EP0525052B1

EP0525052B1 - Fuel oil compositions

Info

Publication number: EP0525052B1
Application number: EP91908144A
Authority: EP
Inventors: Michael David Sexton; Anthony Kitson 18 Western Avenue Woodley Smith; Antonio Gutierrez
Original assignee: Exxon Chemical Patents Inc
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 1990-04-12
Filing date: 1991-04-12
Publication date: 1998-09-30
Anticipated expiration: 2011-04-12
Also published as: ES2121781T3; CA2080496A1; GB9008346D0; JPH05507099A; DE69130287D1; DE69130287T2; IN180348B; ATE171719T1; EP0525052A1; KR0163408B1; WO1991016408A1

Abstract

The addition to diesel or jet fuel of macrocyclic polyamines, especially those derived from PIBSA, or hydrocarbyl polyamines reduces particle emission, especially in association with organic nitrate cetan improvers.

Description

This invention relates to fuel oil compositions, and to additives for use in such compositions. More especially it relates to diesel, heating, and jet fuel oil compositions, and to reduction of particulate emissions on combustion.

Although modern internal combustion engines are highly efficient and give almost complete combustion of the hydrocarbon fuel used, the slight reduction from total efficiency leads to the formation of black smoke, a proportion of which is particulate carbon. Apart from the smoke's being unpleasant to breathe and unsightly, the carbon particles may have absorbed in them polynuclear hydrocarbons, which also result from incomplete combustion, some of which are known carcinogens.

It has been previously proposed to use certain additives to reduce smoke. These additives, which are based on metal salts, reduce smoke at the expense of increasing particulate emission, because the additive is emitted in the form of oxide or sulphate which contributes to the mass of particulates in the exhaust.

There remains a need for an emission-reducing additive for diesel and jet fuel that is itself metal-free and combustible without contributing to the weight of particulates emitted.

The present invention is based on the observation that certain dispersants, if desired in combination with cetane enhancers, when incorporated in a diesel, heating or jet fuel, reduce the emission of particulates.

In its broadest aspect, therefore, the present invention provides the use of an ashless oil soluble macrocyclic polyamine dispersant to reduce particulate emission in the combustion of a fuel oil. More especially, the dispersant is one containing the group -N=C-N-C=O, of which the -N=C-N group forms part of a ring, and of which the carbon and nitrogen atoms of the C-N=C=O form part of a different ring.

The present invention accordingly provides the use as an additive in a fuel oil, to reduce particulate emission on combustion of the fuel oil, other than the reduction resulting from a reduction in injector fouling in a diesel engine, of an oil soluble compound of the formula:

or R¹²R¹³N-(CR¹⁶R¹⁷)_n-[NH(CR¹⁸R¹⁹)_u]_b-NR¹³R¹³ or mixtures of two or more such compounds, wherein a is from 1 to 150, R¹, R² and R³ may be the same or different and are independently hydrogen or a hydrocarbyl substituent having from 2 to 600 carbon atoms, or a keto, halo, hydroxy, nitro, cyano, or alkoxy derivative thereof, provided that at least one of R¹, R² and R³ is a hydrocarbyl substituent having from 2 to 600 carbon atoms or said derivative thereof, or wherein R¹ and R² together form a hydrocarbylene substituent having 4 to 600 carbon atoms or a keto, halo, hydroxy, nitro, cyano or alkoxy derivative thereof, provided that R¹ and R² together with the carbon atom which forms the C-R¹ bond with R¹ and the nitrogen atom which forms the N-R² bond with R² form a ring having at least 5 members, wherein Z represents -R¹⁰[NR¹¹(R¹⁰)]_c- or -[R¹⁰R¹¹N]_dR¹⁰[NR¹¹R¹⁰]_e wherein each R¹⁰, which may be the same or different, represents an alkylene group having from 1 to 5 carbon atoms in its chain, each R¹¹, which may be the same or different, represents a hydrogen atom or a hydrocarbyl group, and c is from 0 to 6, d is from 1 to 4, e is from 1 to 4, provided that d + e is at most 5, R¹² is a hydrocarbyl substituent having from 2 to 400 carbon atoms, each R¹³ is independently hydrogen or a C₁ to C₁₂ hydrocarbyl, R¹⁶, R¹⁷, R¹⁸, and R¹⁹ are independently hydrogen, a hydrocarbyl group having from 1 to 10 carbon atoms, an acyl group having from 2 to 10 carbon atoms, or a monoketo, monohydroxy, mononitro, monocyano or alkoxy derivative of a hydrocarbyl group having from 1 to 10 carbon atoms or of an acyl group having from 2 to 10 carbon atoms, n is from 1 to 6, u is from 1 to 6, and b is from 0 to 12.

Advantageously, when c is zero, there are at least two carbon atoms in the R¹⁰ alkylene chain.

As used in this specification the term "hydrocarbyl" refers to a group having a carbon atom directly attached to the rest of the molecule and having a hydrocarbon or predominantly hydrocarbon character. Among these, there may be mentioned hydrocarbon groups, including aliphatic, (e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl or cycloalkenyl), aromatic, aliphatic- and alicyclic-substituted aromatic, and aromatic-substituted aliphatic and alicyclic groups. Aliphatic groups are advantageously saturated. Examples include methyl, ethyl, propyl, butyl, isobutyl, pentyl, hexyl, octyl, decyl, octadecyl, cyclohexyl, and phenyl. These groups may, as indicated above, contain non-hydrocarbon substituents provided they do not alter the predominantly hydrocarbon character of the group. Examples include keto, halo, hydroxy, nitro, cyano, alkoxy and acyl. If the hydrocarbyl group is substituted, a single (mono) substituent is preferred. Examples of substituted hydrocarbyl groups include 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl, 2-ketopropyl, ethoxyethyl, and propoxypropyl. The groups may also or alternatively contain atoms other than carbon in a chain or ring otherwise composed of carbon atoms. Suitable hetero atoms include, for example, nitrogen, oxygen and sulfur. The term "hydrocarbylene" is used analogously; such a group is attached to the rest of the molecule at least at one end and preferably at both ends through a carbon atom.

Advantageously, there is used a compound of the formula:

wherein R⁷ is hydrogen or a hydrocarbyl substituent having from 1 to 600 carbon atoms, R⁸ is hydrogen or a C₁ to C₁₂ hydrocarbyl substituent and, if there is more than one R⁸ in a compound, they may be the same or different, R⁹ is a hydrocarbylene substituent having from 2 to 600 carbon atoms, two of which carbon atoms are bonded to the α-carbon atoms of the succinic anhydride based ring, X₁ represents hydrogen or an alkyl group having from 1 to 12 carbon atoms, X₂ represents hydrogen, an alkyl group having from 1 to 12 carbon atoms, a hydroxy group, or an alkoxy group, having from 1 to 12 carbon atoms, or X₁ and X₂ may together represent an oxygen or sulphur atom, Z has the meaning given above, and h is from 1 to 20. Advantageously h represents 1.

Although in R¹⁰ the alkylene chain may have at most 5 carbon atoms, it may be branched, and the length of the branch or branches is not limited. When R³ represents a hydrocarbyl substituent, and Z contains a nitrogen atom, the hydrocarbyl substituent is advantageously linked to the, or a, nitrogen atom. The nitrogen-hydrocarbyl linkage may in that case be, e.g., an amide linkage.

Preferably there is used a macrocyclic polyamine compound of the formula:

or

or mixtures of two or more such compounds, wherein R¹² is a hydrocarbyl substituent having from 2 to 400 carbon atoms, R¹³ is hydrogen or a C₁ to C₁₂ hydrocarbyl substituent, R¹⁴ is a hydrocarbylene substituent having from 4 to 400 carbon atoms, two of which carbon atoms are bonded to the α-carbon atoms of the succinic anhydride based ring, and Z represents -CH₂CH₂CH₂-; -(CH₂CH₂CH₂NH)_nCH₂CH₂CH₂-, where n is 1 to 6, or -(CH₂CH₂CH₂NH)_m(CH₂)_p(NHCH₂CH₂CH₂)_q- where m and q are each at least 1 and m+q = 2 to 5, p is 1 to 5, and a is 1 to 20.

The invention also provides a method of reducing particulate emission resulting from the combustion of a fuel oil, which comprises mixing a compound of the formula I or II, more especially a compound of the formula III, IV, or V, as defined above, with the fuel oil before burning the fuel oil. Also provided is a method of reducing particulate emission resulting from burning fuel oil, which comprises the combustion of a fuel oil containing an above-mentioned compound.

A method for the preparation of the macrocyclic polyamines of the formulae above is described, for example, in U.S. Patent No. 4 637 886. Formation of the macrocyclic and optionally polymacrocyclic compounds proceeds by the aminolysis of hydrocarbyl succinic anhydride, monocarboxylic acid or polycarboxylic acid, adding the acid or anhydride to the di or polyamide compound, as described in more detail in the above-referenced U.S. Patent.

The hydrocarbyl and hydrocarbylene substituents R¹² and R¹⁴ are advantageously derived from a polymer based on a major amount of a C₂ to C₅ olefin, for example homo or copolymers of ethylene, propylene, butylene (1- or 2-), pentylene and, especially, isobutylene.
Polyisobutylene is especially preferred. When the polymer is a copolymer, it may be a copolymer of two or more of the specified monomers, or a copolymer of one or more of the specified monomers with a copolymerizable unsaturated monomer; when the polymer is a copolymer it may be a block or a random copolymer.

The polymer advantageously has from 5 to 300 carbon atoms, preferably 10 to 200 carbon atoms and most preferably 20 to 100 carbon atoms. Preparation of the alkyl and alkenyl succinic anhydrides which form convenient reactants for the cyclodehydration reaction by which the macrocyclic polyamine may be produced is described, for example, in U.S. Patents Nos. 3 018 250 and 3 024 195.

Suitable amine reactants are of the formula NH₂-Z-NH₂, where Z has the meaning given above. Preferred amines include 1,3-propane diamine; 3,3'-imino-bis-propylamine, N,N'-bis (3-aminopropyl)ethylene diamine; N,N'-bis(3-aminopropyl)-1,3-propane diamine; other suitable amines include ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentamethylene hexamine, dipropylene triamine, tripropylene tetramine, tetrapropylene pentamine and pentapropylene hexamine.

The mole ratio of alkenyl or alkyl succinic anhydride to polyamine used in the preferred preparation of the macrocyclic polyamines may vary, for example, from 0.2:1 to 5:1, and is preferably from 0.5:1 to 2:1, and most preferably from 0.5:1 to 1.5:1.

As monocarboxylic acid there may be used an acid of the formula: R¹⁵-COOH where R¹⁵ is hydrogen, or a substituted or unsubstituted alkyl, cycloalkyl, alkenyl, cycloalkenyl, or aryl group. Examples of such acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, palmitic acid, stearic acid, cyclohexanecarboxylic acid, 2-methylcyclohexane carboxylic acid, 4-methylcyclohexane carboxylic acid, oleic acid, linoleic acid, linolenic acid, cyclohex-2-eneoic acid, benzoic acid, 2-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, salicylic acid, 2-hydroxy-4-methylbenzoic acid, 2-hydroxy-4-ethylsalicylic acid, p-hydroxybenzoic acid, 3,5-di-tert-butyl-4-hydroxybenzoic acid, o-aminobenzoic acid, p-aminobenzoic acid, o-methoxybenzoic acid and p-methoxybenzoic acid.

As dicarboxylic acid there may be used an acid of the formula: HOOC-(CH₂)_t-COOH where t is zero or an integer, including e.g. oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid and suberic acid, or an acid of the formula:

where t is zero or an integer, y is zero or an integer and x and y may be equal or different and R¹⁵ is as defined above. Examples of such acids include the alkyl or alkenyl succinic acids, 2-methylbutanedioic acid, 2-ethylpentanedioic acid, 2-n-dodecylbutanedioic acid, 2-n-dodecenylbutanedioic acid, 2-phenylbutanedioic acid, and 2-(p-methylphenyl)butanedioic acid. Also included are polysubstituted alkyl dicarboxylic acids wherein other R¹⁵ groups as described above may be substituted on the alkyl chain. These other groups may be substituted on the same carbon atom or different atoms. Such examples include 2,2-dimethylbutanedioic acid; 2,3-dimethylbutanedioic acid; 2,3,4-trimethylpentanedioic acid; 2,2,3-trimethylpentanedioic acid; and 2-ethyl-3-methylbutanedioic acid.

The dicarboxylic acids also include acids of the formula: HOOC-(C_rH_2r-2)COOH where r is an integer of 2 or more. Examples include maleic acid, fumaric acid, pent-2-enedioic acid, hex-2-enedioic acid; hex-3-enedioic acid, 5-methylhex-2-enedioic acid; 2,3-di-methylpent-2-enedioic acid; 2-methylbut-2-enedioic acid; 2-dodecylbut-2-enedioic acid; and 2-polyisobutylbut-2-enedioic acid.

The dicarboxylic acids also include aromatic dicarboxylic acids e.g. phthalic acid, isophthalic acid, terephthalic acid and substituted phthalic acids of the formula:

where R¹⁵ is as defined above and n = 1, 2, 3 or 4 and when n > 1 then the R groups may be the same or different. Examples of such acids include 3-methylbenzene-1,2-dicarboxylic acid; 4-phenylbenzene-1,3-dicarboxylic acid; 2-(1-propenyl)benzene-1,4-dicarboxylic acid, and 3,4-dimethylbenzene-1,2-dicarboxylic acid.

The preparation of such compounds is described for example in U.S. Patents Nos. 3 438 757, 3 565 804, 3 574 576, 3 671 511, 3 898 056, and 3 960 515, and British Patents No. 1 254 338 and 1 398 067. In this embodiment, the preferred hydrocarbyl substituents represented by R are as given above with reference to the macrocyclic polyamines.

The polyamine used to derive the hydrocarbyl polyamine is advantageously a compound having from 2 to 12 nitrogen atoms and from 2 to 40 carbon atoms. The preferred hydrocarbyl polyamines for use in this invention are compounds derived from polyalkylene polyamines, including alkylene diamines and substituted polyalkylene polyamines. Preferably, the alkylene group contains from 2 to 6 carbon atoms, there being preferably from 2 to 3 carbon atoms between the nitrogen atoms. Examples of such polyamines include ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, di(trimethylene)triamine, propylene diamine, dipropylene triamine, tripropylene tetramine, N-methyl ethylene diamine, N-N,-dimethyl ethylene diamine, N-methyl-1,3-diamino propane and N,N-dimethyl-1,3-diamino propane. Such amines include branched chain polyamines and cyclic structures formed by reaction of linear polyamines. Among the polyalkylene polyamines those containing from 2 to 12 nitrogen atoms and from 2 to 24 carbon atoms are especially preferred.

The mole ratios of alkyl or alkenyl halide to polyamine, used in accordance with the preferred method of making the compounds, are as described above for the succinic anhydride/polyamine reaction.

In further embodiments of this invention, the additive used may be a derivative of the macrocyclic or hydrocarbyl polyamines described above, such derivative being one obtainable by, and preferably one obtained by, post-treatment with, for example, boron oxide, boron oxide hydrate, a boron halide, a boron acid, sulphur, a sulphur chloride, a phosphorus oxide or sulphide, a carboxylic acid or anhydride, an acyl halide, an epoxide, an episulphide or acrylonitrile. Methods for carrying out such treatment are well known in the art; for example boration to incorporate 0.1 to 1 atoms of boron for each nitrogen atom may be carried out as described in U.S. Patent No. 3 254 025.

A preferred post-treatment for the formation of an additive is treatment with polyisobutylene succinic anhydride. Advantageously, the macrocyclic or hydrocarbyl polyamine is treated with 10 to 50 mole % of an anhydride formed from a polyisobutylene of molecular weight 900 to 1200, for example by reaction at 120°C for an hour or until the reaction mixture contains no free anhydride.

In a third embodiment, accordingly, the invention provides the use as a particulate-reducing additive for, and the use in reducing particulate emission in the combustion of, a diesel or jet fuel of a post-treated macrocyclic or hydrocarbyl polyamine as defined above, especially one post treated with a polyisobutylene succinic anhydride.

The additives may be used either alone or in combination with other additives according to the invention or in combination with other fuel additives. Advantageously the concentration of the additive according to the invention in the fuel is in the range of from 0.0005 to 2, preferably from 0.001 to 0.5, and more preferably from 0.005 to 0.3%, based on the weight of the fuel.

The use of other additives does not adversely affect the performance of the macrocyclic compound. In some cases the use of another additive or additives may lead to a reduction in emissions greater than might be expected. Other additives which may be used include, for example, diesel detergents, antifoam additives, antirust additives, and demulsifiers. These other additives may be present in the fuel in a total concentration of 0.001 to 1, preferably 0.005 to 0.2, and most preferably a total concentration of 0.005 to 0.05%, based on the total weight of fuel.

A specific example of such a combination is the use of a macrocyclic compound with a detergent which is the uncyclized reaction product formed from a hydrocarbyl succinic anhydride and a polyamine. The detergent is advantageously present in a concentration of 0.005 to 0.1, preferably 0.005 to 0.5, and most preferably from 0.005 to 0.2%, based on the total weight of the fuel.

It has also been unexpectedly found that the use of a combination of one or more of the additives in accordance with the invention together with a cetane improver gives enhanced particulate emission reduction. Accordingly, the invention also provides such use.

Preferred cetane improvers are organic nitrates; there may also be used, for example, substituted triazoles and tetrazoles, for example those described in European Patent Application No. 230783. Preferred organic nitrates are nitrate esters containing aliphatic or cycloaliphatic groups with up to 30 carbon atoms, preferably saturated groups, and preferably with up to 12 carbon atoms. As examples of such nitrates, there may be mentioned methyl, ethyl, propyl, isopropyl, butyl, amyl, hexyl, heptyl, octyl, iso-octyl, 2-ethylhexyl, nonyl, decyl, allyl, cyclopentyl, cyclohexyl, methylcyclohexyl, cyclododecyl, 2-ethoxyethyl, and 2-(2-ethoxyethoxy) ethyl nitrates.

The cetane improver is advantageously used at a concentration in the fuel in the range of from 0.0005 to 1, preferably 0.005 to 0.5 and most preferably from 0.01 to 0.2%, based on the weight of the fuel.

The following examples, in which all parts and percentages are by weight unless otherwise indicated, illustrate the invention.

Example A

Eight batches of polyisobutylene succinic anhydride (PIBSA) were synthesized by treating 450 MW polyisobutylene (PIB:450g:1 mole) with maleic anhydride. The quantities of maleic anhydride, the reaction times and temperatures and the catalyst concentration are shown in Table 1. The eight batches of thermal PIBSA were combined to give the final product. Analysis of the product gave:
Saponification number = 128.7 mg KOH/g
Free Maleic anhydride < 0.1 %.

The saponification number indicates that the product has an effective molecular weight of 870. The IR spectrum of the product in the carbonyl region (1900-1500 wavenumbers or cm^-1) shows two major peaks at 1863 and 1786 wavenumbers.

Maleic Anhydride (moles)	Temperature (°C)	Reaction Time (hr)	Catalyst (%)
1.00	200	8	1.00
0.75	220	8	1.00
0.75	200	8	0.00
0.75	200	12	0.00
1.00	200	12	1.00
1.00	220	12	0.00
1.00	220	8	0.00
0.75	220	12	1.00

The catalyst was an alkylaryl sulphonic acid and the percentage is based on the charge of PIB.

Example B

A solution of the thermal PIBSA (435g:0.5 moles) from Example A was dissolved in xylene (200 ml) and slowly added (over 20 hours) to a solution of 1,3-diaminopropane (37g:0.5 moles) in xylene (150 ml) at 100°C. When the addition was complete the reaction temperature was increased so that the xylene refluxed and water (16 ml:0.89 moles) was collected using a Dean and Stark trap. When removal of water was complete, the xylene was removed by distilling to 180°C. A vacuum was applied to remove the last traces of solvent. The product was a dark viscous oil containing 2.8% nitrogen (Theory = 3.08%).

The IR spectrum of the product had four peaks between 1900 and 1500 wavenumbers at 1772(w), 1738(m), 1705(s) and 1674(vs) wavenumbers. Such a spectrum is indicative of the presence of a macrocyclic compound. (In contrast the IR spectrum of the uncyclized additives contains only three peaks in the same region of the spectrum. There is a weak absorption at 1771-72 wavenumbers, a strong absorption at 1701-04 wavenumbers and a medium strength absorption at 1667-70 wavenumbers.)

Example C

A solution of thermal PIBSA (435g:0.5 moles) from Example A was dissolved in xylene (200 ml) and slowly added (over 8.25 hours) to a refluxing solution of 3,3'-imino-bis-propylamine (65.6g:0.5 moles) in xylene (150 ml). As the reaction proceeded, the water formed (16.5 ml: 0.92 moles) was collected using a Dean and Stark trap. When the addition was complete and no more water was formed the solvent was removed by heating to 180°C under vacuum. The product was a dark viscous oil containing 4.0% nitrogen (Theory = 4.35%).

The IR spectrum of the product has four peaks between 1900 and 1500 wavenumbers at 1771(w), 1732(w), 1702(s) and 1668(s) wavenumbers.

Example D

The method of Example C was repeated using N,N'-bis-(3-aminopropyl)-ethylenediamine (87g:0.5 moles). The solution of thermal PIBSA was added over 31.5hr and water (17.5ml:0.97 moles) was removed using a Dean and Stark trap. After removing the volatile solvent the product (475g) was a dark viscous oil which contained 5.4% nitrogen (Theory = 5.56%).

The IR spectrum of the product has four peaks between 1900 and 1500 wavenumbers at 1772(w), 1737(vs), 1701(vs) and 1669(vs).

Example E

A batch of PIBSA was synthesized by reacting 960MW PIB with maleic anhydride at high temperature. The resulting material was diluted with solvent 150 base oil to produce a product with a saponification number of 70.7 mg KOH/g. The saponification number indicates that the product has an effective weight of 1584.

Example F

The thermal PIBSA from Example E (500g:0.32 moles) was added to a solution of 1,3-diaminopropane (24g:0.32 moles) in toluene (200 ml) at 25°C. The reaction mixture was heated to reflux and then the solvent and water of reaction were removed by distilling to a pot temperature of 170°C. The reaction mixture was held at a temperature of 170°C for 7 hours. During this time IR spectra of the product were recorded to monitor the formation of the macrocycle.

The product was a dark viscous oil which contained 1.5% nitrogen (Theory = 1.75%). The IR spectrum of the product containing four peaks between 1900 and 1500 wavenumbers at 1773(w), 1739(m), 1706(s) and 1675(vs).

Example G

The method used in Example F was repeated using thermal PIBSA from Example E (500g:0.32 moles) and 3,3'-imino-bis-propylamine (42g:0.32 moles). The product was a dark viscous oil which contained 2.3% nitrogen (Theory = 2.53%). The IR spectrum of the product contained four peaks between 1900 and 1500 wavenumbers at ca. 1770(w), 1730(m), 1702(s) and 1670(s).

Example H

The method used in Example F was repeated using thermal PIBSA from Example E (500g:0.32 moles) and N,N'-bis-(3-aminopropyl)ethylene diamine (56g:0.32 moles). The product was a dark viscous oil which contained 3.2% nitrogen (Theory = 3.29%). The IR spectrum of the product contained four peaks between 1900 and 1500 wavenumbers at 1771(w), 1731(m), 1702(vs) and 1668(vs).

Example I

The method used in Example E was repeated using thermal PIBSA from Example E (500g:0.32 moles) and N,N'-bis-(3-aminopropyl)-1,3-propylene diamine (61g:0.32 moles). The product was a dark viscous oil which contained 3.0% nitrogen (Theory = 3.26%). The IR spectrum of the product contained four peaks between 1900 and 1500 wavenumbers at 1770(w), 1735(m), 1699(s) and 1668(vs).

Example J

The method used in Example F was repeated using thermal PIBSA from Example E (500g:0.32 moles) and pentapropylene hexamine (74g:0.32 moles). The product was a dark viscous oil which contained 3.8% nitrogen (Theory = 3.98%). The IR spectrum of the product contained five peaks between 1900 and 1500 wavenumbers at 1769(w), 1732(m), 1701(s), 1668(vs) and 1618(w).

Example K

A sample of PIBSA was prepared by reacting a 960MW PIB with maleic anhyride. The resulting PIBSA had a saponification number of 96.3 mg KOH/g, so that the effective molecular weight of the PIBSA was 1163.

The PIBSA (300g:0.26 moles) was added to a refluxing solution of N,N'-bis-(3-aminopropyl)ethylene diamine (44.8g:0.26 moles) in toluene (200 ml). When the addition of the PIBSA was complete the solvent and water were removed by distilling the reaction mixture of a temperature of 170°C. The reaction mixture was kept at 170°C under a stream of nitrogen for seven hours. After that time the IR spectrum of the product showed that no more macrocycle was being formed. The product was a dark viscous oil which contained 3.9% nitrogen (Theory = 4.28%). The IR spectrum of the product contained four peaks between 1900 and 1500 wavenumbers at 1771(w), 1733(m), 1701(s) and 1667(vs).

EXAMPLE L

3500 g of N,N'-bis(3-aminopropyl)ethylenediamine was dissolved in 4750 g of xylene and heated to 80°C. Polyisobutylene succinic anhydride (26910g), prepared from polyisobutylene of Mn 1000 via the "ene" reaction, was added to the amine solution over a period of 2 hours. The reaction mixture was then heated to reflux for 10 hours and water removed. After refluxing, the solvent was removed by distillation to give a final product with 3.71% nitrogen and a TBN of 97.7 mg KOH/g.

EXAMPLE 1

The additives from Examples F to K were tested in an engine to determine their effect on particulate emissions. The engine used was a 6 cylinder 4 stroke naturally aspirated DI engine with the following specification:
Swept Volume = 5958cc.
Maximum Power = 100 KW at 2800rpm.
Maximum Torque = 402 NM at 1400rpm.
Compression Ratio = 17.25:1

The fuel used in the tests was a standard UK automotive diesel fuel. A typical analysis was:
Specific Gravity = 0.849 kg/litre
Cetane Index = 51

Distillation	°C
IBP	162
20%	252
50%	286
90%	338
FBP	369

Sulphur Content = 0.23%
Flash Point = 69°C.

The additives were compared at 500ppm using tests run in the following manner:

1. The engine was conditioned prior to testing each additive by running the engine on the test fuel at 75% speed and 75% load for 12 hours.

2. The emissions from the engine were then measured using a standard ECE R49 thirteen mode test.

The results from the test are shown in Table 2.

Additive	Particulate (g/KWhr)
nil	1.08
Example F	0.80
Example G	0.80
Example H	0.86
Example I	0.88
Example J	0.93
Example K	0.87

It is clear from the results in Table 2 that all the additives tested reduce the mass of particulates emitted by the engine during the R49 test. The reduction varies from 13.9% to 25.9%. It is apparent that the size of the macrocyclic ring affects performance. The small ring macrocyclic compounds (Examples F and G) are more effective than the large ring macrocyclic compounds (Examples H to K).

Example 2

The engine and fuel of Example 1 were used to determine the effect of additive concentration on reduction of particulates. The additive from Example L was tested at different concentrations. The tests were run in the following manner:

1. The engine was warmed up over a period of 90 minutes to full speed and full load.

2. A stabilizing test was run using untreated fuel.

3. A test was run on the untreated fuel and emission data were collected.

4. A test was run on the fuel treated with the additive and emission data were collected.

5. Stages 3 and 4 were repeated using different concentrations of the additive.

The emissions measured included the quantity of particulate present in the exhaust. Table 1 shows the % reduction of particulate between stages 4 and 3 with different concentrations of additive.

ADDITIVE(ppm)	REDUCTION IN PARTICULATE(%)
0	0.0
125	2.6
250	5.1
500	10.5
1000	20.3

The effect of the additive in reducing particulate is apparent.

EXAMPLE 3

The additive from Example K was tested alone and in combination with a cetane improver. The cetane improver was an alkyl nitrate made from a C₈ alcohol. The experiments were carried out using the standard ECE R49 thirteen mode test. The tests were run using a VOLVO TD121/122F engine. The fuel used was similar to that used in Example 1. The weight of particulate formed in each stage of the test was measured by collecting the particulate on a pre-weighed filter paper. The overall amount of particulate from the 13 modes was determined using the standard weighting factors for each mode. The results are shown in Table 4.

The Effect of a Macrocyclic Polyamine with and without a Cetane Improver on Particulate Emissions
Macrocyclic Polyamine (ppm)	Cetane Improver (ppm)	Particulate (g/KWhr)
0	0	0.243
500	0	0.226
150	750	0.131

It can be seen that 500ppm of the macrocyclic polyamide alone reduces the weight of particulate by 7%. Reducing the amount of polyamine to 150ppm and using cetane improver (750ppm) reduces the particulate by 46%.

EXAMPLE 4

The additive from Example L was tested alone and in combination with the cetane improver used in Example 3 using the standard ECE R49 thirteen mode test in a PERKINS PHASER 180 Ti engine. The fuel used was similar to that used in Example 1. The weight of particulate formed in each stage of the test was measured as in Example 3. The results are shown in Table 5.

Macrocyclic Polyamine (ppm)	Cetane Improver (ppm)	Particulate (g/KWhr)
0	0	0.911
500	0	0.730
150	750	0.696

It can be seen that 500ppm of the macrocyclic dispersant alone reduces the amount of particulate by 20%. Reducing the amount of dispersant to 150ppm and using cetane improver (750ppm) reduces the particulate by 24%.

Claims

The use as an additive in a fuel oil, to reduce particulate emission on combustion of the fuel oil, other than the reduction resulting from a reduction in injector fouling in a diesel engine, of an oil soluble compound of the formula:
or R¹²R¹³N-(CR¹⁶R¹⁷)_n-[NH(CR¹⁸R¹⁹)_u]_b-NR¹³R¹³ or mixtures of two or more such compounds, wherein a is from 1 to 150, R¹, R² and R³ may be the same or different and are independently hydrogen or a hydrocarbyl substituent having from 2 to 600 carbon atoms, or a keto, halo, hydroxy, nitro, cyano, or alkoxy derivative thereof, provided that at least one of R¹, R² and R³ is a hydrocarbyl substituent having from 2 to 600 carbon atoms or said derivative thereof, or wherein R¹ and R² together form a hydrocarbylene substituent having 4 to 600 carbon atoms or a keto, halo, hydroxy, nitro, cyano or alkoxy derivative thereof, provided that R¹ and R² together with the carbon atom which forms the C-R¹ bond with R¹ and the nitrogen atom which forms the N-R² bond with R² form a ring having at least 5 members, wherein Z represents -R¹⁰[NR¹¹(R¹⁰)]_c- or -[R¹⁰R¹¹N]_dR¹⁰[NR¹¹R¹⁰]_e wherein each R¹⁰, which may be the same or different, represents an alkylene group having from 1 to 5 carbon atoms in its chain, each R¹¹, which may be the same or different, represents a hydrogen atom or a hydrocarbyl group, and c is from 0 to 6, d is from 1 to 4, e is from 1 to 4, provided that d + e is at most 5, R¹² is a hydrocarbyl substituent having from 2 to 400 carbon atoms, each R¹³ is independently hydrogen or a C₁ to C₁₂ hydrocarbyl, R¹⁶, R¹⁷, R¹⁸, and R¹⁹ are independently hydrogen, a hydrocarbyl group having from 1 to 10 carbon atoms, an acyl group having from 2 to 10 carbon atoms, or a monoketo, monohydroxy, mononitro, monocyano or alkoxy derivative of a hydrocarbyl group having from 1 to 10 carbon atoms or of an acyl group having from 2 to 10 carbon atoms, n is from 1 to 6, u is from 1 to 6, and b is from 0 to 12.
The use as claimed in claim 1, wherein the compound is a compound of the formula I and is of the formula:

wherein R⁷ is hydrogen or a hydrocarbyl substituent having from 1 to 600 carbon atoms, R⁸ is hydrogen or a C₁ to C₁₂ hydrocarbyl substituent, and, if there is more than one R⁸ in a compound, they may be the same or different, R⁹ is a hydrocarbylene substituent having from 2 to 600 carbon atoms, two of which carbon atoms are bonded to the α-carbon atoms of the succinic anhydride based ring, X₁ represents hydrogen or an alkyl group having from 1 to 12 carbon atoms, X₂ represents hydrogen, an alkyl group having from 1 to 12 carbon atoms, a hydroxy group, or an alkoxy group having from 1 to 12 carbon atoms, or X₁ and X₂ may together represent an oxygen or sulphur atom, Z has the meaning given in claim 1, and h is from 1 to 20.
The use as claimed in claim 2, wherein the compound is an oil soluble compound of the formula

or mixtures of two or more such compounds, wherein R¹² is a hydrocarbyl substituent having from 2 to 400 carbon atoms, R¹³ is hydrogen or a C₁ to C₁₂ hydrocarbon substituent, and, if there is more than one R¹³ in a compound they may be the same or different, R¹⁴ is a hydrocarbylene substituent having from 4 to 400 carbon atoms, two of which carbon atoms are bonded to the α-carbon atoms of the succinic anhydride based ring and -Z- represents -CH₂CH₂CH₂-; -(CH₂CH₂CH₂NH)_nCH₂CH₂CH₂-, where n is 1 to 6, or -(CH₂CH₂CH₂NH)_m(CH₂)_p(NHCH₂CH₂CH₂)_q- where m and q are each at least 1 and m+q = 2 to 5, p is 1 to 5, and a is 1 to 20.
The use as claimed in any one of claims 1 to 3, wherein at least one of R¹, R² and R³, or wherein at least one of R⁷ and R⁹, or wherein at least one of R¹² or R¹⁴ is derived from a C₂ to C₅ olefin polymer.
The use as claimed in claim 4, wherein the polymer is polyisobutylene.
The use as claimed in claim 4 or claim 5, wherein the polymer contains from 10, preferably from 20, to 200 carbon atoms.
The use as claimed in any one of claims 1 to 6, wherein -Z- represents -(CH₂)₃NH(CH₂)₃-, -(CH₂)₃NHCH₂CH₂NH(CH₂)₃-, or -(CH₂)₃-.
The use as claimed in any one of claims 1 to 7, wherein the oil soluble compound has been prepared by the reaction of a hydrocarbyl reactant and a polyamine reactant in a mole ratio of from 0.2:1 to 5:1, preferably from 0.5:1 to 2:1.
The use as claimed in any one of claims 1 to 8, wherein the oil soluble compound is used in the form of a post-treatment derivative, preferably one formed by post-treatment of the oil soluble compound with boron oxide, boron oxide hydrate, a boron halide, a boron acid, sulphur, a sulphur chloride, a phosphorus oxide or sulphide, a carboxylic acid or anhydride, e.g., polyisobutylene succinic anhydride, an acyl halide, an epoxide, an episulphide or acrylonitrile.
The use as claimed in any one of claims 1 to 9, wherein the oil soluble compound is present in the fuel in a proportion in the range of from 0.0005 to 2%, advantageously 0.001 to 0.5%, preferably 0.005 to 0.3%, by weight, based on the weight of the fuel.
The use as claimed in any one of claims 1 to 10, wherein the oil soluble compound is used in admixture or association with a cetane improver, advantageously an aliphatic or cycloaliphatic nitrate, preferably an alkyl or cycloalkyl nitrate containing up to 30 carbon atoms.
The use as claimed in claim 11, wherein the cetane improver is present in the fuel in a proportion in the range of from 0.0005 to 1%, advantageously 0.005 to 0.5%, preferably 0.05 to 0.2%, by weight, based on the weight of the fuel.
The use as claimed in any one of claims 1 to 12, wherein the oil soluble compound is used in the form of a derivative obtainable by treatment thereof with boron oxide, boron oxide hydrate, a boron halide, a boron acid, sulphur, a sulphur chloride, a phosphorus oxide or sulphide, a carboxylic acid or anhydride, especially polyisobutylene succinc anhydride, an acyl halide, an epoxide, an episulphide, or acrylonitrile.