Reactive structure index for correlation of high temperature thermal stability of saturated hydrocarbons
- Pennsylvania State Univ., University Park, PA (United States)
For the development of advanced jet fuels, it is important to examine how the structure of various (jet fuel range) hydrocarbons affects their thermal stability at temperatures above 400{degrees}C under elevated pressures. The objective of this work is to develop a reactive structure index (RSI) to correlate the molecular structures of saturated hydrocarbons with their decomposition rate constants using a group contribution method. The effects of ring-structure, side-chain length (up to C{sub 10}), steric isomers, and branching on the decomposition rate of open-chain alkanes and cycloalkanes were studied at 450{degrees}C under an initial pressure of 0.79-MPa N{sub 2} in batch reactors. The thermal stability of alkanes/cycloalkanes decreases with increasing chain/side-chain length. Cycloalkanes ({>=}5-membered ring) are more stable than n-alkanes with the same carbon number. The cis isomer usually decomposes about 3-5 times faster than the trans isomer. One exception observed is that trans-1,3-dimethylcyclohexane decomposes about 2.5 times faster than its cis-isomer. The presence of a branch or branches appears to decrease the rate of decomposition as compared to that of the n-alkanes. The RSI can be derived by integrating several sub-indices determined from the structure via a simple group contribution method, including ring index (RI), substitution index (SI), chain length index (CLI), and conformation index (CI). Good correlation between RSI and rate constant were obtained for over 30 saturated hydrocarbons.
- OSTI ID:
- 370772
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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