Range of low temperature oxidation LTO

The increase of pressure effects a shift of the peak maximum temperatures towards lower values (Table 4-197) at equal heating rates. The dependence of the activation energy E and the frequency factor log A on the pressure are shown in figs. 4-168 and 4-169. Now 

Activation Energy E versus Pressure P Curve 1 n-Hexacontane Curve 4 Asphaltenes from 3 Curve 2 w-Hexylpyrene Curve 5 Dispersion Medium from 3 Curve 3 Vacuum Residue 

As expected the asphaltenes possess the highest oxidation stability in the LTO range, which is manifested by the high values of the activation energy, the frequency factor, and thereupon of the half life time. The low values for the kinetic coefficients and log A for n-hexacontane do not noticably affect the half life times. In contrast to the values for Athabasca bitumen (Fig. 4-158), the real systems tested display higher values for their half hfe times, by approximate half a power of ten. 

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