No abstract

It is shown that in the presence of reducing agents -light alkanes (C 3 -C 4 ) or carbon monoxide -the temperature for the elimination of nitrogen(I) oxide over iron-containing zeolite catalysts of various structural types (Y, M, pentasil) is reduced by 70-150°C. In the presence of excess oxygen (SCR process conditions) a greater conversion of N 2 O (90-94%) is achieved at even lower temperatures (up to 50-150°C less) with the use of hydrocarbons, and the activity of the catalysts correlates with the presence of strongly acidic B centers on their surfaces.The recent agreements between countries of the world community on the reduction of the emission of greenhouse gases into the atmosphere requires the development and use of effective technologies, among which catalysis has an important role, especially catalysts to purify emission gases from nitrogen oxides.Denitrification of industrial effluent gases is usually carried out by selective catalytic reduction (SCR) of nitrogen oxides with ammonia or hydrocarbons, hence the conditions for the reaction of N 2 O with various reducing agents (NH 3 , CO, C n H m ) remains a topic of intense study [1][2][3].The wide range of temperatures (250-500°C) of nitrogenous effluent gases, containing NO and N 2 O [4, 5], makes it necessary to develop catalysts for the direct decomposition of N 2 O and the selective reduction of nitrogen(I) oxide, a process which occurs at lower temperatures.It was shown in [6], as a result of testing a series of iron-containing catalysts based on zeolites of various structural types and zirconium dioxide, that the direct decomposition of N 2 O over the most active catalysts occurred at 500-550°C with conversions of 86-96%.In the present work reducing agents -a propane-butane mixture or CO -were added to the reaction mixture with the objective of reducing the temperature for the elimination of N 2 O. Results on the reactivity of iron-containing zeolite catalysts of various structural types (Y, M, pentasil), including those containing zirconium ions, and binary catalysts (zeolite + ZrO 2 ) in the reduction of nitrogen(I) oxide with C 3 -C 4 hydrocarbons and carbon monoxide are presented. The methods for preparation of the catalysts has been reported [6]. The acidic properties of the surfaces of separate samples were investigated by thermal desorption of ammonia and IR spectroscopy. The catalytic activity of the samples was characterised by the degree of conversion of N 2 O to nitrogen, which was determined in a flow apparatus with a gradient less quartz reactor at atmospheric pressure in the temperature range 250-560°C. The standard reaction mixture contained 0.5% N 2 O, 0.2% C 3 H 8 -C 4 H 10 (2 : 1) or 0.5% N 2 O and 0.5% CO. In the study of the effect of excess oxygen 5% (by volume) was added to the reaction mixture. Catalysts samples (2 cm 3 , particle size 1-3 mm) was heated in air with a flow rate of 100 mL/min at 550°C for 1 h. Analysis of 0040-5760/05/4101-0037