How can hydrogen chloride be oxidized to produce chlorine?

Hydrogen chloride can be oxidized to produce chlorine through a method known as the Deacon process.

In this industrial procedure, gaseous hydrogen chloride is mixed with air or oxygen and passed over a catalyst, typically cupric chloride, at elevated temperatures. While the equilibrium constant for this reaction decreases as temperature rises—meaning the reaction is less efficient at higher temperatures—a temperature of approximately 400 °C (750 °F) is utilized in practice to achieve a reasonable rate of conversion. The chemical equation for this oxidation is:1

$$4HCl+O_2\to 2C{l}_2+2H_{2}O$$

Historically, this process was used to recover chlorine from hydrogen chloride, which was a by-product of the Leblanc process for manufacturing soda ash. Today, however, the primary industrial source of chlorine is the electrolytic decomposition of salt (sodium chloride).21