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

Abstract

The vast emission of hydrogen chloride (HCl) in the chlorination industry has raised great interest in producing chlorine (Cl 2 ) 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 Cl 2 . Thermodynamic calculation indicates that the equilibrium conversion of HCl decreases with an increase in the reaction temperature and feed molar ratio n(HCl)/n(O 2 ), and the equal molar HCl/O 2 feed results in a higher HCl conversion. The equal molar HCl/ O 2 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.

Alternate Preparation of Norbornene and Dimethanooctahydronaphthalene via Diels–Alder Reaction: Process Simulation and Experimental Verification

“…And both high and low temperatures were not conducive to the synthesis of citral. It has been shown that the reaction can be carried out more smoothly by changing the temperature and molar ratio of the system, and increasing the pressure was beneficial to both kinetics and thermodynamics. , Zhou et al demonstrated that excessive temperature was not favorable for the D–A reaction of 2-(1-alkynyl)-2-alken-1-ones and enals, and an appropriate reaction temperature was crucial for the D–A reaction. At a reaction temperature of 60 °C with toluene as the solvent, the final product yield can reach 62%.…”

Electrochemical Synthesis of Aryl Chlorides Using HCl as the Chlorine Source

“…Almost 50% of chemical processes involve chlorine, while 50% of the used chlorine is discharged in forms of side products like hydrogen chloride or chloride salts. , Thus, sustainable chlorine recycling becomes crucial for clean production in the chemical industry. To recycle chlorine from HCl, quite a few electrochemical processes has been developed. − For example, the reaction kinetics were well established for deep understanding of catalytic oxidation of HCl , ; a phase change absorbent (MDEA/NHD) was developed for HCl absorption to produce hydrogen and chlorine by electrolysis . However, as the generation of HCl is unavoidable in traditional chlorination processes, the recycling system requires intensive energy input and results in great emissions …”

“…To recycle chlorine from HCl, quite a few electrochemical processes has been developed. 4−7 For example, the reaction kinetics were well established for deep understanding of catalytic oxidation of HCl 8,9 ; a phase change absorbent (MDEA/NHD) was developed for HCl absorption to produce hydrogen and chlorine by electrolysis. 10 However, as the generation of HCl is unavoidable in traditional chlorination processes, the recycling system requires intensive energy input and results in great emissions.…”

Promotion of ZrO2 on RuO2/Al2O3 Catalyst for HCl Catalytic Oxidation: Effect of High Temperature Holding in Nitrogen Atmosphere

“…1,2 In the course of these chlorine-related processes, the utilization ratio of chlorine atoms is less than a half, resulting in a large amount of hydrogen chloride (HCl) emission as byproduct. 3,4 Therefore, converting HCl to Cl 2 to construct a closed circulation of chlorine resource became an inevitable choice to ensure the sustainable development of chlorine-related industries. 5,6 Compared with electrolysis and direct oxidation, the catalytic oxidation of HCl to Cl 2 (Deacon process) has been considered to be the most economical route, and the RuO 2 -based catalyst supported on TiO 2 (rutile) or SnO 2 (cassiterite) was one of the current commercialized catalysts.…”

“…Chlorine (Cl 2 ) is one of the important chemical feedstock widely used in the production of polymers, crop protection, pharmaceuticals, organic fluorine, and others. , In the course of these chlorine-related processes, the utilization ratio of chlorine atoms is less than a half, resulting in a large amount of hydrogen chloride (HCl) emission as byproduct. , Therefore, converting HCl to Cl 2 to construct a closed circulation of chlorine resource became an inevitable choice to ensure the sustainable development of chlorine-related industries. , Compared with electrolysis and direct oxidation, the catalytic oxidation of HCl to Cl 2 (Deacon process) has been considered to be the most economical route, and the RuO 2 -based catalyst supported on TiO 2 (rutile) or SnO 2 (cassiterite) was one of the current commercialized catalysts. , The contrast of the effect of support type (TiO 2 , SnO 2 , SiO 2 , Al 2 O 3 , etc.) on the performance of RuO 2 -based catalysts has been previously investigated by researchers.…”