Process Research On Ceramic Honeycomb Catalyst Molding For NH₃Selective Catalytic Reduction

Nitrogen oxides (NOx) is one of the most prominent air pollutants and the most difficult pollutants for air pollution control and environmental protection. There are two main sources of nitrogen oxides:one is mobile source like motor vehicles and the other is stationary source such as boiler equipment. More than90%of anthropogenic emissions of NOx are from the combustion of fossil fuels including coal, oil, and natural gas. As the major coal production country,74%of China’s primary resources consumption is coal. Meanwhile, the substantial increase in car usage and the development of the boiler power plant have also resulted in increased emissions of nitrogen oxides which can impose enormous pressure on both environment and human health. NOx can cause a series of environmental problems such as acid rain, photochemical smog, ozone depletion and greenhouse effect. Therefore, NOx pollution has become an important topic in environmental governance. In recent years, extensive research and development about the monolithic catalysts have been carried out with a purpose to achieve industrial application. Facing the enormous environmental pressure and the stringent domestic emission standards, the monolithic catalysts have been recognised as an applicable solution to reduce nitrogen oxides emissions. However, the research for the monolithic catalysts process is far from comprehensive.In this paper, the coating type catalysts are prepared using ultrasound-assisted impregnation method and extruded catalysts are prepared through suppress mold. Then, the structure and morphology of the catalyst is characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) methods. The adhesion strength between the coating and their carriers are tested using the ultrasonic cleaning machines while the compression performance of the extruded catalysts are tested through some mechanical strength performance tester. The activity of the catalyst is also studied through the self-designed evaluation device.Through the above characterization, ultrasound-assisted impregnation has been chosen as the method to prepare coating type catalysts. The uniformity of the active components of the catalyst is much better for ultrasound-assisted impregnation than that produced using the room-temperature method. The coating results also show that the pH value of the slurry can control its viscosity and further determing the binding capacity between the catalyst active component and the cordierite carrier. The maximum coating amount can be achieved after impregnation for three times. This ultrasound-assisted impregnation method is simple with no need for other additives.The BET characterization results and the mechanical strength performance tests show that the ideal formula for the extruded catalyst is:5%of methyl cellulose,5%of macrogol-400,5%of ethanolamine, and1%of glass fiber. Active test results show that the extruded catalysts of V2O5-WO3/TiO2and Ce0.3TiOx have higher activity in the lower temperature range between150℃and300℃. The activity of Ceo.3TiOx can reach above95%at150℃.