Mass-spectrometric study of the tungsten-catalyzed decomposition of ammonia

Abstract

The decomposition of ammonia on tungsten at pressure of 1.3 × 10^–2 to 1.3 × 10^–3 N m^–2 and in the temperature range 900–1850 K, has been studied using a quadrupole mass spectrometer. The results suggest the participation of two different mechanisms; transition between these mechanisms occurring at ∼1400 K, Below 1400 K, the reaction showed complex behaviour, the rate and kinetic order decreasing with increasing temperature. By comparison of results obtained with the tungsten wire untreated, oxygen pre-treated and carburized it is shown that carbon diffusion is not an important step in the reaction below 1400 K.