Gasoline compositions

Abstract

The invention provides a gasoline composition comprising a major amount of a gasoline suitable for use in a spark ignition engine; 5 to 1000 ppmw, based on total composition, of a fatty acid salt of an alkoxylated oligoamine of general formula I wherein each moiety A independently represents an alkylene group of 2 to 8 carbon atoms, each moiety R independently represents a C 7-23 alkyl or singly or multiply-unsaturated C 7 to C 23 alkenyl group, optionally substituted by one or more —OH groups, each moiety Z independently represents a C 1-8 alkylene group, a C 3-8 cycloalkylene group, or a C 6-12 arylene or arylalkylene group, m represents 0 or an integer in the range 1 to 5, and the total of all variables x has a value of 50% to 300% of (m+3); and 600 to 2000 ppmw, based on total composition, of a co-additive selected from the group consisting of (a) a nitrogen-containing detergent containing a hydrocarbyl group having a number average molecular weight (Mn) in the range 750 to 6000, (b) a polyalphaolefin having a viscosity at 100° C. in the range 2×10 −6 to 2×10 −5 m 2 /s (2 to 20 centistokes), being an oligomer containing 18 to 80 carbon atoms derived from at least one alphaolefinic monomer containing from 8 to 16 carbon atoms; (c) a polyoxyalkylene compound selected from glycols, mono- and diethers thereof, having number average molecular weight (Mn) in the range 400 to 3000; and mixtures of any two or all three of (a), (b) and (c).

What is claimed is:  
     
         1 . A gasoline composition comprising a major amount of a gasoline suitable for use in a spark ignition engine; 5 to 1000 ppmw, based on total composition, of a fatty acid salt of an alkoxylated oligoamine of general formula I  
       
         
           
           
               
               
           
         
       
       wherein each moiety A independently represents an alkylene group of 2 to 8 carbon atoms, each moiety R independently represents a C 7-23  alkyl or singly or multiply-unsaturated C 7  to C 23  alkenyl group, optionally substituted by one or more —OH groups, each moiety Z independently represents a C 1-8  alkylene group, a C 3-8  cycloalkylene group, or a C 6-12  arylene or arylalkylene group, m represents 0 or an integer in the range 1 to 5, and the total of all variables x has a value of 50% to 300% of (m+3); and 600 to 2000 ppmw, based on total composition, of a co-additive selected from the group consisting of (a) a nitrogen-containing detergent containing a hydrocarbyl group having a number average molecular weight (Mn) in the range 750 to 6000, (b) a polyalphaolefin having a viscosity at 100° C. in the range 2×10 −6  to 2×10 −5  m 2 /s (2 to 20 centistokes), being an oligomer containing 18 to 80 carbon atoms derived from at least one alphaolefinic monomer containing from 8 to 16 carbon atoms; (c) a polyoxyalkylene compound selected from glycols, mono- and diethers thereof, having number average molecular weight (Mn) in the range 400 to 3000; and mixtures of any two or all three of (a), (b) and (c).  
     
     
         2 . The composition according to  claim 1  wherein in formula I each moiety A independently represents a 1,2-ethylene, ethylene, 1,2-propylene or 1,2-butylene group, each moiety R independently represents a singly or multiply-unsaturated C 15-19  alkenyl group, optionally substituted by one or more —OH groups, each moiety Z is a polymethylene group of formula —(CH2)n—, where n is 2 to 6, m is 1 or 2, and the total of all variables x has a value of 75% to 125% of (m+3).  
     
     
         3 . The composition according to  claim 1  wherein the nitrogen-containing detergent (a) is a hydrocarbyl amine or formula R 1 —NH 2 , wherein R 1  represents a group R 2  or a group R 2 —CH 2 —and R 2  is a hydrocarbyl group having a number average molecular weight in the range 950 to 1350.  
     
     
         4 . The composition according to  claim 1 , wherein the poyalphaolefin (b) is derived from an alphaolefinic monomer containing from 8 to 12 carbon atoms, and has viscosity at 100° C. in the range 6×10 −6  to 1×10 −5  m 2 /s (6 to 10 centistokes).  
     
     
         5 . The composition according to  claim 1  wherein the polyoxyalkylene compound (c) has the formula II  
       
         
           
           
               
               
           
         
       
       wherein R 3  and R 4  independently represent hydrogen atoms or C 1-40  hydrocarbyl groups, each R 5  independently represents a C 2-8  alkylene group and n is such that M 2  of the polyoxyalkylene compound is in the range 700 to 2000.  
     
     
         6 . The composition according to  claim 1 , wherein the fatty acid salt is present in an amount in the range 25 to 400 ppmw, based on total composition.  
     
     
         7 . The composition according to  claim 1 , wherein the co-additive is present in an amount in the range 700 to 1500 ppmw, based on total composition.  
     
     
         8 . The composition according to  claim 1  which contains at least 400 ppmw, based on total composition, of (b) and/or (c).  
     
     
         9 . A process for the preparation of a gasoline composition according to  claim 1  which comprises bringing into admixture the gasoline, the fatty acid salt and the co-additive.  
     
     
         10 . A method of operating a spark-ignition internal combustion engine, which comprises bringing into the combustion chambers of said engine a gasoline composition according to  claim 1.