Additives for Cetane Improvement in Middle Distillate Fuels

Abstract

The cetane number of middle distillate fuels may be increased using an additive composition including a polymer that may be a homopolymer or copolymer of olefins, and the like, where the polymer has a weight average molecular weight ranging from about 200,000 to about 5,000,000. The additive composition also includes a free radical initiator component, which may be an alkyl nitrate such as 2-ethylhexylnitrate (2-EHN), and/or a peroxide, such as t-butyl peroxide. In one non-limiting embodiment the amount of polymer in the additive composition is greater than the free radical initiator component. A solvent is also present, which the solvent may include alcohol, an alkyl substituted phenol and/or a heavy aromatic distillate.

1 . A method for improving the cetane number of a middle distillate fuel comprising adding to the distillate fuel an effective amount of an additive composition for improving the cetane number of the middle distillate fuel, the additive composition comprising:
 a polymer selected from the group consisting of homopolymers and copolymers of olefins, and mixtures thereof, where the polymer has a weight average molecular weight ranging from about 200,000 to about 5,000,000;   a free radical initiator component selected from the group consisting of an alkyl nitrate, a peroxide, and combinations thereof; and   an alcohol.   
     
     
         2 . The method of  claim 1  where:
 the amount of the free radical initiator component ranges from about 50 to about 4000 ppm based on the total distillate fuel; 
 the amount of the polymer ranges from about 0.01 to about 20,000 ppm based on the total distillate fuel; and 
 the amount of the alcohol ranges from about 1 to about 60 vol % based on the additive composition. 
 
     
     
         3 . The method of  claim 1  where the alcohol is selected from the group consisting of linear or branched alcohols having 2 to 18 carbon atoms and which may be substituted with oxygen, nitrogen or sulfur. 
     
     
         4 . The method of  claim 1  where the additive composition further comprises a component selected from the group consisting of an alkyl substituted phenol, an alkyl substituted quinone and an alkyl substituted hydroquinone antioxidant and mixtures thereof, and a solvent selected from the group consisting of kerosene, a heavy aromatic distillate and D-2 diesel, and mixtures thereof. 
     
     
         5 . The method of  claim 1  where the cetane number of the middle distillate fuel is the same as or greater than the cetane number achieved when in the additive composition the free radical initiator component is present at the same total additive dosage level for both the polymer and the free radical initiator component and no polymer is present. 
     
     
         6 . The method of  claim 1  where the middle distillate fuel has reduced NOx emissions as compared to an otherwise identical fuel with an additive composition at the same dosage level where:
 only the free radical initiator component is substituted for both the free radical initiator component and the polymer component or 
 only the polymer component is substituted for both the free radical initiator component and the polymer component, 
 where the free radical initiator component is an alkyl nitrate. 
 
     
     
         7 . A method for improving the cetane number of a middle distillate fuel comprising adding to the middle distillate fuel an additive composition comprising:
 from about 0.01 to about 20,000 ppm, based on the total distillate fuel, of a polymer selected from the group consisting of homopolymers and copolymers of olefins and mixtures thereof, where the polymer has a weight average molecular weight ranging from about 200,000 to about 5,000,000;   from about 50 to about 4000 ppm, based on the total distillate fuel, of an alkyl nitrate; and   from about 1 to about 60 vol %, based on the additive composition, of an alcohol selected from the group consisting of linear or branched alcohols having 2 to 18 carbon atoms and which may be substituted with oxygen, nitrogen or sulfur.   
     
     
         8 . The method of  claim 7  where the additive composition further comprises a component selected from the group consisting of an alkyl substituted phenol, an alkyl substituted quinone and an alkyl substituted hydroquinone antioxidant and mixtures thereof, and a solvent selected from the group consisting of kerosene, a heavy aromatic distillate and D-2 diesel, and mixtures thereof. 
     
     
         9 . The method of  claim 7  where the cetane number of the middle distillate fuel is the same as or greater than the cetane number achieved when in the additive composition the free radical initiator component is present at the same total additive dosage level for both the polymer and the free radical initiator component and no polymer is present. 
     
     
         10 . An additive composition for improving the cetane number of middle distillate fuels comprising:
 a polymer selected from the group consisting of homopolymers and copolymers of olefins and mixtures thereof, where the polymer has a weight average molecular weight ranging from about 200,000 to about 5,000,000;   a free radical initiator component selected from the group consisting of an alkyl nitrate, a peroxide, and combinations thereof; and   an alcohol selected from the group consisting of linear or branched alcohols having 2 to 18 carbon atoms and which may be substituted with oxygen, nitrogen or sulfur.   
     
     
         11 . The additive composition of  claim 10  where the volume ratio of polymer to the free radical initiator component ranges from about 100:1 to about 1:100. 
     
     
         12 . The additive composition of  claim 10  where the amount of alcohol ranges from about 1 to about 60 vol %. 
     
     
         13 . The additive composition of  claim 10  where the free radical initiator component is an alkyl nitrate selected from the group consisting of 2-ethylhexyl nitrate (2-EHN), iso-propyl nitrate, iso-amylnitrate, iso-hexylnitrate, cyclohexyl nitrate, dodecyl nitrate, diglycol nitrate and tetraglycol nitrate. 
     
     
         14 . The additive composition of  claim 10  further comprising a component selected from the group consisting of an alkyl substituted phenol, an alkyl substituted quinone and an alkyl substituted hydroquinone antioxidant, and a solvent selected from the group consisting of kerosene, a heavy aromatic distillate and D-2 diesel, and mixtures thereof. 
     
     
         15 . A middle distillate fuel comprising:
 a middle distillate fuel selected from the group consisting of diesel fuel, heating oil, jet fuel, and kerosene; and   an effective amount of an additive composition for improving the cetane number of the middle distillate fuel comprising:
 a polymer selected from the group consisting of homopolymers and copolymers of olefins, and mixtures thereof, where the polymer has a weight average molecular weight ranging from about 200,000 to about 5,000,000; 
 a free radical initiator component selected from the group consisting of an alkyl nitrate, a peroxide, and combinations thereof; and 
 an alcohol. 
   
     
     
         16 . The middle distillate fuel of  claim 15  where:
 the amount of the free radical initiator component ranges from about 50 to about 4000 ppm based on the total distillate fuel; 
 and the amount of the polymer ranges from about 0.01 to about 20,000 ppm based on the total distillate fuel; and 
 the amount of the alcohol ranges from about 1 to about 60 vol % based on the additive composition. 
 
     
     
         17 . The middle distillate fuel of  claim 15  where the free radical initiator component is an alkyl nitrate selected from the group consisting of 2-ethylhexyl nitrate (2-EHN), iso-propyl nitrate, iso-amylnitrate, iso-hexylnitrate, cyclohexyl nitrate, dodecyl nitrate, diglycol nitrate and tetraglycol nitrate. 
     
     
         18 . The middle distillate fuel of  claim 15  where the cetane number of the middle distillate fuel is the same as or greater than the cetane number achieved when in the additive composition the free radical initiator component is present at the same total additive dosage level for both the polymer and the free radical initiator component and no polymer is present. 
     
     
         19 . The middle distillate fuel of  claim 15  where the additive composition further comprises a component selected from the group consisting of an alkyl substituted phenol, an alkyl substituted quinone and an alkyl substituted hydroquinone antioxidant and mixtures thereof, and a solvent selected from the group consisting of kerosene, a heavy aromatic distillate and D-2 diesel, and mixtures thereof. 
     
     
         20 . A middle distillate fuel comprising:
 a middle distillate fuel selected from the group consisting of diesel fuel, heating oil, jet fuel and kerosene; and   an effective amount of an additive composition for improving the cetane number of the middle distillate fuel comprising
 a polymer selected from the group consisting of homopolymers and copolymers of olefins, and mixtures thereof, where the homopolymer has a weight average molecular weight ranging from about 200,000 to about 5,000,000; 
 an alkyl nitrate; and 
 an alcohol 
   where the cetane number of the middle distillate fuel is the same as or greater than the cetane number achieved when in the additive composition the free radical initiator component is present at the same total additive dosage level for both the polymer and the free radical initiator component and no polymer is present.   
     
     
         21 . The middle distillate fuel of  claim 20  where:
 the amount of the alkyl nitrate ranges from about 50 to about 4000 ppm based on the total distillate fuel; 
 the amount of the polymer ranges from about 0.01 to about 20,000 ppm based on the total distillate fuel; and 
 the amount of the alcohol ranges from about 1 to about 60 vol % based on the additive composition, 
 all based on the total distillate fuel. 
 
     
     
         22 . The middle distillate fuel of  claim 20  where the alkyl nitrate is selected from the group consisting of 2-ethylhexyl nitrate (2-EHN), iso-propyl nitrate, iso-amylnitrate, iso-hexylnitrate, cyclohexyl nitrate, dodecyl nitrate, diglycol nitrate and tetraglycol nitrate.