ADDITIVE COMPOSITIONS AND TO FUEL OILS

Abstract

The invention relates to fuel oil compositions comprising an ester of an alkyl neo-monocarboxylic acid having a total number of from 5 to 30 carbon atoms and an aliphatic acyclic (C2 to C18) alkanol having a total number of from 2 to 18 carbon atoms and a total number of from 2 to 8 hydroxyl groups, wherein the aliphatic acyclic (C2 to C18) alkanol includes one or more alkyl chain(s) and each of said one or more alkyl chain(s) may optionally be interrupted by one or more oxygen atom(s), and to associated fuel additive compositions and uses of fuel additives.

Claims

1. A fuel oil composition comprising a major amount of a middle distillate fuel oil having a sulphur content of 0.2% by weight or less, and a minor amount of a fuel oil additive (A) comprising: an ester of an alkyl neo-monocarboxylic acid having a total number of from 5 to 30 carbon atoms, and an aliphatic acyclic (C.sub.2 to C.sub.18) alkanol having a total number of from 2 to 18 carbon atoms and a total number of from 2 to 8 hydroxyl groups, wherein said aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes one or more alkyl chain(s) and each of said one or more alkyl chain(s) may optionally be interrupted by one or more oxygen atom(s).

2. The composition as claimed in claim 1, wherein the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol is represented by a compound of formula I: ##STR00009## wherein: R.sup.1 represents an aliphatic acyclic alkyl chain having a total number of 1 to 17 carbon atoms, which aliphatic acyclic alkyl chain is optionally interrupted by one or more oxygen atoms; (CH.sub.2OH).sub.m represents a primary hydroxyl functional group and m is an integer from 1 to 3; (CH.sub.2OH), represents a primary hydroxyl functional group and n is an integer from 0 to 3; and, (OH) s represents a secondary hydroxyl functional group and s is an integer from 0 to 6; and, the sum of m, n and s is an integer from 2 to 8.

3. The composition as claimed in claim 2, wherein the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes only primary hydroxyl functional groups, and both m and n in a compound of formula I is each independently an integer from 1 to 3 and s is 0.

4. The composition as claimed in claim 3, wherein the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol is selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylolpropane, and di-trimethylolpropane.

5. The composition as claimed in claim 2, wherein the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes one or more secondary hydroxyl group(s) and one or more primary hydroxyl functional group(s), and s in a compound of formula I is an integer from 1 to 6, m in a compound of formula I is an integer from 1 to 3, and n in a compound of formula I is an integer from 0 to 3.

6. The composition as claimed in claim 5, wherein both m and n in a compound of formula I each represents 1, s is an integer from 1 to 3, and the total number of hydroxyl functional groups present in a compound of formula I is from 3 to 6.

7. The composition as claimed in claim 3, wherein R.sup.1 represents an aliphatic acyclic alkyl straight chain having from 1 to 16 total number of carbon atoms.

8. The composition as claimed in claim 5, wherein R.sup.1 represents an aliphatic acyclic alkyl straight chain having from 1 to 16 total number of carbon atoms.

9. The composition as claimed in claim 3, wherein the aliphatic acyclic alkyl chain which R.sup.1 represents is not interrupted by one or more oxygen atoms.

10. The composition as claimed in claim 5, wherein the aliphatic acyclic alkyl chain which R.sup.1 represents is not interrupted by one or more oxygen atoms.

11. The composition as claimed in claim 7, wherein the aliphatic acyclic alkyl chain which R.sup.1 represents is not interrupted by one or more oxygen atoms.

12. The composition as claimed in claim 8, wherein the aliphatic acyclic alkyl chain which R.sup.1 represents is not interrupted by one or more oxygen atoms.

13. The composition as claimed in claim 2, wherein the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol represented by a compound of formula I is selected from glycerol, diglycerol, triglycerol and hexaglycerol.

14. The composition as claimed in claim 13, wherein the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol comprises glycerol.

15. The composition as claimed in claim 1, wherein the alkyl neo-monocarboxylic acid is represented by a compound of formula II: ##STR00010## wherein: R.sup.2 represents hydrogen or a C.sub.1 to C.sub.18 alkyl group, R.sup.3 and R.sup.4 each independently represent a C.sub.1 to C.sub.18 alkyl group, and the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 28.

16. The composition as claimed in claim 15, wherein R.sup.2 in a compound of formula II is a C.sub.1 to C.sub.18 alkyl group.

17. The composition as claimed in claim 15, wherein R.sup.2, R.sup.3 and R.sup.4 each independently represent at each occurrence a linear or branched acyclic C.sub.1 to C.sub.12 alkyl group.

18. The composition as claimed in claim 15, wherein at least one of R.sup.2, R.sup.3 and R.sup.4 represents a branched chain alkyl group.

19. The composition as claimed in claim 15, wherein the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 8.

20. The composition as claimed in claim 15, wherein the alkyl neo-monocarboxylic acid comprises one or more neo-decanoic acids and the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is 8.

21. The composition as claimed in claim 1, wherein the fuel oil additive (A) comprises a compound represented by formula IIIA, IIIB, IIIC, IIID or IIIE: ##STR00011## wherein R.sup.2 represents hydrogen or a C.sub.1 to C.sub.18 alkyl group, R.sup.3 and R.sup.4 each independently represent a C.sub.1 to C.sub.18 alkyl group, and the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 28.

22. The composition as claimed in claim 1, wherein the fuel oil additive (A) is present in an amount of less than 1000 ppm by mass based on the total mass of the fuel oil composition.

23. The composition as claimed in claim 1, further including an antistatic additive (B) present in a minor amount based on the total mass of the fuel oil composition.

24. The composition as claimed in claim 23, wherein the antistatic additive (B) comprises a two-component mixture of a polysulfone and a polymeric polyamine reaction product.

25. A method comprising using a fuel oil additive (A) as an additive, in an effective minor amount, in a middle distillate fuel oil having a sulphur content of less than or equal 0.2 weight %, based on the total weight of the middle distillate fuel oil, to enhance the lubricity performance of said middle distillate fuel oil, wherein the a fuel oil additive (A) comprises: an ester of an alkyl neo-monocarboxylic acid having a total number of from 5 to 30 carbon atoms, and an aliphatic acyclic (C.sub.2 to C.sub.18) alkanol having a total number of from 2 to 18 carbon atoms and a total number of from 2 to 8 hydroxyl groups, wherein said aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes one or more alkyl chain(s) and each of said one or more alkyl chain(s) may optionally be interrupted by one or more oxygen atom(s).

26. A method comprising using a fuel oil additive (A) and an anti-static additive (B) as a combination of additives, in an effective minor amount, in a middle distillate fuel oil having a sulphur content of less than or equal 0.2 weight %, based on the total weight of the middle distillate fuel oil, to increase the electrical conductivity of said middle distillate fuel oil and maintain the electrical conductivity of said middle distillate fuel at a substantially constant level for an extended period of time, wherein the fuel oil additive (A) comprises: an ester of an alkyl neo-monocarboxylic acid having a total number of from 5 to 30 carbon atoms, and an aliphatic acyclic (C.sub.2 to C.sub.18) alkanol having a total number of from 2 to 18 carbon atoms and a total number of from 2 to 8 hydroxyl groups, wherein said aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes one or more alkyl chain(s) and each of said one or more alkyl chain(s) may optionally be interrupted by one or more oxygen atom(s).

27. A method comprising using the fuel oil additive (A) as an additive, in an effective minor amount, in a middle distillate fuel oil having a sulphur content of less than or equal 0.2 weight %, based on the total weight of the middle distillate fuel oil, to reduce the wear rate in a fuel supply system of a combustion apparatus employing said middle distillate fuel oil, wherein the fuel oil additive (A) comprises: an ester of an alkyl neo-monocarboxylic acid having a total number of from 5 to 30 carbon atoms, and an aliphatic acyclic (C.sub.2 to C.sub.18) alkanol having a total number of from 2 to 18 carbon atoms and a total number of from 2 to 8 hydroxyl groups, wherein said aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes one or more alkyl chain(s) and each of said one or more alkyl chain(s) may optionally be interrupted by one or more oxygen atom(s).

28. A fuel additive composition for a middle distillate fuel oil having a sulphur content of 0.2% by weight or less, comprising a fuel additive (A) which is a compound represented by formula IIIA, IIIB, IIIC, IIID or IIIE of claim 21.

29. The fuel additive composition as claimed in claim 28, wherein the composition further includes an inert organic solvent in a minor amount, and wherein fuel Additive (A) is present in a major amount of the composition.

30. The fuel additive composition as claimed in claim 28, wherein fuel additive (A) has a viscosity of less than or equal to 10000 cSt when measured at 0 C.

31. The fuel additive composition as claimed in claim 29 wherein fuel additive (A) has a viscosity of less than or equal to 10000 cSt when measured at 0 C.

32. The composition as claimed in claim 3, wherein R.sup.1 represents an aliphatic acyclic alkyl straight chain having from 1 to 8 total number of carbon atoms.

33. The composition as claimed in claim 3, wherein R.sup.1 represents an aliphatic acyclic alkyl straight chain having from 1 to 4 total number of carbon atoms.

34. The composition as claimed in claim 5, wherein R.sup.1 represents an aliphatic acyclic alkyl straight chain having from 1 to 8 total number of carbon atoms.

35. The composition as claimed in claim 5, wherein R.sup.1 represents an aliphatic acyclic alkyl straight chain having from 1 to 4 total number of carbon atoms.

36. The composition as claimed in claim 21, wherein the fuel oil additive (A) comprises a compound represented by formula IIIA or IIIB.

37. A fuel additive composition for a middle distillate fuel oil having a sulphur content of 0.2% by weight or less, comprising a fuel additive (A) which is a compound represented by formula IIIA, IIIB, IIIC, IIID or IIIE of claim 21.

38. A fuel additive composition for a middle distillate fuel oil having a sulphur content of 0.2% by weight or less, comprising a fuel additive (A) which is a compound represented by formula IIIA or IIIB of claim 21.

39. The composition as claimed in claim 1, further including an antistatic additive (B) present at less than or equal to 10 ppm by mass based on the total mass of the fuel oil composition.

40. The composition as claimed in claim 15, wherein R.sup.2, R.sup.3 and R.sup.4 each independently represent at each occurrence a linear or branched acyclic C.sub.1 to C.sub.6 alkyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION

Fuel Oil Additive (A)

[0090] The fuel oil additive (A) represents an ester of an alkyl neo-monocarboxylic acid, as defined and identified herein, and an aliphatic acyclic (C.sub.2 to C.sub.18) alkanol, as defined and identified herein. The mono-ester is most preferred. Suitably, fuel oil additive (A) may be obtained by an esterification reaction of said alkyl neo-monocarboxylic acid (or reactive derivative thereof) and said aliphatic acyclic (C.sub.2 to C.sub.18) alkanol. [0091] (i) Aliphatic acyclic (C.sub.2 to C.sub.18) alkanol

[0092] The aliphatic acyclic (C.sub.2 to C.sub.18) alkanol has a total number of from 2 to 18 carbon atoms and a total number of from 2 to 8 hydroxyl functional groups. The aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes one or more alkyl chains(s), wherein said one or more alkyl chains are terminated and/or substituted with hydroxyl functional groups, so that the total number of hydroxyl functional groups present in the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol is from 2 to 8.

[0093] Suitably, the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol may be considered to represent a polyol as it includes 2 or more hydroxyl functional groups.

[0094] Suitably, the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes at least one primary hydroxyl functional group. In other words, one or more of said alkyl chain(s) of the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol is terminated with at least one primary hydroxyl functional group, i.e.-CH2-OH group.

[0095] In some embodiments, the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol may include only primary hydroxyl functional groups, i.e. the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes from 2 to 8 hydroxyl functional groups and each of said hydroxyl functional group(s) represents a primary hydroxyl functional group.

[0096] Examples of aliphatic acyclic (C.sub.2 to C.sub.18) alkanols having only primary hydroxyl functional groups include: (C.sub.2 to C.sub.18) alkylene glycols, such as ethylene glycol and neopentyl glycol; (C.sub.2 to C.sub.18) alkylene polyols, such as 1,3-propanediol and 1,4-butanediol; polyethylene glycols, such as diethylene glycol and triethylene glycol; pentaerythritol and pentaerythritol derivatives, such as dipentaerythritol and tripentaerythritol; and, trimethylolpropane and trimethylolpropane derivatives such as di-trimethylolpropane.

[0097] In alternative embodiments, the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol may include a combination of one or more primary hydroxyl functional group(s) and one or more secondary hydroxyl functional group(s).

[0098] Examples of aliphatic acyclic (C.sub.2 to C.sub.18) alkanols which comprise a combination of one or more primary hydroxyl functional group(s) and one or more secondary hydroxyl functional group(s) include: (C.sub.2 to C.sub.18) alkylene polyols, such as 1,2-propanediol and 1,3-butanediol; glycerol and derivatives of glycerol, such as diglycerol, triglycerol and hexaglycerol.

[0099] In a preferred embodiment, the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol comprises a combination of one or more primary hydroxyl functional group(s) and one or more secondary hydroxyl functional group(s). Preferably, the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol having a combination of primary and secondary hydroxyl functional groups comprises glycerol and derivatives of glycerol, such as diglycerol, triglycerol and hexaglycerol, especially glycerol.

[0100] Suitably, the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol does not include a tertiary hydroxyl functional group.

[0101] Suitably, the one or more alkyl chains present in said aliphatic acyclic (C.sub.2 to C.sub.18) alkanol may each independently optionally be interrupted by an oxygen atom. Accordingly, the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol may include one or more oxyalkylenyl moieties, and thus the term aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes aliphatic acyclic (C.sub.2 to C.sub.18) ether-alkanols having a total number of from 2 to 18 carbon atoms and a total number of from 2 to 8 hydroxyl groups. Examples of aliphatic acyclic (C.sub.2 to C.sub.18) ether-alkanols include: derivatives of glycerol, such as diglycerol, triglycerol and hexaglycerol; polyalkylene glycols, such as diethylene glycol, triethylene glycol, dipropylene glycol; derivatives of pentaerythritol, such as dipentaerythritol and tripentaerythritol; and, derivatives of trimethylolpropane such as di-trimethylolpropane.

[0102] In a preferred embodiment, each of said one or more alkyl chains present in said aliphatic acyclic (C.sub.2 to C.sub.18) alkanol is not interrupted by an oxygen atom.

[0103] Suitably, the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol has a total number of from 2 to 8, preferably 3 to 8, more preferably 3 to 6, more preferably 3 or 4, most preferably 3, hydroxyl functional groups.

[0104] The most preferred aliphatic acyclic (C.sub.2 to C.sub.18) alkanol is glycerol.

[0105] Suitably, the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol having a total number of from 2 to 18 carbon atoms and a total number of from 2 to 8 hydroxyl groups, which aliphatic acyclic (C.sub.2 to C.sub.18) alkanol optionally includes one or more oxyalkylenyl moieties, may be represented by a compound of formula I:

##STR00001## [0106] wherein: R.sup.1 represents an aliphatic acyclic alkyl chain having a total number of 1 to 17 carbon atoms, which aliphatic acyclic alkyl chain is optionally interrupted by one or more oxygen atoms; (CH.sub.2OH).sub.m represents a primary hydroxyl functional group and m is an integer from 1 to 3; (CH.sub.2OH), represents a primary hydroxyl functional group and n is an integer from 0 to 3; and, (OH) s represents a secondary hydroxyl functional group and s is an integer from 0 to 6; and, the sum of m, n and s is an integer from 2 to 8.

[0107] It will be appreciated that the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes at least one primary hydroxyl functional group(s), i.e. m in a compound of formula I is an integer from 1 to 3, and the total number of hydroxyl functional groups present in a compound of formula I is from 2 to 8.

[0108] In some embodiments, the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes only primary hydroxyl functional groups, e.g. m and n in a compound of formula I is each independently an integer from 1 to 3 and s is 0. Examples of such aliphatic acyclic (C.sub.2 to C.sub.18) alkanols including only primary hydroxyl functional groups are identified herein.

[0109] Suitably, when the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes only primary hydroxyl functional groups m and n in a compound of formula I is each independently an integer from 1 to 3, s is zero, and the total number of hydroxyl functional groups present in a compound of formula I is from 2 to 6. In an embodiment, when the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes only primary hydroxyl functional groups, the total number of hydroxyl functional groups present in a compound of formula I is 2, e.g. both m and n in a compound of formula I is 1 and s is zero, or m is 2, n and s is zero in a compound of formula I.

[0110] In some embodiments, the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes a combination of one or more primary hydroxyl functional groups and one or more secondary hydroxyl functional groups, i.e. s in a compound of formula I is an integer from 1 to 6, m in a compound of formula I is an integer from 1 to 3, and n in a compound of formula I is an integer from 0 to 3, such that the total number of hydroxyl functional groups present in a compound of formula I is from 2 to 8.

[0111] It is preferred that the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes one or more secondary hydroxyl group(s) in addition to said primary hydroxyl functional group(s), i.e. s in a compound of formula I is an integer from 1 to 6, m in a compound of formula I is an integer from 1 to 3, and n in a compound of formula I is an integer from 0 to 3, such that the total number of hydroxyl functional groups present in a compound of formula I is from 2 to 8. Examples of aliphatic acyclic (C.sub.2 to C.sub.18) alkanols having a combination of primary and secondary hydroxyl functional groups are identified herein.

[0112] Suitably, when the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes a combination of primary and secondary hydroxyl functional groups m and n in a compound of formula I is each independently an integer from 1 to 3, s is an integer from 1 to 6, and the total number of hydroxyl functional groups present in a compound of formula I is from 2 to 8. Preferably, when the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes a combination of primary and secondary hydroxyl functional groups m and n in a compound of formula I each represents 1, s is an integer from 1 to 6, and the total number of hydroxyl functional groups present in a compound of formula Iis from 3 to 8. More preferably, when the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes a combination of primary and secondary hydroxyl functional groups m and n in a compound of formula I each represents 1, s is an integer from 1 to 3, and the total number of hydroxyl functional groups present in a compound of formula I is from 3 to 6. Most preferably, when the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes a combination of primary and secondary hydroxyl functional groups m, n and s in a compound of formula I each represents 1 and the total number of hydroxyl functional groups present in a compound of formula Iis 3.

[0113] Suitably, R.sup.1 in a compound of formula I represents one or more aliphatic acyclic alkyl chain(s) which chain(s) has a total number of from 1 to 17 carbon atoms, and which chain(s) is terminated with one or more primary hydroxyl functional group(s) and optionally substituted with one or more secondary hydroxyl functional group(s), such that the total number of hydroxyl functional groups present in a compound of formula I is from 2 to 8.

[0114] Suitably, the one or more aliphatic acyclic alkyl chains which R.sup.1 represents may form a single contiguous structure. Thus, R.sup.1 may define a linear alkyl chain structure or, where there are sufficient number of carbon atoms, a branched alkyl chain structure. Preferably, R.sup.1 represents an aliphatic acyclic alkyl straight chain having from 1 to 17 total carbon atoms.

[0115] Suitably R.sup.1 may represent an aliphatic acyclic alkyl chain having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17 carbon atoms in total. Suitably, the aliphatic acyclic alkyl chain which R.sup.1 represents may, when there are sufficient number of carbons atoms, be optionally interrupted by one or more oxygen atoms. Preferably, each of said aliphatic acyclic alkyl chain(s) which R.sup.1 represents is not interrupted by an oxygen atom.

[0116] Suitably, R.sup.1 represents an aliphatic acyclic alkyl chain having from 1 to 16, preferably 1 to 12, more preferably 1 to 10, even more preferably 1 to 8, even more preferably 1 to 6, even more preferably 1 to 4, total number of carbon atoms.

[0117] Suitably, R.sup.1 represents an aliphatic acyclic alkyl straight chain having from 1 to 16, preferably 1 to 12, more preferably 1 to 10, even more preferably 1 to 8, even more preferably 1 to 6, even more preferably 1 to 4, total number of carbon atoms.

[0118] Particularly preferred compounds of formula I include compounds wherein: [0119] (i) R.sup.1 represents CH; and, m, n and s each represent 1 (i.e. glycerol); [0120] (ii) R.sup.1 represents a C.sub.4 alkyl straight chain interrupted by a single oxygen atom, m and n each represent 1 and s represents 2 (e.g. diglycerol); [0121] (iii) R.sup.1 represents a C.sub.7 alkyl straight chain interrupted by two oxygen atoms, m and n each represent 1 and s represents 3 (e.g. triglycerol); and [0122] (iv) R.sup.1 represents a C.sub.16 alkyl straight chain interrupted by five oxygen atoms, m and n each represent 1 and s represents 6 (e.g. hexaglycerol).

[0123] The most preferred compound of formula I is where R.sup.1 represents CH; and, m, n and s each represent 1 (i.e. glycerol).

[0124] (ii) Alkyl neo-monocarboxylic acid

[0125] The alkyl neo-monocarboxylic acid may be defined as acetic acid which is substituted at the alpha carbon atom either with three alkyl groups (an a-trialkyl substituted acetic acid) or with two alkyl groups (an a-dialkyl substituted acetic acid). Preferably, the alkyl neo-monocarboxylic acid comprises acetic acid which is substituted at the alpha carbon atom with three alkyl groups (a-trialkyl substituted acetic acid).

[0126] Suitably, the alkyl neo-monocarboxylic acid has a total number of from 5 to 30, suitably 5 to 20, suitably 5 to 14, suitably 5 to 10, carbon atoms.

[0127] The alkyl neo-monocarboxylic acid may be represented by a compound of formula II:

##STR00002##

wherein: R.sup.2 represents hydrogen or a C.sub.1 to C.sub.18 alkyl group, R.sup.3 and R.sup.4 each independently represent a C.sub.1 to C.sub.18 alkyl group, and the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 28.

[0128] Preferably, the alkyl neo-monocarboxylic acid comprises an a-trialkyl substituted acetic acid which may be represented by a compound of formula II, wherein R.sup.2 represents a C.sub.1 to C.sub.18 alkyl group, R.sup.3 and R.sup.4 each independently represent a C.sub.1 to C.sub.18 alkyl group, and the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 28.

[0129] Suitably, the alkyl group which R.sup.2, R.sup.3 and R.sup.4 may each independently represent in a compound of formula II may be selected from a C.sub.1 to C.sub.18 alkyl group, which alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl and all structural isomers thereof. Suitably, the alkyl group which R.sup.2, R.sup.3 and R.sup.4 may each independently represent may be linear or branched, may be cyclic, part cyclic/acyclic, or acyclic.

[0130] Suitably, the alkyl group which R.sup.2, R.sup.3 and R.sup.4 may each independently represent in a compound of formula II comprises a linear or branched acyclic C.sub.1 to C.sub.18 alkyl group. Preferably, the alkyl group which R.sup.2, R.sup.3 and R.sup.4 may each independently represent comprises a linear or branched acyclic C.sub.1 to C.sub.12, more preferably C.sub.1 to C.sub.10, even more preferably C.sub.1 to C.sub.8, even more preferably C.sub.1 to C.sub.6, alkyl group.

[0131] Suitably, at least one of the alkyl groups which R.sup.2, R.sup.3 and R.sup.4 may each independently represent in a compound of formula II comprises a branched acyclic C.sub.1 to C.sub.12, more preferably C.sub.1 to C.sub.10, even more preferably C.sub.1 to C.sub.8, even more preferably C.sub.1 to C.sub.6, alkyl group.

[0132] Suitably, the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together in a compound of formula II is from 3 to 18, more preferably from 3 to 12, even more preferably from 3 to 8.

[0133] The most preferred alkyl neo-monocarboxylic acid is neo-decanoic acid which may be represented by a compound of formula II, wherein R.sup.2, R.sup.3 and R.sup.4 are as defined for a compound of formula II and R.sup.2, R.sup.3 and R.sup.4 together in a compound of formula II is 8.

[0134] Suitable alkyl neo-monocarboxylic acids comprise the a-trialkyl substituted acetic acids such as neo-pentanoic, neo-hexanoic acid, neo-heptanoic acid, neo-octanoic acid, neo-nonanoic acid, neo-decanoic acid and neo-tetradecanoic acid, preferably neo-pentanoic acid, neo-nonanoic acid and neodecanoic acid, especially neo-decanoic acid.

[0135] Suitably, the alkyl-neo-monocarboxylic acid comprises a compound of formula II wherein: R.sup.2 represents methyl or ethyl; R.sup.3 represents C.sub.1 to C.sub.4 acyclic alkyl group; R.sup.4 represents C.sub.1 to C.sub.10 acyclic alkyl group; and, the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 16. Preferably, the alkyl-neo-monocarboxylic acid comprises a compound of formula II wherein: R.sup.2 represents methyl or ethyl; R.sup.3 represents C.sub.1 to C.sub.4 acyclic alkyl group; R.sup.4 represents C.sub.1 to C.sub.6 acyclic alkyl group; and, the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 12. More preferably, the alkyl-neo-monocarboxylic acid comprises a compound of formula II wherein: R.sup.2 represents methyl; R.sup.3 represents C.sub.1 to C.sub.3 acyclic alkyl group; R.sup.4 represents C.sub.1 to C.sub.6 acyclic alkyl group; and, the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 8, preferably 8.

[0136] Suitably, the alkyl neo-monocarboxylic acid(s) as identified herein are commercially available from suppliers such as ExxonMobil Product Solutions (22777 Springwoods Village Parkway Spring, Texas 77389-1425, USA) Chemical and Hexion Inc. Administration (180E Broad Street, Columbus, Ohio 43215, USA). The alkyl neo-monocarboxylic acids may also be prepared by the Koch process from olefins, carbon monoxide and water as described by H. Koch in Brenstaff. Chem. 36, 321 (1955). Further synthetic procedures for preparing the alkyl neo-monocarboxylic acid(s) can be found in UK patents GB 960,011 and GB 998,974, and U.S. Pat. No. 3,349,107.

[0137] Suitably, the fuel oil additive which comprises an ester of an alkyl neo-monocarboxylic acid, as defined and identified herein, and an aliphatic acyclic (C.sub.2 to C.sub.18) alkanol, as defined and identified herein, may be represented by a compound of formula III:

##STR00003## [0138] wherein: R.sup.1, m, n an s are as defined for a compound of formula 1; [0139] X, Y and Z each independently represent an alkyl neo-monocarboxylic acid moiety of formula IV:

##STR00004##

[0140] R.sup.2, R.sup.3, and R.sup.4 are each as defined for a compound of formula II.

[0141] Suitably, preferred additive compounds of formula III comprise additive compounds derived from glycerol and may be represented by compounds of formulae IIIA, IIIB, IIIC, MID and IIIE:

##STR00005##

wherein R.sup.2, R.sup.3, and R.sup.4 are each as defined for a compound of formula II.

[0142] Suitably, in the compounds of formulae IIIA, IIIB, IIIC, IIID and IIIE, R.sup.2 represents methyl or ethyl; R.sup.3 represents C.sub.1 to C.sub.4 acyclic alkyl group; R.sup.4 represents C.sub.1 to C.sub.10 acyclic alkyl group; and, the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 16. Suitably, in the compounds of formulae IIIA, IIIB, IIIC, IIID and IIIE, R.sup.2 represents methyl or ethyl; R.sup.3 represents C.sub.1 to C.sub.4 acyclic alkyl group; R.sup.4 represents C.sub.1 to C.sub.6 acyclic alkyl group; and, the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 12. Suitably, in the compounds of formulae IIIA, IIIB, IIIC, IIID and IIIE, R.sup.2 represents methyl; R.sup.3 represents C.sub.1 to C.sub.3 acyclic alkyl group; R.sup.4 represents C.sub.1 to C.sub.6 acyclic alkyl group; and, the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 8. It is preferred in the compounds of formulae IIIA, IIIB, IIIC, IIID and IIIE that the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is 8.

[0143] Suitably, the fuel oil additive preferably comprises the monoester and compounds of formulae IIIA and IIIB are particularly preferred fuel oil additives, especially compounds of formula IIIB.

[0144] (iii) Preparation of fuel oil additive (A)

[0145] The fuel oil additive may be synthesized by standard chemical esterification techniques well known to those skilled in the art and exemplified herein. For example, the alkyl neo-monocarboxylic acid may be converted to an activated acid derivative, e.g. converted to the corresponding acid halide, and the activated acid derivative subsequently condensed with the appropriate aliphatic acyclic (C.sub.2 to C.sub.18) alkanol.

[0146] A preferred synthetic route for preparing the fuel oil additive comprises converting the alkyl neo-monocarboxylic acid to the corresponding glycidyl ester derivative, for example by reacting the alkyl neo-monocarboxylic acid with epichlorohydrin (see for example US 2014/0316030A), and then subsequent acid catalysed hydrolysis of the epoxide ring to form the glycerol ester derivative.

[0147] It will be appreciated, and common general knowledge to those skilled in the art, that various protection and deprotection group strategies may be employed during the synthetic procedures to maximize the yield of the target ester obtained from the appropriate aliphatic acyclic (C.sub.2 to C.sub.18) alkanol and alkyl neo-monocarboxylic acid.

Antistatic Additive (B)

[0148] Suitably, the anti-static additive (B) comprises an olefin polysulfone and a polymeric polyamine reaction product of epichlorohydrin and an aliphatic primary monoamine or an N-aliphatic hydrocarbyl alkylene diamine, or the sulfonic acid salt of the polymeric polyamine reaction product.

[0149] Suitably, the weight average molecular weight of the polysulfone is in the range of 10,000 to 1,500,000, suitably in the range of 50,000 to 900,000, for example 100,000 to 500,000.

[0150] Suitably the weight ratio of polysulfone component to polymeric polyamine component is in the range of 100:1 to 1:100.

[0151] Suitably, the olefins useful for the preparation of the polysulfones have from 6 to 20 carbon atoms, suitably 6 to 18 carbon atoms. Particularly preferred is 1-decene polysulfone. The preparation of these materials is known in the art as described for example in U.S. Pat. No. 3,917,466.

[0152] The polymeric polyamine component may be prepared by heating an amine with epichlorohydrin in a molar proportion in the range of 1:1 to 1:1.5 and at a temperature of 50 C. to 100 C. Suitable aliphatic primary amines have from 8 to 24 carbon atoms, suitably from 8 to 12 carbon atoms. The aliphatic group is preferably an alkyl group. If an N-aliphatic hydrocarbyl alkylene diamine is used suitably the aliphatic hydrocarbyl group will have from 8 to 24 carbon atoms and will preferably be an alkyl group. Suitably the alkylene group will have 2 to 6 carbon atoms. The preferred N-aliphatic hydrocarbyl alkylene diamine is an N-aliphatic hydrocarbyl 1,3-propylenediamine. These materials are commercially available, one preferred example being the polymeric reaction product of N-tallow-1,3-propylene diamine with epichlorohydrin. Preferably the polymeric polyamine reaction product will have a degree of polymerisation of about 2 to 20. These materials are also described in U.S. Pat. No. 3,917,466.

[0153] Suitably, the polymeric polyamine reaction product is in the form of a sulfonic acid salt. Useful are oil-soluble sulfonic acids such as alkane sulfonic acids or aryl sulphonic acids. A preferred example is dodecyl benzene sulphonic acid.

[0154] The anti-static additive (B) is most preferably the commercial product STADIS 450 available from Innospec Inc., which the applicants understand and intend to be described by the foregoing definition of component (B). STADIS 425, which is believed to be a diluted version of STADIS 450 is also suitable.

[0155] Suitably, other antistatic additive(s) B include for example Cestoil Northshore ST 3425, Dorf Ketal SR 1795 and Afton AvGuard SDA which are each believed to contain sulfonic acid compounds, such as dodecylbenzene sulfonic acid or dinonylnaphthalene sulfonic acid.

[0156] Suitably, the weight: weight ratio of the fuel additive (A) to the anti-static additive (B) in the fuel oil composition is from 5:1 to 1000:1, preferably from 50:1 to 500:1, for example from 100:1 to 500:1.

Fuel Oil Additive Composition

[0157] As discussed herein, the fuel oil additive finds utility in low-sulphur content fuel oils. Advantageously, the fuel oil additive typically exhibits a desirable low viscosity, especially at low ambient temperatures (e.g. at or below 0 C.), which may facilitate addition of neat additive direct to a low-sulphur content fuel oil, particularly at such low ambient temperatures. Accordingly, the fuel oil additive may be supplied neat, or indeed in a highly concentrated form, for addition to a low-sulphur content fuel oil, thereby reducing transportation costs associated with the supply of the additive and reducing top-treat rate requirements.

[0158] If convenient, the fuel oil additive may be in the form of an additive composition (referred to as an additive concentrate). The additive composition may additionally comprise an inert organic liquid which acts to dissolve, solubilize or otherwise disperse the components of the additive composition. The resulting additive composition may be more convenient to use or store and may be easier to meter into fuel oil. Suitable inert organic liquids include hydrocarbon solvents such as naphtha, kerosene, diesel and heater oil, aromatic hydrocarbons such as those sold under the SOLVESSO trade name, alcohols, ethers and other oxygenates and paraffinic hydrocarbons such as hexane, pentane and isoparaffins. The organic liquid should be miscible with the fuel oil in the sense that it is capable of being physically mixed with fuel oil to form either a solution or a dispersion in the fuel oil. The liquid will be chosen having regard to its compatibility with both the additive composition and the fuel oil in question, and is a matter of routine choice for one skilled in the art. Suitably, the additive composition may suitably comprise less than 50, typically lees than 40, suitably less than 30, suitably less than 20, mass % by of inert organic liquid, the remainder being the fuel oil additive (A) and optionally antistatic additive (B) and any additional optional additives required to fulfill different purposes within the fuel oil. Some optional additional additives are described hereinbelow.

Low-Sulphur Content Fuel Oil

[0159] The fuel oil may be a petroleum-based fuel oil, especially a middle distillate fuel oil. Such distillate fuel oils generally boil within the range of from 110 C. to 500 C., e.g. 150 C. to 400 C. The invention is applicable to middle distillate fuel oils of all types, including the distillates having a 90%- 20% boiling temperature difference, as measured in accordance with ASTM D-86, of 50 C. or more.

[0160] The fuel oil may comprise atmospheric distillate or vacuum distillate, cracked gas oil, or a blend in any proportion of straight run and thermally and/or catalytically cracked distillates. The most common petroleum distillate fuels are kerosene, jet fuels, diesel fuels, heating oils and heavy fuel oils. The heating oil may be a straight atmospheric distillate, or may also contain vacuum gas oil or cracked gas oil or both. The fuels may also contain major or minor amounts of components derived from the Fischer-Tropsch process. Fischer-Tropsch fuels, also known as FT fuels, include those that are described as gas-to-liquid fuels, coal and/or biomass conversion fuels. To make such fuels, syngas (CO+H2) is first generated and then converted to normal paraffins and olefins by a Fischer-Tropsch process. The normal paraffins may then be modified by processes such as catalytic cracking/reforming or isomerisation, hydrocracking and hydroisomerisation to yield a variety of hydrocarbons such as iso-paraffins, cyclo-paraffins and aromatic compounds. The resulting FT fuel can be used as such or in combination with other fuel components and fuel types such as those mentioned in this specification.

[0161] The invention is also applicable to fuel oils containing fatty acid alkyl esters made from oils derived from animal or vegetable materials, often called biofuels or biodiesels. Biofuels are believed by some to be less damaging to the environment on combustion and are obtained from a renewable source. Other forms of biofuels are also included in the invention such as hydrogenated vegetable oil (HVO) and oil derived from alternative sources such as algae.

[0162] Animal or vegetable sources of suitable oils are rapeseed oil, canola oil, coriander oil, soyabean oil, cottonseed oil, sunflower oil, castor oil, olive oil, peanut oil, maize oil, almond oil, palm kernel oil, coconut oil, mustard seed oil, jatropha oil, beef tallow and fish oils. Further examples include fuel oils derived from corn, jute, sesame, shea nut, ground nut and linseed oil and may be derived therefrom by methods known in the art. Rapeseed oil, which is a mixture of fatty acids partially esterified with glycerol is available in large quantities and can be obtained in a simple way by pressing from rapeseed. Recycled oils such as used kitchen oils are also suitable.

[0163] As alkyl esters of fatty acids, consideration may be given to the following, for example as commercial mixtures: the ethyl, propyl, butyl and especially methyl esters of fatty acids with 12 to 22 carbon atoms, for example of lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, elaidic acid, petroselic acid, ricinoleic acid, elaeostearic acid, linoleic acid, linolenic acid, eicosanoic acid, gadoleic acid, docosanoic acid or erucic acid, which have an iodine number from 50 to 150, especially 90 to 125. Mixtures with particularly advantageous properties are those which contain mainly, i.e. to at least 50 wt % methyl esters of fatty acids with 16 to 22 carbon atoms and 1, 2 or 3 double bonds. The preferred alkyl esters of fatty acids are the methyl esters of oleic acid, linoleic acid, linolenic acid and erucic acid.

[0164] Commercial mixtures of the stated kind are obtained for example by cleavage and esterification of animal and vegetable fats and oils by their transesterification with lower (ca. C.sub.1 to C.sub.6) aliphatic alcohols. For production of alkyl esters of fatty acids it is advantageous to start from fats and oils which contain low levels of saturated acids, less than 20%, and which have an iodine number of less than 130. Blends of the following esters or oils are suitable, e.g. rapeseed, sunflower, canola, coriander, castor, soyabean, peanut, cotton seed, beef tallow etc. Alkyl esters of fatty acids based on certain varieties of rapeseed oil having more than 80 wt % of unsaturated fatty acids with 18 carbon atoms, are particularly suitable.

[0165] Whilst all of the above biofuels may be used as fuel oils in this invention, preferred are vegetable oil derivatives, of which particularly preferred biofuels are alkyl ester derivatives of rapeseed oil, cottonseed oil, soyabean oil, sunflower oil, olive oil, or palm oil, rapeseed oil methyl ester being especially preferred. Such fatty acid methyl esters are often referred to in the art as FAME.

[0166] Biofuels are commonly used in combination with petroleum-derived fuel oils. The present invention is also applicable to mixtures of biofuel and petroleum-derived fuels in any ratio. Such fuels are often termed Bx fuels where x represents the percentage by weight of biofuel in the biofuel-petroleum blend. Examples include fuels where x is 2 or above, preferably 5 or above, for example up to 10, 25, 50, or 95. Current German legislation is framed around B7 biofuels. Preferably the biofuel component in such Bx base fuels comprises fatty acid alkyl esters, most preferably fatty acid methyl esters.

[0167] The invention is also applicable to pure biofuels. In one embodiment therefore, the fuel oil comprises essentially 100% by weight of a fuel derived from a plant or animal source, preferably essentially 100% by weight of fatty acid alkyl esters, most preferably fatty acid methyl esters.

[0168] Examples of jet fuels include fuels which boil in the temperature range from about 65 C. to about 330 C. and are marketed under designations such as JP-4, JP-5, JP-7, JP-8, Jet A and Jet A-1. JP-4 and JP-5 are specified in the US Military Specification MIL-T-5624-N and JP-8 in the US Military Specification MIL-T-83133-D. Jet A, Jet A-1 and Jet B are specified in ASTM D1655.

[0169] The fuel oil, whether petroleum or vegetable or animal-derived, or synthetic has a low sulphur content. Typically, the sulphur content of the fuel will be less than 1000wppm (parts per million by weight), such as less than 500wppm. Preferably, the sulphur content of the fuel will be less than 100wppm, for example, less than 50wppm, such as less than 20wppm or less than 10wppm.

[0170] In the untreated (i.e. additive-free) state, such fuel oils will normally have low electrical conductivities, usually less than 10 pSm.sup.1, such as around 2-5 pSm.sup.1.

[0171] In an embodiment, a preferred fuel oil comprises diesel fuel (which includes biodiesel fuel).

[0172] The amount of fuel oil additive added to the fuel oil will depend on the inherent electrical conductivity of the fuel oil and the desired target electrical conductivity to be reached. Preferably however, the fuel oil additive is present in the fuel oil in an amount of between 5 and 1000, preferably in an amount of between 5 and 500, more preferably between 5 and 200, parts per million by mass based on the total mass of the fuel oil composition on an active ingredient basis.

[0173] As will be understood, the fuel oil additive may be added to the fuel oil in the form of the additive composition (referred to as an additive concentrate) described hereinabove. In this case, the amount of additive composition used will be with regard to the active ingredient (a.i.) content of the fuel oil additive. For example the addition to a fuel oil of 200 ppm by mass of a concentrate which contains 20% by weight of carrier fluid will provide the fuel oil with 160 ppm by mass of fuel oil additive (A) on an active ingredient basis.

[0174] Suitably, the present invention provides the use of the fuel oil additive or an additive composition (concentrate) comprising the fuel oil additive to a middle distillate fuel oil having a sulphur content of 0.2% by weight or less.

[0175] Further additives commonly added to fuel oils may also be employed together with the fuel oil additive (A). Such further additives may be introduced separately into the fuel oil but may also be combined together in an additive concentrate as described hereinabove. Classes of additives will be known to those skilled in the art and the following examples are not intended to be an exhaustive list.

[0176] One class are additives capable of altering the low-temperature properties of fuel oils. Suitable materials are well known and include flow-improvers such as ethylene-unsaturated ester copolymers and terpolymers, for example, ethylene-vinyl acetate copolymers, ethylene-vinyl 2-ethyl hexanoate copolymers and ethylene-vinyl neodecanoate copolymers, ethylene-vinyl acetate-vinyl 2-ethyl hexanoate terpolymers, ethylene-vinyl acetate-vinyl neononanoate terpolymers, ethylene-vinyl acetate-vinyl neodecanoate terpolymers; comb polymers such as fumarate-vinyl acetate copolymers polyacrylate and polymethacrylate polymers, including those containing nitrogen or copolymerised with nitrogen-containing monomers; hydrocarbon polymers such as hydrogenated polybutadiene copolymers, ethylene/1-alkene copolymers, and similar polymers. Also suitable are additives known in the art as wax anti-settling additives (WASA).

[0177] Other classes of additives are detergents and dispersants, commonly hydrocarbyl-substituted succinimide species; cetane improvers; metal-containing additives used to improve the regeneration of particulate traps attached to the exhaust systems of some diesel engines; lubricity enhancers; other electrical conductivity improvers; dyes and other markers; and anti-oxidants. The present invention contemplates the addition of such further additives; their application in terms of treat rate being known to those skilled in the art. In a preferred embodiment the additive composition of the invention are combined with, or used in combination with, one or both of an ethylene-unsaturated ester copolymer and a wax anti-settling additive. Particularly preferred ethylene-unsaturated ester copolymers are ethylene-vinyl acetate copolymers ethylene-vinyl acetate-vinyl 2-ethyl hexanoate terpolymers, ethylene-vinyl acetate-vinyl neononanoate terpolymers and ethylene-vinyl acetate-vinyl neodecanoate terpolymers. A particularly preferred wax anti-settling additive is the amide-amine salt formed by the reaction of phthalic anhydride with two molar proportions of di-hydrogenated tallow amine.

[0178] The invention further relates to: [0179] 1. A fuel oil composition comprising a major amount of a middle distillate fuel oil having a sulphur content of 0.2% by weight or less, and a minor amount of a fuel oil additive comprising: [0180] (a) an ester of an alkyl neo-monocarboxylic acid having a total number of from 5 to 30 carbon atoms and an aliphatic acyclic (C.sub.2 to C.sub.18) alkanol having a total number of from 2 to 18 carbon atoms and a total number of from 2 to 8 hydroxyl groups, wherein said aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes one or more alkyl chain(s) and each of said one or more alkyl chain(s) may optionally be interrupted by one or more oxygen atom(s). [0181] 2. The composition as paragraphed in paragraph 1, wherein the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol is represented by a compound of formula I:

##STR00006##

wherein: R.sup.1 represents an aliphatic acyclic alkyl chain having a total number of 1 to 17 carbon atoms, which aliphatic acyclic alkyl chain is optionally interrupted by one or more oxygen atoms; (CH.sub.2OH).sub.m represents a primary hydroxyl functional group and m is an integer from 1 to 3; (CH.sub.2OH) n represents a primary hydroxyl functional group and n is an integer from 0 to 3; and, (OH) s represents a secondary hydroxyl functional group and s is an integer from 0 to 6; and, the sum of m, n and s is an integer from 2 to 8. [0182] 3. The composition as paragraphed in paragraph 2, wherein the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes only primary hydroxyl functional groups, and both m and n in a compound of formula I is each independently an integer from 1 to 3 and s is 0. [0183] 4. The composition as paragraphed in paragraph 3, wherein the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol is selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylolpropane, and di-trimethylolpropane. [0184] 5. The composition as paragraphed in paragraph 2, wherein the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol includes one or more secondary hydroxyl group(s) and one or more primary hydroxyl functional group(s), and s in a compound of formula I is an integer from 1 to 6, m in a compound of formula I is an integer from 1 to 3, and n in a compound of formula I is an integer from 0 to 3. [0185] 6. The composition as paragraphed in paragraph 5, wherein both m and n in a compound of formula I each represents 1, s is an integer from 1 to 3, and the total number of hydroxyl functional groups present in a compound of formula I is from 3 to 6. [0186] 7. The composition as paragraphed in any one of paragraphs 3 to 5, wherein R.sup.1 represents an aliphatic acyclic alkyl straight chain having from 1 to 16, preferably 1 to 12, more preferably 1 to 10, even more preferably 1 to 8, even more preferably 1 to 6, even more preferably 1 to 4, total number of carbon atoms. [0187] 8. The composition as paragraphed in any one of paragraphs 3 to 7, wherein the aliphatic acyclic alkyl chain which R.sup.1 represents is not interrupted by one or more oxygen atoms. [0188] 9. The composition as paragraphed in paragraph 2, wherein the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol represented by a compound of formula I is selected from glycerol, diglycerol, triglycerol and hexaglycerol. [0189] 10. The composition as paragraphed in paragraph 9, wherein the aliphatic acyclic (C.sub.2 to C.sub.18) alkanol comprises glycerol. [0190] 11. The composition as paragraphed in any one of the preceding paragraphs, wherein the alkyl neo-monocarboxylic acid is represented by a compound of formula II:

##STR00007##

wherein: R.sup.2 represents hydrogen or a C.sub.1 to C.sub.18 alkyl group, R.sup.3 and R.sup.4 each independently represent a C.sub.1 to C.sub.18 alkyl group, and the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 28. [0191] 12. The composition as paragraphed in paragraph 10, wherein R.sup.2 in a compound of formula II is a C.sub.1 to C.sub.18 alkyl group. [0192] 13. The composition as paragraphed in paragraph 11 or 12, wherein R.sup.2, R.sup.3 and R.sup.4 each independently represent at each occurrence a linear or branched acyclic C.sub.1 to C.sub.12, more preferably C.sub.1 to C.sub.10, even more preferably C.sub.1 to C.sub.8, even more preferably C.sub.1 to C.sub.6, alkyl group. [0193] 14. The composition as paragraphed in any one of paragraphs 11 to 13, wherein at least one of R.sup.2, R.sup.3 and R.sup.4 represents a branched chain alkyl group. [0194] 15. The composition as paragraphed in any one of paragraphs 11 to 14, wherein the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is from 3 to 8. [0195] 16. The composition as paragraphed in paragraph 11 to 15, wherein the alkyl neo-monocarboxylic acid comprises one or more neo-decanoic acids and the total number of carbon atoms of R.sup.2, R.sup.3 and R.sup.4 together is 8. [0196] 17. The composition as paragraphed in any one of the preceding paragraphs, wherein the fuel oil additive (A) comprises a compound represented by formula IIIA, IIIB, IIIC, IIID or IIIE, preferably a compound represented by formula IIIA or IIIB, wherein R.sup.2, R.sup.2 and R.sup.4 are each as defined for a compound of formula II in any one of paragraphs 11 to 16:

##STR00008## [0197] 18. The composition as paragraphed in any one of the preceding paragraphs, wherein the fuel oil additive (A) is present in an amount of less than 1000 ppm by mass based on the total mass of the fuel oil composition. [0198] 19. The composition as paragraphed in any one of the preceding paragraphs, further including an antistatic additive (B) present in a minor amount, preferably in an amount of less than or equal to 10 ppm by mass based on the total mass of the fuel oil composition. [0199] 20. The composition as paragraphed in paragraph 18, wherein the antistatic additive (B) comprises a two-component mixture of a polysulfone and a polymeric polyamine reaction product. [0200] 21. The use of a fuel oil additive (A), as defined in any one of paragraphs 1 to 17, as an additive, in an effective minor amount, in a middle distillate fuel oil having a sulphur content of less than or equal 0.2 weight %, based on the total weight of the middle distillate fuel oil, to enhance the lubricity performance of said middle distillate fuel oil. [0201] 22. The use of a fuel oil additive (A), as defined in any one of paragraphs 1 to 17, and an anti-static additive (B), as defined in paragraph 18 or 19, as a combination of additives, in an effective minor amount, in a middle distillate fuel oil having a sulphur content of less than or equal 0.2 weight %, based on the total weight of the middle distillate fuel oil, to increase the electrical conductivity of said middle distillate fuel oil and maintain the electrical conductivity of said middle distillate fuel at a substantially constant level for an extended period of time. [0202] 23. The use of a fuel oil additive (A), as defined in any one of paragraphs 1 to 17, as an additive, in an effective minor amount, in a middle distillate fuel oil having a sulphur content of less than or equal 0.2 weight %, based on the total weight of the middle distillate fuel oil, to reduce the wear rate in a fuel supply system of a combustion apparatus employing said middle distillate fuel oil. [0203] 24. A fuel additive composition for a middle distillate fuel oil having a sulphur content of 0.2% by weight or less, comprising a fuel additive (A) which is a compound represented by formula IIIA, IIIB, IIIC, IIID or IIIE, preferably a compound represented by formula IIIA or IIIB, as defined in paragraph 17. [0204] 25. The fuel additive composition as paragraphed in paragraph 23, wherein the composition further includes an inert organic solvent in a minor amount, and wherein fuel Additive (A) is present in a major amount of the composition. [0205] 26. The fuel additive composition as paragraphed in paragraph 23 or 24, wherein fuel additive (A) has a viscosity of less than or equal to 10000 cSt when measured at 0 C.

[0206] The invention will now be described by way of the following non-limiting examples.

Lubricity Performance Measurement Procedure

[0207] The lubricity of a fuel or fuel composition is measured using the High Frequency Reciprocating Rig (HFRR) test in accordance with ISO 12156 (2nd Edition, 2018) using a ball-on-plate reciprocating friction and wear test system available from PCS Instruments Ltd of Stanley Gardens, London. Lubricity performance is reported as average wear scar depth (um), where a reduced average wear scar indicates improved lubricity performance of a fuel.

Electrical Conductivity Performance Measurement Procedure

[0208] The electrical conductivity of a fuel or fuel composition is measured using the Standard Test Method for Electrical Conductivity of Aviation and Distillate Fuels in accordance with ASTM D2624-22 using an Emcee 1152 Digital Conductivity meter available from Emcee Electronics Inc. Conductivity performance is reported as picosiemen per meter (pSm.sup.1).

Viscosity Measurement Procedure

[0209] The viscosity measurement of an additive at a particular temperature is measured using an Anton Paar SVM 3001 Viscometer with a temperature ramping programme. All measurements are carried out with neat additive sample.

Diesel Fuels and Additives

[0210] Diesel Fuel 1 A low sulphur Swedish Class diesel fuel having the following characteristics: Density 818 kgm-3; Kv (40 C.) 2.04 cSt; Kv (20 C.) 3.07 cSt; Cetane number 51.5; Sulphur less than 0.0003 wt %.

[0211] Diesel Fuel 2 A low sulphur commercial diesel fuel (Carcal) having the following characteristics: Density 832 kgm-3; Kv (40 C.) 3.21 cSt; Kv (20 C.) 5.23 cSt; Cetane number 55.5; Sulphur less than 0.0034 wt %.

[0212] Additive A Known lubricity additive comprising a diglycol ester of dimerized C.sub.18 oleic acid (U.S. Pat. No. 3,287,273).

[0213] Additive B Glycerol neodecanoate additive synthesized in accordance with Example 2.

[0214] STADIS A static dissipator additive Stadis 450 available from Innospec Inc.

Example 1 Synthesis of Neodecanoic Acid Chloride

[0215] Neodecanoic acid (25 g, 0.145 mol) is cooled to 0 C. and thionyl chloride (75 ml, 3 vol), dimethyl formamide (1.165 ml, 0.0145 mol) are added dropwise. The resulting reaction mixture is stirred at room temperature for 4 h. After completion of the reaction, all the volatiles are removed on a rotary evaporator in-vacuo and co-evaporated with toluene (50 mL), to yield the title compound which is used immediately in Example 2 without further purification.

Example 2 Synthesis of Glycerol Neodecanoate (Additive B)

[0216] The title compound of Example 1, neodecanoic acid chloride (0.145 mol), is added dropwise to a solution of solketal (18.7 g, 0.142 mol), triethylamine (88 g, 0.87 mol) and DMAP (1.77 g, 0.0145 mol) in dry dichloromethane (125 mL) at 0 C., and the resulting reaction mixture is stirred at room temperature for 16 h. After completion of the reaction (thin layer chromatography (TLC)), the reaction mixture is concentrated under reduced pressure to remove all volatiles, quenched with cold water and then extracted with ethyl acetate (3300 ml). The combined organic extracts are washed with water (2500 mL), brine solution (500 mL), dried over sodium sulphate, filtered and concentrated under reduced pressure to yield (2,2-dimethyl-1,3-dioxolan-4-yl)methyl decanoate.

[0217] A solution of (2,2-dimethyl-1,3-dioxolan-4-yl)methyl decanoate (42 g, 0.1955 mol) in 80% acetic acid (200 mL) is stirred at 80 C. for 3 h. The reaction mixture is concentrated under reduced pressure and co-evaporated with toluene (2150 mL). The crude product is purified by column chromatography (silica gel 230-400 mesh: 25-30% ethyl acetate in petroleum ether) to afford the title compound as a pale-yellow liquid (26 g, 68%).

[0218] 1H-NMR (400 MHZ, DMSO-d6): 8 4.83 (br s, 1H), 4.62 (br s, 1H), 3.82-4.00 (m, 2H), 3.62-3.63 (m, 1H), 3.35-3.37 (m, 2H), 1.24 (m, 4H), 1.12 (m, 2H), 1.04-1.11 (m, 4H), 0.74-0.92 (m, 9H). Mol Formula: C.sub.13H2604, Mol. Weight: 246.35, Mass found: 247.2 (M+1) by LCMS: MM-ES+APCI.

Example 3 Lubricity Performance

[0219] The lubricity performance of Additive A in comparison to Additive B was determined using the Lubricity Performance Measurement Procedure described herein with Diesel Fuel 1. The results are presented in Table 1.

TABLE-US-00001 TABLE 1 Wear Scar Concentration Average (m) of Additive Additive Additive Fuel (ppm (a.i.)) A B Diesel 0 636.25 636.25 Fuel 1 50 652 604.5 100 565.8 520.75 150 357.5 356.75 200 360.75 401.5 250 324.25 404.5 300 318.5 331.5 400 314 302.75 500 176 298.75

[0220] The results in Table 1 evidence that Additive B is essentially equally as effective at improving the lubricity of a low sulphur containing diesel fuel as the commercially available Additive A. Further, Additive B exhibits improved performance at a dosage rate of from 50 to 350 ppm (a.i.) compared to Additive A.

Example 4 Electrical Conductivity Performance of Additive B

[0221] The electrical conductivity performance of Additive B (Glycerol Neodecanoate) in both Diesel Fuel 1 and Diesel Fuel 2 was determined in the presence of or absence of the static dissipator additive STADIS using the Electrical Conductivity Performance Measurement Procedure described herein. Each experiment was repeated in triplicate and the average electrical conductivity measurement (pSm.sup.1) is reported in Table 2.

TABLE-US-00002 TABLE 2 STADIS Additive B Average Conductivity Fuel (ppm (a.i.)) (ppm (a.i.)) (pSm.sup.1) Diesel 1.3 Fuel 1 1 157.0 200 2.3 1 200 109.7 Diesel 1.0 Fuel 2 1 97.7 200 1.0 1 200 75.3

[0222] The results in Table 2 evidence for both Diesel Fuel 1 and Diesel Fuel 2: [0223] Addition of STADIS alone to each diesel fuel provides an improvement in the electrical conductivity of the respective base fuel alone not including an additive. [0224] Addition of Additive B alone to each diesel fuel typically does not significantly affect the electrical conductivity of the respective base fuel alone not including an additive. [0225] Addition of a combination of STADIS and Additive B to each diesel fuel provides an improvement in the electrical conductivity of the base fuel alone not including an additive. [0226] The improved electrical conductivity of each respective diesel fuel including a combination of STADIS and Additive B lies between that achieved by STADIS alone and by Additive B alone but it is significantly greater than the required minimum conductivity limit of 25 pSm.sup.1 as specified by ASTM D975.

Example 5 Electrical Conductivity Performance of Combination of STADIS and Additive A or Additive B over Time

[0227] The electrical conductivity of Diesel Fuel 1 including a combination of additives comprising: (a) STADIS and Additive A; and, (b) STADIS and Additive B, was measured over a 28 day period to determine what effect, if any, the presence of each respective additive (Additive A or B) had on electrical conductivity of the fuel with respect to time in the presence of a known static dissipator (i.e. STADIS). Each experiment was repeated in triplicate and the average electrical conductivity measurement(s) (pSm.sup.1) are reported in Table 3.

TABLE-US-00003 TABLE 3 Treat Rate Stadis 450 Day 1 Day 28 Relative Decrease Fuel Additive (a.i. ppm) (a.i. ppm) (pS .Math. m.sup.1) (pS .Math. m.sup.1) (% relative to day 1) Diesel 0 0 1 120.33 84 30.19% Fuel 1 0 0 3 434 355.33 18.13% Additive A 200 1 120.33 63.67 47.09% 200 3 441.67 274.67 37.81% 400 1 91.67 42.67 53.45% 400 3 386.67 186 51.90% Additive B 200 1 77.67 75.33 3.01% 200 3 328 323.33 1.42% 400 1 82.33 74.33 9.72% 400 3 261.67 256 2.17%

[0228] The results in Table 3 evidence the following: [0229] In the presence of STADIS alone the electrical conductivity of the fuel decreases over 28 days (i.e. the effectiveness of STADIS decreases with time). Further, the observed relative decrease in conductivity of the fuel is dependent upon the initial concentration of STADIS present in the fuel. A 30% decrease in relative conductivity of the fuel over 28 days is observed when the fuel is treated with an initial STADIS concentration of 1 ppm, whereas a lower 18% decrease in relative conductivity of the fuel over 28 days is observed when the fuel is treated with a higher initial STADIS concentration of 3 ppm. [0230] When Additive A is used in combination with STADIS, the presence of Additive A does not significantly affect the initial electrical conductivity of the fuel after Day 1 compared with a comparable fuel including STADIS alone. However, with time (e.g. after a 28 day period), the presence of Additive A in combination with STADIS further significantly reduces the electrical conductivity of the fuel compared with a comparable fuel including STADIS alone (i.e. the presence of Additive A has a significant negative impact on the effectiveness of STADIS with time). Further, this significant negative impact on the effectiveness of STADIS with time due to the presence of Additive A is dependent upon the initial concentration of Additive A in the fuel. A higher initial concentration of Additive A in the fuel results in a larger decrease in electrical conductivity of the fuel with time (e.g. after 28 days) compared with a comparable fuel including a lower initial concentration of Additive A. Accordingly, when Additive A is used as a lubricity improver in combination with STADIS, then it is typically necessary to overtreat the fuel initially with an increased amount of the expensive STADIS additive so as to maintain the electrical conductivity of the fuel within required specification limits after a specified time period (e.g. after 28 days). [0231] When Additive B is used in combination with STADIS, the presence of Additive B results in a relatively minor decrease in the initial electrical conductivity of the fuel after Day 1 compared with a comparable fuel including STADIS alone. However with time (e.g. after a 28 day period), and completely unexpectedly, when Additive B is used in combination with STADIS, the presence of Additive B essentially stabilises the electrical conductivity of the fuel compared with either a comparable fuel including STADIS alone or a comparable fuel including a combination of Additive A and STADIS. Accordingly, the use of Additive B in combination with STADIS not only allows the electrical conductivity of the fuel to be improved compared to the untreated fuel alone but also enables the electrical conductivity of the treated fuel to be maintained at an essentially constant level with time (e.g. after 28 days). Suitably, this provides certainty for a fuel formulator and it enables the formulator to provide a fuel having required, and essentially stable, electrical conductivity specifications, without the need for overdosing the fuel with a relatively high initial dosage of the expensive STADIS additive.

Example 6 Viscosity Measurements of Additive A versus Additive B

[0232] The viscosity of Additive B (Glycerol Neodecanoate) and known Additive A was determined at different temperatures using the Viscosity Measurement Procedure described herein. The viscosity measurements (cSt) are reported in Table 4.

TABLE-US-00004 TABLE 4 Temperature Viscosity Additive ( C.) (cSt) Additive A 60 456.0 50 771.3 40 1374.4 30 2807.9 20 6107.0 10 14971 5 24702 0 Unmeasurable - too viscous Additive B 60 40.311 50 69.0 40 131.7 30 278.2 20 672.0 10 1856.4 5 3303.3 0 5660.2

[0233] The results in Table 4 evidence the following: [0234] Additive B has a significantly lower viscosity than Additive A at each respective temperature point. [0235] The viscosity of Additive A increases significantly with a corresponding decrease in temperature. Additive A remains handleable at 20 C. However, significant handleability problems with Additive A arise at temperatures less than 20 C., especially less than or equal to 10 C., due to a significant increase in viscosity of Additive A. At 0 C. Additive A is too viscous to measure. [0236] The viscosity of Additive B, in comparison to Additive A, increases much less with a corresponding decrease in temperature. Additive B remains handleable at temperatures of 0 C. and below. [0237] The viscosity of Additive B at 0 C. is less than the viscosity of Additive A at 20 C., evidencing that it is easier to handle (e.g. pump, dispense, transport) Additive B at 0 C. than Additive A at 20 C. [0238] The lower viscosity of Additive B at low temperature compared with Additive A means Additive B is more suited for use in cold climates than Additive A. Suitably, Additive B may be supplied neat, Additive B is easier to transport and/or store and/or dose a fuel, in cold climates, especially climates with a low ambient temperature of5 C. and below.

[0239] All documents described herein are incorporated by reference herein, including any priority documents and/or testing procedures, to the extent they are not inconsistent with this text.