auto ignition temperature

[rgrokkam]

Is there any relation between auto ignition temperature and C-H ratio?

Many thanks

 

[owg]

In a homologous series of organic compounds, the Auto ignition temperature (AIT) decreases with increasing molecular weight. Also a branched compound will have a higher AIT than the corresponding straight-chain compound. There is a plot for straight chain paraffins in one of the NFPA publications. The subject is discussed in Bodurtha's book on Industrial Explosion Prevention and Protection.

HAZOP at

http://www.curryhydrocarbons.ca

 

[25362]

The only probable exception to owg's statement is acetylene.

From the net:


AIT = Minimum Autoignition Temperature in ^oC under test conditions.

AIT
n-butane 370
n-pentane 260
n-hexane 225
n-heptane 225
n-octane 220
n-decane 210
n-dodecane 204
n-tetradecane 200

2-methylpropane 460
2-methylbutane 420
2-methylpentane 306
2,2,3-trimethylbutane 420
2,2,4-trimethylpentane 415

cyclopentane 380
cyclohexane 245
methylcyclohexane 250

benzene 560
toluene 480
ethyl benzene 430
meta-xylene 463
para-xylene 530
ortho-xylene 530

 

[dcasto]

Ethylene and acetylene auto ignition temperature needs clarification. These two chemicals decompose into C +CH4 + H2, raising the pressure by a factor of three and giving off large amounts of energy. Their auto decomposition temperature is a function of pressure. Quite a tricky pair.