Reaction kinetics using DSC

Arrhenius equation gives the best description of the dependence of the reaction rate upon the temperature, for pyrolysis (cracking) and oxidation reactions. It is possible to extrapolate the reaction rate constant and the half life time to higher or lower temperatures. Therefore the coefficients of the Arrhenius equation, (activation energy E and the frequency (pre-exponential) factor A) were determined using the method according to ASTM E 

DSC oxidation in 7 bar air produce three or four very easily evaluable peaks, which may be related to the three reaction steps low temperature oxidation LTO (peak 1) fuel deposition (peak 2 and sometimes peak 3) and fuel combustion (last peak). 

The value of the first oxidation peak is relevant to practical applications since this peak marks the start of oxidation. In the graph of log versus 1 000/7 , the lines for the bitumen and the corresponding PMB each have a point of intersection, due to the different slopes of the lines, which are defined by the activation energy. This point of intersection for the first oxidation peak appears at nearly identical temperatures for each pair, except B80/ 1-PMB/l  

The half life times of bitumen B80/1 and B80/2 are higher than those of the corresponding PMB/1 and PMB/2 at temperatures below the point of intersection. The pairs B200/3-PMB/3 and B80/4-PMB/4 demonstrate an inverse behavior. The software for the eomputation of the Arrhenius coefficients only provides values of the reaction enthalpy incidentally. This enthalpy is always dependent on the inifial weight, so the results for the oxidation experiment are not valid. The data for the pyrolysis  

The low values of peak 1 of PMB/2 and PMB/3 are evident and cannot be associated with a pyrolysis reaction. 

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