Modifying the structure of red mud by simple treatments for high and stable performance in cox-free hydrogen production from ammonia

Abstract

Red mud (RM) modified by various treatments was used as a catalyst for ammonia decomposition. Catalytic activity measurements performed at 500 degrees C and differential conversions illustrated that the rate increases with a decrease in the size of Fe3Ny nano particles formed during activation in NH3 flow. Measurements at 700 degrees C showed that a catalyst prepared by digesting RM in 6 M HCl followed by calcination at 900 degrees C provides a stable ammonia conversion of 98.8 +/- 0.5% for more than 70 h at a space velocity of 120 000 cm(3) NH3 h(-1) at. This rate is premier among all iron-based catalysts in terms of both activity and stability and even on par with the performance of other non-noble metal catalysts. Detailed characterization indicated Fe3Ny species readily available on the surface as the active species. Results provided here enable the utilization of RM as an environmentally-friendly, highly efficient, and almost cost-free catalyst for COx-free hydrogen production.