Ammonia Synthesis Over an Iron Catalyst with an Inverse Structure

Area of Science:

• Catalysis
• Chemical Engineering
• Materials Science

Background:

• The Haber-Bosch (HB) process is crucial for ammonia synthesis but faces challenges in improving productivity at low temperatures.
• The conventional industrial iron catalyst, developed over a century ago, remains dominant due to its high ammonia synthesis rate per catalyst volume.
• Enhancing ammonia productivity requires overcoming limitations of existing catalysts, particularly at lower operating temperatures.

Purpose of the Study:

• To develop a novel catalyst for the Haber-Bosch process with enhanced ammonia productivity.
• To investigate a new catalyst structure that improves the ammonia synthesis rate/catalyst volume.
• To explore low-temperature ammonia synthesis with high catalytic activity.

Main Methods:

• Preparation of a novel supported metal catalyst with an inverse structure, featuring metallic iron particles loaded with aluminum hydride species.
• Synthesis of the iron catalyst from an α-Fe2O3 precursor.
• Evaluation of catalytic activity for ammonia synthesis at low temperatures, including measurements of apparent activation energy.

Main Results:

• The new iron catalyst achieved more than double the ammonia synthesis rate/catalyst volume compared to the conventional industrial iron catalyst.
• This enhanced performance was observed despite the new catalyst having half the specific surface area of the conventional catalyst.
• Ammonia synthesis was demonstrated with a low apparent activation energy at 50 °C, indicating high efficiency.

Conclusions:

• The novel inverse structure catalyst significantly enhances ammonia productivity in the Haber-Bosch process.
• Increased active sites with strong electron-donating capabilities on the iron catalyst are responsible for the high catalytic activity/catalyst volume.
• This development offers a promising pathway for more efficient low-temperature ammonia synthesis.