High octane unleaded aviation gasoline

Abstract

An unleaded aviation fuel composition with improved octane properties has 20-35 vol. % toluene having a MON of at least 107; 2-10 vol. % aniline; from above 30 to 55 vol % of at least one alkylate or alkylate blend comprising isoparaffins 4-9 carbon atoms, 3-20 vol % C5 isoparaffins, 3-15 vol % C7 isoparaffins, and 60-90 vol % C8 isoparaffins, and less than 1 vol % C10+, based on the alkylate or alkylate blend; at least 8 vol % isopentane, 0.1-10 vol %, straight chain alkyl acetate; and 0.1-10 vol % branched chain alcohol having 4-8 carbon atoms, provided that the branched chain does not contain any t-butyl groups. The volume ratio of straight chain alkyl acetate to branched chain alcohol is in the range of 3:1 to 1:3 and the fuel composition contains less than 1 vol % of C8 aromatics.

1 . An unleaded aviation fuel composition having a MON of at least 99.6, sulfur content of less than 0.05 wt %, CHN content of at least 97.2 wt %, less than 2.8 wt % of oxygen content, a T10 of at most 75° C., T40 of at least 75° C., a T50 of at most 105° C., a T90 of at most 135° C., a final boiling point of less than 190° C., an adjusted heat of combustion of at least 43.5 MJ/kg, a vapor pressure in the range of 38 to 49 kPa, comprising
 from 20 vol. % to 35 vol. % of toluene having a MON of at least 107; 
 from 2 vol. % to 10 vol. % of aniline; 
 from above 30 vol % to 55 vol % of at least one alkylate or alkyate blend having an initial boiling range of from 32° C. to 60° C. and a final boiling range of from 105° C. to 140° C., having T40 of less than 99° C., T50 of less than 100° C., T90 of less than 110° C., the alkylate or alkylate blend comprising isoparaffins from 4 to 9 carbon atoms, 3-20 vol % of C5 isoparaffins, 3-15 vol % of C7 isoparaffins, and 60-90 vol % of C8 isoparaffins, based on the alkylate or alkylate blend, and less than 1 vol % of C10+, based on the alkylate or alkylate blend; 
 at least 8 vol % of isopentane in an amount sufficient to reach a vapor pressure in the range of 38 to 49 kPa; 
 from 0.1 vol % to 10 vol % of a straight chain alkyl acetate having a straight chain alkyl group having 4 to 8 carbon atoms; and 
 from 0.1 vol % to 10 vol % of a branched chain alcohol having from 4 to 8 carbon atoms, provided that the branched chain does not contain any t-butyl groups; 
 wherein the volume ratio of straight chain alkyl acetate to branched chain alcohol is in the range of 3:1 to 1:3; 
 and wherein the fuel composition contains less than 1 vol % of C8 aromatics. 
 
     
     
         2 . An unleaded aviation fuel composition according to  claim 1  wherein the volume ratio of straight chain alkyl acetate to branched chain alcohol is in the range of from 2:1 to 1:2. 
     
     
         3 . An unleaded aviation fuel composition according to  claim 1 , wherein the total content of isopentane, in the fuel composition is from 10 vol. % to 20 vol %. 
     
     
         4 . An unleaded aviation fuel composition according to  claim 1 , further comprising an aviation fuel additive. 
     
     
         5 . An unleaded aviation fuel composition according to  claim 1 , having a freezing point of less than −58° C. 
     
     
         6 . An unleaded aviation fuel composition of  claim 1 , wherein the alkylate or alkylate blend have a C10+ content of less than 0.1 vol % based on the alkylate or alkylate blend. 
     
     
         7 . An unleaded aviation fuel composition of  claim 1 , wherein the straight chain alkyl acetate is n-butyl acetate. 
     
     
         8 . An unleaded aviation fuel composition according to  claim 1 , wherein the branched alcohol is isobutyl alcohol. 
     
     
         9 . An unleaded aviation fuel composition of  claim 1 , having a final boiling point of at most 180° C. 
     
     
         10 . A method for operating an aircraft engine or an aircraft driven by such an engine, comprising:
 introducing into a combustion region of the engine an unleaded aviation fuel composition having a MON of at least 99.6, sulfur content of less than 0.05 wt %, CHN content of at least 97.2 wt %, less than 2.8 wt % of oxygen content, a T10 of at most 75° C., T40 of at least 75° C., a T50 of at most 105° C., a T90 of at most 135° C., a final boiling point of less than 190° C., an adjusted heat of combustion of at least 43.5 MJ/kg, a vapor pressure in the range of 38 to 49 kPa, wherein the unleaded aviation fuel composition comprises:   from 20 vol. % to 35 vol. % of toluene having a MON of at least 107;   from 2 vol. % to 10 vol. % of aniline;   from above 30 vol % to 55 vol % of at least one alkylate or alkyate blend having an initial boiling range of from 32° C. to 60° C. and a final boiling range of from 105° C. to 140° C., having T40 of less than 99° C., T50 of less than 100° C., T90 of less than 110° C., the alkylate or alkylate blend comprising isoparaffins from 4 to 9 carbon atoms, 3-20 vol % of C5 isoparaffins, 3-15 vol % of C7 isoparaffins, and 60-90 vol % of C8 isoparaffins, based on the alkylate or alkylate blend, and less than 1 vol % of C10+, based on the alkylate or alkylate blend;   at least 8 vol % of isopentane in an amount sufficient to reach a vapor pressure in the range of 38 to 49 kPa;   from 0.1 vol % to 10 vol %, preferably from 1 vol % to 8 vol %, of a straight chain alkyl acetate having a straight chain alkyl group having 4 to 8 carbon atoms; and   from 0.1 vol % to 10 vol %, preferably from 2 vol % to 8 vol %, of a branched chain alcohol having from 4 to 8 carbon atoms, provided that the branched chain does not contain any t-butyl groups;   wherein the volume ratio of straight chain alkyl acetate to branched chain alcohol is in the range of 3:1 to 1:3;   and wherein the fuel composition contains less than 1 vol % of C8 aromatics, for the purpose of providing improved octane properties.   
     
     
         11 . The method of  claim 10 , wherein the aircraft engine is a spark ignition piston-driven engine. 
     
     
         12 . The method of  claim 10 , wherein the piston-driven engine is selected from the group consisting of inline, rotary, V-type, radial, and horizontally-opposed engines. 
     
     
         13 . The method of  claim 10 , wherein the amount of the straight chain alkyl acetate having a straight chain alkyl group having 4 to 8 carbon atoms is in the range of from 1 vol % to 8 vol %. 
     
     
         14 . The method of  claim 10 , wherein the amount of the branched chain alcohol having from 4 to 8 carbon atoms is in the range of from 2 vol % to 8 vol %. 
     
     
         15 . An unleaded aviation fuel composition according to  claim 1 , wherein the amount of the straight chain alkyl acetate having a straight chain alkyl group having 4 to 8 carbon atoms is in the range of from 1 vol % to 8 vol %. 
     
     
         16 . An unleaded aviation fuel composition according to  claim 1 , wherein the amount of the branched chain alcohol having from 4 to 8 carbon atoms is in the range of from 2 vol % to 8 vol %.