No abstract

Abstract. It is shown that Ag/Al 2 O 3 is a unique catalytic system for H 2 -assisted selective catalytic reduction of NO x by NH 3 (NH 3 -SCR) with both Ag and alumina being necessary components of the catalyst. The ability of Ag/Al 2 O 3 and pure Al 2 O 3 to catalyse SCR of mixtures of NO and NO 2 by ammonia is demonstrated, the surface species occurring discussed, and a "Fast SCR"-like mechanism of the process is proposed. The possibility of catalyst surface blocking by adsorbed NO x and the *Revised Manuscript Click here to view linked References 2 influence of hydrogen on desorption of NO x were evaluated by FTIR and DFT calculations.

No abstract

a b s t r a c tWe report experimental results for the formation of ammonia from nitric oxide and hydrogen, and from nitric oxide, water and carbon monoxide over silica, alumina and titania supported platinum and palladium catalysts. Temperature programmed reaction experiments in gas flow reactor show a considerable formation of ammonia in the temperature range 200-450 • C, which is suppressed by the presence of excess oxygen. However, oxygen sweep experiments show that for the titania supported catalysts minor amounts of oxygen promotes the ammonia formation at low temperatures. In situ DRIFT spectroscopy measurements indicate that cyanate species on the support play an important role in the ammonia formation mechanism. This work shows that alumina supported palladium is a promising system for passive selective catalytic reduction applications, exhibiting low-temperature activity during the water-gas-shift assisted ammonia formation reaction. Conversely, titania supported samples are less active for ammonia formation as a result of the poor thermal stability of the titania support.

No abstract