Method and use

Abstract

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 polyhydric alcohol of formula H—(OR) n —OH, wherein R is an optionally substituted alkylene group and n is at least 1.

What is claimed is: 
     
         1 . A method of improving lubricity in a diesel engine, 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 polyhydric alcohol of formula H—(OR) n —OH, wherein R is an optionally substituted alkylene group and n is at least 1. 
     
     
         2 . The method 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. 
     
     
         3 . The method according to  claim 1  wherein each R is ethylene or propylene and n is from 1 to 20. 
     
     
         4 . The method 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. 
     
     
         5 . The method 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 1.5:1 to 1:1.5. 
     
     
         6 . The method according to  claim 1  wherein the additive includes compounds having the formula (C1) or (C2): 
       
         
           
           
               
               
           
         
       
     
     
         7 . The method according to  claim 1  wherein the additive comprises the reaction product of a succinic acid or anhydride of formula (A3) or (A4): 
       
         
           
           
               
               
           
         
         and an alcohol of formula H—(OR) n —OH; wherein 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; wherein the alcohol of formula H—(OR) n —OH is selected from 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. 
       
     
     
         8 . The method according to  claim 1  wherein the additive comprises the reaction product of a succinic acid or anhydride having a C 20  to C 24  alkyl or alkenyl substituent and an alcohol selected from 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. 
     
     
         9 . The method according to  claim 1  wherein the additive includes compounds having the formula (E): 
       
         
           
           
               
               
           
         
       
     
     
         10 . The method according to  claim 1  wherein the diesel engine is a modern diesel engine having a high pressure fuel system. 
     
     
         11 . The method according to  claim 1  wherein the diesel engine is a modern diesel engine having a pressure in excess of 1350 bar; the additive is the reaction product of a polycarboxylic acid or an anhydride thereof of formula (A3) or (A4): 
       
         
           
           
               
               
           
         
         and a polyhydric alcohol of formula H—(OR) n —OH, wherein R is an optionally substituted alkylene group and n is at least 1; 
         wherein R 1  is hydrogen, 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; 
         wherein the alcohol of formula H—(OR) n —OH is selected from ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, trehalose, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol and a polyethylene or polypropylene glycol having a number average molecular weight of 300 to 1200; and 
         the additive is present in the diesel fuel composition in an amount of at least 5 ppm and less than 500 ppm. 
       
     
     
         12 . The method according to  claim 1  wherein the diesel fuel composition does not contain ethanol. 
     
     
         13 . The method according to  claim 1  wherein the diesel fuel composition comprises less than 50 ppm sulphur by weight. 
     
     
         14 . The method according to  claim 13  wherein the diesel fuel composition comprises less than 20 ppm sulphur by weight. 
     
     
         15 . The method according to  claim 1  wherein the diesel fuel composition comprises biodiesel. 
     
     
         16 . The method according to  claim 15  wherein the diesel fuel composition comprises at least 5 wt % biodiesel. 
     
     
         17 . The method according to  claim 15  wherein the diesel fuel composition comprises renewable diesel. 
     
     
         18 . The method according to  claim 15  wherein the diesel fuel composition comprises hydrogenated vegetable oil. 
     
     
         19 . The method according to  claim 1  wherein the diesel fuel composition comprises one or more further detergents selected from:
 (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. 
 
     
     
         20 . The method according to  claim 1  wherein the diesel fuel composition comprises a mixture of two or more ester additives. 
     
     
         21 . The method according to  claim 1  which achieves an improvement in performance selected from 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; and 
 an increase in maintenance intervals. 
 
     
     
         22 . The method according to  claim 1  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. 
     
     
         23 . The method according to  claim 1  wherein the diesel fuel composition comprises one or more further additives selected from lubricity improvers, corrosion inhibitors and cold flow improvers.