Ammonia synthesis over multi-promoted iron catalysts obtained by high-energy ball-milling

The feasibility of producing ammonia synthesis catalysts from high-energy ball-milling of a simple mixture of the constituent oxides has been investigated. The effect of ball-milling the fused oxidic precursor of the industrial KM1 ammonia synthesis catalyst has also been studied. The results show that high-energy ball-milling offers some interesting possibilities for preparing novel catalytic materials. It is observed that ball-milling of the powder oxides mixture leads to formation of solid solutions and the catalytic activity is significantly higher than that of the starting material. Furthermore, ball-milling of fused oxidic KM1 precursor is seen to give rise to more homogeneous promoter distribution and slightly higher activity. The quite small activity increase observed in this case probably reflects the fact that the fusion process has already resulted in a close to optimal promoter distribution. The choice of atmosphere during ball-milling is also seen to offer possibilities for regulating the phase composition.