Haber process — Which catalyst is used industrially for ammonia (NH3) synthesis?

Introduction:
The classical Haber–Bosch process continues to produce the majority of world ammonia using iron-based catalysts. While alternative catalysts exist (e.g., ruthenium on carbon), the industry standard remains magnetite-derived iron reduced to an active metallic phase with promoters.

Given Data / Assumptions:

• Synthesis loop conditions: 100–250 bar, 400–500°C.
• Catalyst prepared from Fe3O4 precursor and promoters (K2O, Al2O3, CaO).
• Feed gas is purified H2/N2 at about 3:1 molar ratio.

Concept / Approach:

Commercial catalysts are supplied as promoted iron oxides (magnetite) that are reduced in situ to active metallic iron while retaining promoter distribution. Nickel is primarily used for steam reforming/methanation, vanadium pentoxide for SO2 oxidation, and silica gel is a desiccant not a synthesis catalyst. Although ruthenium-on-carbon catalysts have been deployed in some high-pressure loops, the canonical and most widely used answer is reduced iron oxide.

Step-by-Step Solution:

Verification / Alternative check:

Plant licensor literature and textbooks consistently list promoted Fe as the mainstream catalyst for NH3 synthesis.

Why Other Options Are Wrong:

B: Nickel is not the standard NH3 synthesis catalyst. C: V2O5 is for SO2 → SO3. D: Silica gel is an adsorbent. E: Ru/C exists but is not the widely adopted baseline in general question contexts.

Common Pitfalls:

Confusing catalysts from front-end reforming/methanation with the back-end synthesis loop.

Final Answer:

reduced iron oxide