The Decomposition Of NO With NH₃ On Carbon Nanotubes Supported Manganese Oxides

With the rapid development of the economy in our country, the consumption of energy also mounts up greatly. Consequently, nitrogen oxides（NO_x） has become serious gaseous pollutants, which contributes to the environmental problems such as acid rain, photochemical fog and the depletion of ozone layers,etc. Hence it negatively influence our health and destroy environment. It is high time for us to take efficient measures to control the emission of NO_x.The technology of Ammonia selective catalytic reduction has been widely used in the control of the pollutants of NO_x, the core of the technology is catalyst, including support and activated composite. Normally, the catalyst is prepared by locating metal oxides to the carbonaceous support. As a novel carbon material, carbon nanotubes（CNTs） as the support of catalyst has significant advantage over other carbonaceous material, due to their unique structural, electric and mechanical characteristics.In this paper, the catalyst of carbon nanotubes was treated by mixed acid. Then, manganese oxides was used as the activity material of the catalyst and the MnO_x/CNTs catalyst was prepared. The structure of the prepared catalyst was characterized by TEM, BET, FTIR and XRD. The results indicated that purified CNTs became clean and smooth; the caps and ends of CNTs were partly opened; the oxidative and acid groups was created in the surface of CNTs, which greatly increased the manganese loading and facilitated the adsorption of NH3 in reaction phase; manganese particles were highly dispersed on the inner and outer walls of carbon nanotubes.The effects on the MnO_x/CNTs catalyst of loading, calcinations temperatures, reaction temperatures, W/F and O₂ ratio were studied from the conditions of preparation and reaction. The test showed that the best loading of manganese was 10wt% and the optimum calcinations temperature was 500℃. The best results were obtained when W/F=2mg/（ml/min）.Generally, there was a positive correlation between the NO conversion and the reaction temperature. When reaction temperature beyond 200℃, the NO conversion reached 85%.While when the reaction temperature was up to 280℃,the NO conversion could reach as high as 98%. Finally, the reaction mechanism of MnO_x/CNTs catalyst was studied preliminarily.