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Hydrocarbons - Autoignition Temperatures and Flash Points

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The tables and figures below show the autoignition temperature (AIT) and flash point (FP) for different hydrocarbons. In the figures, the AIT and FP are shown as function of number of carbon atoms in the hydrocarbons, which are grouped as n-alkanes, 1-alkenes, 2-methylalkanes, 3-methylalkanes, 2,2,dimethylalkanes, 2-methylalkenes, cycloalkanes, alkylcyclohexanes, cycloalkenes, alkylbenzenes and alkylnaphthalenes.

  • Autoignition temperature = kindling point
    • is the temperature at which a material spontaneously ignites in a normal atmosphere without an external source of ignition.
    • is the temperature required to supply the activation energy for combustion
    • is usually applied to combustible fuel mixtures
  • Flash point - the lowest temperature at which vapour of a volatile material can be ignited whit an ignition source present

  • Values of autoignition temperature are generally higher than flash point, as given for pure hydrocarbons in the tables and figures below .
  • With an increase in pressure the autoignition temperature decreases. This is particularly important from a safety point of view when hydrocarbons are compressed.
  • Hydrocarbons with high vapor pressures (lighter compounds) have low flash points. Generally, flash point increases with an increase in boiling point.
  • Flash point is an important parameter for safety considerations, especially during storage and transportation of volatile petroleum products (i.e., LPG, light naphtha, gasoline) in a high-temperature environment. The surrounding temperature around a storage tank should always be less than the flash point of the fuel to avoid possibility of ignition.
  • Flash point should not be mistaken with fire point, which is defined as the minimum temperature at which the hydrocarbon will continue to burn for at least 5 s after being ignited by a flame.
  • Temperature classification of equipment in hazardous areas are related to surrounding substances auto-ignition temperature.

See also Flash Point - Fuels






Hydrocarbons - Autoignition Temperatures and Flash Points
IUPAC name Common name Flash point Autoignition temp
°C °F °C °F
Benzene Benzol -11 12 555 1031
But-1-ene 1-butene, 1-butylene, Ethylethylene -80 -112 360 680
But-2-ene Cis-2-butene -72 -98 325 617
But-2-ene Trans-2-butene -73 -99 324 615
1,2-butadiene <-50 <-58 340 644
1,3-butadiene Biethylene, divinylbutadiene, pyrrolylene, vinylethylene -85 -121 415 779
N-butane -60 -76 365 689
Butylbenzene 58 136 410 770
Butylcyclohexane 41 106
Butylcyclopentane 32 90
1-butyne Ethylacetylene <-14 <6.8
2-butyne Crotonylene -25 -13
Cyclobutane <10 <50
Cyclodecane 65 149
Cycloheptane 6 43
1,3-cyclohexadiene -8 18
Cyclohexane Hexamethylene, hexanaphthene -18 0 260 500
Cyclohexene -17 1 265 509
Cyclohexylbenzene 99 210
Cyclooctane 28 82 250 482
Cyclopentane -51 -60 320 608
Cyclopentene -29 -20 309 588
Cyclopropane Trimethylene 495 923
o-cymene 53 127
N-decane 46 115 200 392
2-decanol 85 185
1-decene 44 111 230 446
2,3-dimethyl-2-butene Tetramethylethylene <-20 <-4 400 752
1,2-dimethylbenzen orto-xylene 30 86 465 869
1,3-dimethylbenzen meta-xylene 25 77 540 1004
1,4-dimethylbenzen para-xylene 25 77 540 1004
2,2-dimethylbutane Neohexane -48 -54 435 815
2,3-dimethylbutane Diisopropyl -29 -20 415 779
2,2-dimethylhexane -3 27
2,2-dimethylpentane -21 -6 320 608
3,3-dimethylpentane -15 5 320 608
2,3-dimethylpentane -12 10 330 626
2,4-dimethylpentane <-20 <-4 325 617
2,2-dimethylpropane Neo-pentane, trimethylethane -19 -2 450 842
Diphenyl methane 130 266
N-docosane 211 412
Docosanoic acid Behenic acid 176.3 349
N-dodecane 80 176 200 392
Dodecanoic acid Lauric acid 134.1 273
1-dodecanol Lauryl alcohol 119 246
1-dodecene 76 169 225 437
N-eicosane 187 369
Ethane -135 -211 515 959
Ethene Ethylene 440 824
Ethylbenzene 15

59

Ethylcyclohexane 22

72

Ethylcyclopentane -4

25

Ethyne Acetylene 305 581
N-heptacosane 269 516
N-heptadecane 148 298
N-heptane -7 19 220 428
2-heptanol 59 138
1-heptene 1-heptylene -8 18 250 482
Cis-2-heptene -6 21
Trans-2-heptene -1 30
Cis-3-heptene -7 19 260 500
Trans-3-heptene -6 21
1-heptyne -2 28 245 473
N-hexadecane 135 275
N-hexane Hexane <-20 <-4 230 446
3-hexanol 41.7 107
1-hexene -26 -15 255 491
Cis-2-hexene -25 -13 244 471
Trans-2-hexene -25 -13 244 471
Hexylbenzene 80 176
1-hexyne -20 -4 263 505
3-hexyne -14 7
Isobutylbenzene 55 131
Isopropylbenzene Cumene 31 88 420 788
Methane -135 -211 595 1103
2-methyl-1,3-butadiene Isoprene -54 -65 220 428
2-methyl-1-butene -37 -35
3-methyl-1-butene -58 -72 365 689
1-Methyl-1-cyclohexene -4 25
4-Methyl-1-cyclohexene -1 30
2-methyl-1-heptene 14 57
2-methyl-1-hexene -6 21
2-methyl-1-octene 31 88
2-methyl-1-pentene 1-methyl-1-propylethylene -26 -15 300 572
2-methyl-1-propene Isobutene, Isobutylene -80 -112 465 869
2-methyl-2-butene Trimethylethylene, beta-iso-amylene -45 -49 290 554
Methylbenzene Toluene, toluol 6 43 535 995
2-methylbutane Iso-pentane -51 -60 420 788
Methylcyclohexane Heptanaphthene -4 25 260 500
Methylcyclopentane <-10 <14 315 599
2-methyldecane 50 122
2-methylheptane 6 43
3-methylheptane 6 43 410 770
4-methylheptane 6 43
2-methylhexane -10 14 280 536
3-methylhexane -11 12 280 536
1-methylnaphthalene 94 201 485 905
2-methylnaphthalene 98 208 488 910
2-methylnonane iso-decane 46 115
2-methyloctane isononane, dimethylheptane 26 79
2-methylpentane iso-hexane, i-caproylhydride <-7 <19.4 300 572
3-methylpentane Diethylmethylmethane <-20 <-4 300 572
2-methylpropane iso-butane -83 -117 460 860
2-methylundecane 42 108
Naphthalene 80 176 540 1004
N-nonadecane 168 334
N-nonane 31 88 205 401
2-nonanol 82.2 180
3-nonanol 79.5 175
4-nonanol 79.5 175
1-nonene 26 79
N-octadecane 165 329
N-octane 12 54 205 401
1-octanol Capryl alcohol 81 178 259 497
1-octene 1-caprylene 10 50 240 464
N-pentadecane 114

237

N-pentane -49 -56 260 500
1-pentene n-amylene, propylethylene -51 -60 280 536
Pentylbenzene Phenylpentane, amylbenzene 66 151
1-pentyne Propylacetylene <-20 <-4
Phenanthrene 171 340 >450 >842
Propane -104 -155 470 878
Propene Propylene -108 -162 485 905
Propylbenzene 39 102 450 842
Propylcyclohexane 35 95 248 478
Propylcyclopentane 16 61
Propyne 340 644
Pyrene Benzo(def)phenanthrene 200 392
Styrene 32

90

N-tetradecane 100

212

N-tridecane 79 174
Tridecanoic acid Tridecylic acid 139.6 283
1,2,3-trimethylbenzene 51 124
1,3,5-trimethylbenzene Mesitylene, trimethylbenzol 44 111 550 1022
2,2,4-trimethylpentane Iso-octane -9 16 410 770
N-undecane 61 142 195 383
Undecanoic acid 128 262
3-undecanol 94 201
1-undecene 63 145
o-xylene 17 63
m-xylene 25 77
p-xylene 25 77



In oil industry, the following terms for the different hydrocarbons are used:

Paraffins: Alkenes -  lineare, saturated molecules, straight or branched chains

Olefins: Alkenes - lineare, unsaturated molecules, straight or branched chains  (these are normally not present in unprocessed crude oil)

Naphthenes: Cycloalkanes - saturated ring structures, or cycloalkenes - partly saturated ring structures, with or without substituents connected to the ring

Aromatics: Unsaturated 6-ring structures (3 doble bounds in one ring), with or without substituents

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