Catalytic Reduction of Nitric Oxide with Hydrocarbons

Abstract

The catalytic reduction of nitric oxide with thirteen hydrocarbons was studied by using a flow reactor (inside diameter: 12.0 mm) at atmospheric pressure and temperatures ranging from 270° to 550°C. The catalysts were five kinds of coprecipitated binary metal oxides of 50 mol % composition and Girdler's barium–promoted copper chromite, G22 (average diameter: 1.0 mm), all of which were reduced with hydrogen at 550°C before use. Inlet gas concentrations were 1% NO–0.09~1.20% CmHn, balanced with N2, and the total gas flow rate was 500 N cm3/min for the oxide catalyst of 1.000 g. Under these conditions, the activity sequence of catalysts for benzene was CuO–Al2O3>Fe2O3–Cr2O3>CuO–Cr2O3>CO3O4–Al2O3>Fe2O3–Al2O3>G22. The reactivity sequence over CuO–Al2O3 catalyst was alkylbenzenes>benzene>ethyIene>n–octane>iso–octane>n–hexane>methane. On the basis of the above results together with the report by Ault and Ayen (A. I. Ch. E. Journal, 17, 265 (1971)), it would be deduced that an increase of carbon number resulted in an increase of the reactivity in the homologous hydrocarbons except alkylbenzenes, and the reactivity sequence was acetylenic>olefinic>aromatic>paraffinic hydrocarbons for the same carbon number. The reactivity seems to decreased with decreasing saturation. Comparing hydrocarbons with carbon monoxide, the reactivity of the former was extremely inferior at lower temperatures, but the reverse was true at higher temperatures. © 1973, The Chemical Society of Japan. All rights reserved.