Study of The Thermodynamics of The Propane-Butane Fraction Pyrolysis Process

This study focuses on enhancing the sorption and catalytic properties of high-silica mesoporous zeolites (HSMZs) and investigating the pyrolysis processes of the propane-butane fraction at elevated temperatures. The HSMZ samples were decationized using a 25% ammonium chloride solution and modified to their H-form aluminosilicate states. Various metal oxides such as CuO, Li₂O, La₂O₃, ZnO, Fe₂O₃, and BaO were employed as modifiers in different concentrations. Using the modified zeolites, the thermal and catalytic pyrolysis of propane-butane hydrocarbon mixtures was carried out in a flow reactor at high temperatures (~650–800 °C). To evaluate catalytic activity, a comparative analysis was conducted between thermal and catalytic cracking results. The selectivity and overall yields of unsaturated C₂–C₄ hydrocarbons, including ethylene and propylene, were measured. The catalysts were prepared via extrusion and tabletting methods, and their structures were characterised using infrared spectroscopy (IR) and X-ray phase analysis. The IR spectra revealed absorption bands at 1120, 800, 560, and 460 cm⁻¹, indicating the crystallinity and framework structure of the HSMZs. Thermodynamic calculations of dehydrogenation, cracking, and dehydrocracking of low-molecular-weight saturated hydrocarbons (propane and butane) were performed in the range of 200–800 °C. Based on the changes in Gibbs free energy (∆G⁰) and equilibrium constants (Kₚ), the temperature-dependent stability of each process was assessed. The results allowed for the identification of optimal temperature intervals for obtaining valuable unsaturated hydrocarbons from propane-butane mixtures. These findings provide insights for modelling high-temperature thermal and catalytic processes, improving the use of modified zeolites, and increasing the selectivity of the resulting products.