Catalysts and additives

Catalyst refers to a substance that changes the rate of reaction in a chemical reaction while its composition and mass remain unchanged after the reaction. The catalyst which accelerates the reaction is called a positive catalyst (Positive Catalyst), and the slowed down is called a negative catalyst (Negative Catalyst) or a retarder. Generally referred to as a catalyst is a positive catalyst. Such catalysts are used more in the industry, especially in the organic chemical industry, and have great significance, such as contact sulfuric acid, synthetic ammonia, hydrolysis of esters and polysaccharides, hydrogenation of oils and the like, all require a catalyst. Commonly used catalysts are mainly metals, metal oxides and inorganic acids. If the catalyst is a solid, the reactants are gases, forming a heterogeneous catalytic reaction, sometimes referred to as a catalyst or contact agent. Catalysts are generally selective in that they only accelerate a reaction or a type of reaction. However, some reactions may use a variety of catalysts, such as hydrogenation, platinum, palladium, and nickel are often used, and should be carefully selected. In the catalytic reaction, substances other than the catalyst, called a cocatalyst, are often added to enhance the catalytic action of the catalyst. For example, iron is a catalyst for the ammonia industry. The addition of small amounts of potassium oxide and aluminum oxide enhances the catalytic action of iron. The composition and weight of the catalyst and cocatalyst did not change before and after the reaction. All of the above are inorganic catalysts. Enzyme protein is an important organic catalyst. There are many types of catalysts, which are classified according to the phase of the catalyst and the reaction system, and there are two types of catalysts, homogeneous and heterogeneous. Heterogeneous catalysts are the most widely used, with three states of gas, liquid and solid. The types and applications of solid catalysts are the most. The solid catalyst is fine particles made of metal (nickel, platinum, palladium, chromium, cobalt, titanium, vanadium, etc.) or metal oxides (copper oxide, vanadium pentoxide, lead oxide, etc.) or dispersedly deposited on a carrier. In order to obtain a good dispersion effect and increase the specific surface area. The catalyst requires reliable activity, stability, selectivity, long working life, low toxicity and over-burning, and easy regeneration. In order to increase the catalytic efficiency, a simple metal catalyst is used as an alloy catalyst (such as a nickel-aluminum alloy) and a composite catalyst (a Ziegler Natta catalyst). The composite catalyst consists of a main catalyst and a cocatalyst. Additional components are added to the new high efficiency catalyst. The production and development of high-efficiency catalysts have promoted the development of polymer materials and produced many new generations of high-performance and high value-added polymer functional and structural materials. With the wide application of catalysts and the emergence of some new catalysts, many new chemical reactions can be industrialized to provide an increasing number of chemical products. Some of the original chemical reaction conditions can be improved to improve production efficiency and Product quality, make full use of resources. Constantly selecting and developing a new generation of more and better catalysts has always been an important topic in the field of modern chemical and chemical research. However, the role of the catalyst is not beneficial to humans. For example, the combustion products of supersonic jet fuel as a catalyst can cause the decomposition of ozone in the stratosphere (10-50 km high altitude), so that the absorption of the sun's ultraviolet rays by the atmosphere is weakened, resulting in a certain The number of skin cancer patients has increased in some areas. New supersonic jet fuels are being developed, requiring that their products of combustion do not become catalysts for the decomposition of ozone in the stratosphere. Auxiliary means that in industrial and agricultural production, especially in chemical production, in order to improve the production process, improve product quality and output, or give the product a unique application performance, it is usually necessary to add some auxiliary chemicals. It is a major auxiliary raw material in chemical production, which can give special properties to the product and improve the finished product; it can accelerate the chemical reaction speed and improve the product yield; it can save raw materials and improve processing efficiency. Widely used in the chemical industry, especially in the industrial sector of organic synthesis, post-processing of synthetic materials and petroleum refining, pesticides, pharmaceuticals, dyes, coatings, etc. According to the use, it can be divided into synthetic additives and processing aids. Various auxiliary agents used in the synthesis and polymerization of monomers such as resins, fibers, rubbers, etc., are called auxiliaries for synthesis, including catalysts, initiators, solvents, dispersants, emulsifiers, polymerization inhibitors, regulators, terminators, etc. . Auxiliary chemicals used in the manufacture of rubber, plastic products, and chemical fiber spinning and spinning from raw rubber, called processing aids, including plasticizers, heat stabilizers, antioxidants, light stabilizers. , flame retardant, foaming agent, lubricant, mold release agent, vulcanizing agent, accelerator, softener, scorch retarder, surfactant, oil agent, filler, etc. Among these additives, many are chemical hazardous materials, such as synthetic dibenzoyl peroxide, azobisisobutyronitrile, hydrogen peroxide-ferrous iron, aluminum alkyl, titanium chloride and other initiators, Catalysts are inflammable and explosive materials and should be stored, transported, operated and used in accordance with the relevant provisions of the Regulations on the Safety Management of Chemical Dangerous Goods.