Method for detecting trace diazonium salt in azo compound slurry

Abstract

The present application belongs to the field of detection, and particularly relates to a method for detecting trace diazonium salt in azo compound slurry. The azo compound slurry to be detected is mixed with a detection reagent, and the absorbance of the mixed solution is detected by a UV-visible spectrophotometer, so as to qualitatively and / or quantitatively detect the diazonium salt in the azo compound slurry to be detected. The method for detecting trace diazonium salt is used in reactions consuming diazonium salt, such as coupling reactions in the synthesis of dyes and organic pigments, and the content of trace diazonium salt in the material when the reaction is close to the end point is detected and analyzed, so as to control the addition amount of upstream diazonium salt, improve the utilization rate of diazonium salt, and ensure the product quality.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of detection, and particularly relates to a method for detecting trace diazonium salt in azo compound slurry. BACKGROUND

[0002] Diazonium salt solution is an intermediate product commonly encountered in fine chemical production, which is generally generated by diazotization reaction of aromatic amine and diazotization reagent (such as sodium nitrite, nitrosyl sulfuric acid), and then reacts with coupling components to generate azo compounds, or converts diazonium group into hydroxyl group, cyano group, halogen group, etc., which are used for preparing dyes, organic pigments, and important pesticide, pharmaceutical intermediates and chemical products.

[0003] With the promotion of continuous production of fine chemicals, higher requirements for timeliness and accuracy of the corresponding online detection control system are put forward. In the production of coupling dyes and pigments, excessive trace diazonium salt often causes the color of the product to be dark; the lack of diazonium salt reduces the yield of the product or the intensity of the dye and pigment. Through online detection, the presence or absence of residual diazonium salt and the amount of residual diazonium salt are grasped at any time, and timely adjustment is made according to the process requirements, which plays an important role in ensuring the yield and quality of the product.

[0004] The existing literature reports that pH value and electrode potential value are used for online detection, and the excess of diazonium salt or coupling component in the detection solution is indirectly reflected by the values. For example, patent CN110845860 discloses that the pH value and electrode potential value of the material are related to multiple factors such as material concentration, buffer, acid and alkali amount, etc. The presence or absence of excess diazonium salt or coupling component can be reflected only after each batch of material is calibrated, and the exact excess condition is difficult to determine, which can only be used as reference data.

[0005] Patent US4159264 discloses a method for detecting and controlling coupling reaction by using a colorimeter. This method is mainly used for organic pigments: the pigment slurry to be detected is filtered by air and a dialyzer to obtain trace material to be detected, and then transferred to a buffer solution, and then mixed with another proportionally added diazonium salt or coupling component to form a colored compound. After removing air, the colorimeter is used for detection to obtain a detection signal. This signal is used to control the addition speed of diazonium salt or coupling component in the pigment synthesis process. The disadvantage of this method is that the process is relatively complex, the dialyzer is prone to blockage, and the stability is difficult to guarantee.

[0006] In addition, Liu Bojing et al. introduced the method of detecting the content of diazonium salt by spectrophotometer in the article "Research on the detection method of aniline diazonium salt", and Du Yun et al. introduced the method of detecting the concentration of dichlorobiphenyl diamine diazonium salt in the article "Quantitative detection method of dichlorobiphenyl diamine diazonium salt concentration". The above methods are mainly used for detecting relatively pure diazonium salt solution. However, for the detection of trace diazonium salt in the slurry containing a large amount of coupling dye, it is difficult to accurately detect the content of trace diazonium salt due to the interference of the coupling compound dye, and it cannot meet the needs of automatic control production and rapid feedback regulation. SUMMARY

[0007] To overcome the above technical problems, the purpose of the present application is to provide a method for detecting trace diazonium salt in azo compound slurry.

[0008] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0009] A method for detecting trace diazonium salt in azo compound slurry, the diazonium salt in the azo compound slurry to be detected is mixed with a detection reagent, and the absorbance of the mixed solution is detected by a UV-visible spectrophotometer to qualitatively and / or quantitatively detect the diazonium salt in the azo compound slurry to be detected.

[0010] The azo compound slurry to be detected is mixed with a detection reagent to generate a coupling product through a coupling reaction, the absorbance of the coupling product is detected by a UV-visible spectrophotometer, the absorbance of the coupling product is taken as the independent variable factor x, and the molar concentration of the coupling product is taken as the dependent variable y', which are brought into a regression model, and the y' obtained from the model is used to qualitatively and / or quantitatively detect the diazonium salt in the azo compound slurry to be detected.

[0011] The model formula is as follows:

[0012] y' = ax 2 + bx + c, formula (1)

[0013] Wherein, a and b are the independent variable coefficients of the model, in order to ensure accuracy, the value range of a is -0.001≤a≤0.001, the value range of b is b>0, c is the model correction coefficient, and the value range of c is -0.001≤c≤0.001.

[0014] The molar concentration y of the diazonium salt in the azo compound slurry to be detected is obtained by formula (2),

[0015] y = (1 + n)y' / m, formula (2)

[0016] Wherein, y is the molar concentration of the diazonium salt in the azo compound slurry to be detected, y' is the molar concentration of the coupling product, n is the volume ratio of the detection reagent to the azo compound slurry to be detected, and the value range is 1-100, and m is the reaction molar ratio of the coupling product to the diazonium salt.

[0017] The model formula is established by the following steps:

[0018] I. Preparation of a blank sample: Take the same material as the azo compound slurry to be detected without diazonium salt, add n times of the detection reagent, mix well, and use as a blank sample;

[0019] II. Preparation of a detection solution: Take the blank sample as the solvent, add the coupling product, and stir to dissolve to obtain a detection solution;

[0020] III. Selection of a detection wavelength: Take the blank sample as a reference, detect the full absorption wavelength of the detection solution by ultraviolet-visible spectrophotometry, and select the wavelength at the maximum absorbance as the detection wavelength;

[0021] IV. Absorbance detection and establishment of a regression equation: Measure the absorbance value of the coupling product at different molar concentrations using the selected detection wavelength, and establish a model formula of the molar concentration y' of the coupling product and the absorbance x of the coupling product: y' = ax + bx + c. 2

[0022] When the value of the absorbance x is close to or the same as the absorbance of the blank sample, y' is close to 0 or equal to 0, it can be determined that the diazonium salt content in the azo compound slurry to be detected is less than 1*10 -8 mol / L, i.e., there is no diazonium salt.

[0023] When the absorbance x is greater than 0.05, the azo compound slurry to be detected contains diazonium salt, and the molar concentration of the diazonium salt is obtained by formula (2).

[0024] The detection reagent is a mixed solution of a readily soluble coupling component and a dispersing agent.

[0025] The readily soluble coupling component is a phenol or an aromatic sulfonic acid that can react with the diazonium salt to generate a soluble compound.

[0026] The readily soluble coupling component is one of H acid, G acid, L acid, gamma acid, 1-naphthol-3,7-disulfonic acid, 1-naphthol-3,8-disulfonic acid, salicylic acid, m-diphenol, or N-acetylacetophenyl sulfonic acid amine.

[0027] The dispersing agent is one or two of MF, NNO, and sodium dodecyl benzene sulfonate

[0028] The method can be used to detect the diazonium salt in the azo compound slurry to be detected, and the amount of diazonium salt added in the coupling reaction is adjusted online.

[0029] The method can detect the molar concentration of the diazonium salt in the azo compound slurry in the range of 1*10 -3 ~ 1*10 - ​8 mol / L.

[0030] Advantages of this invention:

[0031] 1. The method for detecting trace amounts of diazonium salts in this invention is used in reactions that consume diazonium salts, such as the synthesis of dyes, organic pigments, and coupling reactions. It detects and analyzes the content of trace amounts of diazonium salts in the material when the reaction is near its endpoint, which is used to regulate the amount of diazonium salts added upstream, thereby improving the utilization rate of diazonium salts and ensuring product quality.

[0032] 2. This invention uses a metering pump to rapidly mix a quantitative sample and a real-time test reagent to automatically prepare the test solution, and obtains the test result through real-time detection.

[0033] 3. The method of this invention can detect trace amounts of diazonium salts, which contain a large number of colored compounds. The rapid dispersant in the detection reagent ensures that the colored compounds in the sample are rapidly and uniformly dispersed, thereby ensuring the stability of the detection results.

[0034] 4. The method of the present invention uses an ultraviolet-visible spectrophotometer with adjustable optical path, which is beneficial to further expand the detection range. Detailed Implementation

[0035] The method for detecting trace amounts of diazonium salts of the present invention involves mixing a slurry of the azo compound to be detected with a detection reagent. The diazonium salt in the slurry undergoes a coupling reaction with the coupling component in the detection reagent to obtain a coupling product. The absorbance of this coupling product is detected by a UV-Vis spectrophotometer. The absorbance of the coupling product is used as the independent variable factor x, and the molar concentration of the coupling product is used as the dependent variable y'. These variables are substituted into a regression model. Based on y' obtained from the model, the diazonium salt in the azo compound slurry to be detected is qualitatively and / or quantitatively detected.

[0036] The model formula is as follows:

[0037] y' = ax 2 Formula (1) +bx+c

[0038] Where a and b are the independent variable coefficients of the model, and c is the model correction coefficient.

[0039] The molar concentration y of the diazonium salt in the azo compound slurry to be tested is calculated using formula (2).

[0040] y=(1+n)y' / m formula (2)

[0041] Where y is the molar concentration of diazonium salt in the material to be tested, y' is the molar concentration of coupling product, n is the volume ratio of the test reagent to the slurry of the azo compound to be tested, and m is the molar ratio of coupling product to diazonium salt.

[0042] The present invention will be further explained and described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0043] Example 1

[0044] During the continuous synthesis of Disperse Yellow 119, the excess of its o-nitro-p-chloroaniline diazonium salt was detected:

[0045] Disperse Yellow 119 slurry was produced by coupling o-nitroaniline diazonium salt solution with coupling component N-methyl-3-cyano-4-methyl-6-hydroxy-2-pyridone solution, and the reaction formula is shown in Formula 1.

[0046]

[0047] The establishment of the model formula includes the following steps:

[0048] The coupling product 1 is generated by the reaction of H acid and o-nitroaniline diazonium salt, and the reaction formula is shown in Formula 2.

[0049]

[0050]

[0051] I. Preparation of blank sample: Take 5 ml of Dispersible Yellow 119 coupling material, which is the same as the material to be tested and does not contain diazonium salts, and add 100 ml of test reagent (the test reagent is a mixed solution of H acid aqueous solution and dispersant NNO, the mass concentration of dispersant NNO is 1%, and the molar concentration of H acid is 1*10). -4 Mix thoroughly (mol / L) and use as a blank sample;

[0052] II. Preparation of the detection solution: Using the blank sample as a solvent, add coupling product 1 and stir to dissolve to obtain the detection solution; the concentration of coupling product 1 is 1*10 -3 ~1*10 -6 ;

[0053] III. Selection of Detection Wavelength: Using a blank sample as a reference, the wavelength at low molar concentrations (2.5*10⁻⁶) was detected by a UV-Vis spectrophotometer. -5 The absorbance of the detection solution at the total absorption wavelength (mol / L) was measured. The wavelength at which the absorbance of the coupling product 1 was relatively maximum was 522.5 nm; the maximum absorption wavelength of H acid was 235 nm; and the maximum absorption wavelength of Disperse Yellow 119 was 440 nm. Since there was a significant difference between the three, the absorption wavelength of 522.5 nm was selected as the detection wavelength.

[0054] IV. Absorbance Detection and Regression Equation Establishment: Using a blank sample as a solvent, different amounts of coupling product 1 were added to prepare detection solutions with different molar concentrations. The absorbance was measured at an absorption wavelength of 522.5 nm under defined detection conditions. The results are shown in the table below:

[0055]

[0056] Based on the data in the table above, a regression model was established using Excel software for statistical analysis.

[0057] A regression model with the absorbance of the coupling product as the independent variable factor x and the molar concentration of the coupling product as the dependent variable y':

[0058] y'=-0.4357E-06x 2 +5.641E-05x–3.475E-07R 2 =0.9999

[0059] During the continuous synthesis of Disperse Yellow 119, the excess of its o-nitroaniline diazonium salt was detected:

[0060] The flow rate of the o-nitroaniline diazonium salt solution was 1000 L / h, with a concentration of 0.3 mol / L. The flow rate of the coupling component, N-methyl-3-cyano-4-methyl-6-hydroxy-2-pyridone solution, was also 1000 L / h, with a concentration of 0.3 mol / L, to produce Disperse Yellow 119 slurry. The absorbance of the completely reacted slurry, measured by a UV-Vis spectrophotometer, was 0.625 for coupling product 1. The molar concentration of the coupling product, calculated using the regression model, was 3.474 × 10⁻⁶. -5 mol / L, n=20, m=1 in formula (2), the molar concentration of o-nitroaniline diazonium salt in Disperse Yellow 119 slurry calculated by formula (2) is 0.730*10 mol / L. -3 mol / L. At this point, the diazonium salt is in excess, and the amount of N-methyl-3-cyano-4-methyl-6-hydroxy-2-pyridone solution to be added is 4.87 L / h. The amount of N-methyl-3-cyano-4-methyl-6-hydroxy-2-pyridone solution introduced is appropriately increased to adjust the coupling reaction of Disperse Yellow 119.

[0061] The coupling material of Dispersible Yellow 119 was taken, filtered, and the resulting liquid was analyzed using conventional detection methods. The concentration of diazonium salt was found to be 0.738 × 10⁻⁶. -3 The two values ​​are in mol / L, with an error of 1.08%.

[0062] Example 2

[0063] During the continuous synthesis of Disperse Red 167:1 dye, the excess of o-chloro-p-nitroaniline diazonium salt was monitored. In continuous synthesis, to ensure material matching and process stability, it is necessary to monitor and control the amount of o-chloro-p-nitroaniline diazonium salt solution added.

[0064] The diazonium salt solution of o-chloro-p-nitroaniline undergoes a coupling reaction with the esterification solution of Ruby to generate Disperse Red 167:1 dye compound, and the reaction formula is shown in Formula 3.

[0065]

[0066] The establishment of the model formula includes the following steps:

[0067] The readily soluble coupling component is m-acetylacetambenzenesulfonic acid, which reacts with o-chloro-p-nitroaniline diazonium salt to generate coupling product 2, and its reaction formula is Formula IV.

[0068]

[0069]

[0070] I. Preparation of blank sample: Take 5 ml of Disperse Red 167:1 dye, identical to the material to be tested and free of diazonium salts, and add 75 L of test reagent (the test reagent is a mixed aqueous solution of m-acetylacetamenobenzenesulfonic acid and MF, wherein the concentration of m-acetylacetamenobenzenesulfonic acid is 1*10). -2 The solution was mixed thoroughly (mol / L, MF concentration was 15 g / L) and used as a blank sample.

[0071] II. Preparation of the detection solution: Using the blank sample as a solvent, add coupling product 2 and stir to dissolve to obtain the detection solution; the concentration of compound 2 is 1*10 -3 ~1*10 -6 mol / L;

[0072] III. Selection of Detection Wavelength: Using a blank sample as a reference, the wavelength at low molar concentrations (2.5*10⁻⁶) was detected by a UV-Vis spectrophotometer. -5 The absorbance of the detection solution at its total absorption wavelength (mol / L) was measured. The wavelength at which the relative absorbance of coupling product 2 was at its maximum was 420–430 nm. M-acetylacetambenzenesulfonic acid and dispersant MF showed virtually no absorption between the detection wavelengths of 400–700 nm. The maximum absorption wavelength of Disperse Red 167:1 was between 460–480 nm. A detection wavelength of 425 nm was selected, as the spectrum at this wavelength was most sensitive for the detection of coupling product 2.

[0073] IV. Absorbance Detection and Regression Equation Establishment: Using blank samples as solvent, different amounts of coupling product 2 were added to prepare detection solutions with different molar concentrations. The absorbance was measured under defined detection conditions using an absorption wavelength of 425 nm. The results are shown in the table below:

[0074] No. Coupling product 2 molarity mol / L Absorbance 1 0.1 0.1 2 0.1 0.1 3 0.1 1 0.320*10 -3 ]]> 0.049 2 0.600*10 -3 ]]> 0.092 3 1.000*10 -3 ]]> 0.155 4 1.600*10 -3 ]]> 0.262 5 2.000*10 -3 ]]> 0.32 6 2.500*10 -3 ]]> 0.407 7 3.200*10 -3 ]]> 0.537

[0075] Based on the data in the table above, a regression model was established using Excel software for statistical analysis.

[0076] A regression model with the absorbance of the coupling product as the independent variable factor x and the molar concentration of the coupling product as the dependent variable y':

[0077] y'=-9.852E-04x 2 +6.488E-03x–7.032E-06R 2 =0.9996

[0078] During the continuous synthesis of Disperse Red 167:1 dye, the excess of o-chloro-p-nitroaniline diazonium salt was tested: the flow rate of o-chloro-p-nitroaniline diazonium salt solution was 1000 L / h, the concentration was 0.2 mol / L, the flow rate of the red esterification solution was 1000 L / h, the concentration was 0.2 mol / L, and the Disperse Red 167:1 dye was produced by coupling. The absorbance of the completely reacted Disperse Red 167:1 slurry was measured using a UV-Vis spectrophotometer; the absorbance of coupling product 2 was 0.072. The molar concentration of the coupling product was calculated to be 0.545 × 10⁻⁶ using the regression model described above. -3 mol / L, n=15, m=1 in formula (2), the molar concentration of diazonium salt of o-chloro-p-nitroaniline in Disperse Red 167:1 slurry calculated by formula (2) is 8.72*10 mol / L. -3 At this concentration of mol / L, the diazonium salt is in excess, and the flow rate of the o-chloro-p-nitroaniline diazonium salt solution needs to be reduced to 87 L / h.

[0079] The 167:1 dispersant red slurry was filtered to obtain a liquid solution. The diazonium salt concentration was determined to be 8.95 × 10⁻⁶ using conventional detection methods. -3 The two values ​​are in mol / L, with an error of 2.57%.

[0080] As can be seen from the above embodiments, the method of the present invention is used to detect and analyze the content of trace diazonium salts in the material when the reaction is close to the endpoint, and to adjust the amount of diazonium salts added in the coupling reaction in an online feedback manner.

Claims

1. A method for detecting trace amounts of diazonium salts in azo compound slurry, characterized in that: The diazonium salt in the azo compound slurry to be tested is mixed with the detection reagent to undergo a coupling reaction to obtain a coupling product. The absorbance of the coupling product is detected by a UV-Vis spectrophotometer. The absorbance of the coupling product is used as the independent variable factor x, and the molar concentration of the coupling product is used as the dependent variable y'. The product is substituted into a regression model. Based on the y' obtained from the model, the diazonium salt in the azo compound slurry to be tested is qualitatively and / or quantitatively detected. The model formula is: y'=ax 2 Formula (1) +bx+c Where a and b are the independent variable coefficients of the model, and c is the model correction coefficient; The molar concentration y of the diazonium salt in the azo compound slurry to be tested is calculated using formula (2). y=(1+n)y' / m formula (2) Where y is the concentration of diazonium salt in the azo compound slurry to be tested, y' is the molar concentration of the coupling product, n is the volume ratio of the detection reagent to the azo compound slurry to be tested, and m is the molar ratio of the coupling product to the diazonium salt. The establishment of the model formula includes the following steps: Ⅰ Preparation of blank sample: Take a material that is the same as the azo compound slurry to be tested and does not contain diazonium salt, add n times the amount of test reagent, mix evenly, and use it as a blank sample; II. Preparation of the test solution: Using the blank sample as a solvent, add the coupling product and stir to dissolve to obtain the test solution; III. Selection of detection wavelength: Using the blank sample as a reference, select the wavelength at the maximum absorbance of the detection liquid as the detection wavelength; IV. Absorbance Detection and Regression Equation Establishment: Using the selected detection wavelength, the absorbance values ​​of the coupling products at different molar concentrations were measured, and the regression model formula was established.

2. The method according to claim 1, characterized in that: The detection reagent is a mixed solution of a readily soluble coupling component and a dispersant.

3. The method according to claim 2, characterized in that: The readily soluble coupling component is a phenol or aromatic sulfonic acid that can undergo a coupling reaction with a diazonium salt to generate a soluble compound.

4. The method according to claim 3, characterized in that: The readily soluble coupling component is one of H acid, G acid, L acid, γ acid, 1-naphthol-3,7-disulfonic acid, 1-naphthol-3,8-disulfonic acid, salicylic acid, m-diphenol, or N-acetylbenzenesulfonic acid.

5. The method according to claim 2, characterized in that: The dispersant is one or two of MF, NNO, and sodium dodecylbenzenesulfonate.

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