Thermal oxidative and thermal stability of acyclic alkenes at 260–325°C

Synthetic kerosenes produced from non-petroleum resources can contain percentage level alkenes that may affect thermal oxidative stability, which is an important requirement for jet fuel. The thermal oxidative stability of several alkenes was evaluated at 260–325°C under conditions of limited oxygen availability to approximate conditions in the jet fuel thermal oxidative stability test (JFTOT). Mixtures of 10 wt.% 1-hexene, 1-decene, 1-dodecene, 2,3-dimethyl-2-butene, and 3,3-dimethyl-1-butene, respectively, in 90 wt.% n-decane were converted under thermal (N₂ atmosphere) and thermal oxidative (air atmosphere) conditions. Products were characterized using gas chromatography, with density and refractive index used as supporting measures to detect macroscopic changes. Conversion was detected both under thermal and thermal oxidative conditions, with the latter resulting in a wider range of products and higher concentration of products. Evidence was found of two modes of free radical initiation: (i) oxidative affecting both saturated and unsaturated compounds, and (ii) thermal affecting unsaturated compounds. It was further found that within the homologous series of 1-alkenes chain length had little impact on the progression of thermal oxidative conversion. Conversely, for alkenes of the same chain length, skeletal structure and alkene-position had a considerable impact on thermal oxidative conversion; not all alkenes were prone to addition product formation.