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Why is a catalyst used when hydrogen chloride is converted into chlorine?

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A labeled diagram of the chlorine element from the periodic table shows its atomic number 17, symbol Cl, electron configuration, and atomic weight range. The box is shaded green to indicate chlorine is a halogen, with icons for orthorhombic crystal structure, gas state at room temperature, and strong acidity. A key explains the icons and colors used. — chlorine Properties of chlorine.

When hydrogen chloride is converted into chlorine through oxidation, a catalyst—such as cupric chloride—is used to achieve a reasonable rate of conversion at a practical temperature of 400 °C (750 °F).1

While the equilibrium constant for this reaction decreases as the temperature increases, meaning the reaction proceeds less extensively at higher temperatures, the catalyst is essential to ensure the process occurs at a commercially viable speed. This method of producing chlorine gas by passing air and hydrogen chloride over a heated catalyst is known as the Deacon process.12