Quaternary ammonium fuel additives

Abstract

The present disclosure provides fuel additives including a quaternary ammonium salt formed by reacting an alkyl carboxylate with a compound formed from a hydrocarbyl substituted acylating agent reacted with a select amine. Also provided herein are fuel compositions including the novel fuel additives and methods of combusting a fuel including the fuel additives herein. The unique quaternary ammonium salts herein are advantageous because they can be made through a simple alkylation process and provide improved detergency at low treat rates by making available a relatively less sterically hindered quaternary nitrogen for detergency activity in the fuel.

What is claimed is: 
     
         1 . A fuel additive comprising a quaternary ammonium salt formed by the reaction of an alkyl carboxylate with a compound obtained by reacting a hydrocarbyl substituted acylating agent and an amine, wherein the amine has the structure 
       
         
           
           
               
               
           
         
       
       wherein
 A is a hydrocarbyl linker with 2 to 10 carbon units and including one or more carbon units thereof independently replaced with a bivalent moiety selected from the group consisting of —O—, —N(R′)—, —C(O)—, —C(O)O—, —C(O)NR′; 
 R 1  and R 2  are independently alkyl groups containing 1 to 8 carbon atoms; and 
 R′ is independently a hydrogen or a group selected from C 1-6  aliphatic, phenyl, or alkylphenyl. 
 
     
     
         2 . The fuel additive of  claim 1 , wherein the alkyl carboxylate is alkyl oxalate, alkyl salicylate, or a combination thereof. 
     
     
         3 . The fuel additive of  claim 1 , wherein the alkyl group in the alkyl carboxylate is C1 to C6 alkyl. 
     
     
         4 . The fuel additive of  claim 1 , wherein A is —(CH 2 ) r —[X—(CH 2 ) r′ ] p — with each of r, r′, and p independently being 1, 2, 3, or 4 and X being O or NR″ with R″ being hydrogen or a hydrocarbyl group. 
     
     
         5 . The fuel additive of  claim 4 , wherein X is oxygen 
     
     
         6 . The fuel additive of  claim 1 , wherein the amine is selected from 3-(2-(dimethyl amino)ethoxy)propylamine, N,N-dimethyldipropylenetriamine, and mixtures thereof. 
     
     
         7 . The fuel additive of  claim 1 , wherein the hydrocarbyl substitued acylating agent is selected from a hydrocarbyl substituted dicarboxylic acid or anhydride derivative thereof, a fatty acid, or mixtures thereof. 
     
     
         8 . The fuel additive of  claim 1 , wherein the hydrocarbyl substituent has a number average molecular weight of about 200 to about 2500 as measured by GPC using polystyrene as a calibration reference. 
     
     
         9 . A fuel composition comprising a major amount of a fuel and a minor amount of a quaternary ammonium salt formed by the reaction of an alkyl carboxylate with a compound obtained by reacting a hydrocarbyl substituted acylating agent and an amine, wherein the formed quaternary ammonium salt has the structure 
       
         
           
           
               
               
           
         
       
       wherein
 A is a hydrocarbyl linker with 2 to 10 carbon units and including one or more carbon units thereof independently replaced with a bivalent moiety selected from the group consisting of —O—, —N(R′)—, —C(O)—, —C(O)O—, —C(O)NR′; 
 R 1 , R 2 , and R 3  are independently alkyl groups containing 1 to 8 carbon atoms; and 
 R′ is independently a hydrogen or a group selected from C 1-6  aliphatic, phenyl, or alkylphenyl; and 
 R 4  and R 5  are independently selected from a hydrogen, an acyl group, or a hydrocarbyl substituted acyl group, wherein if one of R 4  or R 5  is hydrogen, then the other of R 4  and R 5  is the acyl group or the hydrocarbyl substituted acyl group, if both R 4  and R 5  include carbonyl moieties, then one of R 4  and R 5  includes the acyl group and the other of R 4  and R 5  includes the hydrocarbyl substitued acyl group, and R 4  and R 5  together with the N atom to which they are attached, combine to form a ring moiety; and 
 M −  is a carboxylate. 
 
     
     
         10 . The fuel composition of  claim 9 , comprising about 1 to about 100 ppm of the quaternary ammonium salt. 
     
     
         11 . The fuel composition of  claim 9 , wherein the carboxylate is oxalate, salicylate, or combinations thereof. 
     
     
         12 . The fuel composition of  claim 9 , wherein A is —(CH 2 ) r —[X—(CH 2 ) r′ ] p — with each of r, r′, and p independently being 1, 2, 3, or 4 and X being O or NR″ with R″ being hydrogen or a hydrocarbyl group. 
     
     
         13 . The fuel composition of  claim 12 , wherein X is oxygen. 
     
     
         14 . The fuel composition of  claim 12 , wherein A includes a moiety derived from 3-(2-(dimethylamino)ethoxy)propylamine, N,N-dimethyldipropylenetriamine, or mixtures thereof. 
     
     
         15 . The fuel composition of  claim 9 , wherein R 4  and R 5 , together with the nitrogen atom to which they are attached, combine to form a hydrocarbyl substituted succinimide. 
     
     
         16 . The fuel composition of  claim 15 , wherein the hydrocarbyl substituent has a number average molecular weight of about 200 to about 2500 as measured by GPC using polystyrene as a calibration reference. 
     
     
         17 . The fuel composition of  claim 9 , wherein the hydrocarbyl substituent of R 4  or R 5  has a number average molecular weight of about 200 to about 2500 as measured by GPC using polystyrene as a calibration reference. 
     
     
         18 . A method of operating a fuel injected engine to provide improved engine performance, the method comprising combusting in the engine a fuel composition including a major amount of fuel and about 1 to about 100 ppm of a quaternary ammonium salt formed by the reaction of an alkyl carboxylate with a compound obtained by reacting a hydrocarbyl substituted acylating agent and an amine, wherein the amine has the structure 
       
         
           
           
               
               
           
         
       
       wherein
 A is a hydrocarbyl linker with 2 to 10 carbon units and including one or more carbon units thereof independently replaced with a bivalent moiety selected from the group consisting of —O—, —N(R′)—, —C(O)—, —C(O)O—, —C(O)NR′; 
 R 1  and R 2  are independently alkyl groups containing 1 to 8 carbon atoms; and 
 R′ is independently a hydrogen or a group selected from C 1-6  aliphatic, phenyl, or alkylphenyl. 
 
     
     
         19 . The method of  claim 18 , wherein the improved engine performance is an average flow loss of about 45 percent or less when measured according to a CEC F-23-01 (XUD-9) test. 
     
     
         20 . A method of  claim 18 , wherein the formed quaternary ammonium salt has the structure 
       
         
           
           
               
               
           
         
       
       wherein
 A includes 2 to 6 carbon units with one carbon unit thereof independently replaced with —O— or —NH—; 
 R 1 , R 2 , and R 3  are independently alkyl groups containing 1 to 8 carbon atoms; and 
 R 4  and R 5  are independently selected from a hydrogen, an acyl group, or a hydrocarbyl substituted acyl group, wherein if one of R 4  or R 5  is hydrogen, then the other of R 4  and R 5  is the acyl group or the hydrocarbyl substituted acyl group, if both R 4  and R 5  include carbonyl moieties, then one of R 4  and R 5  includes the acyl group and the other of R 4  and R 5  includes the hydrocarbyl substitued acyl group, and R 4  and R 5  together with the N atom to which they are attached, combine to form a ring moiety; and 
 M −  is a carboxylate. 
 
     
     
         21 . The method of  claim 20 , wherein the carboxylate includes oxalate, salicylate, or combinations thereof. 
     
     
         22 . The method of  claim 20 , wherein the hydrocarbyl substituent has a number average molecular weight of about 200 to about 2500 as measured by GPC using polystyrene as a calibration reference.