Fuel Oil Compositions

Abstract

A middle-distillate fuel oil composition is disclosed. The middle-distillate fuel oil composition includes minor amounts of a quaternary ammonium salt of a polycarboxylic acid; and a polyalkylene amine detergent. The concentrations of (A) and (B) endow the composition with better low temperature properties than a corresponding composition in which (A) is replaced with (Aref), an amine salt of a polycarboxylic acid analogous to (A) and which is not a quaternary ammonium salt; and the concentration of (B) is such that it would adversely affect the low temperature properties of (Aref) in the corresponding composition.

1 . A middle-distillate fuel oil composition comprising minor amounts of
 (A) at least one oil-soluble polar nitrogen compound effective as a wax anti-settling additive in the form of a quaternary ammonium salt of a polycarboxylic acid; and   (B) at least one oil-soluble polyalkylene amine detergent,   
       wherein the concentrations of (A) and (B) are such that one or more of the low temperature properties of said fuel oil composition are better than those of an otherwise identical fuel oil composition that contains, in place of (A), (Aref), which is not a quaternary ammonium salt and is an oil-soluble amine salt of a polycarboxylic acid analogous to (A); and 
       wherein the concentration of (B) in said fuel oil composition is such that it would adversely affect one or more of the low temperature properties of (Aref) in said otherwise identical fuel oil composition. 
     
     
         2 . A fuel oil composition according to  claim 1  where one or more of the low temperature properties of said fuel oil composition are the same as or better than an other identical fuel oil composition that contains (Aref) in place of (A) and does not contain (B). 
     
     
         3 . A fuel oil composition according to  claim 1  wherein the quaternary ammonium cation in the or each polar nitrogen compound carries a segment of the formula NR 13 R 14 , where R 13  represents a hydrocarbyl group containing from 8 to 40 carbon atoms, and R 14  represents a hydrocarbyl group containing up to 40 carbon atoms, provided that R 13  and R 14  may be straight chain or branched, and/or may be the same or different. 
     
     
         4 . A fuel oil composition according to  claim 3  wherein the quaternary ammonium cation is represented by the formula ⊕NR 13 R 14 R 2 , where R represents a methyl, ethyl or propyl group. 
     
     
         5 . A fuel oil composition according to  claim 3  wherein R 13  and optionally R 14  represent alkyl groups derived from hydrogenated tallow fat. 
     
     
         6 . A fuel oil composition according to  claim 1  wherein the polycarboxylic acid is phthalic acid. 
     
     
         7 . A fuel oil composition according to  claim 1  wherein (A) is represented by the formula 
       
         
           
           
               
               
           
         
       
       Where R 13  and R 14  each represent alkyl groups derived from hydrogenated tallow fat, and (Aref) is an amide-amine salt obtainable by reacting one molar proportion of phthalic anhydride with two molar portions of dihydrogenated tallow amine. 
     
     
         8 . A fuel oil composition according to  claim 1  wherein the at least one polyalkylene amine detergent is the reaction product of a poly(isobutene)-substituted succinic anhydride and a polyamine. 
     
     
         9 . A fuel oil composition according to  claim 8  wherein the poly(isobutene) substituent has a number average molecular weight in the range of 400 to 2500. 
     
     
         10 . A method of making a middle distillate fuel oil composition comprising minor amounts of at least one polar nitrogen compound effective as a wax anti-settling additive and at least one polyalkylene amine detergent, comprising:
 (i) determining concentrations of (B), as defined in  claim 1 , and of (Aref), as defined in  claim 1 , at which (B) adversely effects one or more of the low temperature properties of (Aref) in a middle distillate fuel oil composition;   (ii) determining concentrations of (A), as defined in  claim 1 , at which one or more of the low temperature properties of a middle distillate fuel oil composition containing (B) at concentrations determined in step (i) are better than those of an otherwise identical middle distillate fuel oil composition containing (Aref) and (B); and   (iii) blending a middle distillate fuel oil composition containing (A) and (B) in the concentrations determined in steps (i) and (ii).   
     
     
         11 . A middle-distillate fuel oil composition comprising minor amounts of
 (A) at least one oil-soluble polar nitrogen compound effective as a wax anti-settling additive in the form of a quaternary ammonium salt of a phthalic acid; and   (B) at least one polyalkylene amine detergent in the form of an N-(polyamine-substituted) polyalkenyl succinimide.