Research progress in the application of catalysts in environmental protection

Research progress on the application of catalysts in environmental protection. 1. Definition of environmental protection catalysts. Environmental catalysts refer to catalysts used to treat toxic and harmful substances directly or indirectly, making them harmless or reduced in quantity, in order to protect and improve the surrounding environment. In a broad sense, the category of environmentally friendly catalysts can be considered as all catalysts that are beneficial to environmental protection, including catalytic synthesis processes that do not or do not produce harmful by-products; Narrowly speaking, it refers to the types of catalysts involved in the improvement of greenhouse effect, ozone layer destruction, expansion of acid rain range, and water pollution. There are two types of environmentally friendly catalysts: direct and indirect. For example, the catalyst used to remove nitrogen oxides (NOX) from the exhaust is direct; The catalysts used to suppress NOX production during the combustion process are indirect. 2. Research progress on the application of environmentally friendly catalysts 2.1 Lean burn vehicle catalysts When diesel engines operate under lean burn conditions, the air fuel ratio (air fuel ratio) of gasoline engines is greater than 17:1 or even higher. At this point, the power performance of the engine can be greatly improved, reducing the emissions of CO, hydrocarbon compounds, and CO2, while the emissions of NOx greatly increase. For the currently popular three way precious metal catalysts, such a high air fuel ratio is beyond the normal operating range, and therefore cannot effectively improve the reduction of NOx. Therefore, it is necessary to develop new automotive catalysts that can improve NOx conversion rate under lean burn conditions. The catalytic reduction of NOx under lean burn conditions has attracted the interest of researchers. Once this catalyst is successfully studied, it will be widely used in vehicles with diesel engines and lean gasoline engines. 2.2 Research on flue gas desulfurization The best method for flue gas desulfurization is to selectively catalyze the reduction of SO2 to elemental sulfur. This method can not only eliminate the pollution source of SO2 in flue gas, but also recover the solid element sulfur, which is not only convenient for transportation but also reusable. Currently, the methods for selectively catalytic reduction of SO2 to obtain elemental sulfur are mostly in the research stage. The existing problems are the interference of excessive oxygen in the flue gas on the reduction process and the poisoning of the catalyst. 2.3 Catalytic oxidation treatment of high concentration refractory organic wastewater With the development of industries such as pharmaceuticals, chemicals, and dyes, there is an increasing number of high concentration refractory wastewater. Their wastewater is characterized by high toxicity of pollutants, high concentration of pollutants, and difficulty in biodegradation; High inorganic salt content. One of the most effective methods for treating such wastewater is chemical oxidation. At present, efficient wet catalytic oxidation technology is a hot research topic. This method can directly oxidize organic pollutants in water or oxidize large molecule organic pollutants into small molecule organic pollutants, in order to improve the biodegradability of wastewater. Combined with biochemical treatment, organic pollutants in water can be effectively removed. This method commonly uses oxidants to increase the ability to catalyze the oxidation of organic pollutants, including air, hydrogen peroxide, ozone, sodium hypochlorite, and chlorine dioxide. The key to this method is the development of efficient heterogeneous oxidation catalysts. 2.4 Types and Utilization Status of Environmental Protection Catalysts There are various aspects of the Earth's environmental issues, and currently the urgent problem to be solved is the greenhouse effect