Research progress on the preparation of alkali/alkaline earth metal-modified metal oxide catalysts and their application to diesel engine exhaust soot particle catalytic purification

With increasingly severe air pollution and improvement in people's environmental awareness, air pollutant treatment, especially for soot particles (PMs), has become a research hotspot in the environmental protection field. At present, catalytic purification technology is one of the most effective and widely used technologies for treating PMs, and the development of efficient and low-cost catalysts is a key factor in the application of catalytic purification technology. Doping alkali/alkaline earth metals in metal oxide catalysts can significantly improve the contact efficiency between the catalyst and PMs and improve active oxygen mobility on the catalyst surface. Therefore, it has been widely used in catalytic soot purification. In this study, preparation methods for alkali/ alkaline earth metal-modified metal oxide catalysts, such as impregnation, hydrothermal, sol-gel, coprecipitation, template, and other methods, are introduced, and the related preparation principles are described. Meanwhile, research progress into the above catalysts in catalytic PM purification and simultaneous soot and nitrogen oxide species (NOx) removal are summarized in detail. Finally, the problems and future development trends in alkali/alkaline earth metal-modified metal oxide catalysts in catalytic PM purification are summarized and discussed.