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

Abstract

The catalytic decomposition processes of NH3 on heated W surfaces were examined by employing laser spectroscopic techniques. H atoms and NH2 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 NH3 is comparable to that of H2. The steady-state densities of NH3 and the stable products, H2 and N2, were also measured by mass spectrometry. When the catalyzer temperature is over 2000 K, the H2 density is comparable to that of residual NH3. H atoms are produced not only by the direct decomposition of NH3 but also by the decomposition of H2.