Research progress on the application of catalysts in environmental protection UV absorber manufacturers

Research progress on the application of catalysts in environmental protection 1. Definition of environmental protection catalysts Environmental protection catalysts refer to the use of direct or indirect methods to deal with toxic and harmful substances to make them harmless or reduce them, so as to protect and improve the surrounding environment. catalyst. 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; in a narrow sense, they are related to the greenhouse effect, ozone layer destruction, and acid rain. The types of catalysts involved in the improvement of pollution and water pollution. Environmental catalysts are divided into direct and indirect. For example, catalysts used to remove nitrogen oxides (NOx) from exhaust gases are direct; catalysts used to suppress NOx production during combustion are indirect. 2. Application research progress of environmental catalysts 2.1 Lean-burn vehicle catalysts When diesel engines operate under lean-burn conditions, the air-fuel ratio (air-to-fuel ratio) of gasoline engines is greater than 17:1, or even higher. At this time, the power performance of the engine can be greatly improved, and the emission of CO, hydrocarbon compounds, and CO2 is reduced, but the emission of NOx is greatly increased. For the currently popular three-way noble metal catalyst, such a high air-fuel ratio is beyond the normal operating range, so it cannot effectively improve the reduction of NOx. Therefore, new automotive catalysts that can improve NOx conversion under lean-burn conditions should be developed. The catalytic reduction of NOx under lean-burn conditions has aroused the interest of researchers. Once this catalyst research is successful, 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 the selective catalytic reduction of SO2 to elemental sulfur. This method can not only eliminate the pollution source of SO2 in the flue gas, but also recover the product, namely solid elemental sulfur, which is not only convenient for transportation but also can be reused. At present, most of the methods of selective catalytic reduction of SO2 to obtain elemental sulfur are in the research stage. The existing problems are the interference of excess oxygen in the flue gas to the reduction process and the poisoning of the catalyst. 2.3 Catalytic oxidation treatment of high-concentration refractory organic wastewater With the development of medicine, chemical industry, dyestuff and other industries, there are more and more high-concentration refractory organic wastewater. Biodegradable; high in inorganic salts. One of the most effective methods of treating such wastewater is chemical oxidation. At present, high-efficiency wet catalytic oxidation technology is a hot research topic. This method can directly oxidize organic pollutants in water or oxidize macromolecular organic pollutants into small molecular organic pollutants to improve the biodegradability of wastewater. Combined with biochemical treatment, it can better remove organic pollutants in water. In this method, oxidants are often used to increase the ability to catalyze the oxidation of organic pollutants. The oxidants that can be used include: air, hydrogen peroxide, ozone, sodium hypochlorite, and chlorine dioxide. The key to this method is the development of highly efficient heterogeneous oxidation catalysts. 2.4 Types of environmental protection catalysts and current status of utilization There are many types of earth environmental problems. At present, the problems that are urgently desired to be solved include: greenhouse effect, ozone layer destruction, expansion of acid rain range, discharge of environmental pollutants such as heavy metals, reduction of tropical rainforest and Soil desertification, etc. The first three of these problems are caused by chemicals emitted into the atmosphere. For example, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are all related to the greenhouse effect, Freon and N2O destroy the ozone layer, sulfur dioxide (SO2) and NOX are the main factors that form acid rain and photochemical smog, remove or reduce These pollutants are mainly solved by chemical methods. Due to the low amount of reactants involved in the discharge process of the above-mentioned pollutants, the reaction temperature is either too high or too low, and the contact time between the reactants and the catalyst is particularly short, so the environmental protection catalyst is comparable to other catalysts for chemical reactions. Compared with catalysts, the requirements for catalyst activity, selectivity and durability are higher, and the production is more difficult. 2.5 New environment-friendly catalysts 2.5.1 Silicate materials Natural clays such as montmorillonite have molecular sieve-like structures, and are catalyst carriers and good adsorbents for treating heavy metal ions in sewage. It is widely used as the carrier of environmental protection catalysts such as automobile exhaust purification, flue gas desulfurization, denitrification and catalytic combustion of organic waste gas. 2.5.2 TiO2 is an N-type semiconductor with good photosensitive conductivity and is often used as a catalyst carrier. Now TiO2 is widely used in photocatalysts and electrode catalysts. Self-cleaning glass, ceramic tiles, furniture, and curtains coated with active TiO2 automatically catalyze and purify indoor air under the irradiation of sunlight and light. 2.5.3 The biocatalytic process usually uses non-toxic and harmless biological materials as raw materials, which can react under normal temperature and pressure, and the process is simple. Biocatalyst is an ideal green catalyst because of its high conversion rate, strong specificity, few by-products, and reusability. 2.5.4 Room temperature ionic liquids can be used not only as acid catalysts but also as green solvents. It has the advantages of convenient production, low toxicity, low price, incombustibility, and adjustable performance. It is predicted to be an environmentally friendly catalyst that may cause a chemical industry revolution and has a good industrial application prospect.