Method and use
A diesel fuel composition comprising as an additive an ester compound which is the reaction product of a polyhydric alcohol of formula H—(OR) n —OH and at least 1.5 molar equivalents of an optionally substituted polycarboxylic acid or an anhydride thereof, wherein R is an optionally substituted alkylene group and n is at least 1.
1. A diesel fuel composition comprising as an additive an ester compound which is the reaction product of a polyhydric alcohol of formula H—(OR) n —OH and at least 1.5 molar equivalents of an optionally substituted polycarboxylic acid or an anhydride thereof, wherein R is an optionally substituted alkylene group and n is at least 1; and wherein the diesel fuel composition comprises less than 50 ppm sulphur by weight.
2. A method of combatting deposits in a modern diesel engine having a high pressure fuel system, the method comprising combusting in the engine a diesel fuel composition comprising as an additive the reaction product of a polyhydric alcohol of formula H—(OR) n —OH and at least 1.5 molar equivalents of an optionally substituted polycarboxylic acid or an anhydride thereof, wherein R is an optionally substituted alkylene group and n is at least 1.
3. The composition according to claim 1 wherein the optionally substituted polycarboxylic acid or anhydride thereof is a hydrocarbyl substituted succinic acid or a hydrocarbyl substituted succinic anhydride.
4. The composition according to claim 1 wherein each R is ethylene or propylene and n is from 1 to 20.
5. The composition according to claim 1 wherein the polycarboxylic acid or anhydride thereof includes an optionally substituted alkyl or alkenyl group having 6 to 100 carbon atoms.
6. The composition according to claim 1 wherein the optionally substituted polycarboxylic acid or hydrocarbyl substituted anhydride and alcohol of formula H—(OR)n-OH are reacted in a ratio of from 2.5:1 to 1.8:1.
7. The composition according to claim 1 wherein the additive comprises compounds of formula (C1), (C2) or (C3):
or isomers or mixtures thereof.
8. The composition according to claim 1 wherein the additive comprises the reaction product of an alcohol of formula H—(OR) n —OH selected from the group consisting of: ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, trehalose, sorbitol, glycerol, pentaerythritol, trimethylolpropane, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol and a polyethylene or polypropylene glycol having a number average molecular weight of 300 to 1200; and at least 1.5 molar equivalents of one or more optionally substituted succinic acids or anhydrides of formula (A3) or (A4):
wherein each R 1 is an alkyl or alkenyl group having 6 to 36 carbon atoms or a polyisobutenyl group having a number average molecular weight of from 200 to 1300.
9. The composition according to claim 1 wherein the additive comprises the reaction product an alcohol selected from the group consisting of: 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, tripropylene glycol and polypropylene glycols having a number average molecular weight of from 300 to 600; and at least 1.5 molar equivalents of a succinic acid or anhydride having a C 20 to C 24 alkyl or alkenyl substituent.
10. The composition according to claim 1 wherein the additive comprises a compound of formula (D):
11. The composition according to claim 1 wherein the diesel engine is a modern diesel engine having a high pressure fuel system.
12. The method according to claim 2 which achieves “keep clean” performance.
13. The method according to claim 2 which achieves “clean up” performance.
14. The method according to claim 2 wherein the deposits are injector deposits.
15. The method according to claim 14 wherein the deposits are internal diesel injector deposits.
16. The method according to claim 2 wherein the diesel fuel composition comprises less than 50 ppm sulphur by weight.
17. The composition according to claim 1 wherein the diesel fuel composition comprises biodiesel.
18. The composition according to claim 1 wherein the diesel fuel composition comprises one or more further detergents selected from the group consisting of:
(i) a quaternary ammonium salt additive;
(ii) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol;
(iii) the reaction product of a carboxylic acid-derived acylating agent and an amine;
(iv) the reaction product of a carboxylic acid-derived acylating agent and hydrazine;
(v) a salt formed by the reaction of a carboxylic acid with di-n-butylamine or tri-n-butylamine;
(vi) the reaction product of a hydrocarbyl-substituted dicarboxylic acid or anhydride and an amine compound or salt which product comprises at least one amino triazole group; and
(vii) a substituted polyaromatic detergent additive.
19. The composition according to claim 1 wherein the diesel fuel composition comprises a mixture of two or more ester additives.
20. The method according to claim 2 which achieves an improvement in performance of one or more of:
a reduction in power loss of the engine;
a reduction in external diesel injector deposits;
a reduction in internal diesel injector deposits;
an improvement in fuel economy;
a reduction in fuel filter deposits;
a reduction in emissions; or
an increase in maintenance intervals.
21. The method according to claim 20 which provides an improvement in performance in modern diesel engines having a high pressure fuel system and provides an improvement in performance in traditional diesel engines.
22. The composition according to claim 1 which further comprises one or more further additives selected from the group consisting of: lubricity improvers, corrosion inhibitors and cold flow improvers.