HIGH OCTANE UNLEADED AVIATION GASOLINE

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 75ºC, T40 of at least 75º C, a T50 of at most 105º C, a T90 of at most 135ºC, 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 oralkyate blend having an initial boiling range of from 32°C to 60°C and a final boiling range of from 105°C to140°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 actetate to branched chain alcohol is in the range of 3:1 to 1:3; and wherein the fuel composition contains less than 15 vol% of C8 aromatics. As well as meeting the requirements of the ASTM D910 specification, the unleaded aviation fuel compositions ofthe present invention have improved octane properties.