Langmuir–Hinshelwood Kinetic Model for Butane Hydrogenolysis on Ir–Pt/Al₂O₃/ZSM-5

A Langmuir–Hinshelwood (LH) kinetic model was developed to represent the reactions of butane hydrogenolysis over Pt–Ir (0.3–0.3 wt %)/Al2O3/ZSM-5. A wide range of experimental data generated from lab reactors was used to optimize kinetic parameters (activation barriers, equilibrium constants, and prefactors). The optimized LH kinetic model showed a good agreement with the experimental data, indicating that the LH model can be used to predict reactor performance within the experimental boundaries: temperature 250–300 °C, hydrogen/butane: 1.0–9.6, and WHSV: 2–160 h–1. Both model and experiments show that butane hydrogenolysis achieves an average of ∼5% methane, ∼79% ethane, and ∼16% propane at the butane conversion level of around 80%, until the reaction temperature reaches 295 °C. Beyond this temperature, secondary reactions such as propane and ethane decomposition result in carbon loss to methane. Screening of process variables using the LH kinetic model predicts that the highest ethane selectivity of ∼80% can be achieved at a temperature of ∼280 °C and hydrogen/butane ratio of 2.0.