A system and method for the continuous production of phosphorus oxybromide

Abstract

This invention belongs to the field of chemical intermediate synthesis technology, specifically relating to a system and method for the continuous preparation of phosphorus oxybromide. The system provided by this invention is designed for continuous production, enabling continuous production of phosphorus oxybromide, improving preparation efficiency, and avoiding the problem of decreased product yield and purity caused by prolonged high-temperature separation. This invention uses phosphorus tribromide as raw material and chloroform as solvent. The mixture is then fed into a reaction tower, where it comes into contact with a mixture of nitrogen dioxide and oxygen entering the tower. Phosphorus tribromide is oxidized to phosphorus oxybromide. Nitrogen dioxide and residual oxygen are recovered and recycled from the top of the reaction tower, reducing waste gas emissions. The mixture of chloroform and phosphorus oxybromide first evaporates most of the solvent in a falling film evaporator, and then evaporates the remaining solvent in a scraped film evaporator, recovering and recycling the solvent. This reduces energy consumption and shortens the time phosphorus oxybromide remains in the evaporator, improving the yield and purity of phosphorus oxybromide.

Description

Technical Field

[0001] This invention belongs to the field of chemical intermediate synthesis technology, specifically relating to a system and method for the continuous preparation of phosphorus oxybromide. Background Technology

[0002] Phosphorus oxybromide, also known as phosphorus tribromooxy, is an important chemical intermediate. The main production process currently involves adding chloroform (as a reaction solvent) to an oxidation reactor, adding phosphorus tribromide dropwise to the reactor, and simultaneously introducing a mixture of oxygen and nitrogen dioxide into the reactor. The reaction is carried out at a certain temperature to obtain phosphorus oxybromide.

[0003] Another common production process for phosphorus oxybromide involves adding P2O5 and PBr3 to a drying tube containing NaOH and CaCl, and then reacting it under the condition of dropwise addition of bromine to obtain phosphorus oxybromide.

[0004] However, existing processes for phosphorus oxybromide production are all batch processes with long reaction times. Due to the long-term high-temperature separation, the yield and purity of phosphorus oxybromide are low. Summary of the Invention

[0005] The purpose of this invention is to provide a system and method for the continuous preparation of phosphorus oxybromide, which improves the yield and purity of phosphorus oxybromide.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a system for the continuous preparation of phosphorus oxybromide, comprising: a reaction tower; a mixer connected to the top sidewall of the reaction tower; a gas mixing tank connected to the bottom sidewall of the reaction tower; a top-through gas mixing tank of the reaction tower; a falling film evaporator connected to the bottom of the reaction tower; a first solvent condenser connected to the top of the falling film evaporator; a first solvent receiving tank connected to the first solvent condenser; a scraped film evaporator connected to the bottom of the falling film evaporator; a second solvent condenser connected to the top of the scraped film evaporator; and a second solvent receiving tank connected to the second solvent condenser.

[0008] Preferably, the reaction tower has 5 to 20 sections, the section height is 0.6 to 1.2 m, and the height of the overflow weir of the section is 0.4 to 0.8 m.

[0009] Preferably, a gas distributor is provided at the bottom of the reaction tower section and a liquid distributor is provided at the top of the tower section; the gas mixing tank is connected to the reaction tower through the gas distributor; and a cooling coil is provided in the tower section of the reaction tower.

[0010] The present invention also provides a method for the continuous preparation of phosphorus oxybromide using the system described above, comprising the following steps:

[0011] (1) Phosphorus tribromide and chloroform are passed into a mixer to obtain a mixture, and nitrogen oxides and oxygen are passed into a gas mixing tank to obtain a mixed gas;

[0012] (2) The mixture is introduced into the top of the reaction tower and the mixed gas is introduced into the bottom of the reaction tower. After the mixed gas reaches the top of the reaction tower, it is introduced into the bottom of the reaction tower through a gas mixing tank for recycling. After the mixture reaches the bottom of the reaction tower, it is introduced into a falling film evaporator for evaporation to obtain gaseous chloroform and phosphorus oxybromide solution.

[0013] (3) The gaseous chloroform is passed through the top of the falling film evaporator into the first solvent condenser and condensed to obtain liquid chloroform, and the liquid chloroform is passed into the first solvent receiving tank;

[0014] (4) The phosphorus oxybromide solution is passed into a scraped film evaporator to evaporate and obtain gaseous residual chloroform and phosphorus oxybromide. The gaseous residual chloroform is passed into a second solvent condenser to condense and obtain liquid residual chloroform. Then the liquid residual chloroform is passed into a second solvent receiving tank.

[0015] Preferably, the mass ratio of chloroform to phosphorus tribromide is 1.2 to 2.5:1.

[0016] Preferably, the molar flow ratio of the nitrogen oxide to oxygen is 1 to 3:1; the nitrogen oxide includes one or more of nitric oxide, nitrogen dioxide, and dinitrogen tetroxide.

[0017] Preferably, the gas velocity in the empty tower of the reaction tower is 0.2–1.5 m / s; the flow rate of the mixed liquid is 1500–10000 kg / h; and the flow rate of the mixed gas is 800–8000 Nm³. 3 / h.

[0018] Preferably, the temperature of the reaction tower section is 15-25°C, and the total reaction time in the tower is 3-10 hours.

[0019] Preferably, the pressure of the falling film evaporator is 80-100 kPa and the temperature is 50-80°C.

[0020] Preferably, the bottom temperature of the scraped film evaporator is 120-135°C, the pressure is 1-5 kPa, and the rotation speed is 100-150 rpm.

[0021] This invention provides a system for the continuous preparation of phosphorus oxybromide. The system provided by this invention is designed for continuous production, enabling improved preparation efficiency and avoiding the problems of decreased product yield and purity caused by prolonged high-temperature separation.

[0022] This invention also provides a method for the continuous preparation of phosphorus oxybromide using the system described above. This invention uses phosphorus tribromide as raw material and chloroform as solvent. The mixture is then fed into a reaction tower, where it comes into contact with a mixture of nitrogen dioxide and oxygen (oxidant) entering the tower. Phosphorus tribromide is oxidized to phosphorus oxybromide. Nitrogen dioxide and residual oxygen are recovered and recycled from the top of the reaction tower, reducing waste gas emissions. The mixture of chloroform and phosphorus oxybromide first evaporates most of the solvent in a falling film evaporator, and then evaporates the remaining solvent in a scraped film evaporator, allowing for solvent recovery and recycling. This reduces energy consumption and shortens the time phosphorus oxybromide remains in the evaporator, improving the yield and purity of phosphorus oxybromide, making it suitable for industrial production. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram of the system for the continuous preparation of phosphorus oxybromide according to the present invention;

[0025] Reference numerals: 1 is a mixer, 101 is the first feed pump, 102 is the second feed pump, 103 is the first liquid storage tank, 104 is the second liquid storage tank, 2 is a gas mixing tank, 201 is the first flow meter, 202 is the first gas storage tank, 203 is the second flow meter, 204 is the second gas storage tank, 3 is a reaction tower, 301 is a gas distributor, 302 is a liquid distributor, 303 is a cooling coil, 4 is a buffer tank, 5 is a compressor, 6 is a reaction tower discharge pump, 7 is a falling film evaporator, 8 is the first solvent condenser, 9 is the first solvent receiving tank, 10 is the first solvent discharge pump, 11 is the crude product discharge pump, 12 is a scraped film evaporator, 13 is the second solvent condenser, 14 is the second solvent receiving tank, 15 is the second solvent discharge pump, 16 is the product discharge pump, 17 is the first solvent storage tank, 18 is a nitrogen pipeline, 19 is the product storage tank, and 20 is the second solvent storage tank. Detailed Implementation

[0026] The present invention provides a system for continuous preparation of phosphorus oxybromide, comprising a reaction tower 3; a mixer 1 connected to the top sidewall of the reaction tower 3; a gas mixing tank 2 connected to the bottom sidewall of the reaction tower 3; and a top-circulating gas mixing tank 2 of the reaction tower 3.

[0027] A falling film evaporator 7 connected to the bottom of the reaction tower 3; a first solvent condenser 8 connected to the top of the falling film evaporator 7; and a first solvent receiving tank 9 connected to the first solvent condenser 8.

[0028] A scraped film evaporator 12 connected to the bottom of the falling film evaporator 7; a second solvent condenser 13 connected to the top of the scraped film evaporator 12; and a second solvent receiving tank 14 connected to the second solvent condenser 13.

[0029] The system for continuous preparation of phosphorus oxybromide provided by the present invention includes a reaction tower 3; the top of the reaction tower 3 is preferably connected to the gas mixing tank 2 via a buffer tank 4 and a compressor 5 in sequence; the bottom of the reaction tower 3 is preferably connected to a falling film evaporator 7 via a reaction tower discharge pump 6.

[0030] In this invention, the number of reaction tower sections is preferably 5 to 20, specifically 5, 7, 9, 10, 12, 15, 18, or 20. The height of each tower section is preferably 0.6 to 1.2 m, specifically 0.6 m, 0.8 m, 1 m, or 1.2 m. The height of the overflow weir in each tower section is preferably 0.4 to 0.8 m, specifically 0.4 m, 0.5 m, 0.6 m, 0.65 m, 0.7 m, 0.75 m, or 0.8 m. The mixed liquid overflows through the overflow weir to the lower tower section.

[0031] In this invention, a gas distributor 301 is preferably provided at the bottom of the reaction tower 3, and a liquid distributor 302 is preferably provided at the top of the tower section; the gas mixing tank 2 is preferably connected to the reaction tower 3 through the gas distributor 301; and a cooling coil 303 is preferably provided in the tower section of the reaction tower 3. The mixed gas in the lower tower section rises into the liquid distributor in the upper tower section and mixes with the liquid again.

[0032] The continuous phosphorus oxybromide preparation system provided by the present invention includes a mixer 1 connected to the top sidewall of the reaction tower 3; the mixer 1 is preferably connected to a first liquid storage tank 103 via a first feed pump 101; the mixer 1 is preferably connected to a second liquid storage tank 104 via a second feed pump 102. The present invention uses the mixer 1 to mix phosphorus tribromide and chloroform to obtain a mixture of phosphorus tribromide and chloroform.

[0033] The system for continuous preparation of phosphorus oxybromide provided by this invention includes a gas mixing tank 2 connected to the bottom sidewall of the reaction tower 3; the gas mixing tank 2 is preferably connected to a first gas storage tank 202 via a first flow meter 201; the gas mixing tank 2 is preferably connected to a second gas storage tank 204 via a second flow meter 203. This invention uses the gas mixing tank 2 to mix nitrogen dioxide and oxygen to obtain a mixed gas of nitrogen dioxide and oxygen.

[0034] The system for continuous preparation of phosphorus oxybromide provided by the present invention includes a falling film evaporator 7 connected to the bottom of the reaction tower 3; the falling film evaporator 7 is preferably connected to a scraped film evaporator 12 via a crude product discharge pump 11.

[0035] The continuous phosphorus oxybromide preparation system provided by this invention includes a first solvent condenser 8 connected to the top of the falling film evaporator 7. This invention uses the first solvent condenser 8 to condense the gaseous solvent evaporated from the falling film evaporator 7 to obtain a liquid solvent.

[0036] The system for continuous preparation of phosphorus oxybromide provided by the present invention includes a first solvent receiving tank 9 connected to the first solvent condenser 8; the first solvent receiving tank 9 is preferably connected to a first solvent storage tank 17 via a first solvent discharge pump 10.

[0037] The continuous phosphorus oxybromide preparation system provided by this invention includes a scraped film evaporator 12 connected to the bottom of the falling film evaporator 7; the bottom of the scraped film evaporator 12 is preferably connected to a product storage tank 19 via a product discharge pump 16; a nitrogen pipeline 18 is preferably connected between the scraped film evaporator 12 and the product discharge pump 16. This invention introduces nitrogen through the nitrogen pipeline 18 to provide an inert atmosphere protection for the product.

[0038] The continuous phosphorus oxybromide preparation system provided by this invention includes a second solvent condenser 13 connected to the top of the scraped film evaporator 12. This invention uses the second solvent condenser 13 to condense the gaseous solvent evaporated from the scraped film evaporator 12 to obtain a liquid solvent.

[0039] The continuous phosphorus oxybromide preparation system provided by this invention includes a second solvent receiving tank 14; the second solvent receiving tank 14 is preferably connected to a second solvent storage tank 20 via a second solvent discharge pump 15. The specific structure of the continuous phosphorus oxybromide preparation system provided by this invention is as follows: Figure 1 As shown.

[0040] The present invention also provides a method for the continuous preparation of phosphorus oxybromide using the system described above, comprising the following steps:

[0041] (1) Phosphorus tribromide and chloroform are introduced into mixer 1 to obtain a mixture, and nitrogen oxides and oxygen are introduced into gas mixing tank 2 to obtain a mixed gas;

[0042] (2) The mixture is introduced into the top of the reaction tower 3, and the mixed gas is introduced into the bottom of the reaction tower 3. After the mixed gas reaches the top of the reaction tower 3, it is introduced into the bottom of the reaction tower 3 through the gas mixing tank 2 for recycling. After the mixture reaches the bottom of the reaction tower 3, it is introduced into the falling film evaporator 7 for evaporation to obtain gaseous trichloromethane and phosphorus oxybromide solution.

[0043] (3) The gaseous trichloromethane is passed through the top of the falling film evaporator 7 and condensed into the first solvent condenser 8 to obtain liquid trichloromethane, and the liquid trichloromethane is passed into the first solvent receiving tank 9.

[0044] (4) The phosphorus oxybromide solution is passed into the scraped film evaporator 12 to evaporate and obtain gaseous residual chloroform and phosphorus oxybromide. The gaseous residual chloroform is passed into the second solvent condenser 13 to condense and obtain liquid residual chloroform. Then the liquid residual chloroform is passed into the second solvent receiving tank 14.

[0045] In this invention, phosphorus tribromide and chloroform are mixed in a mixer 1 to obtain a liquid mixture, and nitrogen oxides and oxygen are mixed in a gas mixing tank 2 to obtain a gas mixture. In this invention, the mass ratio of chloroform to phosphorus tribromide is preferably 1.2–2.5:1, specifically 1.2:1, 1.5:1, 1.8:1, 2.0:1, 2.2:1, or 2.5:1.

[0046] In this invention, the molar flow ratio of nitrogen oxides to oxygen is preferably 1 to 3:1, specifically 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.4:1, 2.7:1 or 3:1; the nitrogen oxides preferably include one or more of nitric oxide, nitrogen dioxide and dinitrogen tetroxide.

[0047] After obtaining the mixed liquid and mixed gas, the present invention introduces the mixed liquid into the top of the reaction tower 3 and the mixed gas into the bottom of the reaction tower 3. After the mixed gas reaches the top of the reaction tower 3, it is circulated back to the bottom of the reaction tower 3 through the gas mixing tank 2. After the mixed liquid reaches the bottom of the reaction tower 3, it is evaporated into the falling film evaporator 7 to obtain gaseous trichloromethane and phosphorus oxybromide solution.

[0048] In this invention, the gas velocity in the empty tower of the reaction tower 3 is preferably 0.2–1.5 m / s, specifically 0.2 m / s, 0.5 m / s, 0.8 m / s, 1.0 m / s, 1.2 m / s, or 1.5 m / s; the flow rate of the mixed liquid is preferably 1500–10000 kg / h, specifically 1500 kg / h, 1800 kg / h, 2500 kg / h, 3000 kg / h, 5000 kg / h, 7000 kg / h, 9000 kg / h, or 10000 kg / h; and the flow rate of the mixed gas is preferably 800–8000 Nm³. 3 / h, specifically 800Nm 3 / h, 960Nm 3 / h, 1100Nm 3 / h, 1400Nm 3 / h, 2000Nm 3 / h, 4000Nm 3 / h, 6000Nm 3 / h or 8000Nm 3 / h.

[0049] In this invention, the temperature of the reaction tower 3 is preferably 15-25°C, specifically 15°C, 18°C, 20°C, 22°C or 25°C, and the reaction time in the tower is preferably 3-10h, specifically 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h.

[0050] In this invention, the pressure of the falling film evaporator 7 is preferably 80-100 kPa, specifically 80 kPa, 85 kPa, 90 kPa, or 100 kPa, and the temperature is preferably 50-80°C, specifically 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C. More than 90% of the solvent can be evaporated through the falling film evaporator.

[0051] After obtaining gaseous chloroform, this invention condenses the gaseous chloroform through the top of a falling film evaporator 7 into a first solvent condenser 8 to obtain liquid chloroform, which is then passed into a first solvent receiving tank 9. This invention achieves the recycling of chloroform through condensation and recovery.

[0052] After obtaining the phosphorus oxybromide solution, the present invention passes the phosphorus oxybromide solution into a scraped film evaporator 12 for evaporation to obtain gaseous residual chloroform and phosphorus oxybromide. The gaseous residual chloroform is then passed into a second solvent condenser 13 for condensation to obtain liquid residual chloroform. The liquid residual chloroform is then passed into a second solvent receiving tank 14.

[0053] In this invention, the bottom temperature of the scraped film evaporator 12 is preferably 120–135°C, specifically 120°C, 125°C, 128°C, 132°C, or 135°C; the pressure is preferably 1–5 kPa, specifically 1 kPa, 2 kPa, 3 kPa, 4 kPa, or 5 kPa; and the rotation speed is preferably 100–150 rpm, specifically 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, or 150 rpm. After the mixture passes through the scraped film evaporator 12, a small amount of residual chloroform is further separated.

[0054] To further illustrate the present invention, the following detailed description of the invention's solutions, in conjunction with the accompanying drawings and embodiments, is provided, but should not be construed as limiting the scope of protection of the present invention.

[0055] Example 1

[0056] (1) Trichloromethane at a flow rate of 1500 kg / h and phosphorus tribromide at a flow rate of 1000 kg / h are pumped to mixer 1 respectively. After mixing, a mixture is obtained and enters the reaction tower 3 from the top of the reaction tower 3.

[0057] (2) Nitrogen dioxide and oxygen are respectively metered by flow meters from storage tanks, and then mixed in gas mixing tank 2 to obtain a mixed gas. The mixed gas enters the reaction tower 3 from the gas distributor 301 at the bottom of the reaction tower 3, with a gas flow rate of 960 Nm. 3 / h, the molar flow rate ratio of nitrogen dioxide to oxygen is 1.5:1.

[0058] (3) The gas velocity in the empty tower of reaction tower 3 is 0.34 m / s.

[0059] (4) The reaction tower 3 has 17 sections, each section is 1m high, and the internal overflow weir is 0.8m high; the temperature of each section is 20℃, and the residence time of the mixed liquid in the reaction tower 3 is 7h.

[0060] (5) The mixed liquid at the bottom of the reaction tower 3 is sent from the bottom of the reaction tower 3 to the falling film evaporator 7 at a flow rate of 2560 kg / h. It enters the gas-liquid separator of the falling film evaporator 7 to obtain gaseous chloroform and phosphorus oxybromide solution. The gaseous chloroform enters the first solvent condenser 8 from the top of the gas-liquid separator and is condensed and recovered. The phosphorus oxybromide solution is pumped to the scraped film evaporator 12. The pressure of the falling film evaporator 7 is 80 kPa and the gas phase temperature is 55 °C.

[0061] (6) The phosphorus oxybromide solution at the bottom of the falling film evaporator 7 is fed into the scraped film evaporator 12 at a flow rate of 1238 kg / h. The bottom temperature of the scraped film evaporator 12 is 130℃, the pressure is 3 kPa, and the rotation speed is 150 rpm, to obtain phosphorus oxybromide. The purity of phosphorus oxybromide is 96.3%, and the yield of phosphorus oxybromide is 97.18%.

[0062] Example 2

[0063] (1) Trichloromethane at a flow rate of 1100 kg / h and phosphorus tribromide at a flow rate of 700 kg / h are pumped to mixer 1 respectively. After mixing, a mixture is obtained and enters the reaction tower 3 from the top of the reaction tower 3.

[0064] (2) Nitrogen dioxide and oxygen are respectively metered by flow meters from storage tanks, and then mixed in gas mixing tank 2 to obtain a mixed gas. The mixed gas enters the reaction tower 3 from the gas distributor 301 at the bottom of the reaction tower 3, with a gas flow rate of 1100 Nm. 3 / h, the molar flow rate ratio of nitrogen dioxide to oxygen is 1.2:1.

[0065] (3) The gas velocity in the empty tower of reaction tower 3 is 0.4 m / s.

[0066] (4) The reaction tower 3 has 17 sections, each section is 1m high, and the internal overflow weir is 0.8m high; the temperature of each section is 16℃, and the residence time of the mixed liquid in the reaction tower 3 is 9.5h.

[0067] (5) The mixed liquid at the bottom of the reaction tower 3 is sent from the bottom of the reaction tower 3 to the falling film evaporator 7 at a flow rate of 1798 kg / h. It enters the gas-liquid separator of the falling film evaporator 7 to obtain gaseous chloroform and phosphorus oxybromide solution. The gaseous chloroform enters the first solvent condenser 8 from the top of the gas-liquid separator and is condensed and recovered. The phosphorus oxybromide solution is pumped to the scraped film evaporator 12. The pressure of the falling film evaporator 7 is 85 kPa and the gas phase temperature is 57 °C.

[0068] (6) The phosphorus oxybromide solution at the bottom of the falling film evaporator 7 is fed into the scraped film evaporator 12 at a flow rate of 850 kg / h. The bottom temperature of the scraped film evaporator 12 is 131℃, the pressure is 3 kPa, and the rotation speed is 150 rpm, yielding phosphorus oxybromide. The purity of phosphorus oxybromide is 98.5%, and the yield of phosphorus oxybromide is 98.1%.

[0069] Example 3

[0070] (1) Trichloromethane at a flow rate of 1800 kg / h and phosphorus tribromide at a flow rate of 1200 kg / h are pumped to mixer 1 respectively. After mixing, a mixture is obtained and enters the reaction tower 3 from the top of the reaction tower 3.

[0071] (2) Nitrogen dioxide and oxygen are respectively metered by flow meters from storage tanks, and then mixed in gas mixing tank 2 to obtain a mixed gas. The mixed gas enters the reaction tower 3 from the gas distributor 301 at the bottom of the reaction tower 3, with a gas flow rate of 1400 Nm. 3 / h, the molar flow rate ratio of nitrogen dioxide to oxygen is 1.1:1.

[0072] (3) The gas velocity in the empty tower of reaction tower 3 is 0.5 m / s.

[0073] (4) The reaction tower 3 has 17 sections, each section is 1m high, and the internal overflow weir is 0.8m high; the temperature of each section is 20℃, and the residence time of the mixed liquid in the reaction tower 3 is 6.5h.

[0074] (5) The mixed liquid at the bottom of the reaction tower 3 is sent from the bottom of the reaction tower 3 to the falling film evaporator 7 at a flow rate of 2690 kg / h. It enters the gas-liquid separator of the falling film evaporator 7 to obtain gaseous chloroform and phosphorus oxybromide solution. The gaseous chloroform enters the first solvent condenser 8 from the top of the gas-liquid separator and is condensed and recovered. The phosphorus oxybromide solution is pumped to the scraped film evaporator 12. The pressure of the falling film evaporator 7 is 90 kPa and the gas phase temperature is 59 °C.

[0075] (6) The phosphorus oxybromide solution at the bottom of the falling film evaporator 7 is fed into the scraped film evaporator 12 at a flow rate of 1305 kg / h. The bottom temperature of the scraped film evaporator 12 is 133℃, the pressure is 3 kPa, and the rotation speed is 150 rpm, to obtain phosphorus oxybromide. The purity of phosphorus oxybromide is 98.3%, and the yield of phosphorus oxybromide is 96.76%.

[0076] As can be seen from the above embodiments, the continuous preparation method of phosphorus oxybromide provided by the present invention improves the yield and purity of phosphorus oxybromide, and the solvent and mixed gas are recycled, which is environmentally friendly, reduces costs, and is suitable for industrial production.

[0077] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for continuous preparation of phosphorus oxybromide, characterized in that, The system used in the continuous preparation method of phosphorus oxybromide includes a reaction tower (3); a mixer (1) connected to the top side wall of the reaction tower (3); a gas mixing tank (2) connected to the bottom side wall of the reaction tower (3); and a top return gas mixing tank (2) of the reaction tower (3). A falling film evaporator (7) connected to the bottom of the reaction tower (3); a first solvent condenser (8) connected to the top of the falling film evaporator (7); and a first solvent receiving tank (9) connected to the first solvent condenser (8). A scraped film evaporator (12) connected to the bottom of the falling film evaporator (7); a second solvent condenser (13) connected to the top of the scraped film evaporator (12); and a second solvent receiving tank (14) connected to the second solvent condenser (13). The continuous preparation method of phosphorus oxybromide includes the following steps: (1) Phosphorus tribromide and chloroform are introduced into a mixer (1) to mix and obtain a mixture. Nitrogen oxides and oxygen are introduced into a gas mixing tank (2) to mix and obtain a mixed gas. (2) The mixture is introduced into the top of the reaction tower (3), and the mixed gas is introduced into the bottom of the reaction tower (3). After the mixed gas reaches the top of the reaction tower (3), it is introduced into the bottom of the reaction tower (3) through the gas mixing tank (2) for recycling. After the mixture reaches the bottom of the reaction tower (3), it is introduced into the falling film evaporator (7) for evaporation to obtain gaseous chloroform and phosphorus oxybromide solution. (3) The gaseous trichloromethane is passed through the top of the falling film evaporator (7) and condensed into liquid trichloromethane by the first solvent condenser (8). The liquid trichloromethane is then passed into the first solvent receiving tank (9). (4) The phosphorus oxybromide solution is passed into a scraped film evaporator (12) to evaporate and obtain gaseous residual chloroform and phosphorus oxybromide. The gaseous residual chloroform is passed into a second solvent condenser (13) to condense and obtain liquid residual chloroform. Then the liquid residual chloroform is passed into a second solvent receiving tank (14).

2. The method for continuous preparation of phosphorus oxybromide according to claim 1, characterized in that, The reaction tower (3) has 5 to 20 tower sections, with a tower section height of 0.6 to 1.2 m and a tower section overflow weir height of 0.4 to 0.8 m.

3. The method for continuous preparation of phosphorus oxybromide according to claim 1 or 2, characterized in that, The bottom of the reaction tower (3) is provided with a gas distributor (301) and the top of the tower is provided with a liquid distributor (302); the gas mixing tank (2) is connected to the reaction tower (3) through the gas distributor (301); the tower section of the reaction tower (3) is provided with a cooling coil (303).

4. The method for continuous preparation of phosphorus oxybromide according to claim 1, characterized in that, The mass ratio of chloroform to phosphorus tribromide is 1.2~2.5:

1.

5. The method for continuous preparation of phosphorus oxybromide according to claim 1 or 4, characterized in that, The molar flow ratio of nitrogen oxides to oxygen is 1~3:1; The nitrogen oxides include one or more of nitric oxide, nitrogen dioxide, and dinitrogen tetroxide.

6. The method for continuous preparation of phosphorus oxybromide according to claim 1, characterized in that, The gas velocity in the empty tower of the reaction tower (3) is 0.2~1.5 m / s; the flow rate of the mixed liquid is 1500~10000 kg / h; and the flow rate of the mixed gas is 800~8000 Nm³. 3 / h.

7. The method for continuous preparation of phosphorus oxybromide according to claim 1 or 6, characterized in that, The temperature of the section of the reaction tower (3) is 15~25℃, and the total reaction time in the tower is 3~10h.

8. The method for continuous preparation of phosphorus oxybromide according to claim 1, characterized in that, The pressure of the falling film evaporator (7) is 80~100kPa and the temperature is 50~80℃.

9. The method for continuous preparation of phosphorus oxybromide according to claim 1 or 8, characterized in that, The bottom temperature of the scraped film evaporator (12) is 120~135℃, the pressure is 1~5kPa, and the rotation speed is 100~150rpm.

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