Radical Species Formed by the Catalytic Decomposition of NH3on Heated W Surfaces

The catalytic decomposition processes of NH 3 on heated W surfaces were examined by employing laser spectroscopic techniques. H atoms and NH 2 radicals were identified as primary decomposition products on the catalyzer surfaces. The effective enthalpies for the production of these species were both determined to be 150 kJ/mol. NH radicals were also identified, but the production of this species is ascribed to secondary processes. N atoms are minor products in both the primary and secondary processes. The absolute density measurements show that the decomposition efficiency of NH 3 is comparable to that of H 2 . The steady-state densities of NH 3 and the stable products, H 2 and N 2 , were also measured by mass spectrometry. When the catalyzer temperature is over 2000 K, the H 2 density is comparable to that of residual NH 3 . H atoms are produced not only by the direct decomposition of NH 3 but also by the decomposition of H 2 .