Method and use
A diesel fuel composition comprising as an additive an ester compound which is the reaction product of an optionally substituted polycarboxylic acid or an anhydride thereof and a compound or formula H—(OR) n —OR 1 , wherein R is an optionally substituted alkylene group, R 1 is an optionally substituted hydrocarbyl 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 an optionally substituted polycarboxylic acid or an anhydride thereof and a compound or formula H—(OR) n —OR 1 , wherein R is an optionally substituted alkylene group, R 1 is an optionally substituted hydrocarbyl group and n is at least 1; wherein the optionally substituted polycarboxylic acid or hydrocarbyl substituted anhydride and compound of formula H—(OR) n —OR 1 are reacted in a molar ratio of from 1.5:1 to 1:1.5; and
wherein when the optionally substituted polycarboxylic acid or an anhydride thereof is a polyisobutenyl substituted succinic acid or anhydride thereof, R 1 is a C 10 to C 20 alkyl group.
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 an optionally substituted polycarboxylic acid or an anhydride thereof and a compound of formula H—(OR) n —OR 1 , wherein R is an optionally substituted alkylene group, 10 is an optionally substituted hydrocarbyl 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 40.
5. The composition according to claim 1 wherein R 1 is a C 10 to C 20 alkyl group.
6. 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.
7. The method according to claim 2 wherein the optionally substituted polycarboxylic acid or hydrocarbyl substituted anhydride and compound of formula H—(OR) n —OR 1 are reacted in a ratio of from 1.5:1 to 1:1.5.
8. The composition according to claim 1 wherein the additive is the reaction product of a succinic acid or anhydride having a C 20 to C 24 alkyl or alkenyl substituent and a C 12 to C 16 alkyl ether of a polypropylene glycol having 5 to 20 propylene groups.
9. The method according to claim 2 which achieves “keep clean” performance.
10. The method according to claim 2 which achieves “clean up” performance.
11. The method according to claim 2 wherein the deposits are injector deposits.
12. The method according to claim 11 wherein the deposits are internal diesel injector deposits.
13. The composition according to claim 1 wherein the diesel fuel composition comprises less than 50 ppm sulphur by weight.
14. The composition according to claim 1 wherein the diesel fuel composition comprises biodiesel.
15. 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.
16. The composition according to claim 1 wherein the diesel fuel composition comprises a mixture of two or more ester additives.
17. 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.
18. The method according to claim 17 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.
19. 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.