The application of composite energy methods to n-butyl radical β-scission reaction kinetic estimations

Hydrocarbon cracking reactions are key steps in petroleum refinery processes and understanding reaction kinetics has very important applications in the petroleum industry. In this work, G3 and complete basis set (CBS) composite energy methods were applied to investigate butyl radical β-scission reaction kinetics and energetics. Experimental thermodynamic and kinetic data were employed to evaluate the accuracy of these calculations. The CBS compound model proved to have excellent agreement with the experimental data, indicating that it is a reliable method for studying other large hydrocarbon cracking reactions. Furthermore, a reaction kinetic model with pressure and temperature effects was proposed. For P ≤ P₀, k = 2.04 × 10⁹ × P^0.51 × e^(-9745.70/T); for P > P ₀, k = 9.43 × 10¹³ × e ^{(-15135.70/T)}, where k is the reaction rate constant in units of s^-1; P is pressure in units of kPa, T is temperature in units of Kelvin, and the switching pressure is P₀ = 1.53 × 10 ⁹ × e^{(-10610.24/T)}. This model can be easily applied to different reaction conditions without performing additional expensive and complicated calculations.