Diesel fuel and a method of operating a diesel engine

Abstract

A diesel fuel based on a blend of a diesel fuel derived from a Fischer-Tropsch process, and a mineral oil based diesel fuel having a sulfur content of less than 100 ppmw; and a method of operating a diesel engine, which method involves combusting such diesel fuel in the diesel engine.

We claim: 
     
         1 . A diesel fuel blend that provides a relative reduction to the emission of oxides of nitrogen when combusted in a heavy duty diesel engine, the diesel fuel blend comprising:
 (a) a diesel fuel derived from a Fischer-Tropsch process; and   (b) a mineral oil based diesel fuel having a sulfur content of less than 100 ppmw;   
       wherein the weight fraction of component (a) in the blend is between 0.28 and 0.5. 
     
     
         2 . The diesel fuel blend as defined in  claim 1  wherein the weight fraction of component (a) in the blend is between 0.28 and 0.4. 
     
     
         3 . The diesel fuel blend as defined in  claim 1  wherein the weight fraction of component (a) in the blend is between 0.3 and 0.35. 
     
     
         4 . The diesel fuel blend as defined in  claim 1  wherein the diesel fuel further comprises one or more additives selected from the group consisting of detergents, dehazers, anti-foaming agents, anti-rust agents, anti-static agents, pipeline drag reducers, flow improvers, lubricity additives, antioxidants and wax anti-settling agents. 
     
     
         5 . The diesel fuel blend as defined in  claim 1  wherein the diesel fuel further comprises a lubricity additive. 
     
     
         6 . The diesel fuel blend as defined in  claim 1  wherein, when combusted, said diesel fuel produces an emission of oxides of nitrogen from said combustion which is P % lower than an emission of oxides of nitrogen which can be calculated on the basis of a linear blending behavior of components (i) and (ii), P is relative to the emission of oxides of nitrogen caused by the said mineral oil based diesel fuel, and P is defined by the equation
     P=A·X (1 −X ), 
 
       in which equation A is a number in the range of from 10 to 25, and X is the weight fraction of component (i) in the blend, expressed as a number in the range of from 0 to 1. 
     
     
         7 . The diesel fuel blend as defined in  claim 1  wherein upon combustion, said fuel blend produces an emission of oxides of nitrogen that is lower than an emission of oxides of nitrogen that can be calculated on the basis of linear blending behavior of components (a) and (b). 
     
     
         8 . A diesel fuel blend providing a relative reduction to the emission of oxides of nitrogen when combusted in a heavy duty diesel engine, the diesel fuel blend comprising:
 (a) a diesel fuel derived from a Fischer-Tropsch process; and   (b) a mineral oil based diesel fuel having a sulfur content of less than 100 ppmw and a T 90  of more than 261° C.,
 wherein the weight fraction of component (a) in the blend is between 0.28 and 0.5. 
   
     
     
         9 . The diesel fuel blend as defined in  claim 8  wherein the mineral oil based diesel fuel has a T 90  of more than 275° C. 
     
     
         10 . The diesel fuel blend as defined in  claim 8  wherein the mineral oil based diesel fuel has a T 90  of more than 285° C. 
     
     
         11 . The diesel fuel blend as defined in  claim 8  wherein the diesel fuel further comprises one or more additives selected from the group consisting of detergents, dehazers, anti-foaming agents, anti-rust agents, anti-static agents, pipeline drag reducers, flow improvers, lubricity additives, antioxidants and wax anti-settling agents. 
     
     
         12 . The diesel blend fuel as defined in  claim 8  wherein the diesel fuel further comprises a lubricity additive. 
     
     
         13 . The diesel blend fuel of  claim 8  wherein the diesel fuel derived from a Fischer-Tropsch process, component (a), exhibits:
 a boiling range of from about 150° C. to 400° C.; 
 a T90 of from 280° C. to 340° C.; 
 a density of from 0.76 g/mL to 0.79 g/mL at 15° C; a cetane number of at least 60; and 
 a viscosity of from 2.5 centistokes to 4 centistokes at 40° C. 
 
     
     
         14 . The diesel fuel of  claim 8  wherein the mineral oil based diesel fuel, component (b), exhibits:
 a boiling range of from 158° C. to 355° C.; 
 a polynuclear aromatics (PNA) content of at most 20%; 
 a cetane number of at least 25; 
 a Ramsbottom on 10% of at most 0.15; 
 a nitrogen content of at mot 100 ppmw; and 
 a cyclic paraffin content of at least 5% by weight. 
 
     
     
         15 . The diesel fuel of  claim 14  wherein the mineral oil based diesel fuel, component (b), exhibits:
 a boiling range of from 158° C. to 355° C.; 
 a polynuclear aromatics (PNA) content of at most 20%; 
 a cetane number of at least 25; 
 a Ramsbottom on 10% of at most 0.15; 
 a nitrogen content of at mot 100 ppmw; and 
 a cyclic paraffin content of at least 5% by weight. 
 
     
     
         16 . The diesel fuel blend as defined in  claim 8  wherein, when combusted, said diesel fuel produces an emission of oxides of nitrogen from said combustion which is P % lower than an emission of oxides of nitrogen which can be calculated on the basis of a linear blending behavior of components (i) and (ii), P is relative to the emission of oxides of nitrogen caused by the said mineral oil based diesel fuel, and P is defined by the equation
     P=A·X (1 −X ) 
 
       in which equation A is a number in the range of from 10 to 25, and X is the weight fraction of component (i) in the blend, expressed as a number in the range of from 0 to 1. 
     
     
         17 . The diesel fuel blend as defined in  claim 8  wherein upon combustion, said fuel blend produces an emission of oxides of nitrogen that is lower than an emission of oxides of nitrogen that can be calculated on the basis of linear blending behavior of components (a) and (b). 
     
     
         18 . The diesel fuel blend of  claim 8  wherein the blend has a boiling range of from 160° C. to 355° C.; a T 90  of at least 310° C.; an aromatic content less than or equal to 20% w; a cetane number of at least 42; a sulfur content of less than 50 ppm; a Ramsbottom on 10% of less than 0.15; and a nitrogen content of less than 10 ppm. 
     
     
         19 . The diesel fuel blend of  claim 8  wherein the diesel fuel derived from the Fischer-Tropsch process, component (a) comprises:
 at least 90% w of iso and linear paraffins; 
 a boiling range of from about 150° C. to 400° C.; 
 a T 90  of from 280° C. to 340° C.; 
 a density of from 0.76 g/mL to0.79 g/mL at 15° C.; 
 a cetane number of at least 60; and 
 a viscosity of from 2.5 centistokes to 4 centistokes at 40° C. 
 
     
     
         20 . A diesel fuel blend that provides a relative reduction to the emission of oxides of nitrogen when combusted in a heavy duty diesel engine, the diesel fuel blend comprising:
 (a) a diesel fuel derived from a Fischer-Tropsch process, diesel fuel derived from the Fischer-Tropsch process comprising at least 90% w of iso and linear paraffins, a boiling range of from about 150° C. to 400° C., a T 90  of from 280° C. to 340° C., a density of from 0.76 g/mL to0.79 g/mL at 15° C., a cetane number of at least 60, and a viscosity of from 2.5 centistokes to 4 centistokes at 40° C.; and   (b) a mineral oil based diesel fuel having a sulfur content of less than 100 ppmw;   wherein the weight fraction of component (a) in the blend is between 0.28 and 0.5; and   wherein, when combusted, said diesel fuel blend produces an emission of oxides of nitrogen from said combustion which is P % lower than an emission of oxides of nitrogen which can be calculated on the basis of a linear blending behavior of components (i) and (ii), P is relative to the emission of oxides of nitrogen caused by the said mineral oil based diesel fuel, and P is defined by the equation
     P=A·X (1 −X ), 
   
       in which equation A is a number in the range of from 10 to 25, and X is the weight fraction of component (i) in the blend, expressed as a number in the range of from 0 to  1 .