[Overview]
Phosphorus pentasulfide, commonly known as tetraphosphorus decasulfide-P4S10 internationally, is an important inorganic chemical raw material. In the pesticide industry, it can be used to synthesize parathion, systemic phosphate, phoxim, malathion, trithion, ethion, imidion, methyl rice powder, ethyl rice powder, Diphosphos, phorate, mesophos, phosphos, mesophos, pyrazophos, chlorpyriphos, strophos, phosphos, pyrophos, geofenthion, paraphos The basic raw materials of organophosphorus pesticides such as phosphine, phosphine, phosphin, phoxim, tert-butylphos, fenfenthion, chloralphos and other organophosphorus pesticides; in the lubricating oil industry, it is used to synthesize phosphine. Zinc alkyl dithiophosphate accounts for 80% of the total lubricating oil additives; it can also be used for non-ferrous metal mineral processing; in the match industry, it is used to prepare sulfur-containing compounds.
[Physical and Chemical Properties]
Characteristics: Gray to yellow crystals with an odor similar to hydrogen sulfide. Melting_point 286~290℃ Boiling_point 514℃ Relative Density 2.03 Solubility Dissolves in sodium hydroxide solution and generates sodium thiophosphate. Slightly soluble in carbon disulfide, insoluble in cold water.
[Preparation method]
1. Gas phase method: The reaction is carried out at a high temperature of 500°C (the pressure is usually 0.14 ~ 0.15 MPa), and the heat of the reaction is used to refine the generated phosphorus pentasulfide. However, the temperature of this method is high, which causes the reactor exhaust pipe to be easily blocked, posing certain difficulties to the operation and requiring high technical requirements. The gas phase method is represented by PCUK Company of France and Monsanto Company of the United States. The process is shown in Figure 1.
Figure 1 is a schematic diagram of the production of P2S5 by gas phase method
The main process conditions are: operating pressure 0.05MPa, reactor temperature 500°C, and cooler temperature 375°C. The main raw materials consume 28okg/t phosphorus and 720~725kg/t sulfur, and the reaction yield is close to 100%. The operation process is: continuously add liquid yellow phosphorus and sulfur in proportion to the reactor at the same time, and react at 500°C. During the reaction, electric heating is used to generate P2S5 steam that condenses at about 375°C, and then continues under NZ protection. Press into tablets and further powder to obtain powdered P2S5. The tail gas released during the reaction process of this method can be directly discharged after being condensed and recovered, basically meeting the emission standards. The advantages of this method are simple process, high product purity and high activity, and the tableting technology can be used to provide P2S5 with different activities according to the different requirements of users. Its disadvantage is that it operates at high temperatures and has high technical requirements. If it is not handled properly, it is easy to get clogged and cause explosion accidents.
2. Liquid phase method The liquid phase method can be continuous or intermittent, and the reaction temperature is slightly lower than the gas phase method. The requirements for raw materials are extremely high. For yellow phosphorus with a content of 99.6%, concentrated H2SO4 needs to be used; for further refinement, the finished product P2S5 will no longer be refined. This method is represented by Stauffer Company in the United States and Hoeehst Company in Germany. The main process flow diagram is shown in Figure 2.
Figure 2 is a schematic diagram of the production of P2S5 by liquid phase method
Add high-purity refined P2S5 into the reaction kettle with a stirrer in a molten state at 60°C and 127°C at a molar ratio of 2:5. The P2S5 mother liquor has been reserved in the kettle. The reaction temperature 340~360℃, reaction pressure 0.14Mpa, control the reaction temperature with the feeding speed. The synthesis of P2S5 is an exothermic reaction, and the heat of reaction is removed by air cooling. If it continues to rise, first reduce the amount of phosphorus and then reduce the amount of sulfur. If the control is invalid, the feeding will be completely stopped. When the reaction is nearing the end, measure the ratio of P and S in the materials in the reaction tank, and adjust if necessary to make P/S = 2:5 (molar ratio). When the temperature no longer rises, the reaction ends. When discharging, except for the mother liquor for the next batch left in the kettle, the rest is put into the intermediate tank under N2 protection, and then cooled and granulated to obtain P2S5. The raw material phosphorus used is transported by water pressure, while sulfur is transported by a submersible pump. The reaction system has a safety alarm device. Feeding should be stopped under the following circumstances: (l) Stop adding sulfur and stirring when the temperature is high to prevent excessive torque from damaging the mixer (a torque meter is installed on the kettle). (2) When the temperature is too low, stop feeding. (3) When the cooling water is interrupted, stop feeding. The advantage of this method is that the raw materials are refined first, each process is protected by N2, and it can be produced semi-continuously or intermittently. The tail gas is absorbed and treated by liquid alkali, and it is more convenient to control the feeding. The disadvantage is that the unit consumption is slightly higher than that of the gas phase method.
[Process Technology]
1. Raw material preparation Sulfur: After the solid sulfur is melted in the sulfur kettle, it enters the sinking tank. After sinking for a period of time, it enters the clarifier and is pumped into the liquid sulfur tank for later use. Phosphorus: After solid yellow phosphorus is melted in the phosphorus melting tank, it is pumped into the liquid phosphorus storage tank for later use. The molten phosphorus tank is a large hot water pool where water is used to isolate phosphorus from the air.
2.Reaction
Figure 3 shows the reaction formula for synthesizing phosphorus pentasulfide
The liquid sulfur and yellow phosphorus in the storage tank are pumped into the reactor respectively. The flow rate and ratio of sulfur and phosphorus are strictly and automatically controlled. The heat generated by the reaction is used in the next step of distillation. Monitor the phosphorus content of amino silicone oil emulsion in the finished product by measuring the viscosity of the finished liquid online. The phosphorus content has a big impact on subsequent slices. When the phosphorus content is >28.5%, the slicing operation is more difficult. From the perspective of production practice, the best phosphorus content is 27.0%, and the suitable range is when the phosphorus content is 27.9% to 28.3%. At this time, not only the reaction process is easy to control, but also the reaction process is easy to control.�, and the subsequent processing steps can also be carried out smoothly. In order to balance the reaction heat, there is a large amount of reaction liquid circulation between the reaction kettle and the distillation kettle. When the reaction temperature exceeds the normal range, send cold air to the reactor jacket to cool it down.
3. The purpose of the distillation process is to remove impurities in the finished product and replace the raw material for refining. The steamed gaseous phosphorus pentasulfide is cooled into a liquid by heat transfer oil in the condenser and then enters a storage tank with an insulation jacket. Pour thermal oil into the middle. The residue at the bottom of the tower is regularly sent to the residue distillation system, and the active ingredient phosphorus pentasulfide is recovered at the top of the tower. The residue at the bottom of the tower can be treated as pollution-free waste.
4. Flaking, crushing and packaging. Liquid phosphorus pentasulfide is pumped into the flaking machine. The material liquid is evenly stained on the surface of the drum as the number of revolutions rotates, and is cooled into thin flakes by the incoming cooling water. After the scraper scrapes off the flakes, they are broken into small pieces, and then sent to the grinder to grind into finished products of different particle sizes according to the customer’s requirements (different grinding discs can be changed to grind different particle sizes). The ground finished products are sent to the automatic packaging system. The entire process from reaction to packaging is carried out under nitrogen protection. There is also a thermal oil system, whose main functions are: ① Insulation and preventing liquid phosphorus pentasulfide from condensing. ② Used as a cooling medium for the condenser in the distillation system. After the heat transfer oil that has absorbed the heat comes out of the condenser, part of it goes to the steam generator, and the generated steam is used by this device.
[Application]
Phosphorus pentasulfide (commonly known as tetraphosphorus decasulfide-P4S10 internationally) is a basic chemical raw material with a wide range of uses and can be widely used in ① organophosphorus pesticides. Dimethoate, omethoate, ethyl 1605, Cincoline pigments, phosphorus, synergized phosphorus and many other varieties; ② Lubricating oil additives. Mainly used for T108 (isobutyl barium sulfate) and T202 (zinc dialkyl disulfide phosphate). T108 is mainly used in internal combustion engine oil and thickened engine oil to clean, disperse and resist oxidation. T202 is mainly used in internal combustion engine oil and gear oil, and plays the role of anti-aging, anti-oxidation, anti-friction, anti-corrosion, and extending the service life; ③ Non-ferrous metal mineral processing and flotation agent. Mainly used for flotation of aluminum-zinc ore. Such as: No. 25 black drug, phenol black drug, butyral black drug, etc.; ④ Medicine. Mainly used for arabinoside, Yajining, etc.
[Main reference materials]
[1] Zhao Hongxin. New progress in the production of phosphorus pentasulfide [J]. Chemical Engineering Design Communications, 2000(04):46-49.
[2]Cao Guanghong. Progress in production technology of phosphorus pentasulfide[J]. Guizhou Chemical Industry, 1994(01):25-28.
[3] Zhao Hongxin. Introduction to the production status of phosphorus pentasulfide[J]. Chemical Engineer, 2000(03):46-47.
