How does the Kroll process produce titanium metal?

The Kroll process is the primary method used to produce titanium metal. Because titanium is highly reactive at elevated temperatures, it cannot be produced by simply reducing its oxide with carbon, which would form a stable carbide instead.12

The process involves several key steps:

• Chlorination: Titanium ores, such as ilmenite or rutile, are treated with carbon and chlorine at high temperatures to produce titanium tetrachloride ($TiC{l}_4$), which is then purified by fractional distillation.1
• Reduction: The $TiC{l}_4$ is reduced using molten magnesium in a sealed steel vessel. This reaction occurs at approximately 800 to 1,000 °C (1,450 to 1,800 °F) within an inert argon atmosphere to prevent contamination by air or moisture.31
• Recovery: The resulting product is a porous material known as titanium sponge, which contains entrapped magnesium chloride salts. These salts are removed via acid leaching or high-temperature vacuum distillation.31
• Casting: Finally, the sponge is typically fused in an electric arc under an inert atmosphere and cast into ingots.1