Preparation Of Mn-based Nano-catalysts And Their Application In Catalytic Destruction Of Chlorobenzene And NOx

With the development of industry and economy, environmental pollution has attracted great attention all over the world. Dioxins and Nitrogen oxides (NOx) are major environmental pollutants and show detrimental effects on human health. Due to the increasing threat of dioxins and NOx to our surviving, many approaches have been developed to reduce its emission, among which selective catalytic oxidation/reduction technique is proved to be an effective way. The research and development of catalysts with high performance at low temperature is the key to the selective catalytic technique.In this thesis, the related research and progress on catlysts for catalytic destruction of NO and dioxins were reviewed, the main concern is focused on the preparation through wet synthesis methods, phase structure, morphologic and catalytic activities of MnOx/TiO2, MnOx/TiO2-CNTs, MnOx-CeO2/TiO2-CNTs and unsupported MnO2 nanocatalysts, respectively.MnOx/TiO2 composites with different atomic ratio of Mn/Ti were prepared by sol-gel, solvothermal and coprecipitation method, respectively. The catalytic tests on chlorobenzene (CB) removal ability of all 15 catalysts were performed in a fixed-bed flow reactor and compared to each other. Experimental results showed that when the atomic ratio of Mn/Ti reached 1:4, the activity of the catalysts prepared by three methods reached their highest value, particularly the catalyst with the Mn/Ti atomic ratio of 1:4 prepared by sol-gel method showed higher catalytic activity than the catalysts with the same atomic ratio prepared by other methods at temperature between 100 and 300℃. From the microstructure characterization, it could be known that the combined TiO2 phases of anatase and rutile and a good dispersion of manganese oxides contributed to a good catalytic performance in the catalyst prepared by the sol-gel method. The work reveals an optimal atomic ratio of Ti/Mn, which contribute a lot to the design of Ti-Mn based catalysts.MnOx/TiO2-CNTs composite catalysts were successfully prepared by wet synthesis methods. The introduction of CNTs decreases the particle size and increase the surface area of the catalysts. The catalysts containing CNTs showed higher CB removal efficiencies and had higher Turnover Frequency than catalysts without CNTs. The work reveals the significant promotion effect of introduction of CNTs on the activity, which suggests CNTs has a great potential in the catalysis field.MnOx-CeO2TiO2 composites supported on active carbons (AC) and carbon nanotubes (CNTs) were synthesized by sol-gel method. MnOx-CeO2TiO2-CNTs composite showed the highest catalytic activity for NOx removal by NH3 especially at low reaction temperatures, such that a de-NOx efficiency of up to 99.5% at 125℃was achieved under a gas hourly space velocity (GHSV) of-36,000 h-1. The difference in catalytic activities among Mn-Ce/Ti, Mn-Ce/Ti-AC and Mn-Ce/Ti-CNTs indicates that the introduction of CNTs has promotion effect on the acivity at low temperature. Moreover, the de-NOx efficiency up to 99.6% was always observed between 100℃and 250℃in 250ppm SO2 environment, implying the promotion of SO2 for NOx reduction with NH3.MnO2 nanotubes, nanorods, and nanoparticles were prepared using a hydrothermal method, after which the different activities for selective catalytic reduction (SCR) of nitrogen oxides (NOx) were compared. MnO2 nanorods performed the highest activity for reduction of NOx under a gas hourly space velocity of 36,000 h-1 between 100-300℃. From the catalysts characterization, we can ascribe the high activity of MnO2 nanorods to low crystallinity, more lattice oxygen, high reducibility, and a large number of strong acid sites. The apparent activation energy of the SCR reaction on the surface of nanorods was calculated to be 20.9 KJ/mol, which favored the reaction better than the other catalysts...