Yes, it is theoretically possible to reduce titanium dioxide (TiO₂) to titanium metal (Ti) using sodium in liquid anhydrous ammonia, although this would be an unconventional and challenging method.

Here’s a breakdown of why it might work and the challenges involved:

Theoretical Basis

Titanium dioxide (TiO₂) can be reduced to titanium metal through various methods, and one potential method involves using a strong reducing agent like sodium (Na). Sodium, being a highly reactive alkali metal, could potentially reduce the titanium dioxide to titanium metal by donating electrons to the titanium ions in TiO₂.

The reaction could follow a general form like this:

TiO2+4Na→Ti+2Na2O

In this case, sodium (Na) reduces Ti⁴⁺ (from TiO₂) to metallic titanium (Ti), while sodium itself is oxidized to form sodium oxide (Na₂O).

Role of Anhydrous Ammonia

Anhydrous ammonia (NH₃) is a strong solvent that can stabilize alkali metals like sodium in their liquid state, as well as facilitate certain reduction reactions. In liquid ammonia, sodium is more reactive and could potentially facilitate the reduction of TiO₂. Ammonia also acts as a medium that might lower the activation energy for the reaction and help maintain a low temperature, which is beneficial for reactions involving alkali metals.

Potential Mechanism

Nucleophilic Attack: Sodium in liquid ammonia could interact with TiO₂, likely through a nucleophilic attack on the titanium atom. Sodium could donate electrons to titanium, reducing it from Ti⁴⁺ to Ti⁰.

Stabilization of Sodium: In liquid ammonia, sodium exists as solvated Na⁺ cations, which could facilitate electron transfer and make the reduction process more efficient. The ammonia would also stabilize the highly reactive sodium metal.

Practical Challenges

Temperature Control: The reaction between sodium and titanium dioxide would likely be highly exothermic. Handling the reaction at temperatures appropriate for liquid ammonia (−33.3 °C at standard pressure) would be crucial to avoid uncontrolled reactions.

Formation of Na₂O: Sodium oxide (Na₂O) would form as a by-product, and removing this product from the reaction could be challenging. Na₂O is hygroscopic, meaning it would absorb moisture from the air and form NaOH, so controlling the reaction environment is critical.

Reaction Kinetics: The reaction between sodium and titanium dioxide could be slow or require specific conditions to proceed efficiently. Sodium typically reacts more readily with oxygen compounds, but reducing titanium from its highest oxidation state in TiO₂ to metallic titanium might need careful tuning of the reaction conditions.

Safety Hazards: Sodium metal is highly reactive, especially in the presence of water, and ammonia is a toxic, corrosive gas. Handling these chemicals requires proper safety precautions, including inert atmospheres and temperature control.

Alternative Methods

The most common industrial methods for reducing titanium dioxide to titanium metal are the Kroll process and the Hunter process. These processes involve reducing titanium tetrachloride (TiCl₄) with magnesium or sodium in high-temperature reactors, and they are far more established than the potential sodium-ammonia route.

In summary, while it is theoretically possible to reduce TiO₂ to Ti using sodium in liquid ammonia, this would be a highly experimental and difficult process. It would require precise control of temperature, atmosphere, and the reaction environment to work effectively.