Haber–Bosch promoter package — Identify a catalyst promoter used in catalytic ammonia synthesis over iron.

Introduction:
Industrial ammonia synthesis employs an iron-based catalyst containing multiple promoters that enhance activity, stability, and resistance to poisons. Recognizing common promoters is a fundamental aspect of catalytic process knowledge.

Given Data / Assumptions:

• Base catalyst: magnetite-derived iron reduced in situ.
• Promoters include alkali/alkaline species for electronic promotion and oxides for structural stability.
• Operating conditions: ~400–500°C, 100–250 bar, H2:N2 ≈ 3:1.

Concept / Approach:

Potassium oxide (K2O) is a classic electronic promoter for iron in the Haber–Bosch process, increasing the electron density at active sites and improving N2 dissociation. While alumina (Al2O3) is often present as a structural/textural promoter, the most commonly cited specific activity promoter is K2O. Chromium oxide and manganese oxide are not standard promoters in modern iron ammonia catalysts; silica may be used in traces as a structural additive but is not the prime electronic promoter.

Step-by-Step Solution:

Verification / Alternative check:

Commercial catalyst specs (e.g., magnetite with K, Al, Ca promoters) corroborate the prominent role of K2O.

Why Other Options Are Wrong:

A: Al2O3 is mainly a structural promoter; the question emphasizes activity promotion. B/D: Not standard for Haber–Bosch iron catalysts today. E: SiO2 is not the principal promoter for activity.

Common Pitfalls:

Confusing structural supports with electronic promoters; both exist but play different roles.

Final Answer:

K2O