Method for measuring salifying conversion rate in diazotization reaction

Abstract

The invention discloses a method for determining the salifying conversion rate in diazotization reaction. The determination method comprises the following steps: (1) taking a diazotization salt-forming reaction solution, adding toluene, fully and uniformly mixing, and standing for liquid separation; taking supernatant liquid and neutralizing the supernatant liquid to be neutral to obtain a sample to be detected; (2) performing fitting calculation according to the standard working solution to obtain a relation constant K among the aniline standard working solution, the toluene standard working solution and the peak area; and performing gas chromatographic analysis on the to-be-detected sample, calculating the percentage content of aniline in the to-be-detected sample in combination with the relation constant K, and further calculating the salifying conversion rate of the to-be-detected sample. The method can rapidly determine the conversion rate of the salt forming reaction, and has the advantages of convenient steps and high accuracy.

Description

Technical Field

[0001] The invention belongs to the field of fluorine chemical product analysis and detection, and in particular relates to a method for determining the salt conversion rate in a diazotization reaction. Background Art

[0002] As an important basic raw material of aromatic fluoride, fluorobenzene can not only be used in the synthesis of medicines, pesticides and dyes, but also can be further synthesized into a variety of fluorobenzene derivatives through chemical reactions such as nitration, chlorination, bromination, acylation and reduction. These derivatives are also suitable for the above-mentioned fields. In recent years, fluorobenzene has also been developed for the identification of resin polymers and thermoplastic engineering plastics. Its uses are becoming more and more extensive, and the market demand is also increasing.

[0003] At present, anhydrous hydrogen fluoride, aniline and sodium nitrite are mainly used as raw materials at home and abroad, and diazotization technology is used to prepare fluorobenzene. In this process, it is necessary to determine the conversion rate of the intermediate process to guide production and research and development. However, since the existing process involves anhydrous hydrogen fluoride, if it is directly introduced into a gas chromatograph for analysis, it will corrode the instrument pipeline, thereby affecting the yield of fluorobenzene in the whole process. In addition, for the conversion rate determination of the salt-forming step in the diazotization reaction, a unified national standard or industry standard has not yet been established. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a method for determining the salt conversion rate in a diazotization reaction to solve the inconvenience and adverse effects of the existing testing methods.

[0005] The purpose of the present invention is achieved through the following technical solutions: A method for determining the salt conversion rate in a diazotization reaction comprises the following steps: (1) Add aniline to anhydrous hydrofluoric acid at -10~5°C, and then perform salt formation reaction at 0~10°C to obtain a reaction solution; add toluene to the reaction solution and mix thoroughly, then stand the solution for separation, take the upper layer and neutralize it to neutrality, and then take the neutralized upper layer as the sample to be tested; (2) Dissolving the aniline standard in different amounts of toluene to obtain a series of standard working solutions; performing gas chromatography analysis on the series of standard working solutions, and obtaining the relationship constant K between aniline, toluene and peak area by fitting calculation; (3) The sample to be tested is subjected to gas chromatography analysis, and the percentage of aniline in the sample to be tested is calculated in combination with the relationship constant K, and then the salt conversion rate of the sample to be tested is calculated.

[0006] Preferably, in step (1), aniline is added to anhydrous hydrofluoric acid at -5 to 5°C.

[0007] Preferably, in step (1), the temperature of the salt-forming reaction is 6-9°C.

[0008] Preferably, in step (1), the method of neutralizing to neutrality is: neutralizing to neutrality by adding sodium hydroxide solution.

[0009] Preferably, in step (2), the concentration of aniline in a series of standard working solutions is 25-60 wt %.

[0010] Preferably, in step (2) and step (3), the conditions for gas chromatography analysis are: the chromatographic column is a capillary chromatographic column (30m×0.25mm×0.5μm); nitrogen is used as the carrier gas, and the flow rate is 20~50L / min; the hydrogen flow rate is 20~50L / min, and the air flow rate is 200~400L / min; programmed temperature is adopted, the initial temperature is 50~100℃, and it is maintained for 2~5min; the temperature is increased to 200~240℃ at a heating rate of 10~30℃ / min, and it is maintained for 2~8min; the injection port temperature is 260℃, the split ratio is 40~60:1, and the injection volume is 0.4μL; the detector temperature is 150~230℃.

[0011] Preferably, the detector is a hydrogen flame ionization detector.

[0012] Preferably, the capillary chromatographic column uses a medium polarity stationary phase, and more preferably, the composition of the medium polarity stationary phase is 7% cyanopropyl-7% phenyl-86% methylpolysiloxane.

[0013] Preferably, in step (2), the calculation formula of the relationship constant k between aniline, toluene and peak area is: k=(A 苯胺 ×m 甲苯 ) / (A 甲苯 ×m 苯胺 ), In the formula, m 甲苯 is the mass of toluene standard in the standard working solution; m 苯胺 A is the mass of aniline standard in the standard working solution; 甲苯 is the peak area of ​​toluene standard in the gas chromatogram of the standard working solution, A 苯胺 is the peak area of ​​aniline standard in the gas chromatogram of the standard working solution.

[0014] Preferably, in step (3), the calculation formula for the percentage content (ω%) of aniline in the sample to be tested is as follows: ω%=(m' 甲苯 ×A' 苯胺 ) / (m' 样品 ×A' 甲苯 ×k)×100%, Wherein, ω% is the percentage of aniline in the sample to be tested; k is the relationship constant between aniline, toluene and peak area; m' 甲苯 is the mass of toluene in the sample to be tested; m' 样品 is the mass of the reaction solution in the sample to be tested; A' 苯胺 A' is the peak area of ​​aniline in the gas chromatogram of the sample to be tested, 甲苯 is the peak area of ​​toluene in the gas chromatogram of the sample to be tested.

[0015] Preferably, the calculation formula for the salt conversion rate in step (3) is as follows: c%=(m' 苯胺- ω×m' 反应液 ) / m' 苯胺 ×100%, Wherein, c% is the salt conversion rate; ω is the content of aniline in the sample to be tested; m' 苯胺 is the amount of aniline added in the salt-forming reaction of the sample to be tested; m' 反应液 It is the total mass of aniline and anhydrous hydrofluoric acid fed into the salt-forming reaction of the sample to be tested.

[0016] Compared with the prior art, the beneficial effects of the present invention include: The present invention provides a method for determining the conversion rate of a diazotization salt-forming reaction. The method determines the substance content by gas chromatography, and calculates the conversion rate of aniline according to the measured content. The method can quickly determine the conversion rate of the salt-forming reaction, and has the characteristics of simple steps and high accuracy. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] Example 1 A method for determining the salt conversion rate in a diazotization reaction, the steps are as follows: (1) Preparation of aniline and toluene mixed standard working solution: Accurately weigh 1.0 g of aniline standard to an accuracy of 0.0001 g; dissolve in 1.0, 1.5, 2.0, 2.5, and 3.0 g of toluene standard, respectively, to an accuracy of 0.0001 g; shake well to obtain a mixed standard working solution; (2) Salt-forming reaction and sample treatment: Weigh 40.35g of anhydrous hydrofluoric acid, slowly add 41.65g of aniline at -10°C, keep warm at 6-9°C for reaction after the addition is completed, and take samples during the reaction; weigh the reaction liquid after the salt-forming reaction for 0.5h and 1h, which are 1.5035g and 1.4879g respectively, and then dissolve them in 1.0638g and 1.1196g of toluene respectively, mix them thoroughly, let them stand and separate the liquid, take the upper layer, add sodium hydroxide solution to neutralize it to neutral, shake well, and analyze it by gas chromatography; (3) Gas chromatography conditions: The chromatographic column is a capillary column (30m×0.25mm×0.5μm); nitrogen is used as the carrier gas, and the flow rate is 30L / min; the hydrogen flow rate is 30L / min, and the air flow rate is 300L / min; the programmed temperature is adopted, the initial temperature is 50℃, and it is maintained for 2min; the temperature is increased to 220℃ at a heating rate of 20℃ / min, and it is maintained for 4min; the injection port temperature is 200℃, the split ratio is 50:1, and the injection volume is 0.4μL; the detector is a hydrogen flame ionization detector (FID) at a temperature of 200℃; (4) Quantitative methods: 1. Fitting of the standard curve According to the gas chromatography analysis results of the mixed standard working solution of toluene and aniline, the relationship between the mass and peak area of ​​the two substances is shown in Table 1.

[0019] Table 1 Standard working solution substances and peak area data of Example 1

[0020] The relationship constant k=0.6634 between aniline, toluene and peak area was obtained through fitting calculation.

[0021] 2. Perform gas chromatography analysis on the sample in step (2), and calculate the percentage of aniline in the sample using the relationship constant K as follows: ω%=(m' 甲苯 ×A' 苯胺 ) / (m' 样品 ×A' 甲苯 ×k)×100%, Wherein, ω% is the percentage of aniline in the sample to be tested; k is the relationship constant between aniline, toluene and peak area; m' 甲苯 is the mass of toluene in the sample to be tested; m' 样品 is the mass of the reaction solution in the sample to be tested; A' 苯胺 A' is the peak area of ​​aniline in the gas chromatogram of the sample to be tested, 甲苯 is the peak area of ​​toluene in the gas chromatogram of the sample to be tested.

[0022] Then the salt conversion rate of the sample to be tested is calculated, and the calculation formula is as follows: c%=(m' 苯胺- ω×m' 反应液 ) / m' 苯胺 ×100%, Wherein, c% is the salt conversion rate; ω is the content of aniline in the sample to be tested; m' 苯胺 is the amount of aniline added in the salt-forming reaction of the sample to be tested; m' 反应液 It is the total mass of aniline and anhydrous hydrofluoric acid fed into the salt-forming reaction of the sample to be tested.

[0023] The statistical results of the conversion rate and related parameters of the above-mentioned salt-forming reaction for 0.5h and 1h are shown in Table 2.

[0024] Table 2 Conversion rate and related parameter statistics of salt formation reaction time 0.5h and 1h

[0025] It can be seen from Table 2 above that the conversion rate of the salt-forming reaction for 1 hour is only 0.09% higher than that for 0.5 hour, so 0.5 hour can be selected as a more preferred reaction time.

[0026] Example 2 A method for determining the salt conversion rate in a diazotization reaction, the steps are as follows: (1) Preparation of aniline and toluene mixed standard working solution: Accurately weigh 1.0 g of aniline standard to an accuracy of 0.0001 g; dissolve in 1.0, 1.5, 2.0, 2.5, and 3.0 g of toluene standard, respectively, to an accuracy of 0.0001 g; shake well to obtain a mixed standard working solution; (2) Salt-forming reaction and sample treatment: Weigh 40.35g of anhydrous hydrofluoric acid, slowly add 41.65g of aniline at -10℃, keep warm at 6~9℃ for reaction after the addition is completed, and take samples during the reaction; weigh the reaction liquid after the salt-forming reaction for 0.5h and 1h, which are 1.5639g and 1.5562g respectively, and then dissolve them in 1.1158g and 1.2531g of toluene respectively, mix them thoroughly, let them stand and separate the upper liquid, add sodium hydroxide solution to neutralize it to neutral, shake well, and analyze it by gas chromatography; (3) Gas chromatography conditions: The chromatographic column is a capillary column (30m×0.25mm×0.5μm); nitrogen is used as the carrier gas, and the flow rate is 30L / min; the hydrogen flow rate is 30L / min, and the air flow rate is 300L / min; the programmed temperature is adopted, the initial temperature is 60℃, and it is maintained for 2min; the temperature is increased to 220℃ at a heating rate of 15℃ / min, and it is maintained for 4min; the injection port temperature is 200℃, the split ratio is 50:1, and the injection volume is 0.4μL; the detector is a hydrogen flame ionization detector (FID) at a temperature of 200℃; (4) Quantitative methods: 1. Fitting of the standard curve According to the gas chromatography analysis results of the mixed standard working solution of toluene and aniline, the relationship between the mass and peak area of ​​the two substances is shown in Table 3.

[0027] Table 3 Standard working solution substances and peak area data of Example 2

[0028] The relationship constant k=0.6784 between aniline, toluene and peak area was obtained through fitting calculation.

[0029] 2. Perform gas chromatography analysis on the sample in step (2), and calculate the percentage of aniline in the sample using the relationship constant K as follows: ω%=(m' 甲苯 ×A' 苯胺 ) / (m' 样品 ×A' 甲苯 ×k)×100%, Wherein, ω% is the percentage of aniline in the sample to be tested; k is the relationship constant between aniline, toluene and peak area; m' 甲苯 is the mass of toluene in the sample to be tested; m' 样品 is the mass of the reaction solution in the sample to be tested; A' 苯胺 A' is the peak area of ​​aniline in the gas chromatogram of the sample to be tested, 甲苯 is the peak area of ​​toluene in the gas chromatogram of the sample to be tested.

[0030] Then the salt conversion rate of the sample to be tested is calculated, and the calculation formula is as follows: c%=(m' 苯胺- ω×m' 反应液 ) / m' 苯胺 ×100%, Wherein, c% is the salt conversion rate; ω is the content of aniline in the sample to be tested; m' 苯胺 is the amount of aniline added in the salt-forming reaction of the sample to be tested; m' 反应液 It is the total mass of aniline and anhydrous hydrofluoric acid fed into the salt-forming reaction of the sample to be tested.

[0031] The statistical results of the conversion rate and related parameters of the above-mentioned salt-forming reaction for 0.5h and 1h are shown in Table 4.

[0032] Table 4 Conversion rate and related parameter statistics of salt formation reaction time 0.5h and 1h

[0033] In Example 1 and Example 2, the results of measuring the conversion rate of the same sample showed that the measurement error was within the allowable range, which indicates that the method has high accuracy and good stability when measuring the conversion rate of the salt-forming reaction.

[0034] Comparative Example 1 The reaction solution after the reaction for 1 hour in Examples 1 and 2 was purged with nitrogen at 25°C to remove excess hydrofluoric acid, and then filtered and vacuum dried at 30°C to obtain 46.64g of dry aniline hydrofluoride, while the theoretical amount of aniline hydrofluoride that can be obtained is 50.61g, so the estimated yield is 92.16%. This yield is within the allowable error range compared with the conversion rates of 92.24% and 92.22% measured in the above scheme, which shows that the reaction has high selectivity and proves that the test method of the present invention is effective.

[0035] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for determining the salt conversion rate in a diazotization reaction, characterized in that: The steps include: (1) Add aniline to anhydrous hydrofluoric acid at -10~5°C, and then perform salt formation reaction at 0~10°C to obtain a reaction solution; add toluene to the reaction solution and mix thoroughly, then stand the solution for separation, take the upper layer and neutralize it to neutrality, and then take the neutralized upper layer as the sample to be tested; (2) Dissolving the aniline standard in different amounts of toluene to obtain a series of standard working solutions; performing gas chromatography analysis on the series of standard working solutions, and obtaining the relationship constant K between aniline, toluene and peak area by fitting calculation; (3) The sample to be tested is subjected to gas chromatography analysis, and the percentage of aniline in the sample to be tested is calculated in combination with the relationship constant K, and then the salt conversion rate of the sample to be tested is calculated.

2. The method for measuring the salt conversion rate in the diazotization reaction according to claim 1, wherein In step (1), aniline is added to anhydrous hydrofluoric acid at -5 to 5°C; In step (1), the temperature of the salt-forming reaction is 6-9°C.

3. The method for measuring the salt conversion rate in the diazotization reaction according to claim 1 or 2, characterized in that, The method of neutralizing to neutrality in step (1) is: neutralizing to neutrality by adding sodium hydroxide solution.

4. The method for measuring the salt conversion rate in the diazotization reaction according to claim 1, wherein The concentration of aniline in the series of standard working solutions in step (2) is 25-60 wt %.

5. The method for measuring the salt conversion rate in the diazotization reaction according to claim 1, characterized in that, The conditions for the gas chromatography analysis in step (2) and step (3) are: the chromatographic column is a capillary chromatographic column; nitrogen is used as the carrier gas, and the flow rate is 20~50L / min; the hydrogen flow rate is 20~50L / min, and the air flow rate is 200~400L / min; a programmed temperature is adopted, the initial temperature is 50~100°C, and it is maintained for 2~5min; the temperature is increased to 200~240°C at a heating rate of 10~30°C / min, and it is maintained for 2~8min; the injection port temperature is 260°C, the split ratio is 40~60:1, and the injection volume is 0.4μL; the detector temperature is 150~230°C.

6. The method for measuring the salt conversion rate in the diazotization reaction according to claim 5, characterized in that: The detector is a hydrogen flame ionization detector.

7. The method for measuring the salt conversion rate in the diazotization reaction according to claim 1, characterized in that, The capillary chromatographic column adopts a medium polarity stationary phase.

8. The method for measuring the salt conversion rate in the diazotization reaction according to claim 1, characterized in that: The calculation formula of the relationship constant k between aniline, toluene and peak area in step (2) is: k=(A 苯胺 ×m 甲苯 ) / (A 甲苯 ×m 苯胺 ), In the formula, m 甲苯 is the mass of toluene standard in the standard working solution; m 苯胺 A is the mass of aniline standard in the standard working solution; 甲苯 is the peak area of ​​toluene standard in the gas chromatogram of the standard working solution, A 苯胺 is the peak area of ​​aniline standard in the gas chromatogram of the standard working solution.

9. The method for measuring the salt conversion rate in the diazotization reaction according to claim 8, characterized in that: The calculation formula for the percentage of aniline in the sample to be tested in step (3) is as follows: ω%=(m' 甲苯 ×A' 苯胺 ) / (m' 样品 ×A' 甲苯 ×k)×100%, Wherein, ω% is the percentage of aniline in the sample to be tested; k is the relationship constant between aniline, toluene and peak area; m' 甲苯 is the mass of toluene in the sample to be tested; m' 样品 is the mass of the reaction solution in the sample to be tested; A' 苯胺 A' is the peak area of ​​aniline in the gas chromatogram of the sample to be tested, 甲苯 is the peak area of ​​toluene in the gas chromatogram of the sample to be tested.

10. The method for measuring the salt conversion rate in the diazotization reaction according to claim 9, characterized in that: The calculation formula for the salt conversion rate in step (3) is as follows: c%=(m' 苯胺- ω×m' 反应液 ) / m' 苯胺 ×100%, Wherein, c% is the salt conversion rate; ω is the content of aniline in the sample to be tested; m' 苯胺 is the amount of aniline added in the salt-forming reaction of the sample to be tested; m' 反应液 It is the total mass of aniline and anhydrous hydrofluoric acid fed into the salt-forming reaction of the sample to be tested.

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