System and method for continuously preparing phosphorus oxybromide

Abstract

The invention belongs to the technical field of synthesis of chemical intermediates, and particularly relates to a system and a method for continuously preparing phosphorus oxybromide. According to the system provided by the invention, through continuous preparation design, continuous production of phosphorus oxybromide can be realized, the preparation efficiency is improved, and the problem that the product yield and purity are reduced due to long-time high-temperature separation is avoided. Phosphorus tribromide is used as a raw material, trichloromethane is used as a solvent, the phosphorus tribromide and the trichloromethane are mixed to obtain a mixed solution, the mixed solution enters the reaction tower and is in contact with a mixed gas of nitrogen dioxide and oxygen entering the reaction tower, phosphorus tribromide is oxidized into phosphorus oxybromide, nitrogen dioxide and residual oxygen are recycled from the top of the reaction tower, waste gas emission is reduced, and the production cost is reduced. The mixed solution of trichloromethane and phosphorus oxybromide firstly passes through the falling film evaporator to evaporate most of the solvent, and then passes through the scraper film evaporator to evaporate the residual solvent, so that the solvent is recycled, the energy consumption is reduced, the time of the phosphorus oxybromide staying in the evaporator is reduced, and the yield and purity of the phosphorus oxybromide are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical intermediate synthesis, and in particular relates to a system and method for continuously preparing phosphorus oxybromide. Background Art

[0002] Phosphorus oxybromide, also known as phosphorus oxybromide tribromide, is an important chemical intermediate. The main production process is to add chloroform (as a reaction solvent) to an oxidation kettle, drop phosphorus tribromide into the oxidation kettle, and start to pass a mixed gas of oxygen and nitrogen dioxide into the oxidation kettle at the same time, react at a certain temperature to obtain phosphorus oxybromide.

[0003] Another common production process of phosphorus oxybromide is to add P2O5 and PBr3 into a drying tube filled with NaOH and CaCl, and then react in one step under the condition of adding bromine to obtain phosphorus oxybromide.

[0004] However, the existing processes for phosphorus oxybromide are all intermittent production 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 object of the present invention is to provide a system and method for continuously preparing phosphorus oxybromide. The method provided by the present invention improves the yield and purity of phosphorus oxybromide.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a system for continuously preparing phosphorus oxybromide, comprising a reaction tower; a mixer connected to the top side wall of the reaction tower; a gas mixing tank connected to the bottom side wall of the reaction tower; a gas mixing tank for returning to the top 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 number of tower sections of the reaction tower is 5 to 20, the height of the tower sections is 0.6 to 1.2 m, and the height of the tower section overflow weir is 0.4 to 0.8 m.

[0009] Preferably, a gas distributor is provided at the bottom of the tower section of the reaction tower, 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 continuously preparing phosphorus oxybromide using the system described in the above scheme, comprising the following steps:

[0011] (1) introducing phosphorus tribromide and chloroform into a mixer to obtain a mixed liquid, and introducing nitrogen oxides and oxygen into a gas mixing tank to obtain a mixed gas;

[0012] (2) passing the mixed liquid into the top of a reaction tower, passing the mixed gas into the bottom of the reaction tower, and after the mixed gas reaches the top of the reaction tower, passing it into the bottom of the reaction tower through a gas mixing tank for recycling, and after the mixed liquid reaches the bottom of the reaction tower, passing it into a falling film evaporator for evaporation to obtain gaseous chloroform and phosphorus oxybromide solution;

[0013] (3) passing the gaseous chloroform through the top of the falling film evaporator into a first solvent condenser to condense into liquid chloroform, and passing the liquid chloroform into a first solvent receiving tank;

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

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

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

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

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

[0019] Preferably, the falling film evaporator has a pressure of 80-100 kPa and a temperature of 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] The present invention provides a system for continuously preparing phosphorus oxybromide. The system provided by the present invention is designed for continuous preparation, can realize continuous production of phosphorus oxybromide, improves preparation efficiency, and avoids the problem of decreased product yield and purity caused by long-term high-temperature separation.

[0022] The present invention also provides a method for continuously preparing phosphorus oxybromide using the system described in the above scheme. In the present invention, phosphorus tribromide is used as a raw material and chloroform is used as a solvent. The two are mixed to obtain a mixed liquid, which enters a reaction tower and contacts with a mixed gas of nitrogen dioxide and oxygen (oxidant) entering the reaction tower. The phosphorus tribromide is oxidized to phosphorus oxybromide. The nitrogen dioxide and the remaining oxygen are recycled from the top of the reaction tower, thereby reducing waste gas emissions. The mixed liquid of chloroform and phosphorus oxybromide is first evaporated by a falling film evaporator for most of the solvent, and then evaporated by a scraped film evaporator for the residual solvent. The solvent is recycled and reused, which reduces energy consumption and reduces the time that phosphorus oxybromide stays in the evaporator, thereby improving the yield and purity of phosphorus oxybromide, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is a schematic diagram of the structure of the system for continuously preparing phosphorus oxybromide according to the present invention;

[0025] Figure numerals: 1 is a mixer, 101 is a first feed pump, 102 is a second feed pump, 103 is a first liquid storage tank, 104 is a second liquid storage tank, 2 is a gas mixing tank, 201 is a first flow meter, 202 is a first gas storage tank, 203 is a second flow meter, 204 is a 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 a first solvent condenser, 9 is a first solvent receiving tank, 10 is a first solvent discharge pump, 11 is a crude product discharge pump, 12 is a scraped film evaporator, 13 is a second solvent condenser, 14 is a second solvent receiving tank, 15 is a second solvent discharge pump, 16 is a product discharge pump, 17 is a first solvent storage tank, 18 is a nitrogen pipeline, 19 is a product storage tank, and 20 is a second solvent storage tank. DETAILED DESCRIPTION

[0026] The present invention provides a system for continuously preparing phosphorus oxybromide, comprising 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; a gas mixing tank 2 recirculated from the top 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; a first solvent receiving tank 9 connected to the first solvent condenser 8;

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

[0029] The system for continuously preparing phosphorus oxybromide provided by the present invention comprises a reaction tower 3; the top of the reaction tower 3 is preferably connected to a 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 the present invention, the number of tower sections of the reaction tower 3 is preferably 5 to 20, specifically 5, 7, 9, 10, 12, 15, 18 or 20, the tower section height is preferably 0.6 to 1.2 m, specifically 0.6 m, 0.8 m, 1 m or 1.2 m, and the height of the tower section overflow weir 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 to the lower tower section through the overflow weir.

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

[0032] The system for continuously preparing phosphorus oxybromide provided by the present invention comprises a mixer 1 connected to the top side wall of the reaction tower 3; the mixer 1 is preferably connected to the first liquid storage tank 103 through a first feed pump 101; the mixer 1 is preferably connected to the second liquid storage tank 104 through a second feed pump 102. The present invention mixes phosphorus tribromide and chloroform through the mixer 1 to obtain a mixed liquid of phosphorus tribromide and chloroform.

[0033] The system for continuously preparing phosphorus oxybromide provided by the present invention comprises a gas mixing tank 2 connected to the bottom side wall of the reaction tower 3; the gas mixing tank 2 is preferably connected to the first gas storage tank 202 through a first flowmeter 201; the gas mixing tank 2 is preferably connected to the second gas storage tank 204 through a second flowmeter 203. The present invention mixes nitrogen dioxide and oxygen through the gas mixing tank 2 to obtain a mixed gas of nitrogen dioxide and oxygen.

[0034] The system for continuously preparing phosphorus oxybromide provided by the present invention comprises 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 system for continuously preparing phosphorus oxybromide provided by the present invention comprises a first solvent condenser 8 connected to the top of the falling film evaporator 7. The present invention condenses the gaseous solvent evaporated from the falling film evaporator 7 through the first solvent condenser 8 to obtain a liquid solvent.

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

[0037] The system for continuously preparing phosphorus oxybromide provided by the present invention comprises 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 through a product discharge pump 16; and a nitrogen pipeline 18 is preferably connected between the scraped film evaporator 12 and the product discharge pump 16. In the present invention, nitrogen is introduced through the nitrogen pipeline 18 to protect the product with an inert atmosphere.

[0038] The system for continuously preparing phosphorus oxybromide provided by the present invention comprises a second solvent condenser 13 connected to the top of the scraper film evaporator 12. The present invention condenses the gaseous solvent evaporated by the scraper film evaporator 12 through the second solvent condenser 13 to obtain a liquid solvent.

[0039] The system for continuously preparing phosphorus oxybromide provided by the present invention comprises a second solvent receiving tank 14; the second solvent receiving tank 14 is preferably connected to the second solvent storage tank 20 via a second solvent discharge pump 15. The structure of the system for continuously preparing phosphorus oxybromide provided by the present invention is as follows: Figure 1 shown.

[0040] The present invention also provides a method for continuously preparing phosphorus oxybromide using the system described in the above scheme, comprising the following steps:

[0041] (1) introducing phosphorus tribromide and chloroform into a mixer 1 to obtain a mixed liquid, and introducing nitrogen oxides and oxygen into a gas mixing tank 2 to obtain a mixed gas;

[0042] (2) passing the mixed liquid into the top of the reaction tower 3, passing the mixed gas into the bottom of the reaction tower 3, and after the mixed gas reaches the top of the reaction tower 3, passing it into the bottom of the reaction tower 3 through the gas mixing tank 2 for recycling, and after the mixed liquid reaches the bottom of the reaction tower 3, passing it into the falling film evaporator 7 for evaporation to obtain gaseous chloroform and phosphorus oxybromide solution;

[0043] (3) passing the gaseous chloroform through the top of the falling film evaporator 7 into the first solvent condenser 8 to condense into liquid chloroform, and passing the liquid chloroform into the first solvent receiving tank 9;

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

[0045] In the present invention, phosphorus tribromide and chloroform are introduced into a mixer 1 to mix to obtain a mixed liquid, and nitrogen oxides and oxygen are introduced into a gas mixing tank 2 to mix to obtain a mixed gas. In the present invention, the mass ratio of chloroform to phosphorus tribromide is preferably 1.2 to 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 the present invention, the molar flow ratio of the 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 nitrogen tetroxide.

[0047] After obtaining the mixed liquid and the mixed gas, the present invention passes the mixed liquid into the top of the reaction tower 3, passes the mixed gas into the bottom of the reaction tower 3, and after the mixed gas reaches the top of the reaction tower 3, passes into the bottom of the reaction tower 3 through the gas mixing tank 2 for recycling. After the mixed liquid reaches the bottom of the reaction tower 3, it passes into the falling film evaporator 7 for evaporation to obtain gaseous chloroform and phosphorus oxybromide solution.

[0048] In the present invention, the gas superficial velocity 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 inlet 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; the inlet flow rate of the mixed gas is preferably 800-8000 Nm 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 the present invention, the tower section 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 the present 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 by the falling film evaporator.

[0051] After obtaining gaseous chloroform, the present invention passes the gaseous chloroform through the top of the falling film evaporator 7 into the first solvent condenser 8 for condensation to obtain liquid chloroform, and passes the liquid chloroform into the first solvent receiving tank 9. The present invention realizes the recycling of chloroform through condensation 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 passed into a second solvent condenser 13 for condensation to obtain liquid residual chloroform, and then the liquid residual chloroform is passed into a second solvent receiving tank 14.

[0053] In the present invention, the bottom temperature of the scraper thin film evaporator 12 is preferably 120-135°C, specifically 120°C, 125°C, 128°C, 132°C or 135°C, the pressure is preferably 1-5kPa, specifically 1kPa, 2kPa, 3kPa, 4kPa or 5kPa, and the rotation speed is preferably 100-150rpm, specifically 100rpm, 110rpm, 120rpm, 130rpm, 140rpm or 150rpm. After the mixed solution passes through the scraper thin film evaporator 12, a small amount of chloroform remains for further separation.

[0054] In order to further illustrate the present invention, the scheme of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be understood as limiting the protection scope of the present invention.

[0055] Example 1

[0056] (1) Chloroform at a flow rate of 1500 kg / h and phosphorus tribromide at a flow rate of 1000 kg / h are respectively delivered to mixer 1 by pumps, and a mixed solution is obtained after mixing. The mixed solution enters reaction tower 3 from the top of reaction tower 3.

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

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

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

[0060] (5) The mixed liquid at the bottom of the reaction tower 3 is sent to the falling film evaporator 7 at a flow rate of 2560 kg / h, and 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 to the scraped film evaporator 12 at a flow rate of 1238 kg / h. The bottom temperature of the scraped film evaporator 12 is 130° C., the pressure is 3 kPa, and the rotation speed is 150 rpm to obtain phosphorus oxybromide. The purity of the phosphorus oxybromide is 96.3%, and the yield of the phosphorus oxybromide is 97.18%.

[0062] Example 2

[0063] (1) Chloroform at a flow rate of 1100 kg / h and phosphorus tribromide at a flow rate of 700 kg / h are respectively delivered to mixer 1 by pumps, and a mixed solution is obtained after mixing. The mixed solution enters reaction tower 3 from the top of reaction tower 3.

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

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

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

[0067] (5) The mixed liquid at the bottom of the reaction tower 3 is sent to the falling film evaporator 7 at a flow rate of 1798 kg / h, and 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 to the scraped film evaporator 12 at a flow rate of 850 kg / h. The bottom temperature of the scraped film evaporator 12 is 131° C., the pressure is 3 kPa, and the rotation speed is 150 rpm to obtain phosphorus oxybromide. The purity of the phosphorus oxybromide is 98.5%, and the yield of the phosphorus oxybromide is 98.1%.

[0069] Example 3

[0070] (1) Chloroform at a flow rate of 1800 kg / h and phosphorus tribromide at a flow rate of 1200 kg / h are respectively delivered to mixer 1 by pumps to obtain a mixed solution after mixing. The mixed solution enters reaction tower 3 from the top of reaction tower 3.

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

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

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

[0074] (5) The mixed liquid at the bottom of the reaction tower 3 is sent to the falling film evaporator 7 at a flow rate of 2690 kg / h, and 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 to the scraped film evaporator 12 at a flow rate of 1305 kg / h. The bottom temperature of the scraped film evaporator 12 is 133° C., the pressure is 3 kPa, and the rotation speed is 150 rpm to obtain phosphorus oxybromide. The purity of the phosphorus oxybromide is 98.3%, and the yield of the phosphorus oxybromide is 96.76%.

[0076] It can be seen from the above examples that the method for continuously preparing 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 embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A system for continuously preparing phosphorus oxybromide, comprising 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 gas mixing tank (2) recirculated at the top 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).

2. The system according to claim 1, characterized in that The number of tower sections of the reaction tower (3) is 5 to 20, the height of the tower sections is 0.6 to 1.2 m, and the height of the tower section overflow weir is 0.4 to 0.8 m.

3. The system according to claim 1 or 2, characterized in that: A gas distributor (301) is provided at the bottom of the tower section of the reaction tower (3), and a liquid distributor (302) is provided at the top of the tower section; the gas mixing tank (2) is connected to the reaction tower (3) via the gas distributor (301); and a cooling coil (303) is provided in the tower section of the reaction tower (3).

4. A method for continuously preparing phosphorus oxybromide using the system according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) introducing phosphorus tribromide and chloroform into a mixer (1) to mix to obtain a mixed liquid, and introducing nitrogen oxides and oxygen into a gas mixing tank (2) to mix to obtain a mixed gas; (2) passing the mixed liquid into the top of a reaction tower (3), passing the mixed gas into the bottom of the reaction tower (3), after the mixed gas reaches the top of the reaction tower (3), passing it into the bottom of the reaction tower (3) through a gas mixing tank (2) for recycling, and after the mixed liquid reaches the bottom of the reaction tower (3), passing it into a falling film evaporator (7) for evaporation to obtain gaseous chloroform and phosphorus oxybromide solution; (3) passing the gaseous chloroform through the top of the falling film evaporator (7) into a first solvent condenser (8) to condense into liquid chloroform, and passing the liquid chloroform into a first solvent receiving tank (9); (4) passing the phosphorus oxybromide solution into a scraped film evaporator (12) to evaporate to obtain gaseous residual chloroform and phosphorus oxybromide, passing the gaseous residual chloroform into a second solvent condenser (13) to condense to obtain liquid residual chloroform, and then passing the liquid residual chloroform into a second solvent receiving tank (14).

5. The method according to claim 4, characterized in that The mass ratio of the chloroform to phosphorus tribromide is 1.2-2.5:

1.

6. The method according to claim 4 or 5, characterized in that: The molar flow ratio of the nitrogen oxides to oxygen is 1 to 3:1; The nitrogen oxides include one or more of nitrogen monoxide, nitrogen dioxide and nitrogen tetroxide.

7. The method according to claim 4, characterized in that The gas velocity of the reaction tower (3) is 0.2-1.5 m / s; the flow rate of the mixed liquid is 1500-10000 kg / h; the flow rate of the mixed gas is 800-8000 Nm 3 / h.

8. The method according to claim 4 or 7, characterized in that: The tower section temperature of the reaction tower (3) is 15 to 25° C., and the total reaction time in the tower is 3 to 10 hours.

9. The method according to claim 4, characterized in that The falling film evaporator (7) has a pressure of 80-100 kPa and a temperature of 50-80°C.

10. The method according to claim 4 or 9, characterized in that: The bottom temperature of the scraped film evaporator (12) is 120-135°C, the pressure is 1-5 kPa, and the rotation speed is 100-150 rpm.

Images