| The diesel engine is widely used than before and has gradually become the first choice for automobiles, because of its higher fuel economy and lower HC and CO emissions. However, the higher NOx emissions slow down the development of diesel engines. Nitrogen oxides are one kind of gaseous pollutants that contribute to the acid rain formation, the photochemical air pollution, and the depletion of the ozone layer. Other problems linked with the presence of nitrogen oxides in the atmosphere are health problems to humans. The legislation has now become stringent to the extent that engine management alone is not enough to make engines compliant with the regulations, and exhaust gas after-treatment in one form or another must be introduced to solve this environment problem. Selective Catalytic Reduction (SCR) is one of efficient measures for controlling the NOx pollution.In recent years metallic monoliths are becoming increasingly popular due to their high thermal conductivity, lower heat capacities, toughness, greater thermal and mechanical shock resistance. Due to their excellent properties, they are becoming more prevalent in a wide range of applications which include heat exchangers, fuel cells, heat collectors and metal supports for exhaust gas catalyst and so on. Because of the low specific surface area, it is necessary to deposit the ceramic oxide coating with high surface area over metallic monoliths. The traditional coating is porous material (e.g., Al2O3), but thermal expansion coefficient of the metallic monoliths is different from the ceramic oxide coating's, so the major problem is how to achieve better adhesion to the metallic supports and the coating. In order to solve the difficulty, inorganic and nonmetallic coating has become the key of research in recent years.In our experiments, we chose NiCrFe as supports and investigated a novel glass coating which have a number of outstanding characteristics in comparison with the traditional ceramics coating, it can solve well the problem of peeling due to the difference in thermal expansion coefficients between the metallic supports and coating. This work presents a fundamental study on a three-step method for preparing glass coating on metallic support: (1) support pre-treatment; (2) sol gel preparation; and (3) coating deposition, through which the glass ceramic layer and the metallic support can adhere very well. Several methods of NiCrFe alloy supports surface pre-treatment are studied in this thesis. The glass coating which can get fastness load of catalyst, is produced by NiCrFe alloy supports surface pretreatment. During the study, the influencing factors on the coating adhesion between the glass ceramic layer and the metallic support were considered, including the support pre-treatment, the sol gel loading, coating drying temperature and calcination temperature. The microstructure and surface character of the metallic supports and glass ceramic coating were investigated by XRD and SEM , the bonding strength between the coating and metallic substrate was measured by ultrasonic vibration, thermal shock and tensile test.. Through research in this thesis, the glass coating is obtained on NiCrFe alloy supports.In order to investigate the effects of different oxidation temperatures, the NiCrFe alloy supports were calcined at three main temperatures: 800℃,900℃and 1000℃for 5h . From these groups of tests, the optimal oxidation time was determined. The morphology of metallic surfaces pre-oxidized at 900℃for 5h, it was found that all oxidized surfaces crystallized, and surface relief structures formed, which greatly increases the specific surface area of the oxidized layer. The glass coatings were calcined at 550℃,650℃,750℃and 850℃in a tubular furnace, then quenched under room temperature. Research on the change of the specific surface area, it shows that the biggest specific surface area is at 650℃. Phase structure of the glass coating has been confirmed by X-ray diffraction analysis, the structure is in a glassy state at 650℃for 5min. After next 10h calcining, the structure maintains the glassy state. The XRD analysis also reveals that the glass ceramic coating has the better thermal stability. Coating adhesion was measured by ultrasonic adhesion and thermal shock test. The weight loss data from the ultrasonic adhesion and thermal shock tests shows that the samples had the best coating adhesion, with the average weight loss of only 20wt.% in the ultrasonic test and the average weight loss of only 10wt.% in the thermal shock tests. After ultrasonic test for next 30min, the average weight loss of about 25wt.%. The glass coating can adapt to temperature variation and severe vibration. This text has expounded the fact of the domestic and international nitrogen oxide and the current situation of the technology that the nitrogen oxide controlled, emphatically introduced the Selective Catalytic Reduction technology, the using application and relative chemical equation. Our experiments regard the MnCr2O4 spinel-type complex oxides as the catalyst, use HC as reducing agent and get rid of NOx in the exhaust gas of simulation, investigate the result of getting rid of NOx, the formation amount of CO and CO2. The structures of the catalyst are characterized by XRD , the results demonstrate that the MnCr2O4 retains intacted spinel-type structure, the average crystal diameter is about 7.16nm.The selective catalytic reduction of NOx by C6H6 was investigated over MnCr2O4, airspeed is 10000 h-1, temperature is 245℃, the conversion ratio of NOx is up to 78%, the conversion ratio of C6H6 is up to 81%.The maximum formation amount of CO is 387ppm, nearly completely produce CO2.The result shows that the catalyst exhibits high catalytic activity at low temperature and has good redox property.
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