EFFECT OF POTASSIUM ON THE KINETICS OF AMMONIA-SYNTHESIS AND DECOMPOSITION OVER FUSED IRON CATALYST AT ATMOSPHERIC-PRESSURE

Ammonia synthesis and decomposition have been performed over a doubly promoted (Al2O3, CaO) and a triply promoted (Al2O3, CaO, K2O) fused ir on catalyst at atmospheric pressure, Additionally, the temperature-pro grammed surface reaction (TPSR) of N-ads with H-2 has been studied ove r both catalysts. No effect of potassium on the turnover frequency of NH3 synthesis was found, On the contrary, a significant fivefold incre ase in the rate of NH3 decomposition in the presence of potassium was observed. The effect was found to be strongly dependent on the concent ration of NH3 in the gas phase, The promoting mechanism of potassium i s discussed in relation to the surface structure of the catalyst under varying operating conditions. (C) 1997 Academic Press.