WO2000042133A1 - Improved fuel compositions - Google Patents

Abstract

An additive for reducing emissions during the combustion of liquid fuels.

Description

Improved Fuel Compositions

This invention relates to the reduction in undesirable emissions, particularly particulate emissions, during the combustion of liquid fuels, particularly middle distillate fuel oils such as diesel fuel, heating oil and fuel oil.

The problem of incomplete products of combustion is well known in the art. In particular, the problem of particulate emissions has been linked to health risks and urban pollution. Legislative efforts to reduce the permitted levels of particulate and other emissions have gathered momentum during the 1990s.

Whilst engineering and other advances in fuel combustion systems such as gasoline engines, diesel engines and heating oil burners and furnaces have led to reductions in emissions, there remains a need for further reductions in emissions such as particulates. In particular, there remains a need for emissions reductions in the large population of existing engines, burners and furnaces in operation. For these combustion devices, upgrading or modification maybe unavailable or prohibitively expensive.

The present invention provides the use of a particular chemical additive, in a liquid fuel composition, to reduce the particulate emissions resulting from the combustion of the fuel. This solution is readily applicable to existing combustion devices and can provide a cost effective solution to controlling emissions levels.

WO-N-9741092 describes certain alkoxy acetic acid derivatives and their use as additives for fuels intended for internal combustion engines. These materials are described as giving rise to advantageous engine cleanliness effects.

Japanese Patent Application (Kokai) No. 59-232176 discloses a fuel composition for diesel engines containing, as an essential element, a 400-600 average molecular weight polyoxyalkylene compound represented by the general formula: Ri - O -(CH - CH - O)-_nR₃

R² Wherein Rj denotes an organic residue with 1 to 10 carbon atoms, R₂ denotes a C_2-5 alkyl group, and R₃ denotes a C_1-30 hydrocarbon group, and n is an integer of 5 to 40. The compound is described as reducing levels of hydrocarbons, carbon monoxide and particulates in the engine exhaust gas. The application indicates that this effect is linked to the identity of R : analogues in which R₂ is hydrogen or methyl (i.e. polyoxyalkylenes derived from ethylene oxide and/or propylene oxide) do not show the same advantageous character.

It has now surprisingly been discovered that polyoxyalkylene derivatives derived from ethylene oxide or propylene oxide or both can reduce the particulate emissions produced during combustion of liquid fuels such as gasoline, kerosene, diesel fuel, heating oil and fuel oil. These materials can prove surprisingly effective at low treat rates, and provide a cost-effective solution to the emissions problem. In a first instance, the invention provides the use of a polyoxyalkylene derivative comprising:

(i) one or more polyoxyalkylene segments comprising oxyethylene or oxypropylene units or both, and

(ii) one or more hetero-atom containing substituents other than polyoxyalkylene, in a liquid fuel composition, to reduce the particulate emissions resulting from the combustion of the composition.

Other aspects of the invention include a fuel composition containing the additive and a method for reducing particulate emissions resulting from the combustion of a liquid fuel composition, comprising the addition thereto of the additive.

The invention will now be described in further detail as follows: The Additive

The additive comprises one or more polyoxyalkylene segments (i) comprising oxyethylene or oxypropylene units or both. One or more of the segments may comprise oxyalkylenes other than oxyethylene and oxypropylene, provided that at least one segment fulfils the requirement of comprising oxy(ethylene) or oxypropylene units. Each segment which comprises oxyethylene or oxypropylene may additionally comprise other oxyalkylene units, such as those derived from butylene oxide or pentylene oxide.

The polyoxyalkylene segments may preferably have a number average molecular weight in the range of 500 to 5,000, more preferably 1,000 to 3,000, and most preferably 1,500 to 2,000 (as measured by GPC).

Preferably, the additive comprises one or more polyoxyalkylene segments comprising oxypropylene units, optionally in combination with oxyethylene units. Where both are present, the total number of oxypropylene units preferably exceeds the total number of oxyethylene units in the molecule, such that the ratio of oxypropylene units to oxyethylene units is more than 1. More preferably, the number of oxypropylene units exceeds the number of oxyethylene units by a ratio of 2: 1 , and more preferably 3:1. Most preferably, the ratio is at least 4: 1.

The one or more hetero-atom-containing substituents (ii) impart further functionality to the molecule. Such substituents include those comprising one or more functional groups selected from the following:

(a) an ester group

(b) an amide group

(c) an amine salt group

(d) an imine group

(e) an imide group

(f) a carbamate group,

(g) an amine group

(h) a carboxylic acid group

(i) a carboxylic acid salt group, and (j) a nitrate group. Poly(oxyalkylene)amines are described, for example, in US Patents Nos. 4,985,047 and 4,332,595, in EP-A-440 248, EP-A-310 875, EP-A-206 976 and WO-A-85 01956. The Poly(oxyalkylene) carbamate detergents comprise an amine moiety and a poly(oxyalkylene) moiety linked together through a carbamate linkage, i.e.,

--O-C (O) -N- (IX)

These poly(oxyalkylene) carbamates are known in the art and representative examples are disclosed for example in US Patent No. 4,191,537, US Patent No. 4,160,648, US Patent No. 4,236,020, US Patent No. 1,270,930, US Patent No. 4,288,612 and US Patent No. 4,881,945. Particularly preferred poly(oxyalkylene) carbamates for use in the present fuel composition include OGA-480 (a poly(oxyalkylene) carbamate which is available commercially from Oronite).

The poly(alkenyl)-N-substituted carbamate detergents utilised are of the formula:

O

R - A - C - OR¹ (X) in which R is a poly(alkenyl) chain; R is a hydrocarbyl or substituted hydrocarbyl group; and A is an N-substituted amino group. Poly(alkenyl)-N-substituted carbamates are known in the art and are disclosed in US Patent No. 4,936,868.

A polyoxyalkylene carbamate is preferred. Particularly preferred is a polyoxyalkylene ester, amide or ester-amide.

The functional group or groups within substituent (ii) preferably connect the remaining portion of the substituent to the polyoxyalkylene segment or segments (i). More preferably, the or each substituent (ii) comprises one or more hetero-atom containing groups, for example, those outlined under (a) to (g) above, in addition to the functional group connecting the substituent (ii) to the polyoxyalkylene segment (i). Thus, for example, the substituent (ii) may contain one or more of the groups (a) to (g) as a connecting group and one or more additional amide groups (g) imparting further functionality to the substituent (ii). Alternatively, the additional group or groups may be hydroxy groups. Preferably, 1 to 10 amine or hydroxy groups (or both) may be present as additional groups, more preferably 1 to 6, such as 2 to 6.

Preferably, the additive contains one substituent (ii), this substituent preferably being terminally connected to a polyoxyalkene segment.

Particularly preferred additives include those wherein each, or preferably the, polyoxyalkylene segment bears a substituent (ii) comprising one or more amine groups and linked to the polyoxyalkylene segment(s) via a further hetero-atom containing group such as an ester group, amide group or carbamate group.

The polyoxyalkene segment may be made by conventional epoxide polymerisation techniques known in the art and described for example in Kirk Othmer Encyclopedia, Vol.18, pp. 633-645, and in US Patent Nos. 4,992,590 and 4,973,414.. The substituent (ii) may be linked to the or each polyoxyalkylene segment via reaction of the terminal hydroxy-group or functional equivalent thereof with a suitable functional group on the precursor to substituent (ii), such as a suitable acylating group (e.g. a carboxylic acid, ester or anhydride group) or leaving group, Alternatively, the terminal polyoxyalkylene unit of the or each polyoxyalkylene segment may be oxidised to form an acylating group which may thereafter react with a suitable nucleophilic group on the precursor to substituent (ii), such as an amine group. Such reactions may be carried out under conventional acylating conditions.

Preferably, the additive is formed by the reaction of a diamine or polyalkylene polyamine (such as polyethylene polyamine) or mixture thereof with a polyoxyalkylene segment (i) terminally-oxidised to form an acylating group (such as a carboxylic acid, ester or anhydride group). The polyalkylene polyamine preferably contains from 3 to 10, more preferably 3 to 7, nitrogen atoms and is preferably a polyethylene polyamine. Tetraethylene pentamine and triethylene tetramine are particularly preferred, as are mixtures comprising one or both of these polyamines.

The additive may further comprise one or more hydrocarbyl substituents (iii). It is preferred that the additive comprise at least one such group. The or each group (iii) contains from 1 to 300, preferably 5 to 100, more preferably 5 to 50, most preferably 8 to 30 carbon atoms. A range of 10 to 26 is particularly preferred. The precursor to substituent (iii) may be an alcohol, preferably an alkanol, on to which an polyoxyalkylene segment may be built by polymerisation.

In a particular embodiment of the additive there are provided alkoxy acetic acid derivatives of general formula I:-

wherein R is the residue of an amine, an aminoalcohol or a polyol linked to the or each -

CHR'CO- moiety via an amide or ester linkage;

R' is hydrogen or C_]-4 alkyl;

R¹ is an optionally substituted hydrocarbyl group of 1 to 300 carbon atoms; one of R and R is independently selected from hydrogen and optionally substituted hydrocarbyl of 1 to 10 carbon atoms, the other of R and R being independently selected from optionally substituted hydrocarbyl of 1 to 10 carbon atoms; m is from 3 to 200; n is from 0 to 20, provided that m/n is at least 1 ; p is from 1 to 5. Preferably, when n is 0, one or more polyoxyalkylene segments of the formula

R² R³

(-CH — CH -O)_m- comprise oxypropylene units

Whilst R' may be hydrogen or a _-4 alkyl group, e.g. a methyl, ethyl, n-propyl, n-butyl or 2-methylpropyl; R' is preferably a hydrogen atom.

The value of p is preferably in the range 1 to 3, advantageously 1 or 2.

The value of m is preferably from 3 to 150, more preferably 3 to 120, advantageously 3 to 50, and especially 3 to 30. Values of n from 0 to 10 eg. 1 to 10 are preferred. Preferably m/n is at least 2, more preferably at least 3.

As used herein, the term "hydrocarbyl" represents a radical formed by the removal of one or more hydrogen atoms from a carbon atom of a hydrocarbon (not necessarily the same carbon atom). Useful hydrocarbyls are aliphatic, acyclic or cyclic. Preferably, the hydrocarbyls are aryl, alkyl, alkenyl or cycloalkyl and are straight-chain or branched-chain. Representative hydrocarbyls include methyl, ethyl, butyl, pentyl, methylpentyl, hexenyl, ethyhexyl, dimethylhexyl, octamethylene, octenylene, cyclooctylene, methylcycloactylene, dimethylcyclooctyl, isooctyl, dodecyl, hexadecenyl, octyl, eicosyl, hexacosyl, triacantyl and phenylethyl. When the hydrocarbyl is substituted, it contains a functional group such as carbonyl, carboxyl, nitro, tertiary amino(no N-H linkages), oxy, cyano, sufonyl and sulfoxyl. The majority of the atoms, other than hydrogen, in substituted hydrocarbyls are carbon, with the heteroatoms (e.g. oxygen, nitrogen and sulphur) representing only a minority, 33% or less, of the total non-hydrogen atoms present.

Those skilled in the art will appreciate that functional groups such as nitro and cyano in a substituted hydrocarbyl group will displace one of the hydrogen atoms of the hydrocarbyl, whilst functional groups such as carbonyl, carboxyl, tertiary amino (-N-), oxy, sulfonyl and sulfoxyl in a substituted hydrocarbyl group will displace a -CH- or -CH2- moiety of the hydrocarbyl. In "optionally substituted hydrocarbyl of 1 to 300 carbon atoms", "1 to 300 carbon atoms" represents the total number of carbon atoms in the optionally substituted hydrocarbyl group. The same applies to "optionally substituted hydrocarbyl" of lower numbers of specified carbon atoms.

In derivatives of general formula I wherein p is 1, R may contain one or more, e.g. 1 to 3, substituents of formula IV:-

R '

-O-CH-CO-R (IV) or one or more, e.g. 1 to 3, substituents of formula V:-

wherein R, R, R , R , m and n are as defined above in relation to formula I, subject to the total number of carbon atoms in R being not more than 300. Thus, for example R may be of the formula:- Y-CH₂-CH₂- or Y-CH₂-CH-CH₂-

Z where Y is of formula IV or V above and Z is of formula IV or is V above.

R is preferably a hydrocarbyl group of I to 300 carbon atoms, more preferably a hydrocarbyl group of 1 to 100 carbon atoms. When R is hydrocarbyl of a relatively high number of carbon atoms, i.e. greater than about 50 carbon atoms, R may conveniently be a polymeric hydrocarbyl such as polyisobutylene, polybutene, polypropylene or polyalphaolefin. In particularly preferred derivatives of formula I, R¹ represents a Cl-20 alkyl group, a phenyl or benzyl group or a (Cι_-15 alkyl) phenyl or (Cι_₁₅ alkyl) benzyl group. R may very conveniently represent a C_1-18 alkyl group, e.g. a C_12-15 alkyl group.

Preferably one of R and R is independently selected from hydrogen and hydrocarbyl of 1 to 10, preferably 1 to 4 carbon atoms, the other of R and R being independently selected from hydrocarbyl of 1 to 10, preferably 1 to 4, carbon atoms. Conveniently, one of R² and R³ is hydrogen, the other being hydrocarbyl, preferably a _-3 alkyl group. Preferably, one of R 2 and R 3 is hydrogen and the other is a methyl, the moieties -CHR²-CHR -O- then being derived from 7 2 3 propylene oxide. When the moieties -CHR -CHR -O- contain two or more different R and/or R

2 groups, the moiety -(CHR -CHR -O)_m- may represent a block copolymeric group or a random

2 3 copolymeric group. Derivatives of formula I wherein one of R and R is hydrogen and the other is a methyl group have been found to be very suitable.

The amines, aminoalcohols and polyols of which R in formula I represents the residue are known in the art or may be prepared by analogous methods to those used for preparing the known amines, aminoalcohols and polyols. For example, various amines and their preparation are described in US Patents Nos. 3,275,554, 3,438,757, 3,454,555, 3,565,804, 3,755,433 and 3,922,209. Complex amines such as "Starburst" (trade mark) dendrimers may be used, e.g. the compound of formula [CH₂N((CH₂)₂CONH(CH₂)₂NH₂)₂]₂.

Examples of polyols include ethylene glycol, glycerol, trimethylolethane, trimethylolpropane, 1,2-butanediol, 2,3-hexanediol, 2,4-hexanediol, pinacol, erythritol, arabitol, sorbitol, mannitol pentaerythritol, dipentaerythritol and tripentaerythritol.

Preferred derivatives of formula I are those wherein the compound of R(H)p, of which R represents the residue, has the general formula II:- HX[(CR⁴R⁴ )_aO]_b [(CR⁵R⁵)_cNR⁶]_d(R")_s(CHR⁵)_eR⁷]_f[(CR⁵R⁵)_g(R⁸)_h)_iR⁹ (II) wherein X is O or NR ; each R independently represents hydrogen, hydrocarbyl of 1 to 10 carbon atoms or hydrocarbyl of 1 to 10 carbon atoms substituted by at least one hydroxy group; each R independently represents hydrogen or hydrocarbyl of 1 to 10 carbon atoms; each R independently represents hydrogen or hydrocarbyl of 1 to 10 carbon atoms; R represents a C_5-7 cycloalkanediyl-NH- or 1 ,4-piperazinediyl moiety optionally substituted by one or more hydrocarbyl groups of 1 to 10 carbon atoms; each R independently represents NR or CHR ; R represents hydrogen, hydrocarbyl of 1 to 30 carbon atoms or a

-CO(CHOH)_t(CR⁵R⁵)_j(NR⁵ MCR^^OH group; R¹⁰ represents a -(CR⁵R⁵)_rNR⁶R⁹ group; R" represents a C_5-7 cycloalkanediyl moiety optionally substituted by one or more hydrocarbyl groups of 1 to 10 carbon atoms; a is 1 to 10, b is 0 to 10, c is 1 to 10, d is 0 to 10, e is 1 to 10, f is 0 or 1, g is 1 to 10, h is 0 or 1 i is 0 to 10 j is 1 to 10, k is 0 or 1,

1 is 1 to 10, r is 1 to 10, s is 0 or 1, and t is 0 or 1 and integers b, d, f and i indicate numbers of associated moieties present, and the various moieties [(CR R⁴ )_aO], [(CR⁵R⁵)_CNR⁶], I(CHR⁵)_eR⁷] and [(CR⁵R⁵)_g(R⁸)_h] may be in any linear order.

Preferably in formula II X is O or NR⁶; each R⁴ independently represents hydrogen, C^ alkyl or ^ hydroxyalkyl; each R⁵ independently represents hydrogen or ^ alkyl; each R represents hydrogen or methyl; R⁷ represents a 1 ,4-piperazinediyl moiety or a cyclohexanediyl-

NH- moiety optionally substituted by up to three methyl groups; each R independently represents NR¹⁰ or CHR¹⁰; R⁹ represents hydrogen, methyl or a -CO (CHOH) _t (CHR⁵) _j (NR⁵) _k (CHR⁵) i OH group; R¹⁰ represents a -(CHR⁵)_rNHR⁹ group; R¹¹ represents a cyclohexanediyl moiety optionally substituted by up to three methyl groups, a is 1 to 5, b is 0 to 5, c is 1 to 6, d is 0 to 5, e is 1 to 5, f is 0 or 1, g is 1 to 5, h is 0 or 1, i is 0 to 5, j is 1 to 5, k is 0 or 1, 1 is 1 to 5, r is 1 to 5, s is 0 or 1 and t is 0 or 1. Advantageously, X is O or NH; each R independently represents hydrogen, methyl or hydroxymethyl; each R⁵ independently represents hydrogen or methyl; each R⁶ represents hydrogen or methyl; R represents a 1 ,4piperazinediyl moiety or a cyclohexanediyl-NH- moiety optionally substituted by up to 3 methyl groups; each R independently represents NR or CHR¹⁰; R⁹ represents hydrogen, methyl, or a -CO(CHOH)_t(CHR⁵)_j(NR⁵)_k(CHR⁵),OH group; R¹⁰ represents a (CHR⁵)_rNHR group, a is 2 or 3, b is 0 to 3, c is 2 to 6, d is 0 to 4, e is 3, f is 0 or 1, g is 2 or 3, h is 1, i is 0 or l,j is 1 to 4, k is 0 or 1, 1 is 1 to 4, r is 1 or 2, s is 0 or 1 and t is 0 or 1.

Examples of preferred such moieties R are the following:- -NHCH₂CH₂N(CH₂CH₂NH₂)₂, -O(CH₂C(CH₂OH)₂O)_bH where b is 1 to 3, preferably 1, -NH(CH₂CH₂NH)_dH where d is 1 to 4, -NHCH₂CH₂NHCH₂CH₂OH, -NH(CH₂)_CNH₂, where c is 2 to 6, preferably 2 to 4, -NH(CH₂)₃NH(CH₂)₂NH(CH₂) ₂, -NH(CH₂CH₂O)₂CH₂CH₂NH₂, -NH(CH₂CH₂O)₂H,

-NH (CH₂) ₃ (1, 4-piperazinediyl) (CH₂) ₃NH₂, -NH (1, 4- is cyclohexanediyl) CH₂ (1, 4- cyclohexanediyl) NH₂, -NHCH₂ (1, 3, 3-trimethyl-5-aminocyclohexyl) , -NH (CH₂CH₂CH₂NH) ₂H, -NH (CH₂) ₃CH (CH₂NH₂) (CH₂) ₄NH₂, -NHCH₂CH₂N (CH₂CH₂NHCO (CH₂) ₂CH (CH₃) OH) ₂, -NHCH₂CH₂N(CH₂CH₂NHCOCH₂N(CH₃)CH₂CH₂OH)₂, -NHCH₂C(CH₃)₂CH₂NH₂, - NH(CH₂)₃N(CH₃)₂(all when p = 1); and -NH(CH₂CH₂NH).- and -NHCH₂CH₂N(CH₂CH₂NH₂)CH₂CH₂NH(when p = 2).

Most preferably, R(H)p is selected from the group consisting of pentaerythritol, triethylenetetramine and tris(2-aminoethyl)amine.

The alkoxy acetic acid derivative of general formula I as defined above may be prepared by reacting a compound of general formula III:-

wherein R', R¹, R², R³, m and n are as defined above and L represents a leaving group, with a compound of general formula R(H)_p, wherein R is as defined above, in molar ratio of compound of formula III : compound of formula R(H)_P of substantially L:p, optionally followed by converting the resulting acid derivative of formula I into another acid derivative of formula I with different group R as defined above.

Although the leaving group L may be, for example, a halogen atom, such as chlorine or bromine atom, L is preferably a hydroxy group.

Reaction between the compound of formula III and the compound of formula R(H)p may conveniently be effected in the presence of an inert solvent, e.g. an aromatic hydrocarbon such as toluene or xylene.

When L is a hydroxy group, the reaction may conveniently be effected at a temperature in the range from 10°C to the reflux temperature of the reaction mixture. Water may advantageously be removed, e.g. by means of a Dean-Stark extractor and condenser. When R(H) _p is a polyol, advantageously an acid, such as para-toluene sulphonic acid, is present.

Conversion of one R group into a different R group as defined above is most likely to be done when the desired final product of formula I as defined above contains one or more R moieties, wherein R⁹ is a -CO(CHOH)_t(CHR⁵)_j(NR⁵)_k(CHR⁵)ιOH group. For example, a compound of formula I wherein R is hydrogen may be converted into a compound of formula I wherein R⁹ is a CO(CH₂)₂CH(CH₃)OH group, a COCH₂N(CH₃)CH₂CH₂OH group or a CO(CHOH)C(CH₃) CH₂OH group respectively by reaction with gamma-valerolactone, N- methylmorpholinone or pantolactone.

Compounds of formula III as defined above wherein L is other than a hydroxy group can be prepared in known manner from the corresponding compound of formula III wherein L is a hydroxy - group.

Compounds of formula III wherein L is a hydroxy compound may be prepared by reaction of an alpha-halo carboxylic acid of general formula VI:-

R*

I

Q— CH-COOH or an alkali metal salt thereof, wherein R' is as defined above and Q is a halogen, preferably chlorine, atom with a compound of formula VII:-

R'-Of-

where R¹, R², R³, m and n are as defined above, in the presence of a suitable base and an inert solvent. Suitable bases include sodium and potassium hydrides and amides, for which solvents such as tetrahydrofuran and xylene are suitable, and potassium tertiary butoxide, for which tertiary butanol is suitable as solvent. In an aprotic solvent, sodium metal may be used to generate suitably basic conditions. When n is 1 to 20 (i.e. greater than 0), milder bases can be employed, such as sodium and potassium hydroxides, e.g. using toluene as solvent.

Compounds of formula VII wherein n is 1 to 20 may be generated by reacting a compound of formula VII wherein n is 0 with ethylene oxide in molar ratio compound of formula VII : ethylene oxide l:n.

A compound of formula VII wherein n is I to 20 may be converted into an alkoxyacetic acid of general formula III wherein L is a hydroxy group, R' is hydrogen and n is 0 to 19 by a process similar to that described in US Patent No. 5,390,930, In such a process, the compound of formula VII wherein n is 1 to 20 is conveniently reacted with a stable free radical nitroxide, such as piperidine-1-oxyl, in the presence of nitric acid and an oxidising agent, e.g. air or gaseous oxygen, in the presence or absence of a solvent. Alkoxy acetic acid derivatives of formula I may alternatively, in principle, be prepared by reacting a compound of general formula VIII:-

where R' and p are as defined above and R" is R as above or a protecting group with appropriate alkylene oxides in suitable order, followed by end-capping the resulting product in order to produce the desired alkoxyacetic acid derivative of formula I, or when R' is a protecting group, with reaction with a compound R(H)_p as defined above to displace the protecting group and finally obtain the desired alkoxy acetic acid derivative of formula I.

The additive has useful application in minor amounts both in fuel compositions for spark- ignition engines (gasoline compositions) and in fuel compositions for compression ignition engines (diesel fuel compositions) as well as in heating oil or fuel oil composition. Preferably, the additive has useful application in minor amounts in fuel compositions for compression ignition engines (diesel fuel compositions).

The "minor amount" referred to above is preferably less than 10% wt of the composition, more preferably less than 1% wt and advantageously in the range of 0.01% wt (100 ppmw) to 0.5% wt (5000 ppmw) (parts per million by weight) of the composition. In preferred fuel compositions the additive is present in an amount in the range 300 to 2,500 ppmw of the fuel composition. Amounts above 0.05% w (500 ppmw), especially in the range of 0.05 to 0.20% wt (500 to 2000 ppmw) have been found to be particularly effective, especially in middle distillate fuel oils such as diesel fuel, and heating and fuel oils.

For gasoline compositions, the fuel will be a fuel boiling in the gasoline boiling range, and it may consist substantially of hydrocarbons or it may contain blending components. Alternatively, e.g. in countries such as Brazil, the fuel may consist substantially of ethanol.

Suitable liquid hydrocarbon fuels of the gasoline boiling range are mixtures of hydrocarbon boiling in the temperature range from about 25°C to about 232°C, and comprise mixtures of saturated hydrocarbons, olefinic hydrocarbons and aromatic hydrocarbons. Preferred are gasoline mixtures having a saturated hydrocarbon content ranging from about 40% to about 80% by volume, an olefinic hydrocarbon content from 0% to about 30% by volume and an aromatic hydrocarbon content from about 10 to about 60% by volume. The base fuel is derived from straight run gasoline, polymer gasoline, natural gasoline, dimer and trimerized olefins, synthetically produced aromatic hydrocarbon mixtures, from thermally or catalytically reformed hydrocarbons, or from catalytically cracked or thermally cracked petroleum stocks, and mixtures of these. The hydrocarbon composition and octane level of the base fuel are not critical. The octane level, (R+M)/2, will generally be above about 85 (where R is Research Octane Number and M is Motor Octane Number).

Any conventional base gasoline can be employed in the practice of the present invention. For example, hydrocarbons in the gasoline can be replaced by up to a substantial amount of conventional alcohols or ethers, conventionally known for use in fuels. The base gasolines are desirably substantially free of water since water could impede a smooth combustion.

Normally, the gasoline to which the invention is applied may be leaded or unleaded although are preferably substantially lead-free, and may contain minor amounts of one or more blending agents such as methanol, ethanol, tertiary butanol, ethyl tertiary butyl ether, ethyl tertiary butyl ether, and the like, at from about 0.1% by volume to about 25% by volume of the base fuel, although larger amounts (e.g. up to 40%v) may be utilised. The gasoline can also contain conventional additives including antioxidants such as phenolics, e.g. 2,6-di-tert- butylphenol or phenylenediamines, e.g. N,N'-di-sec-butyl-p-phenylenediamine, dyes, metal deactivators, dehazers such as polyester-type ethoxylated alkylphenolformaldehyde resins. Corrosion inhibitors, such as that commercially sold by Rhein Chemie, Mannheim, Germany as "RC 4801 ", or a polyhydric alcohol ester of a succinic acid derivative having on at least one of its alpha-carbon atoms an unsubstituted or substituted aliphatic hydrocarbon group having from 20 to 500 carbon atoms, for example, pentaerythritol diester of polyisobutylene-substituted succinic acid, the polyisobutylene group having an average molecular weight of about 950, in an amount from about 1 ppmw to about 1000 ppmw, may also be present. The fuels can also contain antiknock compounds such as methyl cyclopentadienylmanganese tricarbonyl, tetraethyl lead or other lead-containing compounds, and ortho-azodiphenol as well as co-antiknock compounds such as benzoyl acetone.

A preferred gasoline composition of the invention may additionally contain a minor amount of at least one additional additive compound selected from the group consisting of polyalkenyl amines, Mannich amines, polyalkenyl succinimide, poly(oxyalkylene)amines, poly(oxyalkylene)carbamates, and poly(alkenyl)-N-substituted carbamates.

An effective amount of one or more additives are introduced into the fuel in a variety of ways. A preferred method is to add a minor amount of one or more additives to the gasoline. For example, one or more additives are added directly to the gasoline or are blended with one or more carriers and/or one or more hydrocarbon-soluble alkali metal or alkaline earth metal salts and/or one or more additional detergents before being added to the gasoline.

The amount of additive used will depend on the particular variation of formula I used, the engine, the fuel, and the presence or absence of carriers, additional detergents and diluents.

The carrier, when utilised, may conveniently have an average molecular weight from about 250 to about 5000. Suitable carriers, when utilised, include hydrocarbon based materials such as polyisobutylenes (PIB), polypropylenes (PP) and polyalphaolefins (PAO), all of which may be hydrogenated or unhydrogenated but are preferably hydrogenated; polyether based materials such as polybutylene oxides (poly BO), polypropylene oxides (poly PO), polyethylene oxides (poly EO), polyhexadecene oxides (poly HO) and mixtures thereof (i.e. both (poly BO) + (poly PO) or both (poly-PO)+ (polyEO)); and mineral oils such as those sold by member companies of the Royal Dutch/Shell group under the designations "HVI" and "XHVI" (trade mark) , Exxon Naphthenic 900 sus mineral oil and high viscosity index oils in general. The carrier is preferably selected from PIB, poly BO and poly PO with poly PO being the most preferred.

A particularly prepared carrier fluid comprises a combination of a polyalphaolefin having a viscosity at 100°C in the range 2 x 10^" to 2 x 10^" m /s (2 to 20 centistokes) being a hydrogenated oligomer containing 18 to 80 carbon atoms derived from at least one alphaolefinic monomer containing from 8 to 16 carbon atoms, and a polyoxyalkylene compound selected from glycols, mono- and diethers thereof, having number average molecular weight (Mn) in the range 400 to 3000, the weight ratio polyalphaolefin: polyoxyalkylene compound being in the range 1 : 10 to 10:1.

The polyalphaolefins are primarily trimers, tetramers and pentamers, and synthesis of such materials is outlined in Campen et al., "Growing use of synlubes", Hydrocarbon Processing, February 1982, pages 75 to 82. The polyalphaolefin is preferably derived from an alphaolefinic monomer containing from 9 to 12 carbon atoms. Polyalphaolefins derived from decene-1 have been found to be very effective. The polyalphaolefin preferably has viscosity at 100°C in the range of 6 x 10^' to 1 x 10^"5 m²/s (6 to 10 centistokes). Polyalphaolefin having a viscosity at

100°C of 8 x

(8 centistokes) has been found to be very effective.

Preferred polyoxyalkylene compounds for use in combination with these polyalphaolefins are described in EP-A-588429. The carrier concentration in the final fuel composition is up to about 1000 ppm weight. When a carrier is present, the preferred concentration is from about 50 ppm by weight to about 400 ppm by weight, based on the total weight of the fuel composition once the carrier is blended with one or more compounds of formula I and any other desired components, the blend is added directly to the fuel or packaged for future use.

The hydrocarbon-soluble alkali metal or alkaline earth metal salt, when utilised, may be one of those described in WO 87/01126, and the compounds of formula I are particularly suitable for incorporation, as additional component, in fuel compositions as described in WO 87/01126. Preferred hydrocarbon-soluble alkali metal or alkaline earth metal salts are, however, alkali metal or alkaline earth metal salts of a succinic acid derivative. Such a salt of a succinic acid derivative, when utilised, will have as a substituent on one of its alpha-carbon atoms an unsubstituted or substituted aliphatic hydrocarbon group having from 20 to 200 carbon atoms.

Alternatively, the succinic acid derivative will have as a substituent on one of its alpha- carbon atoms an unsubstituted or substituted hydrocarbon group having from 20 to 200 carbon atoms which is connected to the other alpha-carbon atom by means of a hydrocarbon moiety having from 1 to 6 carbon atoms, forming a ring structure. Suitable such salts are described for example in EP-A-207560 and in EP-A-491139. The salts of the succinic acid derivative can be monobasic or dibasic. Monobasic salts in which the remaining carboxylic acid group has been transformed into an amide or ester group may also be used. Suitable alkali metal salts of a partial ester of an alkyl polyether alcohol with a succinic acid derivative are described in EP-A-491439.

Suitable metal salts include lithium, sodium, potassium, rubidium, caesium and calcium salts. Particularly preferred salts are described in EP-A-207560.

The aliphatic hydrocarbon substituent(s) of the succinic acid derivative is suitably derived from a polyolefin, the monomers of which have 2 to 6 carbon is atoms. Thus, convenient substituents include polyethylene, polypropylene, polybutylenes, polypentenes, polyhexenes or mixed polymers. Particularly preferred is an aliphatic hydrocarbon group which is derived from polyisobutylene.

The hydrocarbon group may include an alkyl and/or an alkenyl moiety and may contain substituents. One or more hydrogen atoms may be replaced by another atom, for example halogen, or by a non-aliphatic organic group, e.g. an (un)substituted phenyl group, a hydroxy, ether, ketone, aldehyde or ester. A very suitable substituent in the hydrocarbon group is at least one other metal succinate group, yielding a hydrocarbon group having two or more succinate moieties.

The aliphatic hydrocarbon group should contain 20 to 200, preferably 35-150, carbon atoms. When a polyolefin is used as substituent the chain length is conveniently expressed as the number average molecular weight. The number average molecular weight of the substituent, e.g. determined by osmometry, is advantageously from 400 to 2000.

The succinic acid derivative may have more than one C₂₀.₂oo aliphatic hydrocarbon group attached to one or both alpha-carbon atoms, but preferably it has one C₂o_-2oo aliphatic hydrocarbon group on one of its alpha-carbon atoms and on the other alpha-carbon atom either no substituent or a hydrocarbon of only a short chain length, e.g. _-6 group. The latter group can be linked with the C₂₀.₂oo hydrocarbon group forming a ring structure.

The gasoline compositions of the present invention may also contain one or more additional additives such as detergents. When additional detergents are utilised, the gasoline composition will comprise a mixture of a major amount of hydrocarbons in the gasoline boiling range as described hereinbefore, a minor amount of one or more compounds of formula I as described hereinbefore and a minor amount of an additional detergent selected from polyalkenyl amines, e.g. polybutyleneamines, such as "KEROCOM" (trademark) polyisobutyleneamine, available ex BASF, Mannich amines, polyalkenyl succinimides, poly(oxyalkylene)amines, poly(oxyalkylene) carbamates, poly(dikenyl)-N-substituted carbamates, and mixtures thereof. As noted above, a carrier as described hereinbefore may also be included. The "minor amount" is preferably less than about 10% by weight of the total fuel composition, more preferably less than about 1% by weight of the total fuel composition and yet more preferably less than about 0.1% by weight of the total fuel composition. The polyalkenyl amine detergents utilised comprise at least one monovalent hydrocarbon group having at least 50 carbon atoms and at least one monovalent hydrocarbon group having at most five carbon atoms bound directly to separate nitrogen atoms of a diamine. Preferred polyalkenyl amines are polyisobutenyl amines. Polyisobutenyl amines are known in the art and representative examples are disclosed in various US Patents including US Patent No. 3,753,670, US Patent No. 3,756,793, US Patent No. 3,574,576 and US Patent No. 3,438,757. Particularly preferred polyisobutenyl amines for use in the present fuel composition include N- polyisobutenyl-N', N'-dimethyl-l, 3-diaminopropane (PIB-DAP), OGA-472 (a polyisobutenyl ethylene diamine available commercially from Oronite) , N-polyisobutenyl diethylene triamine (PIB-DETA) and N-polyisobutenyl triethylene tetramine (PIB-TETA).

The Mannich amine detergents utilised comprise a condensation product of a high molecular weight alkysubstituted hydroxyaromatic compound, an amine which is contains an amino group having at least one active hydrogen atom (preferably a polyamine), and an aldehyde. Such Mannich amines are known in the art and are disclosed in US Patent No. 4,231,759. Preferably, the Mannich amine is an alkyl substituted Mannich amine. The polyalkenyl succinimide detergents comprise the reaction product of a dibasic acid anhydride with either a polyoxyalkylene diamine, a hydrocarbyl polyamine or mixtures of both. Typically the succinimide is substituted with the polyalkenyl group but the polyalkenyl group may be found on the polyoxyalkylene diamine or the hydrocarbyl polyamine. Polyalkenyl succinimides are also known in the art and representative examples are disclosed in various patent references including US Patent No. 3,443,918, EP-A-208560, DE-OLS 3,126,404, US Patent No. 4,234,435, Us Patent No. 4,810,261, US Patent No. 4,852,993, US Patent No. 4,968,321, US Patent No. 4,985,047, US Patent No. 5,061,291 and US Patent No. 5,147,414.

Particularly effective succinimide detergents are those obtained by reacting at least one amine, with a polyalkenyl derivative of a monoethylenically unsaturated C_4-ι₀ dicarboxylic acid material in which the ratio of dicarboxylic acid moieties per polyalkenyl chain is not greater than 1.2:1 and the number average molecular weight (Mn) of the polyalkenyl chain is in the range from 1600 to 5000, e.g. as described in EP-A-587250 (Applicants reference T1665).

Amines employed in the preparation of said succinimide detergents are preferably Cι_₃₀, more preferably .ι₈, and especially C_8-12, amines containing 1 to 8 nitrogen atoms. Such amines may be branched or unbranched, saturated aliphatic, primary or secondary amines, containing 1 to 8 nitrogens, preferably mono- or diamines, such as ethylamine, butylamine, sec. butylamine, diethylamine and 3-dimethylamino-l-propylamine, but including higher polyamines such as alkylene polyamines, wherein pairs of nitrogen atoms are joined by alkylene groups of 2 to 4 carbon atoms.

The one or more additional detergents are added directly to the fuel boiling in the gasoline boiling range, blended with one or more carriers, blended with one or more acid derivatives of formula I, or blended with one or more acid derivatives of formula I and one or more carriers before being added to the fuel. The concentration of the one or more additional detergents in the final fuel composition is generally up to about 1000 ppmw for each additional detergent. When one or more additional detergents are utilised, the preferred concentration for each additional detergent is from about 10 ppmw to about 400 ppmw, based on the total weight of the fuel composition, even more preferably from about 25 ppmw to about 250 ppmw, based on the total weight of the fuel composition.

Additive components can be added separately to the gasoline or can be blended with one or more diluents, forming an additive concentrate, and added to the gasoline together. Suitable gasoline-compatible diluents are hydrocarbons and mixtures of hydrocarbons with alcohols or ethers, such as methanol, ethanol, propanol, 2-butoxyethanol, methyl tert-butyl ether, or higher alcohols such as "Dobanol 91", (Trade Mark) available from member companies of the Royal Dutch/Shell group.

Preferably the diluent is an aromatic hydrocarbon solvent such as toluene, xylene, mixtures thereof or mixtures of toluene or xylene with an alcohol. Additionally preferred diluents include "Shellsol AB", "Shellsol R", (Trade Marks) and low aromatic white spirit (LAWS), which are available from member companies of the Royal Dutch/Shell group.

For diesel fuel applications, the fuel will be a diesel oil, which may be a hydrocarbon fuel (a middle distillate fuel oil), which may be a conventional fuel or a low-sulphur fuel having a sulphur concentration below 500 ppmw, preferably below 350 ppmw, such as below 50 ppmw, advantageously below 10 ppmw. Diesel fuels typically have initial distillation temperature about 160°C and 90% point of 290-360°C, depending on fuel grade and use. Vegetable oils may also be used as diesel fuels per se or in blends with hydrocarbon fuels. Low-sulphur fuels will typically require a lubricity additive to reduce fuel pump wear.

Additive concentrates suitable for incorporating in diesel fuel compositions will contain the additive and a fuel-compatible diluent, which may be a non-polar solvent such as toluene, xylene, white spirits and those sold by member companies of the Royal Dutch/Shell Group under the Trade Mark "SHELLSOL", and/or a polar solvent such as esters and , in particular, alcohols, e.g. hexanol, 2-ethylhexanol, decanol, isotridecanol and alcohol mixtures such as those sold by member companies of the Royal Dutch/Shell Group under the Trade Mark "LINEVOL", especially "LINEVOL" 79 alcohol which is a mixture of C_7-9 primary alcohols, or the Cι_2-ι₄ alcohol mixture commercially available from Sidobre Sinnova, France under the Trade Mark "SIPOL".

Additive concentrates and diesel fuel compositions prepared therefrom may additionally contain additional additives such as low molecular weight amine co-detergents, dehazers, e.g. alkoxylated phenol formaldehyde polymers such as those commercially available as "NALCO" (Trade Mark) 7D07 (ex Nalco), and "TOLAD" (Trade Mark) 2683 (ex Petrolite; anti-foaming agents (e.g. the polyether-modified polysiloxanes commercially available as "TEGOPREN" (Trade Mark) 585,IL, Q 25907 (ex Dow Corning) or "RHODORSIL" (Trade Mark) (ex Rhone Poulenc)); ignition improver (e.g. 2-ethylhexyl nitrate, cyclohexyl nitrate, di-tertiary-butyl - lό - peroxide and those disclosed in US Patent No. 4,208,190 at Column 2, line 27 to Column 3, line 21); anti-rust agents (e.g. that commercially sold by Rhein Chemie, Mannheim, Germany as "RC 4801", or polyhydric alcohol esters of a succinic acid derivative, the succinic acid derivative having on at least one of its alpha-carbon atoms an unsubstituted or substituted aliphatic hydrocarbon group containing from 20 to 500 carbon atoms, e.g. the pentaerythritol diester of polyisobutylene-substituted succinic acid), reodorants, anti-wear additives; anti-oxidants (e.g. phenolics such as 2,6-di-tert-butylphencl, or phenylenediamines such as N,N -di-sec-butyl-p- phenylenediamine), metal deactivators and lubricity agents (e.g. those commercially available as EC831 (ex Paramins) or "HITEC" (Trade Mark) 580 (ex Ethyl Corporation)).

Preferred low molecular weight amine co-detergents are C 10-20 alkylamines. Aliphatic primary monoamines, particularly linear aliphatic primary monoamines, having 10 to 20 carbon atoms are particularly preferred. The alkylamine preferably has 10 to 18, e.g. 12 to 18, more preferably 12 to 16 carbon atoms. Dodecylamine is particularly preferred.

Unless otherwise stated, the (active matter) concentration of each additive in the diesel fuel is preferably up to 1 percent by weight more preferably in the range from 5 to 1000 ppmw (parts per million by weight of the diesel fuel). The (active matter) concentration of the compound of formula I in the diesel fuel is preferably 50 to 1000 ppmw.

The (active matter) concentration of the dehazer in the diesel fuel is preferably in the range from 1 to 20, more preferably from 1 to 15, still more preferably from 1 to 10 and advantageously from 1 to 5 ppmw. The (active matter) concentrations of other additives (with the exception of the ignition improver and the lubricity agent) are each preferably in the range from 0 to 20, more preferably from 0 to 10 and advantageously from 0 to 5 ppmw. The (active matter) concentration of the ignition improver in the diesel fuel is preferably in the range from 0 to 600 and more preferably from 0 to 500 ppmw. If an ignition improver is incorporated into the diesel fuel, it is conveniently used in an amount of 300 to 500 ppmw. If a lubricity agent is incorporated into the diesel fuel, it is conveniently used in an amount of 100 to 500 ppmw.

The diesel oil itself may be an additised (additive-containing) oil or an unadditised (additive-free) oil. If the diesel oil is an additised oil, it will contain minor amounts of one or more additives, e.g. one or more additives selected from anti-static agents, pipeline drag reducers, flow improver (e.g. ethylene/vinyl acetate copolymers or acrylate/maleic anhydride copolymers) and wax anti-settling agents (e.g. those commercially available under the Trade Marks "PARAFLOW" (e.g. "PARAFLOW" 450; ex Paramins), "OCTEL" (e.g. "OCTEL" W 5000; ex Octel) and "DODIFLOW" (e.g. "DODIFLOW" V 3958; ex Hoechst).

The present invention still further provides a method of operating an internal combustion engine (e.g. a spark-ignition engine or a compression-ignition engine) which comprises introducing into the combustion chambers of said engine a fuel composition (e.g. a gasoline composition or diesel fuel composition, as appropriate) as defined above.

The invention will be further understood from the following illustrative examples in which Examples I to V relate to the preparation of intermediate acids, and Examples 1 to 2 to compounds of formula 1. In the examples, various polyether starting material of the general formula:

wherein R represents a C_12-15 alkyl group are designated as follows

Polyether A is a polyoxypropylene glycol hemiether (monoether) corresponding to formula Q wherein m is in the range 17 to 23 and n is 0, prepared using a mixture of C₁₂.₁₅ alcohols as initiator, and having Mn in the range 1200 to 1500 and a kinematic viscosity in the range 72 to 82 mn²/s at 40°C according to ASTM D 445.

Polyether B is a Polyoxypropylene glycol hemiether (monoether) corresponding to formula Q wherein m is in the range 3.5 to 5.5 and n is O, prepared using a mixture of C_12-ι₅ alkanols as initiator, and having Mn in the range 435 to 505 and a kinematic viscosity in the range 16 to 21 mn²/s at 40°C according to ASTM D 445.

Polyether C is a polyoxypropylene glycol hemiether (monoether) corresponding to formula Q wherein m is about 120 and n is 0, prepared using a mixture of Cι_2-15 alkanols as initiator, having a hydroxyl value of 0.14 milliequivalents per gram according to ASTM D 4274- 88 and Mn calculated therefrom (on the basis of one hydroxyl group per molecule) of 7150, and a kinematic viscosity in the range of 2300 to 2400 mm²/s at 40'C according to ASTM D 445;

Polyether D is a polyalkylene glycol hemiether (monoether)corresponding to formula Q wherein m is 19 and n is 5, prepared by reacting a sample of Polyether A with ethylene oxide in molar ratio 1 :5 in the presence of potassium hydroxide as base, at 125°C, under pressure.

Polyether D had hydroxyl value of 0.625 milliequivalents per gram according to ASTM 1) 4274-88 and a kinematic viscosity of 98-3 mm²/s at 4C"C according to ASTM D 445.

Various abbreviations are employed in the examples as follows:-

"AV" denotes acid value, and this was determined using a "Metrohm 670" (trademark) potentiometric titrometer according to a method based upon ASTM D 661-89 with modified solvent system (75% w toluene, 12.5% w acetonitrite, 12.5% w acetic acid);

"TBN" denotes total basic nitrogen, and this was determined using a "Metrohm 67011 (trade mark) potentiometric titrometer according to a method based upon ASTM D 2896 with modified solvent system (75% w toluene, 12.5% w acetonitrile, 12.5% w acetic acid);

"AM" denotes active matter content, and this was determined by separating inactive material from the desired active matter in obtained product on a silica column using hexane as eluant, and is expressed as a percentage relative to the obtained product.

"megg^" " denotes milliequivalents per gram.

In the examples and tests which follow, all parts and percentages are by weight unless stated otherwise, and temperatures are in degrees Celsius. Intermediate acids, in the form of alkoxy acetic acids derivatives of general formula:

R*-O ^•(- (R)

wherein R represents a C_12-15 alkyl group, were prepared from the above polyether starting materials as follows :-

EXAMPLE I

Preparation of alkoxy acetic acid A (m = 17 to 23, n = 0)

To a 3000 ml flask, equipped with mechanical stirrer and nitrogen purge, was added sodium hydride (88 g, 2.2 mol, 60% dispersion in oil) and tetrahydrofuran (500 ml). To the resulting agitated mixture, a solution of Polyether A (1500g, 1 mol) in tetrahydrofuran (1500 ml) was added, gradually over a period of approximately 3 hours. The mixture was then heated to reflux, with stirring, for 3 hours, cooled to 40-50°C and a solution of chloroacetic acid (94.5 g, 1 mol) in tetrahydrofuran (100 ml) was added over approximately 2 hours. The reaction mixture was heated to reflux for 3 hours, cooled to ambient temperature (20°C) and then acidified with hydrochloric acid (2 N aqueous solution) (addition continued until sufficient to render the mixture acidic). The reaction mixture was extracted with diethylether (3 x 1 L)and the combined organic phase was washed with water (3 x 1 L). The organic phase was dried over MgS0 , filtered and evaporated to afford the desired product as 1560 g of a pale yellow oil, AV = 0.596 megg^"1, AM = 85.5%.

This product was also prepared by variations of this process in which ethylchloroacetate or sodium chloroacetate were used instead of chloroacetic acid, wherein tertiary butanol or xylene were used as solvent instead of tetrahydrofuran and wherein potassium tertiary butoxide, sodamide or sodium metal (with xylene as solvent) were used instead of sodium hydride. EXAMPLE II Preparation of alkoxy acetic acid B (m = 3.5 to 5.5, n = 0)

To a 3000 ml flask, equipped with mechanical stirrer and nitrogen purge, was added sodium hydride (88 9, 2.2 mol, 60% dispersion in oil) and tetrahydrofuran (500 ml). To this agitated mixture, a solution of Polyether B (555 g, 1 mol) in tetrahydrofuran (1000 ml) was added, gradually over a period of approximately 3 hours. The mixture was stirred, for 3 hours and a solution of chloroacetic acid (108 9, 1.1 mol) in tetrahydrofuran (500 ml) was added over approximately 4 hours. The reaction mixture was heated to reflux for 14 hours, cooled and then acidified with hydrochloric acid (2 N aqueous solution). The reaction mixture was extracted with diethylether (3 x 1 L) and the combined organic phase was washed with water (3 x 1 L). The organic phase was dried over Na S0 , filtered and evaporated to afford the desired product as 604 g of a pale yellow oil, AV 10 1.72 megg^" .

EXAMPLE III

Preparation of alkoxy acetic acid C (m = 120, n = 0)

To a 2000 ml flask, equipped with mechanical stirrer and nitrogen surge, was added sodium hydride (8.8 g, 0.22 mol, 60% dispersion in oil) and tetrahydrofuran (250 ml). This mixture was heated to reflux, with stirring, and a solution of Polyether C (460 g, 0.1 mol) in tetrahydrofuran (1000 ml) added dropwise over 2 hours. After 3 hours a solution of chioroacetic acid (10.4 g, 0.11 mol) in tetrahydrofuran (50 ml) was added and the mixture maintained under reflux, with stirring, for a further 4 hours. The mixture was cooled, acidified with hydrochloric acid (2 N aqueous solution) and extracted with ether (3 x 750 ml). The combined organic phase was washed with saturated aqueous sodium chloride solution (3 x 200 ml), dried over MgS0₄, filtered and evaporated to afford 452 g of the desired product as a pale yellow oil, AV = 0.25 megg^"1.

EXAMPLE IV Preparation of alkoxy acetic acid D (m = 19, n = 5)

To a 500 ml flask equipped with Dean-stark extractor and condenser, was added Polyether D (150 g, 0.09 mol), toluene (250 ml) and a solution of sodium hydroxide (3.6 g, 0.1 mol) in water (20 ml). The mixture was heated at reflux temperature until all the water from the reaction mixture had been removed through the Dean-Stark extractor. The mixture was cooled sufficiently to allow the addition of the sodium salt of chloroacetic acid (11.6 g, 0.1 mol) and the mixture heated under reflux for 14 hours. The mixture was cooled, acidified with hydrochloric acid (2 N aqueous solution) and the phases separated. The organic phase was washed with saturated aqueous sodium chloride solution (2 x 50 ml), dried over MgSO4, filtered and evaporated to afford the desired product as 149 g of a pale yellow oil, AV = 0.23 megg ^"' .

This product was also prepared by variations of this process wherein aqueous potassium hydroxide solution or potassium hydroxide pellets were used instead of aqueous sodium hydroxide solution, and wherein chloroacetic acid was used instead of the sodium salt of chloroacetic acid. EXAMPLE V Preparation of alkoxy acetic acid E (m = 19, n = 4)

To a round-bottomed flask equipped with magnetic stirrer was added Polyether D (12 g), dichloromethane (25 ml), nitric acid (695c„ 1 ml) and 2,2,6,6-tetramethylpiρeridine-l-oxyl (0.3 q, 2.5% w/w, based on Polyether D). The resulting mixture was stirred at 35°C whilst oxygen was bubbled through at a rate of 30 ml/minute for 3 hours at ambient pressure. The mixture was then cooled to ambient temperature (20°C) , washed with brine (3 x 50 ml), dried over MgSO4, filtered and evaporated to afford the desired product as 10.4 g of a pale yellow oil, AV = 0.41 megg ^"1. This product was also prepared by variations of this process in which 4-hydroxy-2,2,6,6- tetramethylpiperidine-1-oxyl or 4-acetamido-2,2,6,6-tetramethylpiperidine-l-oxyl were used instead of 2,2,6,6-tetramethylpiperidine-l-oxyl, wherein air was used instead of gaseous oxygen and in the absence of dichloromethane (solvent).

Alkoxy acetic acid derivations of general formula:

CH,

R , ι'-O-t-CH₂-CH-O -HCH₂-CH₂-O H- CH₂-CO - -R

wherein R represents a C_12-15 alkyl group, were prepared from the above intermediate acids as follows :-

EXAMPLE 1 (alkoxy acetic acid derivative of formula (1 ) wherein m = 19, n = 5, p = 1 , R = -

NH-(CH₂CH₂NH)₃-H)

To a 150 ml flask, equipped with magnetic stirrer, Dean- Stark extractor and condenser, was added alkoxy acetic acid D (30 g, 0.02 mol), toluene (40 ml) and triethylenetetraamine (4.7 9, 0.03 mol). The resulting mixture was heated to reflux temperature and maintained at that temperature, with stirring, for 8 hours whilst removing water evolved from the reaction mixture. The resulting mixture was cooled and evaporated. The resulting residue was dissolved in chloroform (50 ml) and washed with saturated aqueous sodium chloride solution (2 x 25 ml) and water (25 ml). The organic phase was dried over MgSO₄, filtered and evaporated to afford the desired product as 33 g of a pale yellow oil. TBN = 1.15%N

EXAMPLE 2 (alkoxy acetic acid derivative of formula (a) wherein m = 19, n = 4, p = 1, R = - NH-(CH₂CH₂NH)₃-H)

To a 500 ml flask, equipped with magnetic stirrer, air sparge with 200 micron frit, Dean- Stark collector and condenser, was added alkoxy acetic acid E (200 0.12 mol) and triethylenetetramine (15 g, 0.1 mole) The resulting mixture was heated to 90-110°C, with an air sparge rate of 100-200 ml/min and maintained at that temperature, with stirring, for 5 hours whilst removing water evolved from the reaction mixture. The resulting residue was dissolved in chloroform (350 ml) and washed with saturated aqueous sodium chloride solution (3 x 150 ml) . The organic phase was dried over MgSO₄, filtered and evaporated to afford the desired product as 186 g of a brown oil. TBN = 0.76%N Performance Testing A Mercedes OM 364 A engine (type 364.979.40 with Bosch DLLA 142 S 792 injector nozzles) was installed on a computer controlled test cell and preconditioned for 8 hours through operation over the 13 mode test cycle (Table 1).

Table 1 : 13 Mode test conditions for OM 364 engine

Prior to each test, the test cell fuel filters were replaced and the test cell fuel system and engine were flushed with the test fuel. The engine was conditioned for 1 hour using a cycle shown in Table 2. The engine was then operated for 5 minutes at 2600 rev/min, 85 Kw and a final 5 minutes at 1800 rev/min, 67 Kw, in order that the dilution tunnel and filter paper sampling system temperatures could be assessed.

Table 2 : Additised fuel OM 364 engine pre-test conditioning cycle

The test fuel was then assessed over the cycle outlined in Table 2 with gaseous emission samples being taken from the raw exhaust line prior to the exhaust system back pressure valve. The samples were extracted over a Horiba heated line set to 80°C with a sample pre-heater. Each sample was then analysed for regulated emissions with a calibrated Horiba Mexa 9000 DEGR system. Particulate mass was determined at each test mode using a mini-dilution tunnel. Particulate filter paper samples were taken over a measured time interval of 15 minutes for each idle phase and 10 minutes for all other phases. The filter papers were conditioned for at least 24 hours before testing and a further 24 hours after sample collection before weighing.

The properties of the base fuel used throughout this evaluation are shown in Table 3. Table 3 : Properties of base fuel used throughout the OM 364 evaluation.

Results

Two separate OM 364 tests were run with the additive of Example 1 formulated into package A and the additive of Example 2 formulated into package D. These were compared against polyethers A and C formulated into packages B and C respectively. All packages contain identical concentrations of dehazer, cetane improver and anti-foam components. The base fuel also contains a standard injector cleanliness detergent package.

The results from these tests are shown in Table 4 clearly showing the significant reduction (15- 16%) in particulates for packages A and D compared to that for typical treat of a standard injector cleanliness detergent package (Base fuel). Similarly package A shows significant benefits over packages B and C demonstrating that the reduction in particulates is not derived from the polyether backbone alone but from the specific combination of polyoxyalkylene and hetero-atom containing substituent.

Table 4 : Summary of the results from the OM 364 evaluation

Table 5: Additive Formulations

Claims

C L A I M S

1. The use of an alkoxy acetic acid derivative of general formula:

in a liquid fuel composition, to reduce the particulate emissions resulting from the combustion of the fuel composition, wherein R is the residue of an amine, an aminoalcohol or a polyol linked to the or each -CHR' -CO- moiety via an amide or ester linkage:

R' is hydrogen or C_M alkyl;

R¹ is an optionally substituted hydrocarbyl group of 1 to 300 carbon atoms; one of R² and R³ is independently selected from hydrogen and optionally substituted hydrocarbyl of 1 to 10 carbon atoms, the other of R² and R³ being independently selected from optionally substituted hydrocarbyl of 1 to 10 carbon atoms; m is from 3 to 200; n is from 0 to 20, provided that m/n is at least 1 ; and p is from 1 to 5.

2. The use according to claim 1, wherein R¹ is hydrogen.

3. The use according to either claim 1 or claim 2, wherein p is 1 or 2.

4. The use according to any of the preceding claims, wherein m is from 3 to 150 and n is from O to 10.

5. The use according to any one of the preceding claims, wherein one of R 2 and R 3 is hydrogen, the other being a Ci-3 alkyl group.