Fuel modifiers for natural gas reciprocating engines

Abstract

Described herein are fuel modifiers for natural gas reciprocating engines, while recognizing the application of the inventions herein may be applied more broadly, to other natural gas-based engine systems. The fuel modifiers are primarily free-radical initiators, and the presence of this fuel modifier allows the engine operator to operate the engine under leaner conditions because, while employing the same ignition energy, more free-radicals are formed, thus overcoming the problems associated with dilution of the pool of free-radicals in the flame.

What is claimed is: 
     
         1 . A modified fuel, comprising a base fuel and a fuel modifier selected from the group consisting of azo compounds, dialkylsulfides, alkyl sulfones, nitroalkyls, peroxygens, and hydrocarbons which contain symmetrically substituted carbon-carbon bonds where that bond is relatively weak. 
     
     
         2 . The modified fuel of  claim 1 , wherein the base fuel is natural gas. 
     
     
         3 . The modified fuel of  claim 2 , wherein the fuel modifier is selected from the group consisting of azo compounds having a molecular weight of between 80 and 500 g/mol, and a decomposition temperature between 80 and 300° C. 
     
     
         4 . The modified fuel of  claim 2 , wherein the fuel modifier is selected from the group consisting of azobisisoalkyls represented by structures (1) and (2): 
       
         
           
           
               
               
           
         
         wherein R 1  through R 4  are each independently selected from the group consisting of hydrogen; hydroxyl; methyl; 2-cyanoprop-2-yl; and linear or branched, substituted or unsubstituted C 1 -C 15  alkyl groups, C 1 -C 15  alkenyl groups, C 1 -C 15  hydroxyalkyl groups, C 1 -C 15  alkoxyalkyl groups, C 1 -C 15  aminoalkyl groups, C 1 -C 15  carboxyalkyl groups, C 1 -C 15  aminocarboxyalkyl groups and C 1 -C 15  hydroxycarboxyalkyl groups. 
       
     
     
         5 . The modified fuel of  claim 4 , wherein the fuel modifier is azobisisobutylnitrile. 
     
     
         6 . The modified fuel of  claim 2 , wherein the fuel modifier is selected from the group consisting of dialkylsulfides represented by structure (3): 
       
         
           
           
               
               
           
         
         wherein R 5  and R 6  are each independently selected from the group consisting of hydrogen; hydroxyl; methyl; and linear or branched, substituted or unsubstituted C 1 -C 15  alkyl groups, C 1 -C 15  alkenyl groups, C 1 -C 15  hydroxyalkyl groups, C 1 -C 15  alkoxyalkyl groups, C 1 -C 15  aminoalkyl groups, C 1 -C 15  carboxyalkyl groups, C 1 -C 15  aminocarboxyalkyl groups, C 1 -C 15  hydroxycarboxyalkyl groups, C 1 -C 15  aryl groups, and C 1 -C 15  alkylaryl groups. 
       
     
     
         7 . The modified fuel of  claim 6 , wherein the fuel modifier is dismethylsulfide. 
     
     
         8 . The modified fuel of  claim 2 , wherein the fuel modifier is selected from the group consisting of selected from the group consisting of sulfones represented by structure (4): 
       
         
           
           
               
               
           
         
         wherein R 7  and R 8  are each independently selected from the group consisting of hydrogen; hydroxyl; methyl; and linear or branched, substituted or unsubstituted C 1 -C 15  alkyl groups, C 1 -C 15  alkenyl groups, C 1 -C 15  hydroxyalkyl groups, C 1 -C 15  alkoxyalkyl groups, C 1 -C 15  aminoalkyl groups, C 1 -C 15  carboxyalkyl groups, C 1 -C 15  aminocarboxyalkyl groups and C 1 -C 15  hydroxycarboxyalkyl groups. 
       
     
     
         9 . The modified fuel of  claim 8 , wherein the fuel modifier is dismethylsulfone. 
     
     
         10 . The modified fuel of  claim 2 , wherein the fuel modifier is selected from the group consisting of nitro compounds represented by structure (5): 
       
         
           
           
               
               
           
         
         wherein R 9  is selected from the group consisting of hydrogen; hydroxyl; methyl; and linear or branched, substituted or unsubstituted C 1 -C 15  alkyl groups, C 1 -C 15  alkenyl groups, C 1 -C 15  hydroxyalkyl groups, C 1 -C 15  alkoxyalkyl groups, C 1 -C 15  aminoalkyl groups, C 1 -C 15  carboxyalkyl groups, C 1 -C 15  aminocarboxyalkyl groups, C 1 -C 15  hydroxycarboxyalkyl groups, C 1 -C 15  aryl groups, and C 1 -C 15  alkylaryl groups. 
       
     
     
         11 . The modified fuel of  claim 10 , wherein the fuel modifier is nitromethane. 
     
     
         12 . The modified fuel of  claim 2 , wherein the fuel modifier is selected from the group consisting of peroxygens compounds represented by structure (6): 
       
         
           
           
               
               
           
         
         wherein R 10  and R 11  are independently selected from the group consisting of hydrogen; methyl; and linear or branched, substituted or unsubstituted C 1 -C 15  alkyl groups, C 1 -C 15  alkenyl groups, C 1 -C 15  hydroxyalkyl groups, C 1 -C 15  alkoxyalkyl groups, C 1 -C 30  carboxyalkyl groups, C 1 -C 30  hydroxycarboxyalkyl groups, C 1 -C 15  aryl, and C 1 -C 15  alkylaryl groups. 
       
     
     
         13 . The modified fuel of  claim 12 , wherein the fuel modifier is selected from the group consisting of linear and branched C 1 -C 5  alkyl peroxides. 
     
     
         14 . The modified fuel of  claim 13 , wherein the fuel modifier is di-tert-butyl peroxide. 
     
     
         15 . The modified fuel of  claim 13 , wherein the fuel modifier is dimethoxymethane. 
     
     
         16 . The modified fuel of  claim 2 , wherein the fuel modifier is selected from the group represented by the formula below:
   R 13 —C(R 14 , R 12 )—C(R 14 , R 12 , R 13 )
   wherein R 12 , R 13 , and R 14  are independently selected from the group consisting of hydrogen; methyl; and linear or branched, substituted or unsubstituted C 1 -C 15  alkyl groups, C 1 -C 15  alkenyl groups, C 1 -C 15  hydroxyalkyl groups, C 1 -C 15  alkoxyalkyl groups, C 1 -C 30  carboxyalkyl groups, C 1 -C 30  hydroxycarboxyalkyl groups, C 1 -C 15  aryl, and C 1 -C 15  alkylaryl groups. Exemplary hydrocarbon compounds which contain symmetrically substituted carbon-carbon bonds include 2,3-dimethyl-2,3-diphenylbutane.