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7/31/2019 Final Octane Number Assignment Sharing
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An important property of the Hydrocarbon fuels is their
autoignition temperature, the temperature at which
the fuel will ignite and burn without any source of
ignition.
The autoignition temperature of H/C is related to its molecular
composition and structure.
Effects of the molecular composition and structure of H/C are
explained in the following paragraphs:
Effect of Molecular Composition :As the number of Carbon atoms
increases, autoignition temperature
decreases, and that one can observe from the data represented
here.
e.g.
n-pentane--> 260 C
n-Hexane --> 225 C and so on....
Effect of Structure : As the amount of branching (isomerization)
or the number of rings increases, autoignition
temperature increases. In similar way, as number of double and
triple bonds increases, autoignition
temperature increses, that can be observed from the data
represented here.
n-pentane --> 260 C (R.O.N 62)
iso-pentane --> 420 C (R.O.N. 92.3)
n-hexane -->225 C (R.O.N. 24.8)
1-hexene --> 253 C (R.O.N. 76.4)
cyclohexane -->245 C (R.O.N. 83)
Benzene --> 560 C (R.O.N. 98)
Autoignition Temperature is having major influence on the Octane
Number, that can be observed from the data
represented. Higher the autoignition temperature, higher the
Octane number.
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Paraffins
H/C ChemicalFormula
Normal BoilingPoint (
oC)
RON MON Auto-IgnitionTemperature (C)
Methane CH4 -161.49 107.5 580
Ethane C2H6 -88.6 107.1 515
Propane C3H8 -42.05 105.7 480
n-Butane C4H10 -0.5 94 420
n-Pentane C5H12 36.07 62 260
n-Hexane C6H14 68.73 24.8 225
n-Heptane C7H16 98.43 0 0 222
n-Octane C8H18 125.68 -19 220
n-Nonane C9H20 150.72 -34 205n-Decane C10H22 174 -53 210
Olefins
H/CChemical
Formula
Normal Boiling
Point (oC)
RON MONAuto-Ignition
Temperature (C)
Ethylene C2H4 -78.27 100.2 490
Propylene C3H6 -12.05 100.4 458
1-butylene C4H8 -6.38 97.4 385
2-butylene C4H8 1 99.6 325
1-Pentylene C5H10 29.96 91 298
1-hexylene C6H12 63.72 76.4 253
1-Heptene C7H14 93.64 60
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Aromatics
H/CChemical
Formula
Normal Boiling
Point (oC)
RON MONAuto-Ignition
Temperature (C)
Benzene C6H6 80.09 98 91 560
Ethyl Benzene C8H10 136.2 107 98 460
Toluene C7H8 110.63 110 103 530
P-Xylene C8H10 138.36 117 111 530
M-Xylene C8H10 139.12 118 115 527
O-Xylene C8H10 144.43 120 102 463
Naphthenes
H/CChemical
Formula
Normal Boiling
Point (oC)
RON MONAuto-Ignition
Temperature (C)
cyclo-Hexane C6H12 80.72 83 77 245
Cyclopentane C5H10 49.25 101.3 84.9 361
Isomers
H/CChemical
Formula
Normal Boiling
Point (oC)
RON MONAuto-Ignition
Temperature (C)
2-methyl heptane (iso-
octane)C8H18 23
iso-Pentane C5H12 27.84 92.3 90.3 420
2,2,4-Trimethylpentane
(iso-Octane)C8H18 99.24 100 100 447
iso-Butane C4H10 -11.72 102 462
