GB2156848A - Fuel additive - Google Patents

Abstract

Combinations of an ashless dispersant, an oil soluble phenolic compound and an oil soluble amine are used as additives for distillate fuels to reduce the corrosion of storage tanks and lines and to improve the oxidation stability of the fuel and reduce deposits forming on combustion.

Description

SPECIFICATION Additive for middle distillate fuel oils This invention relates to the use of certain mixtures of additives to improve performance especially the combustion properties of diesel fuels and to reduce their corrosive effect and inhibit their oxidation.

We have found that a three component mixture of a certain type of antirust additive, an ashless dispersant of the type frequently used in lubricating oils and an amine containing antioxidant is an especially useful additive combination for diesel fuels.

The present invention therefore provides an additive combination for fuels boiling in the range 120"C to 600"C comprising (i) An ashless dispersant compound.

(ii) A fuel soluble phenolic compound.

(iii) A fuel soluble amine antioxidant.

The invention further provides a distillate fuel boiling in the range 120"C to 600"C containing from 20 to 500 parts per million of an additive combination comprising (i) An ashless dispersant.

(ii) A fuel soluble phenolic compound. and (iii) A fuel soluble amine antioxidant.

The distillate fuels in which the additive combination of the present invention is used are typical middle distillate fuels traditionally used as diesel fuels and heating oils. The additive combination of this invention may be used in either application since its rust prevention and antioxidant properties are generally useful. The presence of the dispersant is particularly useful for diesel fuels in that it helps keep the diesel engine clean so improving performance, fuel economy and engine life.

The ashless dispersant used may be any of the typical lubricating oil ashless dispersant compounds such as derivatives of long chain hydrocarbon substituted carboxylic acids in which the hydrocarbon groups contain 50 to 400 carbon atoms. These will generally be a nitrogen containing ashless dispersant having a relatively high molecular weight aliphatic hydrocarbon oil solubilising group attached thereto or an ester of a succinic acid/anhydride with a high molecular weight aliphatic hydrocarbon attached thereto and derived from monohydric and polyhydric alcohols, phenols and naphthols.

These dispersants include fuel-soluble salts, amides, imides, oxazolines and esters of monoand dicarboxylic acids (and where they exist the corresponding acid anhydrides) of various amines and nitrogen containing materials having amino nitrogen or heteroxyclic nitrogen and at least one amido or hydroxy group capable of salt, amide, imide, oxazoline or ester formation.

Other nitrogen containing dispersants which may be used in this invention include those wherein a nitrogen containing polyamine is attached directly to the long chain aliphatic hydrocarbon as shown in U.S. Patents 3,275,554 and 3,565,804 where the halogen group on the halogenated hydrocarbon is displaced with various alkylene polyamines.

Another class of nitrogen containing dispersants which may be used are those containing Mannich base or Mannich condensation products as they are known in the art. Such Mannich condensation products generally are prepared by condensing about 1 mole of an alkyl substituted phenol with about 1 to 2.5 moles of formaldehyde and about 0.5 to 2 moles polyalkylene polyamine as disclosed, e.g. in U.S. Patent 3,442,808. Such Mannich condensation products may include a long chain, high molecular weight hydrocarbon on the phenol group or may be reacted with a compound containing such a hydrocarbon, e.g. alkenyl succinic anhydride as shown in said aforementioned 3,442,808 patent.

Monocarboxylic acid dispersants have been described in U.K. Patent Specification 983,040.

Here, the high molecular weight monocarboxylic acid can be derived from a polyolefin, such as polyisobutylene, by oxidation with nitric acid or oxygen; or by addition of halogen to the polyolefin followed by hydrolyzing and oxidation. Another method is taught in Belgian Patent 658,236 where polyolefins, such as polymers of C2 to C5 monoolefin, e.g. polypropylene or polyisobutylene, are halogenated, e.g. chlorinated, and then condensed with an alpha-betaunsaturated, monocarboxylic acid of from 3 to 8, preferably 3 to 4, carbon atoms, e.g. acrylic acid, alpha-methyl-acrylic acid, etc. Esters of such acids, e.g. mthyl methacrylate, may be employed if desired in place of the free acid.

The most commonly used dicarboxylic acid is alkenyl succinic an hydride wherein the alkenyl group contains about 50 to about 400 carbon atoms.

Primarily because of its ready availability and low cost, the hydrocarbon portion of the monoor dicarboxylic acid or other substituted group is preferably derived from a polymer of a C2 to C5 monoolefin, said polymer generally having a molecular weight of about 700 to about 5000.

Particularly preferred is polyisobutylene.

Polyalkyleneamines are usually the amines used to make the dispersant. These polyalkyleneamines include those represented by the general formula: H2N(CH2)n ~~~ [NH(CH2)n]m ~~~ NH(CH2)nNH2 wherein n is 2 or 3, and m is 0 to 10. Examples of such polyalkyleneamines include diethylene triamine, tetraethylene pentamine, octaethylene nonamine, tetrapropylene pentamine, as well as various cyclic polyalkyleneamines.

Dispersants formed by reacting alkenyl succinic anhydride, e.g. polyisobutenyl succinic anhydride and an amine are described in U.S. Patents 3,202,678, 3,154,560, 3,172,892, 3,024,195, 3,024,237, 3,219,666, 3,216,936 and Belgium Patent 662,875.

Alternatively the ashless dispersants may be esters derived from any of the aforesaid long chain hydrocarbon substituted carboxylic acids and from hydroxy compounds such as monohy dnc and polyhydric alcohols or aromatic compounds such as phenols and naphthols etc. The polyhydric alcohols are the most preferred hydroxy compound and preferably contain from 2 to about 10 hydroxy radicals, for example, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, diproplyene glycol, and other alkylene glycols in which the alkylene radical contains from 2 to about 8 carbon atoms. Other useful polyhydric alochols include glycerol, mono-oleate of glycerol, monostearate of glycerol, monomethyl ether of glycerol, pentaerythritol.

The ester dispersant may also be derived from unsaturated alcohols such as allyl alcohol, cinnamyl alcohol, propargyl alcohol, 1-cyclohexane-3-ol, and oleyl alcohol. Still other classes of the alcohols capable of yielding the esters of this invention comprise the ether-alcohols and amino-alcohols including, for example, the oxy-alkylene, oxy-arylene-, amino-alkylene-, and amino-arylene-substituted alcohols having one or more oxy-alkylene, amino-alkylene or aminoarylene oxy-arylene radicals. They are exemplified by Cellosolve, Carbitoi, N,N,N',N'-tetrahydroxy-trimethylene di-amine, and the like. For the most part, the ether-alcohols having up to about 1 50 oxy-alkylene radicals in which the alkylene radical contains from 1 to about 8 carbon atoms are preferred.

The ester dispersant may be di-esters of succinic acids or acidic esters, i.e., partially esterified succinic acids; as well as partially esterified polyhydric alcohols or phenols, i.e., esters having free alcohols or phenolic hydroxyl radicals. Mixtures of the above illustrated esters likewise are contemplated within the scope of this invention.

The ester dispersant may be prepared by one of several known methods as illustrated for example in U.S. Patent 3,522,179.

Hydroxyamines which can be reacted with any of the aforesaid long chain hydrocarbon substituted carboxylic acids to form dispersants include 2-amino-1-butanol, 2-amino-2-methyl-1propanol, p-(beta-hydroxyethyl)-aniline, 2-amino-l-propanol, 3-amino-l-propanol, 2-amino-2-me thyl- 1 , 3-propane-d iol, 2-amino-2-ethyl- 1, 3-propanediol, N-(beta-hydroxy-propyi)-N '-(beta-aminoe- thyl)-piperazine, tris(hydroxmethyl) amino-methane (also known as trismethylolaminomethane), 2-amino-1-butanol, ethanolamine, beta-(beta-hydroxyethoxy)-ethylamine, and the like. Mixtures of these or similar amines can also be employed.

The preferred dispersants are those derived from polyisobutenyl succinic anhydride and polyethylene amines, e.g. tetraethylene pentamine, polyoxyethylene and polyoxypropylene amines, e.g. polyoxypropylene diamine, trismethylolaminomethane and pentaerythritol, and combinations thereof. One particularly preferred dispersant combination involves a combination of (A) polyisobutenyl succinic anhydride with (B) a hydroxy compound, e.g. pentaerythritol, (C) a poiyoxy-alkylene polyamine, e.g. polyoxypropylene diamine, and (D) a poly-alkylene polyamine, e.g. polyethylene diamine and tetra-ethylene pentamine using about 0.01 to about 4 equivalents of (B) and (D) and about 0.01 to about 2 equivalents of (C) per equivalent of (A) as described in U.S. Patent 3,804,763.Another preferred dispersant combination involves the combination of (A) polyisobutenyl succinic anhydride with (B) a polyalkylene polyamine, e.g.

tetraethylene pentamine, and (C) a polyhydric alcohol or polyhydroxy-substituted aliphatic primary amine, e.g. pentaerythritol or tris-methylolaminomethane as described in U.S. Patent 3,632,511.

Phenols traditionally used as antirust additives may be used and Examples of fuel soluble phenolic compounds are alkyl phenols of the general formula

where R, and R2 are hydrogen or hydrocarbyl groups which impart solubility to the compounds.

Octyl, nonyl and dodecyl phenol are particularly suitable materials.

The fuel soluble amines which are used an antioxidants may be those compounds traditionally used as lubricant antioxidants have been found particularly useful. Examples include secondary and tertiary amines containing from 8 to 24 carbon atoms especially amines such as octamine "Primine 81"R and cyclohexyl amines such as methyl and dimetyl amines and mixtures of such amines. A mixture of methyl and dimethyl cyclohexylamine has been found to be particularly useful.

The relative proportions of the three components that should be used depend upon the nature of the distillate fuel and the use to which it is to be put. We prefer however that for every part of the dispersant there be from about 0.007 to about 2 parts preferably 0.05 to 1 part by weight of the oil soluble phenolic compound and from about 0.01 to about 4 parts by weight of the oil soluble amine.

The additive combination of the present invention may be used in combination with other additives for distillate fuels especially those used to improve the low temperature flow properties of such fuels. For example they may be used with halogenated polymers of ethylene especially chlorinated polyethylene and more preferably copolymers of ethylene with other unsaturated monomers. More generally these additives which improve the flow of the distillates are ethylene copolymers typically characterized as wax crystal modifiers of Vapor Pressure Osmometric (V.P.O.) Mn 500 to 10,000 containing 3 to 40, preferably 4 to 20 moles of ethylene per mole of a second ethylenically unsaturated monomer.

The unsaturated monomers which may be copolymerized with ethylene, include unsaturated mono and diesters of the general formula:

wherein R3 is hydrogen or methyl; R2 is a -OOCR5 group wherein R5 is hydrogen or a C, to C28, more usually C, to C17, and preferably a C, to C8, straight or branched chain alkyl group; or R2 is a -COOR5 group wherein R5 is as previously described but is not hydrogen and R4 is hydrogen or -COOR5 as previously defined. The monomer, when R2 and R4 are hydrogen and R2 is -OOCR5, includes vinyl alcohol esters of C, to C29, more usually C, to C,8, monocarboxylic acid, and preferably C2 to C5 monocarboxylic acid. Examples of such esters include vinyl acetate, vinyl isobutyrate, vinyl laurate, vinyl myristate and vinyl palmitate; vinyl acetate being the preferred vinyl ester.When R2 is -COOR8 and R3 is hydrogen, such esters include methyl acrylate, isobutyl acrylate, methyl methacrylate, lauryl acrylate, C,3 Oxo alcohol esters of methacrylic acid, etc. Examples of monomers where R3 is hydrogen and R2 and R4 are -COOR5 groups, include mono and diesters of unsaturated dicarboxylic acids such as mono C,3 Oxo fumarate, did,3 Oxo fumarate, diisopropyl maleate, di-lauryl fumarate and ethyl methyl fumarate. The copolymers of ethylene and vinyl acetate are preferred.

The additives of the present invention may be used in distillate fuels in combination with polar compounds, either ionic or non ionic, which have the capability in fuels of acting as wax crystal growth inhibitors. Polar nitrogen containing compounds have been found to be especially effective when used in combination with the glycol esters, ethers or ester/ethers of the present invention and these are generally the C30-C300 preferably C50-C,50 amine salts and/or amides formed by reaction of at least one molar proportion of hydrocarbyl substituted amines with a molar proportion of hydrocarbyl acid having 1-4 carboxylic acid groups or their anhydrides; ester/amides may also be used. These nitrogen compounds are described in U.S. Patent 4,211,534.Suitable amines are usually long chain C,2-C40 primary, secondary, tertiary or quarternary amines or mixtures thereof but shorter chain amines may be used provided the resulting nitrogen compound is fuel soluble and therefore normally containing about 30 to 300 total carbon atoms. The nitrogen compound should also have at least one straight chain C8-C40 alkyl segment.

Suitable amines include primary, secondary, tertiary or quaternary, but preferably are secondary. Tertiary and quaternary amines can only form amine salts. Examples of amines include tetradecyl amine, cocoamine, hydrogenated tallow amine and the like. Examples of secondary amines include dioctadecyl amine, methyl-behenyl amine and the like. Amine mixtures are also suitable and many amines derived from natural materials are mixtures. The preferred amine is a secondary hydrogenated tallow amine of the formula HNR,R2 wherein R, and R2 are alkyl groups derived from hydrogenated tallow fat composed of approximately 4% C14, 31% C16, 59% C18.

Examples of suitable carboxylic acids for preparing these nitrogen compounds (and their anhydrides) include cyclohexane dicarboxylic acid, cyclohexene dicarboxylic acid, cyclopentane dicarboxylic acid, dialpha-naphthyl acetic acid, naphthalene dicarboxylic acid and the like.

Generally these acids will have about 5-13 carbon atoms in the cyclic moiety. Preferred acids useful in the present invention are benzene dicarboxylic acids such as phthalic acid, tere-phthalic acid, and ortho-phthalic acid. Ortho-phthalic acid or its an hydride is the particularly preferred embodiment.

When such a nitrogen containing compound is present it is preferred that it have at least one straight chain alkyl segment extending from the compound containing 8-40, preferably 14-24 carbon atoms. Also at least one ammonium salt, amine salt or amide linkage is required to be present in the molecule. The particularly preferred amine compound is that amide-amine salt formed by reacting 1 molar portion of phthalic anhydride with 2 molar portions of dihydrogenated tallow amine. Another preferred embodiment is the diamide formed by dehydrating this amide-amine salt. The fuel oil composition may also contain a lube oil pour depressant.

This has been found particularly useful in distillate fuels having higher final boiling points especially those with final boiling points above 385"C. Examples of the preferred lube oil pour depressants are alkyl aromatics such as those made by the Friedel Crafts condensation of a halogenated wax, preferably a straight chain wax with an aromatic hydrocarbon such as naphthalene. Typically suitable halogenated waxes are those containing from 1 5 to 60, e.g., 1 6 to 50 carbon atoms and from 5 to 25 wt % preferably 10 to 18 wt % halogen, preferably chlorine.

Alternatively the lube oil pour depressant may be the well known oil soluble esters and/or higher olefin polymers and if so it will generally have a number average molecular weight in the range of about 1000 to 200,000, e.g., 1,000 to 100,000, preferably 1000 to 50,000, as measured, for example by Vapor Pressure Osmometry such as by a Mechrolab Vapor Pressure Osmometer, or by Gel Permeation Chromatography. These second polymers including copolymers with other unsaturated monomers, e.g. olefins, other than ethylene. Typical polymers are described in published United Kingdom Patent Application 2023645 A.

Alternatively the fuel may contain the polyoxyalkylene esters, ethers, ester/ethers or mixtures thereof claimed as distillate additives in European Patent Application 82301557.3. The fuel may contain mixtures of the various cold temperature flow improvers described above. Where cold temperature flow improvers are present we prefer that they be present in an amount from 0.0001 to 0.5 wt.% e.g. 0.001 to 0.5 wt.% based on the weight of the fuel.

The additives of the present invention are conveniently supplied as concentrated oil solutions for incorporation into the bulk distillate fuel and such concentrates are also within the scope of the present invention.

It is preferred that the concentrate contain from 90 wt.% to 50.wt.% preferably 80 wt.% to 20 wt.% of the additive combination of the present invention. The concentrate may also contain the other additives to be incorporated into the distillate fuel such as the cold temperature flow improvers described above.

We have found that when the additive combination of the present invention is used in distillate fuels corrosion and rust formation in tanks and lines containing the fuels is reduced. In addition injector or burner nozzle fouling in diesel engines or heating oil burners is reduced and the oxidative stability of the fuel is increased thus reducing both sediment formation and darkening of its colour.

The present invention is illustrated by the following Examples which the additive compounds used were as follows.

(a) a 50 wt.% in oil solution of a condensation product of polyisobutylene succinic anhydride containing between 100 and 120 carbon atoms and tetraethylene pentamine in a 2.8:1 molar ratio.

(b) p-nonyl phenol trioxyethanol.

(c) A mixture of methyl and dimethyl cyclohexylamine.

and a mixture was formed of 45 wt.% A, 1 5 wt. % B and 40 wt.% C.

100 parts per million of the mixture was incorporated in a fuel (Fuel 1) having the following properties.

Fuel 1 Fuel Data Wax Appearance Point ("C) -3 Cloud Point ('C) O Pour Point ('C) -6 Aniline Point (%) 64.5 Specific Gravity 0.8588 Flash Point (PMC Auto, C)* 75 Distillation (ASTM D86) Temperature % Distilled ( C) IBP 180 5% 217 10% 231 20% 249 30% 263 40% 274 50% 284 60% 295 70% 307 80% 322 90% 340 95% 354 FBP 365 2% Residue and was compared with the same fuel containing no additive in a Petter AV--1 engine by running for 120 hours and measuring exhaust temperature every 3 with the following results.

n TEST EXHAUST TEMPERATURES Untreated Fuel ~ Treated Fuel Time of Absolute Relative Absolute Relative Measurement StmNperatúre Temperature* Temperature Temperature* (hr) (C) (C) ('C) (*C) 3 321 -1 325 1 6 322 0 326 2 9 322 0 324 0 12 323 1 324 0 15 325 3 330 6 18 325 3 329 5 21 321 -1 328 4 24 321 -1 330 6 27 322 0 327 3 30 326 4 328 4 33 327 5 328 4 36 330 8 331 7 39 328 6 329 5 42 330 8 333 9 45 332 10 337 13 48 333 11 329 5 51 340 18 330 6 54 343 21 337 13 57 337 15 333 9 60 332 10 335 11 63 347 25 340 16 66 338 16 337 13 69 339 17 338 14 72 340 18 332 8 75 338 16 333 9 78 333 11 331 7 81 337 15 327 3 84 334 12 325 1 87 334 12 324 0 90 331 9 325 1 93 332 10 329 5 96 334 12 335 11 99 326 4 329 5 102 330 8 337 13 105 330 8 332 8 108 333 11 328 4 111 336 14 331 7 114 337 15 336 12 117 333 11 334 10 120 335 13 328 4 The relative temperature was the increase in temperature over the 'initial low running temperature', defined as the mean of the first four temperature readings. For the base case this was exactly 322"C. For the treated case, this was 324:75eC, but was rounded down to 3244C.

This made the treated case results slightly pessimistic, to counter any biases in the determinations.

Paired t-Test Analysis on Relative Temperatures t= 3.404, 39 d.f., difference between two fuels is significant at a 99% confidence level (twotailed test).

The smoke emission was measured every 6 hours and little difference in smoke levels was found and at no time did an injector foul so badly that it had to be replaced.

As shown in the table the exhaust temperatures did rise, and an increase in exhaust temperature can be correlated with fouling of the injector. Statistical analysis shows that the treated fuel gave significantly lower temperature readings, and so reduced injector fouling except for the first day's running, when the temperature was slightly elevated for the treated sample: this may be due to a temporary blockage of the injector caused by the extreme dirtiness of the fuel.

Example 2 The antirust properties of the additive combination of Example 1 were evaluated in Fuel 1 and Fuels 2 and 3 (summarised below) using test ASTM D665/A which measures the rusting of metal pins in contact with a fuel/water mixture. The additive was used at a 100 ppm concentration.

Fuels 2 and 3 Fuels 2 and 3 were blends of the fuel given below with 10 wt.% and 20 wt.% untreated cracked stock resectively.

Cloud Point - 1 'C Wax Appearance Point - 4.5"C Initial Boiling Point 188"C 20% Boiling Point 238"C 50% Boiling Point 278"C 90% Boiling Point 344"C Final Boiling Point 375"C The Results were as follows: Sample Results Fuel 1 Fail. Pins covered with 50% rust Fuel 1 + 100 Pass. Pins completely free of rust ppm of additive Fuel 2 Fail. Pins covered with 50 to 70% rust Fuel 2 + 100 Pass. Pins completely free of rust ppm of additive Fuel 3 Fail. Pins covered with about 90% rust Fuel 3 + 100 Pass. Pins completely free of rust ppm of additive Example 3 The antioxidant effect of the additive was evaluated in the AMS 77.061 Accelerated Stability test using Fuels 1 to 3 and a 100 ppm of additive The results were as follows: Sediment Sample Colour Before Colour After (mug/100 ml) Fuel 1 < 4.0 < 5.5 1.00 Fuel 1 + 100 < 4.0 < 5.0 0.34 ppm Additive Fuel 2 < 1.0 1.5 0.36 Fuel 2+100 < 1.0 < 1.5 0.03 ppm Additive Fuel 3 < 1.5 < 2.5 0.8 Fuel 3+100 < 1.5 2.0 0.04 ppm Additive The sediment was compared with a fuel containing no additive, and with additives B and C and a mixture of B and C with the following results.

Additive Sediment C 0.26 B 1.07 B S C 0.33 Additive of the Invention 0.1 6 None 1.04 All those containing additive contained 50 parts per million of additive.

Claims (4)

1. An additive combination for fuels boiling in the range 1 20 C to 600"C comprising (i) An ashless dispersant compound.

(ii) A fuel soluble phenolic compound.

(iii) A fuel soluble amine antioxidant.

2. A distillate fuel boiling in the range 120"C to 600'C containing from 20 to 500 parts per million of an additive combination comprising (i) An ashless dispersant.

(ii) A fuel soluble phenolic compound.

and (iii) A fuel soluble amine antioxidant.

3. The use of an additive combination comprising (i) An ashless dispersant compound.

(ii) A fuel soluble phenolic compound.

(iii) A fuel soluble amine antioxidant.

for improving the performance of fuels boiling in the range 120"C to 600"C.

4. An additive concentrate comprising an oil solution containing 5 to 90 wt.% of an additive combination comprising: (i) An ashless dispersant compound.

(ii) A fuel soluble phenolic compound.

(iii) A fuel soluble amine antioxidant.