Understanding the Catalytic Oxidation of Hydrogen Chloride to Chlorine from Thermodynamics and Reaction Kinetics

The vast emission of hydrogen chloride (HCl) in the chlorination industry has raised great interest in producing chlorine (Cl2) directly from HCl. In this work, thermodynamic analysis and kinetic studies were carried out to understand the engineering of the catalytic oxidation of HCl to Cl2. Thermodynamic calculation indicates that the equilibrium conversion of HCl decreases with an increase in the reaction temperature and feed molar ratio n(HCl)/n(O2), and the equal molar HCl/O2 feed results in a higher HCl conversion. The equal molar HCl/O2 feed also leads to a minimum adiabatic temperature rise, which would be beneficial to both equilibrium conversion of HCl and catalyst. Regarding catalysts prepared in this work, the influence of internal and external diffusion on the reaction was analyzed, in which both of their effects can be ignored. Finally, based on the Langmuir–Hinshelwood mechanism, the kinetic model of HCl conversion with surface reaction as the rate-controlling step was established. The reliability of the kinetic model was verified by a satisfactory agreement between the experimental data and model calculation.