Oxidation stabilized fuels having enhanced corrosion resistance

Abstract

A method of improving oxidation properties of biodiesel-containing fuel composition. The method provides combining a major amount of middle distillate fuel containing more than about 5 volume percent biodiesel components with a minor amount of a synergistic mixture of (A) a hydrocarbyl-substituted succinimide dispersant and (B) a compound of the formula: and tautomers and enantiomers thereof. In the formula, R 2 is a hydrocarbyl group having a number average molecular weight ranging from 100 to 5000. The synergistic mixture has a weight ratio of A:B ranging from 2:1 to 10:1.

1 . A method of improving oxidation-stability of a biodiesel-containing fuel composition, comprising: combining a major amount of middle distillate fuel containing more than about 5 volume percent of at least one biodiesel component with a minor amount of a synergistic mixture consisting essentially of (A) a hydrocarbyl-substituted succinimide dispersant and (B) a compound of the formula: 
       
         
           
           
               
               
           
         
         and tautomers and enantiomers thereof, wherein R 2  is a hydrocarbyl group having a number average molecular weight ranging from 100 to 5000 and wherein a weight ratio of A:B ranges from 2:1 to 10:1. 
       
     
     
         2 . The method of  claim 1 , wherein component A of the mixture comprises a reaction product of polyalkenyl succinic acid or anhydride with tetraethylene pentamine. 
     
     
         3 . The method of  claim 2 , wherein the polyalkenyl succinic acid or anhydride is derived from polyisobutylene having a number average molecular weight ranging from 800 to 1100 daltons. 
     
     
         4 . The method of  claim 3 , wherein the polyisobutylene comprises a high reactivity polyisobutylene having at least 60% or more terminal olefinic double bonds. 
     
     
         5 . The method of  claim 1 , wherein the middle distillate fuel comprises from 200 to 600 ppm by weight of the mixture of A and B. 
     
     
         6 . The method of  claim 1 , wherein R 2  is a polyolefin radical having a number average molecular weight of from 200 to 3,000 daltons. 
     
     
         7 . The method of  claim 1 , wherein the middle distillate fuel is substantially devoid of disalicylidene diaminoalkane compounds. 
     
     
         8 . The method of  claim 1 , wherein the fuel containing A and B has a total insolubles amount of no more than 2.5 mg/100 ml a determined by ASTM D-2274. 
     
     
         9 . The method of  claim 1 , wherein the middle distillate fuel is substantially devoid of metal deactivators. 
     
     
         10 . The method of  claim 1 , wherein the weight ratio of A:B in the middle distillate fuel ranges from about 3.5:1 to about 5:1. 
     
     
         11 . A method for operating an engine on a middle distillate fuel containing more than about 5 volume percent of at least one biodiesel component, comprising formulating the fuel with a minor amount of a synergistic mixture consisting essentially of (A) a hydrocarbyl-substituted succinimide dispersant and (B) a compound of the formula: 
       
         
           
           
               
               
           
         
         and tautomers and enantiomers thereof to provide an oxidation resistant fuel composition, wherein R 2  is a hydrocarbyl group having a number average molecular weight ranging from 100 to 500 and wherein a weight ratio of A:B ranges from 2:1 to 10:1; and operating the engine on the fuel composition. 
       
     
     
         12 . The method of  claim 11 , wherein component A of the mixture comprises a reaction product of polyalkenyl succinic acid or anhydride with tetraethylene pentamine. 
     
     
         13 . The method of  claim 12 , wherein the polyalkenyl succinic acid or anhydride is derived from polyisobutylene having a number average molecular weight ranging from 800 to 1100 daltons. 
     
     
         14 . The method of  claim 13 , wherein the polyisobutylene comprises a high reactivity polyisobutylene having at least 60% or more terminal olefinic double bonds. 
     
     
         15 . The method of  claim 11 , wherein the middle distillate fuel comprises from 200 to 600 ppm by weight of the mixture of A and B. 
     
     
         16 . The method of  claim 11 , wherein R 2  is a polyolefin radical having a number average molecular weight of from 200 to 3,000 daltons. 
     
     
         17 . The method of  claim 11 , wherein the middle distillate fuel is substantially devoid of disalicylidene diaminoalkane compounds. 
     
     
         18 . The method of  claim 11 , wherein the middle distillate fuel is substantially devoid of metal deactivators. 
     
     
         19 . Use of a synergistic mixture consisting essentially of (A) a hydrocarbyl-substituted succinimide dispersant and (B) a compound of the formula: 
       
         
           
           
               
               
           
         
         and tautomers and enantiomers thereof, wherein R 2  is a hydrocarbyl group having a number average molecular weight ranging from 100 to 5000 and wherein a weight ratio of A:B ranges from 2:1 to 10:1 in a middle distillate fuel containing at least 7 volume percent of at least one biodiesel component to improve the oxidation stability of the fuel according to ASTM D-2274. 
       
     
     
         20 . The use as in  claim 19 , wherein the oxidation stability of the fuel according to ASTM D-2274 is less than 2.5 mg/100 ml insolubles compared to the oxidation stability of the fuel without the synergistic mixture having greater than 2.5 mg/100 ml insolubles.