Reactivity of nitrogen containing organic intermediates in the selective catalytic reduction of NOx with organic compounds: A model study with tert-butyl substituted nitrogen compounds

The reactivity of different nitrogen-containing compounds, which may be for med as intermediates during the selective catalytic reduction of nitrogen o xides with organic compounds over alumina (HC-SCR), has been investigated i n the temperature range of 60-610 degrees C in a flow reactor system equipp ed with an FTIR gas analyzer. Tert-butylnitrile N-oxide (t-CNO), t-butyl is ocyanate (t-NCO) and t-butyl cyanide (t-CN) were used as model compounds. T he reactivity tests comprised the decomposition and oxidation reactions in a stream of O-2 and Nz, and in mixtures of NO2 or NO with O-2 (HC-SCR condi tions). These studies revealed that t-CNO isomerizes readily to t-NCO and t hen decomposes to CO2 and I-butylamine. The latter rapidly reacts with NO2 to form N-2 or further decomposes into isobutene and NH3, which may be foll owed by the conventional SCR with NH3 as a reducing agent. This suggests th at once nitrile N-oxides are formed under HC-SCR conditions they are readil y converted to N-2 through several reaction steps. (C) 1998 Elsevier Scienc e B.V. All rights reserved.