Research progress on the application of catalysts in environmental protection-TMPDA-Tetramethylpropylenediamine

Progress in Research on the Application of Catalysts in Environmental Protection 1. Definition of Environmental Protection Catalysts Environmental catalysts refer to the treatment of toxic and harmful substances by direct or indirect methods to render them harmless or reduce them in order to protect and improve the surrounding environment. catalyst. In a broad sense, the category of environmentally friendly catalysts can be considered to be all catalysts that are beneficial to environmental protection, including catalytic synthesis processes that do not require or produce harmful by-products; in a narrow sense, they are related to the greenhouse effect, ozone layer destruction, and the expansion of acid rain. Catalyst types involved in the improvement of chemicals and water pollution. Environmentally friendly catalysts are divided into two types: direct and indirect. For example, catalysts used to remove nitrogen oxides (NOX) from exhaust gas are direct; while catalysts used to suppress the production of NOX during combustion are indirect. 2. Research progress in the application of environmentally friendly catalysts 2.1 Catalysts for lean-burn vehicles When the diesel engine operates under lean-burn conditions, the air-fuel ratio (ratio of air and fuel) of the gasoline engine is greater than 17:1, or even higher. At this time, the engine’s power performance can be greatly improved, and the emissions of CO, hydrocarbon compounds, and CO2 are reduced. However, the emissions of NOx are greatly increased. For the currently popular three-way precious 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 vehicle catalysts should be developed that can improve the NOx conversion rate under lean combustion conditions. Catalytic reduction of NOx under lean combustion conditions has aroused the interest of researchers. Once this catalyst is successfully researched, 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 catalytically reduce SO2 to elemental sulfur. This method can not only eliminate the pollution source of SO2 in flue gas, but also recover the product, solid elemental sulfur, which is not only easy to transport but can also be reused. At present, most methods for selective catalytic reduction of SO2 to obtain elemental sulfur are 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 pharmaceutical, chemical, dye and other industries, there are more and more high-concentration refractory wastewaters. Their wastewater is characterized by high pollutant toxicity, high pollutant concentration, and difficult to Biodegradable; high inorganic salt content. One of the most effective methods for treating such wastewater is chemical oxidation. High-efficiency wet catalytic oxidation technology is currently a hot research topic. This method can directly oxidize organic pollutants in water or oxidize large molecular organic pollutants in water into small molecular organic pollutants to improve the biodegradability of wastewater. After combined with biochemical treatment, organic pollutants in water can be better removed. This method commonly uses oxidants to increase the ability to catalytically oxidize 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 efficient heterogeneous oxidation catalysts. 2.4 Types of Environmentally Friendly Catalysts and Current Utilization There are many types of global environmental problems. Problems that are currently urgently wanted to be solved include: greenhouse effect, ozone layer destruction, expansion of acid rain, emissions of heavy metals and other environmental pollutants, reduction of tropical rainforests, and Soil desertification, etc. The first three problems are caused by chemicals released into the atmosphere. For example, carbon dioxide (CO2), methane (CH4) and nitrogen 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 through chemical methods. Due to the low amount of reactants involved in the emission process of the above pollutants, the reaction temperature is either too high or too low, and the contact time between the reactants and the catalyst is particularly short. Therefore, environmentally friendly catalysts are comparable to catalysts used in other chemical reactions. Compared with other catalysts, the requirements for catalyst activity, selectivity and durability are higher, and the production is more difficult. 2.5 New environmentally friendly catalysts 2.5.1 Silicate materials Natural clays such as montmorillonite have a molecular sieve-like structure and are catalyst carriers and good adsorbents for treating heavy metal ions in sewage. It is widely used as the carrier of environmentally friendly 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. TiO2 is now widely used as a photocatalyst and electrode catalyst. 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. It can react at normal temperature and pressure, and the process is simple. Biocatalysts have high conversion rates, strong specificity, few by-products, and can be used repeatedly, so they are an ideal green catalyst. 2.5.4 Room temperature ionic liquid can be used as both an acid catalyst and a green solvent. It has the advantages of easy production, low toxicity, low price, non-flammability, and adjustable performance. It is predicted to be an environmentally friendly catalyst that may cause a chemical industrial revolution and has good industrial application prospects.