| Nowadays, the number of vehicles is growing very fast with the rapid economic development. Vehicles bring us more convenience to our daily life, but also arise a series of environmental problems. The emission of nitrogen oxides ?NOx? in the automobile led to environmental pollution. Selective catalytic reduction ?SCR? is an efficient way for the reduction of NOx. It is well-known that supported noble metals are excellent catalysts for SCR. However, the noble metal catalysts are scarcity in the earth's crust and cost prohibitive. Despite scattered metals are a kind of rare metal in a worldwide scope, they are a characteristic metal resource of China. Thus, the development of value-added scattered metal catalysts is of great importance in China.CxHy compounds have been reported as the reducants for the rare and scattered metal-indium ?In? catalyzed SCR. Despite hydrocarbons ?HC? show some activity, they have some problems such as insufficient activity at low temperature, narrow reaction temperature window, sulfur sensitive. Considering that carbon monoxide ?CO? exists in the car exhausts, it should be a very promising and economic agent for NOx reduction. Moreover, the reduction of NO by CO over In-based catalyst has not been studied previously. In this thesis, the activity of In-based catalyst for the reduction of NO using CO as the reductant has been fully studied. The detailed work is as follows:1. Preparation and activity evaluation of In-Ag-O/?-Al2O3 catalystThe ?-Al2O3 supported In-based catalysts using silver ?Ag?, iron ?Fe?, tungsten ?W?, copper ?Cu?, nickel ?Ni?, cobalt ?Co? as the additive were prepared. The effect of additive on CO-SCR-NO activity was studied. The results indicate that Ag and In species may form AgInO2, which is helpful to stabilize the In species in the reactant gas. Meanwhile, the onset temperature can be lowered down with the addition of Ag species to In-based catalysts.2. Preparation and activity evaluation of In-Ag-O/TiO2-?-Al2O3 catalystDifferent additives have been added to activated alumina ??-Al2O3? to broaden the reaction temperature window. The results showed that the addition of titanium dioxide ?TiO+2? can increase the dispersibility and the surface active sites, enhance the nitric oxide ?NO? adsorption, thus improve reaction activity. When the TiO+2 loading in the carrier is 15 wt%, the content of In or Ag of the catalysts is 8 wt%?In8Ag8/15TA?, the catalyst showed the best activity for CO-SCR-NO.3. Study onIn8Ag8/15TA catalytic processesIn8Ag8/15TA was used as the catalyst for CO-SCR-NO. The influence of calcination temperature, space velocity, O2 concentration, CO/NO ratio on In-Ag-O/TiO2-?-Al2O3 catalyst was fully studied. It has been found that the space velocity and O2 concentration have significant influence on CO-SCR-NO catalytic activity. The optimal conditions are as follows:calcination temperature of 600?, space velocity of 15000 h-1, O2 concentration of 0-1.0%, CO/NO ratio of 4-6. Furthermore, In8Ag8/15TA catalyst also exhibited good stability as well as strengthened resistance to SO2, H2O and CO2 poisoning.4. Immobilization of In8Ag8/15TAThe preparation and coating of In8Ag8/15TA cordierite monolithic ?CC? were studied. Oxalic acid is found to be a good reagent for the pretreatment of cordierite. After the treatment, the cordierite crystal structure could be maintained, the specific surface area was increased, and the pore structure was also improved. Microwave coating on cordierite showed higher loading and good stability of TiO2-?-Al2O3 coatingas compared to traditional methods. The In-Ag-O/TiO2-?-Al2O3 supported on cordierite ?In8Ag8/15TA/CC? also showed comparable activity as unsupported catalyst for CO-SCR-NO.5. Application of In8Ag8/15TA cordierite monolithic catalystThe result of small-scale testing showed that In/Ag catalyst could be a promising SCR catalyst for practical application. The conversion of NO, methane ?CH4?and CO was 99.6%,89.3% and 96.0%, respectively ?at 650??. |
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