Studying ammonia (NH₃) decomposition helps in understanding the kinetics of NH₃ synthesis and contributes towards cleaning up NH₃ emissions from sewage and activated sludge. For nearly a century iron catalysts have been used to synthesise NH₃ from hydrogen (H₂) and nitrogen (N₂). However, ruthenium (Ru) materials are now replacing them. The major drawback of Ru catalysts is H₂ poisoning, as H₂ retards the dissociative adsorption of N₂, which is the rate determining step in NH₃ synthesis. As cerium oxide (CeO₂) can stabilise noble metal dispersion and improve H₂ poisoning, it has been used as a catalytic support to promote N₂ activation or NH₃ synthesis.

Scientists from Osaka Municipal Technical Research Institute, Japan, have now used Ru and CeO₂ to prepare a catalyst which decomposes NH₃ with high activity (K. Hashimoto and N. Toukai, J. Mol. Catal. A: Chem ., 2000, 161, (1-2), 171-178). The catalyst consists of Ru-CeO₂ highly dispersed in Y-form zeolite (YZ). Ru-CeO₂/YZ works at conditions where YZ and CeO₂ are inactive.

The catalyst contained (in wt.%): 64.0 SiO₂, 19.5 Al₂O₃, 10.2 CeO₂ and 1.9 Ru. The decomposition rate was first order in NH₃. The Ru particles loaded on CeO₂/YZ reduce inhibition of the decomposition rate by H₂.

IR spectra for the catalyst showed that NH₃ decomposition at 300°C proceeded via formation of intermediate species, such as Ru−NH₃, Ru−NH₂, Ru−N₂ and Ru−H on the Ru surface.