A Comparative Study of the Activity of Oxide Catalysts in the Oxidation of Methane and 1,1-Dimethylhydrazine

The catalytic oxidation of methane and 1,1-dimethylhydrazine ((CH₃)₂N–NH₂, unsymmetrical dimethylhydrazine (UDMH)) with air on oxide catalysts was studied. Two pairs of perovskites (Ca_0.7Sr_0.3FeO_2.5(3.0) and La_0.7Sr_0.3CoO_2.5(3.0), stoichiometric and superstoichiometric with respect to oxygen) and a supported spinel (20%(Cu _x Mg_{1 – x} Cr₂O₄)/-Al₂O₃, IC-12-73) were used as catalysts. The experiments were performed using two laboratory flow-type systems: in a catalytic fixed-bed reactor (the oxidation ofCH₄) and in a gradientless vibrationally fluidized bed reactor (the oxidation of CH₄ and UDMH) at 150–700°C. In the oxidation of CH₄, the IC-12-73 catalyst was more active than the perovskite catalysts, although particular perovskite catalysts can exhibit higher activity in the region of low temperatures. In the oxidation of UDMH, the activity of perovskites in the test temperature region was lower than that of IC-12-73; this correlates with the higher activity of IC-12-73 in the oxidation of CH₄. The Ca_0.7Sr_0.3FeO_3.0 and La_0.7Sr_0.3CoO_2.5(3.0) perovskites exhibited similar activities in the deep oxidation of UDMH, which were higher than the activity of Ca_0.7Sr_0.3FeO_2.5. A comparison between the selectivities of the conversion of fixed nitrogen, which is a constituent of UDMH, into nitrogen oxides demonstrated that, on all of the perovskites, S ^N _NO was higher and was lower than the corresponding values on IC-12-73. Additional information on the possible mechanisms of intermediate formation in the adsorption and oxidation of UDMH on IC-12-73 was obtained using Fourier transform IR spectroscopy.     

Principles of formation of nitrogen oxides in acetonitrile oxidation on copper-chromium and platinum catalysts

The dependence of the conversion of bound nitrogen to oxides on the temperature and concentrations of oxygen and acetonitrile have been determined. On copper-chromium catalysts the nitrogen of acetonitrile is oxidized predominantly to molecular nitrogen, whereas on platinum catalysts the conversion of bound nitrogen to oxides attains up to 90%.

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. , , 90%.

     

Formation of nitrogen oxides during the oxidation of nitromethane on copper-chromium catalyst

Principles of the oxidation of nitromethane on a 30% CuCr₂O₄/-Al₂O₃ catalyst over the temperature range from 210 to 485 °C have been studied. The conversion of bound nitrogen to oxides depends on initial concentrations of nitromethane and oxygen in the range corresponding to the complete conversion of nitromethane (350–485 °C). The composition of oxidation products is determined by the oxygen to nitromethane ratio.

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30% CuCr₂O₄/-Al₂O₃ 210–485°C. (350–485°C) . , .