Preparation method of chemical intermediate phosphorus oxybromide

Abstract

The invention discloses a chemical intermediate phosphorus oxybromide preparation method, which comprises: S1, mixing phosphorus tribromide and [BMIM] Br, and stirring at a temperature of 30-50 DEG C to obtain a mixture I; s2, adding red phosphorus into the mixture 1, and pre-dispersing in a supercritical CO2 medium to obtain a mixture II; s3, stage I: introducing bromine into the mixture II at the temperature of-5 to 0 DEG C, synchronously dropwise adding tetrabutylammonium bromide and crown ether, and maintaining the pH value of the system to be 1.5-2.0; stage II: raising the temperature to 33-37 DEG C; and stage III: raising the temperature to 40-60 DEG C to obtain a crude product of phosphorus oxybromide. According to the invention, the following breakthrough progress is realized through innovative process design: a high-efficiency atom economy synthesis path is combined with a supercritical medium dispersion technology through an ionic liquid concerted catalysis system, so that the bromine reaction activity and the mass transfer efficiency are remarkably improved; the problems of excessive addition of raw materials and large generation amount of byproducts in the traditional process are fundamentally solved, and efficient utilization of bromine resources is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemicals, and in particular to a method for preparing phosphorus oxybromide, a chemical intermediate. Background Art

[0002] Traditional processes often utilize a halogen exchange reaction between phosphorus tribromide and phosphorus oxychloride. This requires a 50-60% excess of phosphorus tribromide to drive the reaction equilibrium, making it difficult to recover unreacted raw materials and resulting in a bromine utilization rate of less than 68%. This process also produces a mixed acidic gas of HCl and HBr. Due to their similar boiling points, these gases are difficult to separate effectively, requiring the use of multi-stage absorption towers, increasing waste gas treatment costs by over 25%.

[0003] Existing technologies rely on vacuum distillation for purification, but due to the thermal sensitivity of phosphorus oxybromide, it is easy to decompose above 120°C to produce by-products such as PBr5, and the purity of the final product can only reach 95-97%. In addition, the distillation residue contains high concentrations of organic halogen pollutants, and the treatment cost accounts for 18-22% of the total production cost. The traditional synthesis route requires a constant temperature of 60-80°C for 8-12 hours to complete the halogen replacement, and the comprehensive energy consumption per unit product is high. In order to increase the reaction rate, Lewis acid catalysts are generally added to the existing process, but such catalysts form stable coordination compounds with the reaction system, which are difficult to recover by conventional filtration. They are eventually discharged in the form of waste residue containing heavy metals, posing a risk of soil acidification.

[0004] Therefore, developing a synthesis process for phosphorus oxybromide that combines high atomic utilization, low energy consumption, easy purification, and environmental friendliness has become a technical challenge that needs to be urgently addressed in this field. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing phosphorus oxybromide, a chemical intermediate, which solves the problems of low atom utilization, high energy consumption, difficult purification and environmental unfriendliness in existing methods.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions: A method for preparing phosphorus oxybromide, a chemical intermediate, comprises the following steps: S1. Mixing phosphorus tribromide and [BMIM]Br, and stirring at 30-50° C. to obtain a mixture I; S2, adding red phosphorus to the mixture 1, which is pre-dispersed in a supercritical CO2 medium, to obtain a mixture II; S3. Stage I: At a temperature of -5-0°C, bromine is introduced into the mixture II, and tetrabutylammonium bromide and crown ether are simultaneously added dropwise to maintain the pH value of the system between 1.5-2.0; Stage II: heating to 33-37°C; Stage III: heating to 40-60°C to obtain a crude product of phosphorus oxybromide.

[0007] In the present invention, phosphorus tribromide and ionic liquid [BMIM]Br are stirred and activated to form an ion coordination intermediate.

[0008] In the present invention, red phosphorus acts as a reducing agent and reacts with bromine to generate a phosphorus tribromide intermediate, which is then oxidized by bromine through insertion of an oxygen atom under the catalysis of tetrabutylammonium bromide, [BMIM]Br and crown ether.

[0009] In the present invention, excessive bromine leads to the formation of phosphorus pentabromide as a byproduct, and the formation of phosphorus pentabromide is suppressed by gradient temperature control (-5-0°C → 40-60°C) and slightly negative pressure conditions.

[0010] The ionic liquid [BMIM]Br and Br in the present invention - The coordination of Br - The nucleophilicity of the crown ether and the phase transfer catalysis of Br2 enhance the mass transfer efficiency of Br2. The ionic liquid [BMIM]Br, tetrabutylammonium bromide (TBAB), and the crown ether form a three-way catalytic system, and the catalyst maintains high activity during recycling.

[0011] The main reaction formula of the present invention is: .

[0012] According to a preferred embodiment of the present invention, the chemical formula of phosphorus oxybromide is PBr3; According to a preferred embodiment of the present invention, the phosphorus oxybromide is miscible in ether, acetone, chloroform, carbon tetrachloride, and carbon disulfide, and is mainly used as an organic synthesis intermediate.

[0013] According to a preferred embodiment of the present invention, the phosphorus oxybromide is purchased from Kaifeng Pufeng Chemical Co., Ltd.

[0014] According to a preferred embodiment of the present invention, the [BMIM]Br is 1-butyl-3-methylimidazolium bromide, also known as 1-butyl-3-methylimidazolium bromide; 1-butyl-3-methylimidazolium bromide.

[0015] According to a preferred embodiment of the present invention, the structural formula of [BMIM]Br is as follows: .

[0016] According to a preferred embodiment of the present invention, the [BMIM]Br is purchased from Hubei Xinhongli Chemical Co., Ltd.

[0017] According to a preferred embodiment of the present invention, the red phosphorus, also known as red phosphorus, is a lustrous, non-toxic, purple-red amorphous powder. It begins to melt when heated to 590°C under high pressure. Without pressure, it sublimes instead of melting, vaporizing and then condensing to produce white phosphorus. Red phosphorus forms a highly polymerized structure of chains or rings with single bonds of P4 tetrahedrons, exhibiting high stability. It is insoluble in water and carbon disulfide, slightly soluble in anhydrous ethanol, and soluble in alkaline solutions. It reacts with nitric acid to form phosphoric acid, which is then heated in chlorine to form chloride. Yellow phosphorus is gradually converted to red phosphorus by heating to 250°C for several days in a vacuum at normal pressure.

[0018] According to a preferred embodiment of the present invention, the red phosphorus is purchased from Guangdong Xiaoda Chemical Co., Ltd.

[0019] According to a preferred embodiment of the present invention, in step S1, the mass ratio of phosphorus tribromide to [BMIM]Br is 100:3.

[0020] According to a preferred embodiment of the present invention, the stirring time in step S1 is 20-40 minutes.

[0021] According to a preferred embodiment of the present invention, in step S2, the mass of the red phosphorus is 4-6% of that of the phosphorus tribromide.

[0022] According to a preferred embodiment of the present invention, the supercritical CO2 medium refers to carbon dioxide whose properties change when the temperature is higher than the critical temperature Tc=31.26°C and the pressure is higher than the critical pressure Pc=72.9atm, and its density is close to that of a liquid, and it serves as a solvent for the reaction.

[0023] According to a preferred embodiment of the present invention, in step S2, the pressure of the supercritical CO2 medium is 7.8 MPa and the temperature is 32°C.

[0024] According to a preferred embodiment of the present invention, the supercritical CO2 medium is purchased from Nantong Huaan Supercritical Extraction Co., Ltd.

[0025] According to a preferred embodiment of the present invention, the bromine is a non-metallic element that is liquid at room temperature and has a chemical formula of Br2.

[0026] According to a preferred embodiment of the present invention, the bromine is purchased from Hubei Taihong New Material Technology Co., Ltd.

[0027] According to a preferred embodiment of the present invention, in step S3, the flow rate of the bromine is 0.4-0.6 L / min.

[0028] According to a preferred embodiment of the present invention, in step S3, the molar ratio of tetrabutylammonium bromide to the crown ether is 1:0.3, and the reaction time after the dropwise addition of tetrabutylammonium bromide and crown ether in stage I is 0-1 h.

[0029] According to a preferred embodiment of the present invention, the tetrabutylammonium bromide, also known as tetrabutylammonium bromide, is an organic salt with a molecular formula of C 16 H 36 BrN, in its pure form, is white crystals or powder, is deliquescent, has a distinctive odor, and is stable at room temperature and pressure. It is soluble in water, alcohol, and acetone, and slightly soluble in benzene.

[0030] According to a preferred embodiment of the present invention, the tetrabutylammonium bromide is purchased from Langfang Qianyao Technology Co., Ltd.

[0031] According to a preferred embodiment of the present invention, the crown ether is 15-crown-5, which can be used as a catalyst in organic reactions.

[0032] According to a preferred embodiment of the present invention, the molecular formula of the crown ether 15-crown-5 is C 10 H 20 O5.

[0033] According to a preferred embodiment of the present invention, the crown ether is purchased from Shuaile Chemical Technology Co., Ltd.

[0034] According to a preferred embodiment of the present invention, in step S3, the reaction time of stage II is 1-3 hours and the pressure is -0.03 MPa; the reaction time of stage III is 3-4 hours.

[0035] According to a preferred embodiment of the present invention, step S3 further includes introducing nitrogen, and the waste gas is treated by a three-stage sodium hydroxide spray tower.

[0036] According to a preferred embodiment of the present invention, the nitrogen is purchased from Beijing Zhongcheng Aerospace Technology Co., Ltd.

[0037] According to a preferred embodiment of the present invention, the sodium hydroxide is purchased from Hebei Senqiao Chemical Co., Ltd.

[0038] According to a preferred embodiment of the present invention, the three-stage sodium hydroxide spray tower is purchased from Henan Tuochuan Equipment Manufacturing Co., Ltd.

[0039] According to a preferred embodiment of the present invention, the present invention also includes purifying the crude product of phosphorus oxybromide, and the step of purifying the crude product of phosphorus oxybromide includes: heating the crude product to 75°C at 1-3°C / min for complete melting, keeping warm for 10-30 minutes, and then cooling in three stages, stage I: from 75°C to 60°C, stage II: from 60°C to 45°C, and stage III: from 45°C to 30°C; then using a mixed solvent of acetone and n-hexane with a volume ratio of 1:3 for ultrasonic coupling cleaning, and finally drying at 40°C under nitrogen protection.

[0040] According to a preferred embodiment of the present invention, the acetone is purchased from Yueyang Xingwang Chemical Co., Ltd.

[0041] According to a preferred embodiment of the present invention, the n-hexane is purchased from Sinorene Energy Co., Ltd.

[0042] In the present invention, dynamic nitrogen disturbance is introduced into the melt crystallization stage, and the crystal particle size D50 is controlled at 15-20 μm.

[0043] According to a preferred embodiment of the present invention, the ultrasonic coupling cleaning refers to using a coupling agent as a medium during the ultrasonic cleaning process to reduce the energy loss of ultrasonic waves during propagation and enhance the ability of the cleaning liquid to remove dirt.

[0044] The beneficial effects of the present invention are: This invention addresses the core challenges of traditional phosphorus oxybromide synthesis processes, including low raw material utilization, insufficient product purity, high energy consumption, and severe environmental pollution. Through innovative process design, it achieves the following breakthroughs: A highly efficient, atom-economical synthesis pathway combines an ionic liquid synergistic catalytic system with supercritical medium dispersion technology to significantly enhance bromine reaction activity and mass transfer efficiency, fundamentally resolving the challenges of excessive raw material addition and high byproduct production in traditional processes, thereby achieving efficient utilization of bromine resources. An innovative gradient temperature control strategy, combined with melt crystallization-solvent coupled purification technology, effectively inhibits heat-sensitive side reactions and precisely removes trace impurities, breaking through the purity bottleneck of traditional distillation methods and meeting the stringent product consistency requirements of high-end electronic chemicals. Enhanced reaction-separation process design (such as micro-negative pressure degassing and supercritical medium recycling) significantly reduces system energy and solvent consumption, while enabling resource recovery of halogen-containing waste gas and significantly improving the process's environmental friendliness. A synergistic mechanism between dynamic pH control and catalyst interaction addresses the uncontrollable reaction process and large batch variability inherent in traditional processes, providing reliable technical support for continuous production. The present invention successfully overcomes the multiple contradictions among efficiency, purity, environmental protection and cost in traditional processes, and provides an innovative solution for the large-scale production of high-performance phosphorus oxybromide. DETAILED DESCRIPTION

[0045] The following specific implementation methods are only used to further illustrate the present application and should not be understood as limiting the scope of protection of the present application. Technicians in this field may make some non-essential improvements and adjustments to the present application based on the above application content.

[0046] Example 1 A method for preparing phosphorus oxybromide, a chemical intermediate, comprises the following steps: Step S1: 100 kg of phosphorus tribromide (technical grade, purity ≥99%) and 3 kg of ionic liquid [BMIM]Br were added to a corrosion-resistant reactor equipped with a double-layer stirring paddle. The temperature was raised to 40°C and stirred at 300 rpm for 30 minutes to form a homogeneous transparent liquid. Step S2: Add 5 kg of red phosphorus to the mixture I, transfer it to a supercritical CO2 reaction system, adjust the pressure to 7.8 MPa and the temperature to 32°C, and disperse it with 50 Hz ultrasonic assistance for 20 min; Step S3: Staged bromination reaction Stage I: Cool to -2°C and introduce bromine at a flow rate of 0.5 L / min. Simultaneously add tetrabutylammonium bromide (1 mol) and crown ether (0.3 mol) dropwise, maintain pH at 1.8, and react for 0.5 h. Stage II: The temperature was raised to 35°C, the pressure was maintained at a slight negative pressure of -0.03 MPa, and the reaction was continued for 2 hours. Nitrogen was introduced for purging, and the HBr waste gas was recovered through a three-stage NaOH spray tower (with a concentration gradient of 5%, 10%, and 15%). Stage III: Heat to 50°C, react for 3.5 hours, and cool to obtain crude phosphorus oxybromide. Step S4: The crude product was heated to 75°C at a rate of 2°C / min to melt and held at that temperature for 20 min. The temperature was then cooled in three stages (75°C → 60°C → 45°C → 30°C, with a cooling rate of 1°C / min in each stage). Impurities were removed by ultrasonic cleaning (40 kHz, 30 min) using a mixed solvent of acetone:n-hexane (volume ratio) of 1:3. The product was then dried under nitrogen at 40°C to obtain a white crystalline powder.

[0047] Example 2 The specific implementation method is the same as that of Example 1, except that, in step S2, the amount of red phosphorus added is 4% of the phosphorus tribromide; Step S3: Bromine flow rate 0.4 L / min; Stage II reaction time 1 h, Stage III reaction time 4 h.

[0048] Example 3 The specific implementation method is the same as that of Example 1, except that: Step S2: supercritical CO2 pressure is 8 MPa, and the temperature is strictly controlled at 32°C; purification process: cooling rate is 1°C / min, and ultrasonic cleaning time is extended to 40 min.

[0049] Comparative Example 1 The specific implementation method is the same as that of Example 1, except that: Step S1: only phosphorus tribromide is used without adding [BMIM]Br; Step S2: red phosphorus is directly added to the reaction system at normal pressure; Step S3: the bromine flow rate is 1.0 L / min, and there is no gradient temperature control.

[0050] Comparative Example 2 The specific implementation method is the same as that of Example 1, except that, in step S1, the mass ratio of phosphorus tribromide to [BMIM]Br is 100:5; and in step S3, the temperature of stage I is 5°C.

[0051] Comparative Example 3 The specific implementation method is the same as that of Example 1, except that, Step S2: supercritical CO2 pressure 5.0 MPa, temperature 40°C.

[0052] 3. Performance Testing 1. Product purity test (HPLC method) 1.1 Test Purpose: To determine the content of the main component and impurity residues of phosphorus oxybromide.

[0053] 1.2 Step: Dissolve 1 g of the dried product in 10 mL of acetonitrile, sonicate, and filter through a 0.22 μm filter. Chromatographic conditions: Column: C18 reversed-phase column (250 mm × 4.6 mm, 5 μm); Mobile phase: acetonitrile:water (85:15, containing 0.1% trifluoroacetic acid); Flow rate: 1.0 mL / min; Detection wavelength: 210 nm; Column temperature: 30°C; Injection volume: 10 μL.

[0054] 1.3 Quantitative analysis: The main peak area ratio was calculated using the external standard method, and the purity was calculated after deducting the solvent peak.

[0055] 2. Red phosphorus utilization test (gravimetric method) 2.1 Test Purpose: To determine the amount of unreacted red phosphorus residue.

[0056] Step 2.2: Take 10 g of the reaction mixture, add 50 mL of 6 M hydrochloric acid and boil for 30 minutes to dissolve the unreacted red phosphorus; Filtration and drying: The filtrated residue (including unreacted red phosphorus) was dried at 105°C to constant weight.

[0057] 2.3 Calculation: Red phosphorus utilization rate = (1-mass of unreacted red phosphorus / initial mass of red phosphorus) × 100%.

[0058] ‌3. Bromine utilization test (ion chromatography)‌ 3.1 Test Purpose: To determine the recovery rate of bromine in waste gas and products.

[0059] 3.2 Step: Waste gas bromine recovery: Collect the tertiary NaOH spray liquid, adjust the pH to neutral, filter, and measure Br - Concentration (ion chromatograph: Dionex ICS-5000); Product bromine content: 0.5 g of product sample was taken and ashed, and then the total bromine content was determined by ion chromatography; 3.3 Calculation: Bromine utilization rate = (bromine content in product + bromine weight recovered from waste gas) / initial bromine input * 100%.

[0060] 4. Waste gas treatment efficiency test (acid-base titration method) 4.1 Test Purpose: To verify the HBr waste gas recovery rate.

[0061] 4.2 Step: Analysis of waste gas absorption liquid: Take the liquid at the outlet of the three-stage spray tower and titrate it with 0.1M NaOH standard solution to the endpoint (pH=7.0); 4.3 Calculation of HBr recovery rate: Recovery rate = (measured HBr mass / theoretical HBr production) * 100%.

[0062] 5. Solvent Residual Test (GC-MS Method) 5.1 Test Purpose: To detect residual solvents such as acetone and n-hexane.

[0063] 5.2 Step: Sample preparation: Dissolve 1 g of the dried product in 5 mL of methanol, extract by ultrasonication, and centrifuge; Instrument conditions: Chromatographic column: DB-5MS (30m×0.25mm, 0.25μm); Program temperature rise: 40℃ (2 min) → 10℃ / min → 250℃ (5 min); Ion source: EI, scan range: m / z 30-40078; 5.3 Limit of Quantitation: Residual solvent <50 ppm (external standard curve method).

[0064] (2) Results: Table 1: Test results of various embodiments and comparative examples

[0065] As can be seen in Table 1, the phosphorus oxybromide produced in Example 1 of the present invention has a product purity of 99.5%, which is excellent. Comparative Example 1, in contrast, uses only phosphorus tribromide without the addition of [BMIM]Br; Step S2: Red phosphorus is directly added to the reaction system at atmospheric pressure; Step S3: Bromine flow rate 1.0 L / min, no gradient temperature control. Product purity, red phosphorus utilization, bromine utilization, waste gas treatment efficiency, solvent residue, and red phosphorus utilization are all significantly reduced. Furthermore, Comparative Example 3, using supercritical CO2 at a pressure of 5.0 MPa and a temperature of 40°C, shows deterioration in various test data compared to Example 1, demonstrating the importance of supercritical CO2 for the preparation of phosphorus oxybromide, a factor not anticipated prior to the experiment.

[0066] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A method for preparing phosphorus oxybromide as a chemical intermediate, characterized in that: The method comprises the following steps: S1. Mixing phosphorus tribromide and [BMIM]Br, and stirring at 30-50° C. to obtain a mixture I; S2, adding red phosphorus to the mixture 1, which is pre-dispersed in a supercritical CO2 medium, to obtain a mixture II; S3. Stage I: At a temperature of -5-0°C, bromine is introduced into the mixture II, and tetrabutylammonium bromide and crown ether are simultaneously added dropwise to maintain the pH value of the system between 1.5-2.0; Stage II: heating to 33-37°C; Stage III: heating to 40-60°C to obtain a crude product of phosphorus oxybromide.

2. The method for preparing phosphorus oxybromide as a chemical intermediate according to claim 1, wherein: In step S1, the mass ratio of phosphorus tribromide to [BMIM]Br is 100:

3.

3. The method for preparing phosphorus oxybromide as a chemical intermediate according to claim 2, wherein: The stirring time in step S1 is 20-40 min.

4. The method for preparing phosphorus oxybromide as a chemical intermediate according to claim 3, wherein: In step S2, the mass of the red phosphorus is 4-6% of that of phosphorus tribromide.

5. The method for preparing phosphorus oxybromide as a chemical intermediate according to claim 4, characterized in that: In step S2, the supercritical CO2 medium has a pressure of 7.8 MPa and a temperature of 32°C.

6. The method for preparing phosphorus oxybromide as a chemical intermediate according to claim 5, wherein: In step S3, the bromine is introduced at a flow rate of 0.4-0.6 L / min.

7. The method for preparing phosphorus oxybromide as a chemical intermediate according to claim 6, wherein: In step S3, the molar ratio of tetrabutylammonium bromide to the crown ether is 1:0.3, and the reaction time after the dropwise addition of tetrabutylammonium bromide and crown ether in stage I is 0-1 h.

8. The method for preparing phosphorus oxybromide as a chemical intermediate according to claim 7, wherein: In step S3, the reaction time of stage II is 1-3 hours and the pressure is -0.03 MPa; the reaction time of stage III is 3-4 hours.

9. The method for preparing phosphorus oxybromide as a chemical intermediate according to claim 8, wherein: Step S3 also includes introducing nitrogen, and the waste gas is treated by a three-stage sodium hydroxide spray tower.

10. The method for preparing phosphorus oxybromide as a chemical intermediate according to any one of claims 1 to 9, wherein: The method further includes purifying the crude phosphorus oxybromide product, wherein the steps of purifying the crude phosphorus oxybromide product include: heating the crude product to 75°C at a rate of 1-3°C / min to completely melt the crude product, keeping the temperature for 10-30 minutes, and then cooling the temperature in three stages: stage I: from 75°C to 60°C, stage II: from 60°C to 45°C, and stage III: from 45°C to 30°C; then using ultrasonic coupling cleaning with a mixed solvent of acetone and n-hexane in a volume ratio of 1:3, and finally drying at 40°C under nitrogen protection.

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