butoxylates and propoxylates and also the corresponding reaction products with ammonia.
Additives containing carboxylic ester groups (e) are preferably esters of mono-, di- or tricarboxylic acids with long-chain alkanols or polyols, in particular those having a minimum viscosity of 2 mm²at 100° C., as described in particular in DE-A 38 38 918, which is fully incorporated herein by reference. The mono-, di- or tricarboxylic acids used may be aliphatic or aromatic acids, and particularly suitable ester alcohols or ester polyols are long-chain representatives having, for example, from 6 to 24 carbon atoms. Typical representatives of the esters are adipates, phthalates, isophthalates, terephthalates and trimellitates of isooctanol, of isononanol, of isodecanol and of isotridecanol. Such products also have carrier oil properties.
Additives containing moieties conventional obtained by conventional Mannich reaction of phenolic hydroxyl groups with aldehydes and mono- or polyamines (f) are preferably reaction products of polyisobutene-substituted phenols with formaldehyde and primary mono- or polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine or dimethylaminopropylamine. The polyisobutenyl-substituted phenols may stem from conventional or highly reactive polyisobutene having Mn=from 300 to 5 000. Such “polyisobutene-Mannich bases” are described in particular in EP-A 831 141, which is fully incorporated herein by reference.
Additives containing moieties derived from carboxylic anhydrides and having hydroxyl and/or amino and/or amido and/or imido groups (g) are preferably corresponding derivatives of dicarboxylic anhydrides, more preferably of succinide anhydride. It is self-evident that the term “moieties derived from carboxylic anhydrides . . . .” does not necessarily require that the starting materials actually have to be the carboxylic anhydrides. It will be appreciated that such moieties may also be obtained by the reaction of other carboxylic acid derivatives which have the required activity, for example carbonyl halides, or else by the reaction of the carboxylic acid itself when suitable activation measures are taken. However, carboxylic anhydrides are particularly suitable derivatives for the conversion to the moieties mentioned.
The polar moiety of component A is more preferably a moiety derived from carboxylic anhydrides and having hydroxyl and/or amino and/or amido and/or imido groups (g), especially having amido and/or imido groups, i.e. N-acyl moieties.
The hydrophobic hydrocarbon radical of the above-described detergent additives (a) to (g) and the hydrophobic R radical of inventive polyamine detergents of the formulae I and II are preferably a homo- or copolymer radical whose repeating units are derived from monomers which are selected from propene, n-butene and isobutene and mixtures thereof.
The homo- or copolymer radicals is more preferably a polyisobutene radical. In particular, the homo- or copolymer radical is a radical which is derived from “reactive” polyisobutenes which differ from the “low-reactivity” polyisobutenes by the content of terminal double bonds. Reactive polyisobutenes differ from low-reactivity polyisobutenes in that they contain at least 50 mol %, preferably at least 60 mol % and more preferably at least 80 mol %, based on the total number of polyisobutene macromolecules, of terminal double bonds. The terminal double bonds may be either vinyl double bonds [—CH═C(CH₃)₂] or vinylidene double bonds [—CH₂—C(═CH₂)—CH₃]. Preference is given in particular to polyisobutenes which have uniform polymer skeletons. Uniform polymer skeletons are in particular those polyisobutenes which are composed to an extent of at least 85% by weight, preferably to an extent of at least 90% by weight and more preferably to an extent of at least 95% by weight, of isobutene units. For example, such reactive polyisobutenes have a number-average molecular weight in the range from 100 to 20 000. Suitable reactive polyisobutenes for preparing fuel additives are in particular those which have a number-average molecular weight in the range from 100 to 3000, such as from 200 to 2500 or from 500 to 1500, for example a number-average molecular weight of about 550, about 800 or about 1000.
Suitable reactive polyisobutenes for preparing lubricant additives are in particular those which have a number-average molecular weight in the range from 1000 to 15 000, more preferably from 1300 to 12 500 and most preferably from 2000 to 10 000, for example a number-average molecular weight of about 1500, about 2000 or about 2300.
The reactive polyisobutenes preferably additionally have a polydispersity of less than 3.0, in particular less than 1.9 and more preferably of less than 1.7 or less than 1.5. Polydispersity refers to the quotient of weight-average molecular weight M_Wdivided by the number-average molecular weight M_N.
Particularly suitable reactive polyisobutenes are, for example, the Glissopal brands of BASF AG, in particular Glissopal 1000 (M_N=1000) and Glissopal V 33 (M_N=550) and Glissopal 2300 (M_N=2300) and mixtures thereof. Other number-average molecular weights may be attained by a manner known in principle, by mixing polyisobutenes of different number-average molecular weights or by extractively enriching polyisobutenes of certain molecular weight ranges.

C2) Cold Flow Improvers

The additives improving cold properties (cold flow improvers) include middle distillate flow improvers (“MDFIs”), paraffin dispersants (“WASAs”) and the combination of the two additives (“WAFIs”).
The suitable cold flow improvers include in particular the following active substance groups, as described, for example, in WO 95/33805:

aa) copolymers of ethylene with at least one further ethylenically unsaturated monomer which are different from the polymers used in accordance with the invention;
ab) comb polymers;
ac) polyoxyalkylenes;
ad) polar nitrogen compounds;
ae) sulfo carboxylic acids or sulfonic acids or their derivatives; and
af) poly(meth)acrylic esters.

In the case of copolymers of ethylene with at least one further ethylenically unsaturated monomer (aa) the monomer is preferably selected from alkenylcarboxylic esters, (meth)acrylic esters and olefins.
Examples of suitable olefins are those having from 3 to 10 carbon atoms, and having from 1 to 3, preferably having 1 or 2, carbon-carbon double bonds, in particular having one carbon-carbon double bond. In the latter case, the carbon-carbon double bond may either be terminal (a-olefin) or internal. However, preference is given to α-olefins, more preferably α-olefins having from 3 to 6 carbon atoms, such as propene, 1-butene, 1-pentene and 1-hexene.
Examples of suitable (meth)acrylic esters are esters of (meth)acrylic acid with C₁-C₁₀-alkanols, in particular with methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, isobutanol, tert-butanol, pentanol, hexanol, heptanol, octanol, 2-ethylhexanol, nonanol and decanol.
Examples of suitable alkenylcarboxylic esters are the vinyl and propenyl esters of carboxylic acids having from 2 to 20 carbon atoms whose hydrocarbon radical may be linear or branched. Among these, preference is given to the vinyl esters. Among the carboxylic acids having branched hydrocarbon radicals, preference is given to those whose branch is in the α-position to the carboxyl group, and particular preference is given to the α-carbon atom being tertiary, i.e. to the carboxylic acid being a neocarboxylic acid. However, preference is given to the hydrocarbon radical of the carboxylic acid being linear.
Examples of suitable alkenylcarboxylic esters are vinyl acetate, vinyl propionate, vinyl butyrate, vinyl-2-ethylhexanoate, vinyl neopentanoate, vinyl hexanoate, vinyl neononanoate, vinyl neodecanoate and the corresponding propenyl esters, although preference is given to the vinyl esters. A particularly preferred alkenylcarboxylic ester is vinyl acetate.
Particular preference is given to selecting the ethylenically unsaturated monomer from alkenylcarboxylic esters.
Copolymers which contain two or more differing copolymerized alkenylcarboxylic esters are also suitable, and these differ in the alkenyl function and/or in the carboxylic group. Copolymers which, in addition to the alkenylcarboxylic ester(s), contain at least one copolymerized olefin and/or at least one copolymerized (meth)acrylic ester are likewise suitable.
The ethylenically unsaturated monomer is copolymerized in the copolymer in an amount of preferably from 1 to 50 mol %, more preferably from 10 to 50 mol % and in particular from 5 to 20 mol %, based on the entire copolymer.
The copolymer (aa) preferably has a number-average molecular weight M_nof from 1000 to 20 000, more preferably from 1000 to 10 000 and in particular from 1000 to 6000.
Examples of comb polymers (ab) are those described in “Comb-Like Polymers. Structure and Properties”, N. A. Platé and V. P. Shibaev, J. Poly. Sci. Macromolecular Revs. 8, pages 117 to 253 (1974). Among those described there, examples of suitable comb polymers are those of the formula II
where

D is R¹⁷, COOR¹⁷, OCOR¹⁷, R¹⁸, COOR¹⁷or OR¹⁷,

E is H, CH₃, D or R¹⁸,

G is H or D,

J is H, R¹⁸, R¹⁸COOR¹⁷, aryl or heterocyclyl,

K is H, COOR¹⁸, OCOR¹⁸, OR¹⁸or COOH,

L is H, R¹⁸, COOR¹⁸, OCOR¹⁸, COOH or aryl,
where

- R¹⁷is a hydrocarbon radical having at least 10 carbon atoms, preferably having from 10 to 30 carbon atoms,
- R¹⁸is a hydrocarbon radical having at least one carbon atom, preferably having from 1 to 30 carbon atoms,
  m is a molar fraction in the range from 1.0 to 0.4 and
  n is a molar fraction in the range from 0 to 0.6.

Preferred comb polymers are obtainable, for example, by copolymerizing maleic anhydride or fumaric acid with another ethylenically unsaturated monomer, for example with an α-olefin or an unsaturated ester such as vinyl acetate, and then esterifying the anhydride or acid function with an alcohol having at least 10 carbon atoms. Further preferred comb polymers are copolymers of α-olefins and esterified comonomers, for example esterified copolymers of styrene and maleic anhydride or esterified copolymers of styrene and fumaric acid. Mixtures of comb polymers are also suitable. Comb polymers may also be polyfumarates or polymaleates. Homo- and copolymers of vinyl ethers are also suitable comb polymers.
Examples of suitable polyoxyalkylenes (ac) are polyoxyalkylene esters, ethers, ester/ethers and mixtures thereof. The polyoxyalkylene compounds preferably contain at least one linear alkyl group, more preferably at least two linear alkyl groups, having from 10 to 30 carbon atoms and a polyoxyalkylene group having a molecular weight of up to 5000. The alkyl group of the polyoxyalkylene radical preferably contains from 1 to 4 carbon atoms. Such polyoxyalkylene compounds are described, for example, in EP-A-0 061 895 and also in U.S. Pat. No. 4,491,455, which are fully incorporated herein by way of reference. Preferred polyoxyalkylene esters, ethers and ester/ethers have the general formula III
R¹⁹[O—(CH₂)_y]_xO—R²⁰ (III)
where
R¹⁹and R²⁰are each independently R²¹, R²¹⁻CO—, R²¹—O—CO(CH₂)_z— or R²¹—O—CO(CH₂)_z—CO—, where R²¹is linear C₁-C₃₀-alkyl,
y is a number from 1 to 4,
x is a number from 2 to 200, and
z is a number from 1 to 4.
Preferred polyoxyalkylene compounds of the formula III in which both R¹⁹and R²⁰are R²¹are polyethylene glycols and polypropylene glycols having a number-average molecular weight of from 100 to 5000. Preferred polyoxyalkylenes of the formula III in which one of the R¹⁹radicals is R²¹and the other is R²¹⁻CO— are polyoxyalkylene esters of fatty acids having from 10 to 30 carbon atoms, such as stearic acid or behenic acid. Preferred polyoxyalkylene compounds in which both R¹⁹and R²⁰are an R²¹—CO— radical are diesters of fatty acids having from 10 to 30 carbon atoms, preferably of stearic or behenic acid.
The polar nitrogen compounds (ad) which are appropriately oil-soluble may be either ionic or nonionic and preferably have at least one, more preferably at least two, substituents of the formula >NR²²where R²²is a C₈-C₄₀-hydrocarbon radical. The nitrogen substituents may also be in quaternized form, i.e. in cationic form. Examples of such nitrogen compounds include ammonium salts and/or amides which are obtainable by reacting at least one amine substituted by at least one hydrocarbon radical with a carboxylic acid having from 1 to 4 carboxyl groups or with a suitable derivative thereof. The amines preferably contain at least one linear C₈-C₄₀-alkyl radical. Examples of suitable primary amines include octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tetradecylamine and the higher linear homologs. Examples of suitable secondary amines include dioctadecylamine and methylbehenylamine. Amine mixtures, in particular amine mixtures obtainable on the industrial scale, such as fatty amines or hydrogenated tallamines, are also suitable, as described, for example, in Ullmanns Encyclopedia of Industrial Chemistry, 6th edition, 2000 electronic release, Chapter “Amines, aliphatic”. Examples of acids suitable for the reaction include cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, naphthalenedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid and succinic acids substituted by long-chain hydrocarbon radicals.
Further examples of polar nitrogen compounds are ring systems which bear at least two substituents of the formula -A-NR²³R²⁴where A is a linear or branched aliphatic hydrocarbon group which is optionally interrupted by one or more groups selected from O, S, NR³⁵and CO, and R²³and R²⁴are each C₉-C₄₀-hydrocarbon radicals which are optionally interrupted by one or more groups selected from O, S, NR³⁵and CO, and/or substituted by one or more substituents selected from OH, SH and NR³⁵R³⁶where R³⁵is C₁-C₄₀-alkyl which is optionally interrupted by one or more moieties which are selected from CO, NR³⁵, O and S, and/or substituted by one or more radicals selected from NR³⁷R³⁸, OR³⁷, SR³⁷, COR³⁷, COOR³⁷, CONR³⁷R³⁸, aryl or heterocyclyl, where R³⁷and R³⁸are each independently selected from H or C₁-C₄-alkyl; and R³⁶is H or R³⁵.
A is preferably a methylene or polymethylene group having from 2 to 20 methylene units. Examples of suitable R²³and R²⁴radicals include 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl, 2-ketopropyl, ethoxyethyl and propoxypropyl. The cyclic system may be a homocyclic, heterocyclic, fused polycyclic or nonfused polycyclic system. The ring system is preferably carbo- or heteroaromatic, in particular carboaromatic. Examples of such polycyclic ring systems include fused benzoid structures such as naphthalene, anthracene, phenanthrene and pyrene, fused nonbenzoid structures such as azulene, indene, hydrindene and fluorene, nonfused polycycles such as diphenyl, heterocycles such as quinoline, indole, dihydroindole, benzofuran, coumarin, isocoumarin, benzthiophene, carbazole, diphenylene oxide and diphenylene sulfide, nonaromatic or partially saturated ring systems such as decalin, and three-dimensional structures such as α-pinene, camphene, bornylene, norbonane, norbonene, bicyclooctane and bicyclooctene.
Further examples of suitable polar nitrogen compounds are condensates of long-chain primary or secondary amines with carboxyl-containing polymers.
The polar nitrogen compounds specified hereinabove are described in WO 00/44857 and also in the references mentioned therein, which are fully incorporated herein by way of reference.
Suitable polar nitrogen compounds are also described in, for example, DE-A-198 48 621, DE-A-196 22 052 and EP-B-398 101, which are incorporated herein by way of reference.
Examples of suitable sulfo carboxylic acids/sulfonic acids and their derivatives (ae) are those of the general formula IV
where
Y is SO₃ ⁻(NR²⁵ ₃R²⁶)⁺, SO₃ ⁻(NHR²⁵ ₂R²⁶)⁺, SO₃ ⁻(NH₂R²⁵R²⁶), SO₃ ⁻(NH₃R²⁶) or SO₂NR²⁵R²⁶,
X is Y, CONR²⁵R²⁷, CO₂ ⁻(NR²⁵ ₃R²⁷)⁺, CO₂ ⁻(NHR²⁵ ₂R²⁷)⁺, R²⁸—COOR²⁷, NR²⁵COR²⁷, R²⁸OR²⁷, R²⁸OCOR²⁷, R²⁸R²⁷, N(COR²⁵)R²⁷or Z⁻(NR²⁵ ₃R²⁷)⁺,

- where
- R²⁵is a hydrocarbon radical,
- R²⁶and R²⁷are each alkyl, alkoxyalkyl or polyalkoxyalkyl having at least 10 carbon atoms in the main chain,
- R²⁸is C₂-C₅-alkylene,
  Z⁻ is one anion equivalent and
  A and B are each alkyl, alkenyl or two substituted hydrocarbon radicals, or, together with the carbon atom to which they are bonded, form an aromatic or cycloaliphatic ring system.

Such sulfo carboxylic acids and sulfonic acids and their derivatives are described in EP-A-0 261 957, which is fully incorporated herein by way of reference.
Suitable poly(meth)acrylic esters (af) are both homo- and copolymers of acrylic and methacrylic esters. Preference is given to acrylic ester/homopolymers derived from C₁-C₄₀alcohols. Preference is also given to copolymers of at least two differing (meth)acrylic esters which differ in respect of the esterified alcohol. The copolymer may also contain a further, different copolymerized olefinically unsaturated monomer. The weight-average molecular weight of the polymer is preferably from 50 000 to 500 000. A particularly preferred polymer is a copolymer of methacrylic acid and methacrylic esters of saturated C₁₄- and C₁₅-alcohols in which the acid groups are neutralized by hydrogenated tallamine. Suitable poly(meth)acrylic esters are described, for example, in WO 00/44857 which is fully incorporated herein by way of reference.

C2) Lubricity Improvers

The customary lubricity improvers include, for example, carboxylic acids, especially fatty acids, esters thereof, especially with polyols, mixtures of these acids and esters, ashlessly burning N-acyl compounds such as polyalkenylsuccinamides, mixtures of the acids and/or esters mentioned with these N-acyl compounds, as described, for example, in WO 96/23855, bis(hydroxyalkyl) fatty amines or hydroxyacetamides.

C3) Diluents

Inventive additives are frequently formulated together with solvents or diluents. Suitable diluents are, for example, the fractions obtained in crude oil processing, such as kerosene, naphtha or brightstock. Additionally suitable are aromatic and aliphatic hydrocarbons and alkoxyalkanols. Diluents used with preference for middle distillates, especially for diesel fuels, are naphtha, kerosene, diesel fuels, aromatic hydrocarbons such as Solvent Naphtha heavy, Solvesso® or Shellsol® and mixtures of these solvents and diluents.

D) Fuels and Lubricants

Fuels which are additized preferably in accordance with the invention are gasoline fuels and middle distillates such as diesel fuel, heating oil or kerosene, of which particular preference is given to diesel fuel.
The diesel fuels are, for example, mineral oil raffinates which typically have a boiling range of from 100 to 400° C. These are usually distillates having a 95% point up to 360° C. or even higher. These may also be “Ultra Low Sulphur Diesel” or “City Diesel”, characterized by a maximum 95% point of, for example, 345° C. and a maximum sulfur content of 0.005% by weight, or by a 95% point of, for example, 285° C. and a maximum sulfur content of 0.001% by weight. Suitable in addition to the diesel fuels obtainable by refining are those which are obtainable by coal gasification or gas liquefaction (“gas-to-liquid” (GTL) fuels). Also suitable are mixtures of the aforementioned diesel fuels with renewable fuels such as biodiesel or bioethanol.
Particular preference is given to using the inventive additive for additizing diesel fuels having a low sulfur content, i.e. having a sulfur content of less than 0.05% by weight, preferably of less than 0.02% by weight, in particular of less than 0.005% by weight and especially of less than 0.001% by weight of sulfur.
The examples which follow illustrate the invention but without restricting it.

EXAMPLES

Preparation Example 1

Preparation of a Polyisobutenylsuccinimide of the Formula II

(R³,R⁴=methyl, x,z=3, y=1, R=polyisobutylene, Mn=550)
A four-neck flask equipped with nitrogen tap, internal contact thermosensor and distillation head with condenser is initially charged under nitrogen with a mixture of polyisobutenylsuccinic anhydride (PIBSA) (polyisobutenyl chain having Mn=550) in 2-ethylhexanol at 140° C. With vigorous stirring, N,N-dimethyldipropylenetriamine (DMAPAPA) is rapidly added dropwise. The molar ratio of PIBSA to amine used is 1:1.05 (succinic acid groups: amine). An exothermic reaction is observed with a temperature rise to 151° C. Subsequently, the reaction mixture is heated to 170° C. and stirred under nitrogen for 2.5 hours. Application of a vacuum of 500 mbar for 30 minutes then removes the alcohol present. Finally, the mixture is diluted to a 50% solution using Solvesso® 150.

Preparation Example 2

Preparation of a Polyisobutenylsuccinimide of the Formula II

(R³,R⁴=methyl, x,z=3, y=1, R=polyisobutenyl, Mn=1000)
The procedure of Example 1 is repeated, except that the corresponding molar amount of PIBSA 1000 (polyisobutenyl chain having Mn=1000) is used instead of PIBSA 550.

Use Example

Determination of the Detergent Activity of Inventive Polyamines

The detergency of inventive polyamines in comparison to a commercial detergent additive was determined in a standardized test engine XUD9 (Peugeot engine) using the CEC F23 A 01 test method. In this test, the degree of carbonization of the nozzles was determined in the injection nozzle via the restriction of an air flow at needle stroke 0.1 mm. 100% flow restriction means full carbonization; 0% means no carbonization.
The following fuels were used:

- Halternann RF 93
- Diesel fuel to EN 590 (S content<50 ppm)
- Diesel fuel to EN 590 (S content<10 ppm)

The following additives having detergent action were used:

- Kerocom PIBSI: polyisobutenesuccinimide obtainable by reacting polyisobutenesuccinic anhydride (polyisobutenyl chain having Mn=1000) and tetraethylenepentamine in a molar ratio of 1:1.05 (succinic acid to amine)
- PIBSI I: according to Preparation Example 1
- PIBSI II: according to Preparation Example 2
- Polyamine: bis[3-(N,N-dimethylamino)propyl]amine (compound of the formula I where R¹, R², R³, R⁴=methyl, x, z=3 and y=1)

For all PIBSIs used, PIBSAs having a comparable degree of succinylation were used.
These additives were examined in the above-specified tests for their detergent action at different dosage in different diesel fuels. The percentage flow restriction values determined are compiled in the following Table 1:


			Flow
			Restriction
Detergent	Dosage [ppm]	Fuel	[%]

Kerocom PIBSI	52	RF 93	75
(comparison)
	70	EN 590 S < 50 ppm	68
	66	EN 590 S < 10 ppm	67
PIBSI I	30	RF 93	37
PIBSI II	30	RF 93	7
	15	RF 93	37
	15	EN 590 S < 10 ppm	61
	15	EN 590 S < 50 ppm	61
Polyamine	15	RF 93	56

Relative to the comparative substance used, the inventive additives exhibit distinctly better detergent activity at simultaneously lower dosage.

Claims

1-18. (canceled)

19. A method for reducing carbonization of nozzles in diesel engines comprising adding a detergent additive to fuel wherein the detergent additive is a compound of the general formula (I):

R¹R²N((CH₂)_xNH)_y(CH₂)_zNR³R⁴ (I)

where

R¹and R²are each independently H or C₁-C₁₀-alkyl but neither R¹and R²are simultaneously H; or R¹and R²together with the nitrogen atom to which they are bonded form a C₄-C₆-dicarboximide ring which is substituted by at least one polyalkenyl radical which has a number-average molecular weight Mn of from 100 to 2500; R³and R⁴are independently C₁-C₁₀-alkyl;

y is an integer from 1 to 100 and

x and z are independently an integer from 2 to 12.

20. The method according to claim 19, wherein the detergent additive of the formula I is added in an amount which brings about a maximum degree of carbonization of 80% determined to CEC F23 A 01 (in an XUD9 test engine at needle stroke 0.1 mm) via the percentage in air flow restriction.

21. The method according to claim 20, wherein the degree of carbonization is 0 to 65%.

22. The method according to claim 19, wherein the compound has the following general formula II

where R is a polyalkenyl radical which has a number-average molecular weight Mn of from 100 to 2500.

23. The method according to claim 22, wherein R is a polyisobutenyl radical.

24. The method according to claim 23, wherein the polyisobutenyl radical has an Mn of from about 500 to 1000.

25. The method according to claim 19, wherein x and z are each independently an integer from 2 to 4 and y is 1, 2 or 3.

26. The method according to claim 19, wherein R³and R⁴are each independently C₁-C₄-alkyl.

27. The method according to claim 19, wherein R¹, R², R³and R⁴are each independently C₁-C₄-alkyl.

28. The method according to claim 19, wherein the compound is an imide of the formula I obtainable by reacting a cyclic C₄-C₆-dicarboxylic anhydride which is substituted by at least one polyalkylene radical which has a number-average molecular weight Mn of from 100 to 2500 with a polyamine of the formula III

H₂N((CH₂)_xNH)_y(CH₂)_zNR³R⁴ (III)

and optionally removing volatile constituents of the reaction mixture.

29. The method according to claim 28, wherein said imide is at least one compound of the formula II:

30. The method according to claim 19, wherein at least one further conventional additive selected from the group consisting of detergent additives, carrier oils, corrosion inhibitors, frictional wear-reducing additives, cetane number improvers, demulsifiers, antifoams, solvents, solubilizers, antioxidants, metal deactivators, deodorants and cold flow improvers other than compounds of the formula I, and mixtures comprising one or more of these additives is combined with the compound of general formula I.

31. A fuel composition comprising, in a majority of a hydrocarbon fuel boiling in the range from 100 to 500° C., an effective amount of at least one detergent additive of the formula I:

R¹R²N((CH₂)_xNH)_y(CH₂)_zNR³R⁴ (I)

where

y is an integer from 1 to 100 and

x and z are independently an integer from 2 to 12.

32. The method according to claim 19, wherein the fuel comprises a middle distillate fuel.

33. A lubricant composition comprising, in a customary lubricant, at least an effective amount of at least one detergent additive of the formula I:

R¹R²N((CH₂)_xNH)_y(CH₂)_zNR³R⁴ (I)

where

y is an integer from 1 to 100 and

x and z are independently an integer from 2 to 12.

34. An additive concentrate comprising at least one detergent additive of the formula I:

R¹R²N((CH₂)_xNH)_y(CH₂)_zNR³R⁴ (I)

where

y is an integer from 1 to 100 and

x and z are independently an integer from 2 to 12,

in combination with at least one further customary fuel or lubricant additive.

35. A process for preparing a diesel fuel composition for effecting a reduction of nozzle carbonization, comprising adding to a commercial diesel fuel composition an effective amount of at least one compound of the formula I:

R¹R²N((CH₂)_xNH)_y(CH₂)_zNR³R⁴ (I)

where

y is an integer from 1 to 100 and

x and z are independently an integer from 2 to 12.

36. A process for preparing a diesel fuel composition for effecting a reduction of nozzle carbonization comprising adding to a commercial diesel fuel composition an effective amount of the additive concentrate according to claim 34.

37. The method according to claim 19, wherein the detergent additive is present in an amount of about 1 to 200 mg/kg of fuel.

38. The method according to claim 19, wherein the detergent additive is present in an amount of about 2 to 16 mg/kg of fuel.