Overview of the preparation of sodium tetraborate (pentahydrate)
Sodium tetraborate (pentahydrate), aliased as borax pentahydrate, the English name of cerium carbonate is Sodium tetraborate pentahydrate, the English alias is borax pentahydrate; Solubor, molecular weight is 291.29, relative density is 1.815g/cm3, melting point 75℃, molecular formula is Na2B4O75(H2O) . Sodium tetraborate (pentahydrate) is a chemical substance that appears as a white crystalline powder. Easily soluble in hot water and glycerin, slightly soluble in ethanol and carbon tetrachloride. The aqueous solution is di-tert-butyl dicarbonate alkaline. Crystal water is completely lost when heated to 120°C.
It is prepared from sodium tetraborate decahydrate solution, controlling the feeding temperature to be higher than 70°C, the crystallization temperature to be higher than 60°C, recrystallization, filtration, and drying below 120°C. It can also be made by dissolving natural boron ore in hot water, filtering and separating, cooling and crystallizing, controlling the crystallization temperature to be higher than 60°C, and washing with mother liquor with a concentration of 25%. It is stable in dry air, but slowly absorbs moisture in the air under humid conditions and becomes borax decahydrate. It has sterilization, disinfection, fluxing and high-temperature adhesive properties. Chemical properties are similar to sodium tetraborate decahydrate.
Used to make special glass. Used as antifreeze and anticoagulant in mining and metallurgy. It is also used as an additive for electroplating solutions and a co-solvent for non-ferrous metals and special alloys. It can be used as a raw material for boron compounds, herbicide, and also used in stained glass, enamel, soil disinfection, etc.
Anhydrous borax is one of the raw materials for manufacturing high-grade glass and glazed tiles. It is widely used in glass, enamel, national defense, agriculture and other fields. In recent years, with the development of my country’s economy, the market demand for high-end glass and ceramic products has increased, so the product market prospects are broad.
Preparation method of sodium tetraborate (pentahydrate)
Method 1 is to use a multifunctional reactor to produce borax pentahydrate, which integrates batching, dissolution, evaporation, crystallization and drying. It has the characteristics of short process, easy operation, high product purity and stable quality. And after years of production, it has been proven that the technology is mature and reliable, and the product quality is stable.
The specific production process is to combine borax decahydrate (Na2B4O7•10H2O ) and tap water are put into the reaction tank at a ratio of 23:1 (mass ratio), and then steam with a pressure of more than 0.2Mpa is introduced into the jacket for heating. When the temperature rises above 100°C, keep it for 5 minutes, and then turn on the vacuum pump to reduce the pressure. Concentrate and at the same time open the condenser water valve to condense the evaporated water vapor into liquid water and enter the condensed water collection tank. At the beginning of concentration, it is best to keep the vacuum in the tank at 0.04-0.05Mpa and control the temperature above 80°C. As the concentration of the solution in the tank gradually increases, the vacuum degree (0.06MPa) should be increased.
After the water in the reaction tank is drained, continue to vacuum for 2 hours and keep the temperature in the tank not lower than 70°C. When it is observed through the sight glass that the material in the reaction tank has good fluidity, no lumps and tumbling, and the material surface is flat and gentle, the reaction ends. Close the vacuum pump and condensate valve, then open the vent valve of the reaction tank, and the discharge valve at the bottom of the tank begins to discharge material into the material truck. After the temperature of the materials in the material truck drops to normal temperature, they are screened and packaged. Qualified materials appear as white, easy-flowing crystal particles. The conversion rate of this process is 100%, and the yield (particle size less than 2.36mm) is more than 99%. The small amount of large crystal blocks produced is returned to the reaction tank for the next reaction. The by-produced condensate water is recycled, and the excess can be used as water in the boiler room. The process flow diagram is shown in Figure 1.
Method 2: Dissolution crystallization method. The traditional production process of borax pentahydrate is the dissolution crystallization method. In the dissolution crystallizer, dissolve borax decahydrate with water or the primary mother liquor from the system (the control temperature is not lower than 70°C), and add materials Adjust the steam pressure from time to time, and strictly control the temperature of the material solution to not be lower than 65°C; after the material is added, continue to maintain this temperature for 10 minutes. The crystallized borax pentahydrate is centrifuged to remove the mother liquor, and the wet crystals are dried by air flow (<120°C) to obtain the finished product of borax pentahydrate.
Na2B4O7•10H2O→Na2B4O7•5H2O+5H2O
This method has a long process flow and difficult operation.�It is complex, and the products produced have small crystals, poor appearance, and unstable product quality. The mother liquor contains a large amount of borax and cannot be completely converted into products due to repeated recycling.
The flow chart of the dissolution crystallization method is shown in Figure 2 below
It can be seen from the comparison between Figure 2 and Figure 1 that compared with the traditional dissolution and crystallization method, the process flow in Figure 1 is shorter. The ingredients, dissolution, evaporation, crystallization, and drying are all completed in one step in the multifunctional reactor. The dissolution crystallization method reduces the number of pieces of equipment by 4, which not only saves labor and time, but also reduces artificial pollution during the operation connection of each unit. The borax pentahydrate crystals produced through the process in Figure 1 have large particles, are shiny, and have very good fluidity. . The borax pentahydrate crystal particles produced by the traditional dissolution crystallization method are small and dull, and the borax pentahydrate content is lower than that of the borax pentahydrate produced by the process in Figure 1. The dissolution crystallization method has a low single-pass yield because the mother liquor contains a large amount of borax for recycling, but the single-pass yield of the process is more than 99%.
Borax Pentahydrate Enterprise Standard
The products produced by the production process in Figure 1 have stable quality and a high pass rate. After practice, the borax pentahydrate produced by this process can fully meet the enterprise standards in Table 1.
Preparation and production uses of sodium tetraborate (pentahydrate)
1. Used in the glass industry to make optical glass and heat-resistant and corrosion-resistant glass. Used to make special glasses.
2. Used as antifreeze and anticoagulant in mining and metallurgy. It is also used as an additive for electroplating solutions and a co-solvent for non-ferrous metals and special alloys.
3. Used as herbicide and soil fungicide.
4. Used as glaze in the enamel industry, applied to metal surfaces, making it strong and durable. Used in the ceramic industry to make glazes with good results.
5. Used as an electrolyte additive and a welding agent for non-ferrous metals in the non-ferrous metal industry.
6. Used as a water softener in cosmetics.
7. Manufacturing of inhibitors and other boron compounds used for anti-corrosion and anti-rust.
References
[1]Wang Xiangdong. New production process of borax pentahydrate[J]. Shandong Chemical Industry, 2005, 34(1):72-72.
