Kinetics and product distribution of n‐hexadecane pyrolysis

Pyrolysis experiments on n‐hexadecane (n‐C16) were conducted at 673–723 K and n‐C16 concentrations of 0.07–1.47 mol/L by using batch type reactors. The main products of n‐C16 pyrolysis were n‐alkanes and 1‐alkenes at all the reaction conditions. The 1‐alkene/n‐alkane ratio decreased with increasing n‐C16 concentration at all the reaction temperatures. The rate of n‐C16 pyrolysis increased to a maximum and then decreased with increasing n‐C16 concentration. The activation energy of the overall rate constant of n‐C16 pyrolysis was 196 kJ/mol at 0.07 mol/L of n‐C16 concentration and 263 kJ/mol at 0.22 mol/L. To describe these phenomena, a mathematical model for the pyrolysis that expresses the radical network reaction, including initiation, isomerization, β‐scission, H abstraction, and termination, was developed. The effect of radical size on the rates of bimolecular reactions (H abstraction and termination) was important for a correct quantitative description. Comparison between the experimental data and the model showed that the rates of bimolecular reactions were inversely proportional to the carbon number i of radical Ri. The model can predict product distribution and n‐C16 pyrolysis rate in a wide range of temperatures (603–893 K) and n‐C16 concentrations (6.86 × 10−3 2.48 mol/L). Furthermore, the model can describe the pyrolysis kinetics of n‐C10–n‐C25 by considering the carbon number of the hydrocarbon.