Oxide catalyst In view of the fact that the platinum catalyst developed in the19th century for oxidizing sulfur dioxide is easily poisoned by arsenic in the feed gas, a process of combining the two catalysts appeared. In the first stage of Mannheim plant in Germany, low-activity iron oxide was used as catalyst, and the remaining sulfur dioxide was converted with platinum catalyst in the second stage. At this stage, a supported vanadium oxide catalyst with high toxicity was developed and used in 19 13 in the new contact sulfuric acid plant of Baden aniline soda company in Germany. Its service life can reach several years to ten years. After the 1920s, vanadium oxide catalyst quickly replaced the original platinum catalyst and became a commercial catalyst. This reform of sulfuric acid catalyst has opened up a broad prospect for oxide catalyst.
Liquid Catalyst 19 19 Standard Oil Company of New Jersey, USA, developed an industrial process for producing isopropanol by hydration of propylene with sulfuric acid as catalyst, and set up a factory in 1920. By 1930, United Carbide Company of the United States had built a plant for producing ethanol by hydration of ethylene. These liquid catalysts are simple chemicals.
Biocatalyst Enzymes are biocatalysts, which are organic substances with catalytic ability produced by plants, animals and microorganisms (most of them are protein). But a small amount of RNA also has biocatalytic function), formerly known as enzyme. Almost all biological chemical reactions are carried out under the catalysis of enzymes. The catalysis of enzymes is also selective. For example, amylase catalyzes the hydrolysis of starch into dextrin and maltose, and protease catalyzes the hydrolysis of protein into peptide. Life uses them to accelerate chemical reactions in the body. Without enzymes, many chemical reactions in living things will proceed very slowly, making it difficult to sustain life. At the temperature of about 37℃ (human body temperature), the enzyme works best. If the temperature is higher than 50℃ or 60℃, the enzyme will be destroyed and can no longer play its role. Therefore, the biological detergent that uses enzymes to decompose stains on clothes is the most effective at low temperature. Enzymes are of great significance in physiology, medicine, agriculture and industry. At present, the application of enzyme preparation is increasingly extensive.
Usually, the cheapest raw material waste is selected as the coal-burning catalyst. Experiments show that many wastes have obvious catalytic combustion effect and environmental protection efficiency. The exhaust gases of commonly used coal-fired catalysts are: first, coal ash. Coal ash is the residue formed by ash in coal during combustion. The ash in coal is an internal catalyst. Too much ash is not conducive to combustion, and too little ash is difficult to catch fire. Second, papermaking black liquor. The alkaline black liquor discharged from paper mill contains a lot of K2CO3, Na2CO3, KOH, NaOH and Ca( OH) 2. It is a good coal-burning catalyst. Adding proper amount of dry black liquor to coal can reduce the ignition temperature of coal by 30℃ ~ 50℃ and promote the complete combustion of coal. In addition, it also has desulfurization effect, and the desulfurization rate can reach 35% ~ 58%, which is beneficial to environmental protection. Third, waste liquid from alkali plant. The waste liquid of alkali plant contains a large amount of CaCO3 and a small amount of CaCl2. Proper addition of this waste liquid is beneficial to the ignition and combustion of coal, and also has desulfurization effect, and the desulfurization rate can reach above 44%. Fourthly, the iron ore powder produced in the process of iron ore mining is rich in Fe2O3, which is a good raw material for coal-fired catalyst. Some iron ores have no mining value. After years of weathering, a large amount of iron ore powder has accumulated on the hillside, which can be collected and utilized. Fifth, plant ash. Plant ash contains KOH, which can be filtered with water to obtain a solution. After drying, crude KOH can be extracted from the solution to be used as a coal-burning catalyst. Sixth, lime. Both quicklime and hydrated lime can be used as raw materials for coal-fired catalysts, and it should be emphasized that Ca2+ has obvious desulfurization effect. In addition to the above, there are many other wastes that can be used as coal-fired catalysts, such as waste white mud, iron-making slag, calcium carbide waste residue, and waste liquid from some chemical plants.
There are semiconductors and photocatalysts. Physically speaking, semiconductor is a material between conductor and insulator. Photocatalysis refers to the separation of photo-generated carriers from semiconductor materials under a certain wavelength of illumination, and then the combination of photo-generated electrons and holes with ions or molecules to generate oxidation or reduction active free radicals, which can degrade organic macromolecules into carbon dioxide or other small organic substances and water. During the reaction, this semiconductor material, that is, the photocatalyst itself, is unchanged. Generally, the material used as a photocatalyst for photocatalytic reaction is a semiconductor material or a substance with semiconductor characteristics.