Achieving volatile potassium promoted ammonia synthesis via mechanochemistry

Abstract

Potassium oxide is used as a promotor in industrial ammonia synthesis, although metallic potassium is better in theory. Here, the authors demonstrate metallic potassium, an unstable metal that easily volatilizes at high temperature, can be used as a promotor for ammonia synthesis. Potassium oxide (K2O) is used as a promotor in industrial ammonia synthesis, although metallic potassium (K) is better in theory. The reason K2O is used is because metallic K, which volatilizes around 400 degrees C, separates from the catalyst in the harsh ammonia synthesis conditions of the Haber-Bosch process. To maximize the efficiency of ammonia synthesis, using metallic K with low temperature reaction below 400 degrees C is prerequisite. Here, we synthesize ammonia using metallic K and Fe as a catalyst via mechanochemical process near ambient conditions (45 degrees C, 1 bar). The final ammonia concentration reaches as high as 94.5 vol%, which was extraordinarily higher than that of the Haber-Bosch process (25.0 vol%, 450 degrees C, 200 bar) and our previous work (82.5 vol%, 45 degrees C, 1 bar).