The Research Of Quantitative Catalytic Oxidation Of NO On Carbon-based Catalyst Under Low-temperature

With the rapid development of economy and a large number of fossil fuels used, some environmental problems, such as photochemical smog, acid rain, ozone depletion, and greenhouse effects, caused by nitrogen oxides (NOx) pollution is gradually serious. Now, how to control and treat these pollutions has become one of the most important issues on environment protection.A superior effective method for NOx removal was presented in this work, which on basis of denitration technoloy of catalytic oxidation of NO. In this paper, we selected transition metal of Mn as catalyst active component, and coconut shell activated carbon as catalyst support. A new type of liquid phase deposition method was used in this paper to prepare supported catalyst of Mn/AC, and the catalyst catalytic activity for NO was also investigated herein. In this research, we examined the influence of catalyst prepare conditions on the performance of catalytic oxidation of NO. In addition, the adsorption properties of NO, N2and O2on four carbon materials, such as coconut shell activated carbon, coal activated carbon and viscose-based activated carbon fiber were also studied. The influence of prepare conditions on catalyst structure and catalytic performance were discussed through some characterization measures. The research works in this paper were summarized as follow:(1) In this paper, adsorption characteristics of nitric oxide (NO), nitrogen (N2) and oxygen (O2) on porous carbon-based materials such as coconut shell activated carbon, coal activated carbon and viscose-based carbon fiber at temperatures ranging from298-343K were investigated using a static volumetric adsorption apparatus. It was found that adsorbed amount of N2and O2were small, and the influence of N2on NO can be ignored in the whole adsorption process. NO adsorbed amount on four carbon materials increased rapidly as partial pressure increasing when at a same adsorption temperature, but NO adsorbed amount decreased rapidly as adsorption temperature when at a same partial pressure. From the adsorption isobars, it can be seen that the influence of adsorption temperature on NO adsorbed amount were greater than the influence of partial pressure.(2) The adsorption equilibrium data for NO adsorbed on four carbon materials were fitted to Freundlich, Dubinin-Radushkevich (D-R) and Sips adsorption isotherm model. Overall, it was found that Sips adsorption isotherm model was more suitable for description of NO adsorption process.(3) Coconut shell activated carbon showed a best adsorption property among the four materials in the NO adsorption process. It may be related with the pore structure and surface functional groups of these carbon materials.(4) Selecting the coconut shell activated carbon as catalyst support, we studied the influence of active component and prepare method on the catalyst performance of catalytic oxidation of NO. It was found that a catalyst prepared by a new type of liquid phase deposition method using transition metal Mn was active component showed a best catalytic performance.Moreover, the effect of prepare conditions, such as Mn adding amount, F:Mn ration, pH value, solution concentration, deposition time and catalyst support, on the catalytic oxidation of NO were also detailed investigated. Experiment results showed that at the following prepare conditions:Mn adding amount is50%, F:Mn ration is4, sedimentary times is1, pH value is8.7, solution concentration is0.03mol/L, deposition time is2h and using coconut shell activated carbon as support, the catalyst showed a good NO catalytic oxidation performance, and gave a62%NO conversion at50℃reaction temperature. NO conversions on the catalyst were all above40%at the whole active evaluation temperature range.(5) The influence of prepare conditions on catalyst structure and catalytic performance were discussed through some characterization measures in this paper. The results showed that MnF2, MnO2and Mn2O3on the catalyst, generated and acted as catalytic active center, have played an important role in the process of catalytic oxidation of NO. Hydrofluoric acid and aqueous ammonia used in the catalyst prepared method were conductive to enhance the performance of catalytic oxidation of NO. Due to using of hydrofluoric acid and aqueous ammonia can not only increase manganese and oxygen content, but also makes the type of alkaline activity center increasing, and intensity strengthened.In addition, formation mechanism of catalyst core-shell structure was preliminary discussed in this paper, and the formation of this core-shell structure was considered having a relationship with the form way of crystal nucleus in the solution.