Autoignition temperatures estimation

Another method of estimating autoignition temperatures is to compare values for a compound with other members of its homologous series on a plot vs. carbon number as the temperature decreases and carbon number increases. Affens gives a formal procedure for such estimation. 

These results thus show that whereas the flashpoint was only moderately influenced by the compound structure (their chemical functionality but especially their atomic composition and vapour), autoignition temperatures seem to be closely linked to the structural factors that affect the chain. So additivity rules for estimation of AIT should be sought. Every time a chemical or physical property is highly influenced by the structure, chemists tried to establish rules that enable one to reduce a molecule to characteristic groups for which the contribution to the value of this property is known. This was done for instance by Kinney for boiling points and Benson2 for thermochemical properties. 

An approximate mathematical analysis is considered to estimate the functional dependence of the gas properties and vessel size on the autoignition temperature. We anticipate that Tc will be close to 7X, so we write... 

Very large reserves of natural gas are believed to lie at depths of 4600-9200 meters (15,000-30,000 feet), called deep gas. Since methane remains stable up to its autoignition temperature of550°C (1022°F), it is found at depths where oil is not found, presumably because oil will be transformed in part to methane at lower temperatures. Deep gas is expensive to drill for, but the quantities are estimated to be very large. Technology has been developed to enhance recovery of deep gas when it is found. 

The relative ease or difficulty of incineration has been estimated on the basis of the heat of combustion, thermal decomposition kinetics, susceptibility to radical attack, autoignition temperature, correlations of other properties, and destruction efficiency measurements made in laboratory combustion tests. Laboratory studies have indicated that no single ranking procedure is appropriate for all incinerator conditions. In fact, a compound that can be incinerated easily in one system may be the most difficult to remove from another incinerator due to differences in the complex coupling of chemistry and fluid mechanics between the two systems. 

Egolf, L.M. and Jurs, P.C. (1992). Estimation of Autoignition Temperatures of Hydrocarbons, Alcohols and Esters from Molecular Structure. Ind.Eng.Chem.Res., 31,1798-1807. 

Reference Pintar, A. J., Estimation of Autoignition Temperature, Technical Support Document DIPPR Project 912, Michigan Technological University, Houghton, 1996. 

Example Estimate the autoignition temperature of 2,3-dimethylpentane. Structure and group information ... 

These QSPR methods can be used to predict any chemical property that is dependent upon molecular structure. Publications are available that provide examples of uses in a wide variety of applications for chemical or physical property estimation or biological activity estimation. Our group has published papers on property estimation dealing with normal boiling points, critical temperatures, surface tension, Henry s law constants, aqueous solubility, supercritical CO2 solubility, autoignition temperature, gas chromatographic retention times, and ion mobility constants. Several specific examples are given as illustrations of the capabilities of the method. 

Attempts have been made to estimate the volumetric heat release rate during autoignition, from pressure records and CARS temperature measurements [106]. It was estimated that the activation temperature for this was in the region of 20,000 K under knocking conditions. Paraffinic fuels gave a higher volumetric heat release rate than aromatic fuels and were more prone to knock severely. 

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