Ammonia decomposition over the carbon-based iron catalyst promoted with potassium

Kinetics of NH3 decomposition over the K+-promoted iron catalysts supported on graphitized carbon (surface area = 440 m(2)/g) have been studied under I bar pressure. Both the ammonia partial pressure dependence (5-20% NH3 in the H-2:N-2 = 3:1 mixture) and temperature dependence of the reaction rates have been determined. The Studies demonstrate that the rate of ammonia decomposition (TOF) over K+-Fe/C is influenced by the size of iron particles: smaller particles exhibit higher TOE The apparent energy of activation for K+-Fe/C (166 kJ/mol) proved to be similar to that for the fused iron catalyst (167 kJ/mol) and significantly higher than the activation energy for K+-Ru/C (139 kJ/mol). The Langmuir-Hinshelwood modeling based on the NH3 decomposition data obtained and corresponding data for NH3 synthesis suggest that the Fe Surfaces of the K+-Fe/C catalyst are strongly covered with atomic nitrogen when operating under the high pressure NH3 synthesis conditions. (C) 2002 Elsevier Science B.V. All rights reserved.