Benzeneacetaldehyde derivatives, methods for their preparation and use, and methods for detecting the content of aniline compounds

Abstract

The present application provides a phenylacetaldehyde derivative as shown in formula (1), and also provides a preparation method of the phenylacetaldehyde derivative and the use of the phenylacetaldehyde derivative as a color developing agent for detecting aniline compounds. The present application also provides a method for detecting the content of aniline compounds and a method for monitoring the discharge of waste brine in an isocyanate production process. The phenylacetaldehyde derivative provided by the present application has strong color developing ability, and can quickly react and show obvious changes in color even at very low content of aniline compounds. The detection method provided by the present application is simple to operate, does not require expensive detection instruments, has accurate and reliable detection results, has low detection limit, and can also realize online detection and analysis. The monitoring method provided by the present application can collect data at different discharge sites in real time and judge the process operation condition in time, so that the abnormal working condition can be handled in time, the occurrence of downstream accidents can be avoided, the production safety is improved, and the environmental protection is also facilitated.

Description

Technical Field

[0001] This invention relates to the field of chemical analysis and detection, specifically to a phenylacetaldehyde derivative, its preparation method, and its use as a colorimetric agent. This invention also relates to a method for detecting the content of aniline compounds, and further to a method for monitoring waste brine discharge during isocyanate production. Background Technology

[0002] Isocyanates are an important raw material for polyurethane (PU) materials. They are produced by the condensation of aniline compounds with formaldehyde under acidic conditions, followed by a series of refining processes to obtain the corresponding amine (i.e., polymethylene polyphenyl polyamine, or polyamine for short). This is then subjected to a phosgenation reaction and subsequent separation to obtain the pure product. Polymethylene polyphenyl polyamine has the following structural formula:

[0003]

[0004] The value of n can be as high as several hundred.

[0005] Because the condensation reaction solution contains a large amount of acid, alkaline solutions such as sodium hydroxide are usually added during the purification process for neutralization, resulting in waste brine containing a large amount of polyamines. This waste brine, after undergoing an amine removal process, can be treated in various ways, including discharge, reuse in chlor-alkali systems, or biochemical bacterial decomposition. Aniline compounds are biotoxic and can damage the chlor-alkali electrolytic membrane; therefore, regardless of the treatment method used, specific content control requirements for aniline compounds are necessary. Therefore, strictly controlling the effectiveness of the amine removal process and preventing excessive levels of aniline compounds in the final brine is crucial for downstream brine treatment and system stability.

[0006] Currently, the determination of aniline compounds is divided into two main categories: spectroscopic methods and chromatographic methods. Spectroscopic methods are mainly based on the national standard "Water Quality - Determination of Aniline Compounds - N-(1-Naphthyl)ethylenediamine azo Spectrophotometric Method" (GB 11889-89), while chromatographic methods are based on the national standard "Water Quality - Determination of Aniline Compounds - Gas Chromatography-Mass Spectrometry".

[0007] The primary method is (HJ 822-2017), with other methods including liquid chromatography and fluorescence spectroscopy. However, these methods are all offline laboratory measurements, requiring manual sample delivery and analysis by professional personnel. The time from sampling to laboratory analysis results generally takes more than 2 hours, and cannot immediately characterize the device's condition at the moment of sampling, delaying troubleshooting. Furthermore, while spectroscopic methods require simple instruments, they still require the pre-preparation of various reagents such as diazotizing agents, colorimetric agents, and reducing agents. The colorimetric process is cumbersome, requiring manual adjustment of reaction conditions and demanding high technical skills from personnel. Chromatography requires expensive instruments, resulting in high analysis costs and poor tolerance to high-salt samples; the instruments themselves require professional maintenance.

[0008] Chinese patent (CN 112161972B) discloses a rapid grading quantitative detection of aromatic amine content in acidic solution test paper set and its application, which uses test paper visual method, and uses color developing agent p-dimethylaminobenzaldehyde to estimate aromatic amine in acidic system. However, the detection method provided by the patent is only suitable for estimating the content interval of aniline compound solution above 0.01%, and the test precision is poor. For waste brine after amine removal treatment, the content of aniline compound (calculated as aniline) is less than 0.001%, generally less than 0.0003%, and the detection method provided by the patent is difficult to apply, and the main reasons may be two: first, the color developing agent p-dimethylaminobenzaldehyde solution is easily oxidized by amine group itself, which is yellow, and the test result is easily disturbed at low content; second, the color change is not strong at low content (less than 0.001%) order of magnitude, and the precision of visual estimation is poor.

[0009] In summary, it is urgent to develop a detection method suitable for detecting low content of aniline compound in waste brine, so as to realize online analysis and detection with high detection sensitivity, and real-time monitoring of waste brine discharge. SUMMARY

[0010] In order to make up for the deficiencies in the prior art, one object of the present application is to provide a phenylacetaldehyde derivative which can be used as a new color developing agent for detecting aniline compounds, especially suitable for low content of aniline compounds in the sample to be detected, such as waste brine produced in the isocyanate production process after amine removal and other steps.

[0011] Another object of the present application is to provide a preparation method and use of the phenylacetaldehyde derivative.

[0012] Another object of the present application is to provide a method for detecting the content of aniline compounds.

[0013] Another object of the present application is to provide a monitoring method for waste brine discharge in the isocyanate production process.

[0014] The first aspect of the present application provides a phenylacetaldehyde derivative as shown in formula (1),

[0015]

[0016] wherein R1, R2 and R3 are each independently C1-C6 alkyl.

[0017] In formula (1), R1, R2 and R3 can each independently be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl and the like alkyl.

[0018] In some preferred embodiments, R1, R2and R3may each independently be a C1-C4 linear or branched alkyl group (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, i-butyl, t-butyl, and the like alkyl groups). In some more preferred embodiments, R1, R2and R3may each independently be a methyl or ethyl group.

[0019] A second aspect of the present application provides a method for preparing the phenylacetaldehyde derivative according to any one of the above technical solutions, comprising the following steps:

[0020] S1: reacting an alkylchlorosilane as shown in formula (2) with 4-bromoanisole sulfide as shown in formula (3) to obtain an intermediate A as shown in formula (4);

[0021] S2: reacting the intermediate A with N,N-dimethylformamide to obtain an intermediate B as shown in formula (5); and

[0022] S3: reacting the intermediate B with ethyl monochloroacetate to obtain an intermediate C as shown in formula (6), and hydrolyzing the intermediate C to obtain the phenylacetaldehyde derivative;

[0023] wherein R1, R2and R3are each independently as defined in the above technical solutions;

[0024]

[0025] In the preparation method provided by the present application, each raw material or reagent can use a commercially available product, or can be prepared by referring to the prior art.

[0026] In the preparation method provided by the present application, in the step S1, the alkylchlorosilane and the 4-bromoanisole sulfide can be reacted in a first organic solvent in the presence of triethylenediamine and a first catalyst to obtain the intermediate A.

[0027] In some preferred embodiments, the first catalyst can be an alkyl lithium catalyst, for example, n-butyllithium, which can be added in the form of a pure substance or dissolved in a solvent to form a solution, for example, can be added to the reaction system in the form of a n-hexane solution of n-butyllithium.

[0028] In some preferred embodiments, the first organic solvent can be one or more of tetrahydrofuran, dichloromethane, and n-hexane.

[0029] In some preferred embodiments, the molar ratio of the alkylchlorosilane, 4-bromo-thioanisole, triethylenediamine and the first catalyst can be 1:0.8-1.2:0.8-1.2:0.8-1.2. In some more preferred embodiments, the molar ratio of the alkylchlorosilane, 4-bromo-thioanisole, triethylenediamine and the first catalyst can be 1:0.95-1.05:0.95-1.05:0.95-1.05.

[0030] In some preferred embodiments, the reaction temperature in step S1 can be -20-20℃, and the reaction time can be 1-5h. In some more preferred embodiments, the reaction temperature in step S1 can be -5-5℃ (e.g. 0℃), and the reaction time can be 2-3h.

[0031] In some preferred embodiments, after the reaction in step S1 is completed, water can be added to quench the reaction, and the precipitate can be extracted with an organic solvent (e.g. saturated alkanes or aromatic hydrocarbons such as n-pentane, n-hexane, etc.), and the extract can be dried (e.g. with anhydrous sodium sulfate) and then the organic solvent can be removed (e.g. by rotary evaporation) to obtain the target product, i.e. intermediate A.

[0032] In the preparation method provided by the present application, in step S2, the intermediate A can be reacted with N,N-dimethylformamide in the presence of phosphorus oxychloride to obtain the intermediate B.

[0033] In some preferred embodiments, the molar ratio of the intermediate A, N,N-dimethylformamide and phosphorus oxychloride can be 1:0.9-1.5:0.8-1.5. In some more preferred embodiments, the molar ratio of the intermediate A, N,N-dimethylformamide and phosphorus oxychloride can be 1:1-1.3:1-1.4.

[0034] In some preferred embodiments, the reaction temperature in step S2 can be 60-120℃, and the reaction time can be 0.5-5h. In some more preferred embodiments, the reaction temperature in step S2 can be 75-85℃ (e.g. 80℃), and the reaction time can be 2-4h.

[0035] In some preferred embodiments, after the reaction in step S2 is completed, the reaction system can be cooled, and the pH of the reaction system can be adjusted to 3.0-4.5, and the obtained solid can be washed with water, filtered and dried to obtain the target product, i.e. intermediate B. In this process, an alkali solution can be used to adjust the pH value, such as an aqueous solution of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, etc.

[0036] In the preparation method, in step S3, the intermediate B and ethyl monochloroacetate can be reacted in the presence of an acid-binding agent and a second catalyst in a second organic solvent to obtain the intermediate C, and the intermediate C is hydrolyzed under an acidic condition with pH < 3 to obtain the phenylacetaldehyde derivative.

[0037] In some preferred embodiments, the second catalyst can be an alkyl ammonium halide catalyst, such as tetrabutylammonium bromide.

[0038] In some preferred embodiments, the acid-binding agent can be one or more of sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide.

[0039] In some preferred embodiments, the second organic solvent can be one or more of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and dichloromethane.

[0040] In some preferred embodiments, the molar ratio of the intermediate, ethyl monochloroacetate, and the second catalyst can be 1:1-2:0.01-0.15. In some more preferred embodiments, the molar ratio of the intermediate, ethyl monochloroacetate, and the second catalyst can be 1:1-1.2:0.08-0.12.

[0041] In some preferred embodiments, the reaction temperature in step S3 can be 15-45°C, and the reaction time can be 10-70 h. In some more preferred embodiments, the reaction temperature in step S3 can be 20-30°C (e.g., room temperature), and the reaction time can be 20-40 h.

[0042] In some preferred embodiments, the acidic alcohol solution with pH = 2-3 can be used to adjust the acidic condition with pH < 3 in step S3. In some more preferred embodiments, the acidic alcohol solution is a methanol solution of sulfuric acid.

[0043] In some preferred embodiments, the hydrolysis is performed under reflux for 0.5-3 h, such as 2-3 h.

[0044] In some preferred embodiments, after the hydrolysis process, the pH can be adjusted to neutral (e.g., about 7) using an alkali solution (e.g., an aqueous solution of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, or the like), extracted using an organic solvent (e.g., dichloromethane), and dried (e.g., with anhydrous sodium sulfate) to remove the organic solvent to obtain the target product, i.e., the phenylacetaldehyde derivative.

[0045] The third aspect of the present application provides the use of the phenylacetaldehyde derivative of any of the above technical solutions as a color developing agent for detecting aniline compounds.

[0046] The phenylacetaldehyde derivative described in the present application can rapidly develop color reaction with aniline compounds under acidic conditions (for example, the reaction formula of aniline is shown below), and can show obvious color change even at very low concentration, and is therefore very suitable for use as a detection color developing agent for aniline compounds.

[0047]

[0048] The aniline compound described in the present application refers to aniline and a class of compounds containing aniline structural fragments, and the content thereof is usually referred to as aniline content. For example, the aniline compound content determined by GB / T 11889-1989 is referred to as aniline content.

[0049] The fourth aspect of the present application provides a method for detecting the content of aniline compounds, comprising the following steps:

[0050] T1: performing color development reaction on the sample to be tested with a color developing agent solution, and determining the color value after reaction, wherein the color developing agent solution contains the phenylacetaldehyde derivative described in any one of the above technical solutions as a color developing agent; and

[0051] T2: obtaining the content of aniline compounds in the sample to be tested from the color value obtained in step T1 by using a working curve of color value versus aniline compound content established in advance.

[0052] In some preferred embodiments, the sample to be tested can be waste brine discharged in the production process of isocyanate, wherein the content of aniline compounds is not more than 0.001wt.% in terms of aniline. In some more preferred embodiments, the content of aniline compounds in the sample to be tested is not more than 0.0005wt.% in terms of aniline, for example, not more than 0.0003wt.%.

[0053] In some preferred embodiments, the sample to be tested can be treated at a constant temperature of 20-40℃ for 10-30min before color development reaction.

[0054] In some preferred embodiments, the color developing agent solution comprises a third organic solvent, an inorganic acid and the color developing agent. In some more preferred embodiments, the third organic solvent can be tetrahydrofuran; the inorganic acid can be hydrochloric acid, sulfuric acid or phosphoric acid, and the volume content thereof can be 2-20% (V / V), preferably 8-12% (V / V); the content of the color developing agent can be 0.05-1wt.%, preferably 0.07-0.1wt.%. In some further preferred embodiments, the color developing agent solution is a tetrahydrofuran solution of hydrochloric acid in which the color developing agent is dissolved, wherein the volume content of hydrochloric acid can be 8-12% (V / V), and the content of the color developing agent can be 0.07-0.1wt.%.

[0055] In some preferred embodiments, the volume ratio of the sample to be tested to the color developing agent solution can be 30-300: 1. In some more preferred embodiments, the volume ratio of the sample to be tested to the color developing agent solution can be 70-130: 1.

[0056] In some preferred embodiments, the reaction temperature of the color developing reaction can be 20-40°C, preferably the same as the temperature during the constant temperature treatment, and the reaction time of the color developing reaction can be 20-40 min.

[0057] In some preferred embodiments, the working curve is established by the following process: taking a sample to be tested with an aniline compound content of no more than 0.00005 wt.%, preferably no more than 0.00003 wt.%, adding different amounts of aniline to it to form 15-25 (for example, 20) samples with aniline compound content in the range of 0.00002-0.001 wt.%, preferably 0.00005-0.0005 wt.%, and determining the aniline compound content in each sample using N-(1-naphthyl)ethylenediamine azo spectrophotometry; testing the color value of each sample by the method of step T1, and correlating the color value with the aniline compound content to obtain the working curve. In some more preferred embodiments, the working curve of the color value and the aniline compound content can be established by partial least squares regression.

[0058] In some preferred embodiments, the color value in step T1 can be detected using a colorimeter, which is respectively connected with a sample buffer tank for containing the sample to be tested and a color developing agent storage tank for containing the color developing agent solution, and the sample buffer tank can also be used for constant temperature treatment of the sample to be tested.

[0059] In some preferred embodiments, the color developing reaction is carried out in a measuring cell of the colorimeter, the sample to be tested is sent from the sample buffer tank to the measuring cell of the colorimeter, the color developing agent solution is sent from the color developing agent storage tank to the measuring cell of the colorimeter, and the color developing reaction is carried out therein. An optical source and a detector are arranged outside the measuring cell, and the optical path passes through the measuring cell. In some more preferred embodiments, the length of the optical path can be 100-200 mm.

[0060] In some preferred embodiments, the material of the measuring cell should be transparent and resistant to long-term corrosion, for example, one or more of quartz glass, silicate glass, and crystal.

[0061] In some preferred embodiments, the colorimeter is respectively connected with the sample buffer tank and the color developing agent storage tank through electromagnetic valves.

[0062] In some preferred embodiments, the colorimeter is connected with the sample buffer tank and the waste liquid tank respectively, and the reaction liquid after color development and the remaining sample to be detected can be discharged into the waste liquid tank.

[0063] In some preferred embodiments, the colorimeter is an online colorimeter, and on-site detection can be realized by using the online colorimeter, and the colorimetric value can be transmitted to the analysis system through an optical cable. The analysis system can pre-store a working curve of the colorimetric value and the content of the aniline compound, and automatic analysis can be realized according to the colorimetric value, so that the detection value can be obtained. The analysis system can be a PC host, which can be arranged in a control room away from the detection site. One analysis system can be used in multiple different detection sites at the same time.

[0064] The fifth aspect of the present application provides a monitoring method for waste brine discharge in an isocyanate production process. The content data of the aniline compound in the waste brine is collected by using the detection method of any one of the above technical solutions every interval time, and the obtained content data is compared with the pre-set maximum limit content of the aniline compound, so as to monitor whether the discharge of the waste brine meets the standard.

[0065] In some preferred embodiments, the interval time of data collection can be 60-90 min, or can be set according to the actual working condition.

[0066] In some preferred embodiments, the maximum limit content of the aniline compound is 0.0003 wt.%, so as to ensure that the discharge standard is met.

[0067] In the monitoring method provided by the present application, the content data of the monitored site can be transmitted to the control room DCS screen by the PC host in a wired or wireless manner, and the DCS high limit alarm is set at the same time.

[0068] The monitoring method provided by the present application can timely monitor the removal effect of the aniline compound in the production process, and when the index of the discharged waste brine is abnormal, the operator can quickly respond, so as to avoid the phenomena such as collapse of the downstream biochemical system, abnormal environmental protection index, etc.

[0069] The technical solution provided by the present application has the following advantages:

[0070] (1) The phenylacetaldehyde derivative provided by the present application has a novel structure, and the color development ability is greatly improved through optimization and adjustment of the functional groups. Even at a very low content of the aniline compound, the reaction can occur quickly and the colorimetric value can change obviously, so the phenylacetaldehyde derivative can be used as a new and efficient color developing agent for detection of the aniline compound.

[0071] (2) The preparation process of the phenylacetaldehyde derivative provided by the application is simple, the raw materials are cheap and easy to obtain, the reaction conditions are mild, and no complex purification process is required, so it is very suitable for industrialized production and application.

[0072] (3) The detection method provided by the application is simple to operate, fast in detection, does not require expensive instruments and equipment, and is accurate and reliable in detection results, and has a lower detection limit. In addition, compared with the conventional laboratory offline analysis detection method, the detection method provided by the application can realize on-site sampling and color development, online analysis of chroma value and corresponding determination of detection results, so that the entire process does not need to be completed in the laboratory, time efficiency is good, and a large amount of labor loss is avoided.

[0073] (4) The monitoring method provided by the application can collect data of different waste brine discharge sites in real time and timely judge the process operation condition, facilitate timely processing of abnormal working conditions, avoid occurrence of downstream accidents, improve production safety, and also benefit environmental protection. BRIEF DESCRIPTION OF DRAWINGS

[0074] Figure 1 It is a structure schematic view of the aniline compound on-site detection device in Example 2.

[0075] In the drawings, the reference signs are as follows: 1, sampling pump; 2, sample buffer tank; 3, color developing agent storage tank; 4, sample sampling electromagnetic valve; 5, color developing agent sampling electromagnetic valve; 6, light source; 7, detector; 8, measuring cell; 9, light path; 10, waste liquid tank.

[0076] Figure 2 It is a correlation curve of the real content of aniline compounds in the waste brine sample and the content analyzed and tested in the laboratory in Example 3.

[0077] Figure 3 It is a correlation curve of the real content of aniline compounds in the waste brine sample and the chroma value measured by the on-site detection device in Example 3.

[0078] Figure 4 It is a correlation curve between the content of aniline compounds obtained by laboratory analysis and testing and on-site detection in Example 3. DETAILED DESCRIPTION

[0079] The technical solutions of the application will be further described in detail below in combination with specific embodiments.

[0080] The raw materials or reagents used in the embodiments of the application are commercially available products unless otherwise specified.

[0081] The percentages used in the embodiments of the application are mass percentages unless otherwise specified.

[0082] The "laboratory analysis test method" used in the embodiments of the present application is the national standard GB / T11889-1989, i.e. "Water quality-Determination of aniline compounds N-(1-naphthyl)ethylenediamine azo spectrophotometric method", which is used to determine the content of aniline compounds in waste brine. The analysis instrument used is a Cary 100 ultraviolet-visible spectrophotometer of Agilent Company, USA.

[0083] Preparation of the color developing agent in Example 1

[0084] (1) Synthesis of intermediate A

[0085] 0.2 mol of trimethylchlorosilane, 0.2 mol of 4-bromoanisole sulfide and 0.2 mol of triethylenediamine were weighed out and dissolved in 350 mL of tetrahydrofuran, 80 mL of 2.5M n-butyllithium in n-hexane was added, the temperature was controlled at 0°C, and after 2h of reaction, water was added to quench the reaction; the precipitate was extracted and dissolved with n-hexane for 3 times and then dried with anhydrous sodium sulfate, and n-hexane was removed by vacuum rotary evaporation to obtain intermediate A, with a reaction conversion rate of 87%. The reaction formula is as follows:

[0086]

[0087] 1 H NMR (DMSO-d6, 300 MHz): 0.21 (s, 9H), 2.12 (s, 2H), 7.43 (d, J = 14.4 Hz, 2H), 7.60 (d, J = 14.4 Hz, 2H).

[0088] (2) Synthesis of intermediate B

[0089] 0.15 mol of intermediate A, 0.15 mol of N,N-dimethylformamide and 0.15 mol of phosphorus oxychloride were weighed out and reacted at 80°C for 3h, an aqueous sodium hydroxide solution (the concentration of NaOH was 10wt.%) was added dropwise to adjust the pH to 4, the precipitate was washed with pure water and suction filtered 3 times, and the suction filtered product was dried to obtain intermediate B, with a reaction conversion rate of 90%. The reaction formula is as follows:

[0090]

[0091] 1 H NMR (DMSO-d6, 300 MHz): 0.21 (s, 9H), 2.12 (s, 2H), 7.43 (d, J = 14.4 Hz, 2H), 7.60 (d, J = 14.4 Hz, 2H).

[0092] (3) Synthesis of the color developing agent from intermediate B

[0093] Take 0.1 mol of intermediate B, 0.1 mol of ethyl monochloroacetate and 0.01 mol of tetrabutylammonium bromide, then add 100 mL of anhydrous tetrahydrofuran for dilution, add 0.01 mol of potassium carbonate, and react at room temperature for 30 h; after the reaction is completed, adjust the pH of the reaction system to <3.0 by adding a pH = 2-3 methanol solution of sulfuric acid, then hydrolyze at reflux for 2 h, adjust the pH to neutral after hydrolysis is completed by adding a 10 wt.% sodium hydroxide solution, extract the reaction system with 45 mL of dichloromethane three times, remove the water with anhydrous sulfuric acid, and then vacuum rotary evaporate to obtain the final product, with a reaction conversion rate of 47%. The reaction formula is as follows:

[0094]

[0095] 1 H NMR (DMSO-d6, 300 MHz): 0.21 (s, 9H), 2.12 (s, 2H), 7.28 (d, J = 14.4 Hz, 2H), 7.34 (d, J = 14.4 Hz, 2H), 3.66 (d, J = 6.5 Hz, 2H), 9.72 (t, J = 6.5 Hz, 1H).

[0096] Example 2

[0097] The on-site detection device used in this example is shown in Figure 1 which the sample pump 1 is connected to the sample buffer tank 2 for conveying the sample to be tested; the sample buffer tank 2 and the chromogenic agent storage tank 3 are respectively connected to the measuring cell 8 of the online colorimeter (model Optek C4000-AF26-VB-PV, which also includes a light source 6, a detector 7 and a light path 9 formed therebetween) through the sample sampling electromagnetic valve 4 and the chromogenic agent sampling electromagnetic valve 5 for conveying the sample to be tested and the chromogenic agent solution into the colorimeter, respectively, so that the color change of the test solution caused by the reaction of the sample to be tested and the chromogenic agent can be used to determine the content of aniline compounds (calculated as aniline) in the sample to be tested; the colorimeter is connected to the waste tank 10 for discharging the waste liquid after detection; the waste tank 10 is also connected to the sample buffer tank 2, and the excess sample to be tested in the sample buffer tank 2 is also discharged into the waste tank 10.

[0098] The test steps are as follows:

[0099] (1) A prepared chromogenic agent solution is added to the chromogenic agent storage tank 3, and the preparation method of the chromogenic agent solution is as follows: 1 g of the chromogenic agent prepared in Example 1 is added to 100 mL of 37% hydrochloric acid solution and 900 mL of tetrahydrofuran, and stirred uniformly to obtain the chromogenic agent solution;

[0100] (2) The sample to be tested is introduced into the sample buffer tank 2 through the sample pump 1, and kept at 30°C for 20 min;

[0101] (3) After the sample to be tested is kept at a constant temperature, the connecting pipeline between the measuring cell 8 and the sample buffer tank 2 is opened by the sample adding electromagnetic valve 4, and the connecting pipeline between the measuring cell 8 and the chromogenic agent storage tank 3 is opened by the chromogenic agent adding electromagnetic valve 5, 50 mL of the sample to be tested and 0.5 mL of the chromogenic agent solution are accurately moved into the quartz glass measuring cell 8, respectively. The chromogenic agent and the aniline compound in the sample to be tested react to cause the colorimetric value of the test solution to rise. After the reaction is kept at 30°C for 30 min, the colorimetric value of the test solution after the reaction is detected by the colorimeter, and the content of the aniline compound in the sample to be tested is determined by using the working curve (as shown in Table 3 of Example 3) of the colorimetric value and the content of the aniline compound that is preselected and determined. Figure 3

[0102] Example 3

[0103] The working curve is determined by the following process:

[0104] (1) 20 waste brine samples collected at different places and at different times are analyzed by a laboratory analysis test method to determine the content of the aniline compound in the waste brine sample with the lowest aniline compound content (the content of the aniline compound is 0.000028 wt.%), and different contents of aniline are artificially added to the sample. The content of the added aniline is 0-0.0005%, which is distributed in an arithmetic progression, 20 samples with different contents of the aniline compound are obtained, and the laboratory analysis content of the aniline compound in the samples is determined by using the laboratory analysis test method. The linear relationship curve between the true content and the laboratory analysis content of the aniline compound in the sample is as shown in Table 1, and the correlation coefficient R Figure 2 2 = 0.9977, which shows that the laboratory analysis test result can represent the true content of the aniline compound in the waste brine sample.

[0105] (2) The 20 waste brine samples with added aniline in (1) are subjected to colorimetric determination by the on-site detection device, and the detection device and the test steps are consistent with those of Example 2.

[0106] (3) The true content of the aniline compound in the 20 waste brine samples with added aniline in (1) is associated with the colorimetric value detected by the on-site detection device, and the working curve of the content of the aniline compound in the waste brine sample is established by using the partial least squares regression method, as shown in Table 3, and the correlation coefficient R Figure 3 2 = 0.9944, which shows that the colorimetric value can accurately reflect the content of the aniline compound in the waste brine.

[0107] ​​​In addition, using the established working curve, the remaining 19 waste brine samples in (1) were analyzed for aniline compound content using the detection device and test procedure of Example 2, and the aniline compound content obtained by the laboratory analysis test method in (1) was compared. The correlation curve of the two analysis methods is shown in Figure 4 The correlation coefficient R 2 = 0.9888, indicating that the analysis value determined by the detection method of the present application has high accuracy and can meet the actual needs.

[0108] Example 4

[0109] The detection method and detection device related to Examples 2-3 were applied to the determination of aniline compounds in refined waste brine after organic matter removal in the isocyanate production process. The specific steps are as follows:

[0110] (1) Install the on-site detection device described in Example 2 at the designated position corresponding to the specific site of the waste brine and the specific height of the storage tank;

[0111] (2) The color value of the reaction measurement cell collected at each site is transmitted to the PC host, and the PC host analyzes and calculates the content of aniline compounds in the sample using the data and the working curve established in Example 3. The analysis results are transmitted to the DCS screen in the control room, with a test interval of 60 min (or longer), and manual control can also be used for determination;

[0112] (3) When the analyzed aniline compound content is higher than the set alarm value (the set alarm value is 0.0003%), the DCS sends an alarm, and the operator needs to timely switch the high aniline compound content waste brine to the unqualified waste brine tank, and immediately investigate whether the upstream working condition has fluctuated until the analysis value returns to normal and then switch back to the qualified waste brine tank.

[0113] Unless specifically limited, the terms used in the present application have the meanings generally understood by those skilled in the art.

[0114] The embodiments described in the present application are for illustrative purposes only and are not intended to limit the scope of protection of the present application. Those skilled in the art can make various other replacements, changes and improvements within the scope of the present application, and therefore the present application is not limited to the above embodiments, but is limited only by the claims.

Claims

1. A phenylacetaldehyde derivative as shown in formula (1), wherein R1, R2 and R3 are each independently C1-C6 alkyl.

2. The phenylacetaldehyde derivative according to claim 1, characterized in that, R1, R2 and R3 are each independently C1-C4 linear or branched alkyl.

3. The phenylacetaldehyde derivative according to claim 2, characterized in that, R1, R2 and R3 are each independently methyl or ethyl.

4. Process for the preparation of the phenylacetaldehyde derivatives according to any one of claims 1 to 3, characterized in that, comprising the following steps: S1: reacting an alkylchlorosilane as shown in formula (2) with 4-bromo-thioanisole as shown in formula (3) to obtain an intermediate A as shown in formula (4) ; S2: reacting the intermediate A with N, N-dimethylformamide to obtain an intermediate B as shown in formula (5) ; and S3: reacting the intermediate B with ethyl monochloroacetate in the presence of an acid binding agent and a second catalyst in a second organic solvent to obtain the intermediate C, and hydrolyzing the intermediate C under acidic conditions with pH < 3 to obtain the phenylacetaldehyde derivative; wherein R1, R2 and R3 are each independently as defined in any one of claims 1-3, 5. The preparation method according to claim 4, characterized in that, In the step S1, the alkylchlorosilane and 4-bromo-thioanisole are reacted in a first organic solvent in the presence of triethylenediamine and a first catalyst to obtain the intermediate A; the first catalyst is an alkyl lithium catalyst.

6. The preparation method according to claim 5, characterized in that, The first catalyst is n-butyllithium.

7. The preparation method according to claim 5, characterized in that, The first organic solvent is one or more of tetrahydrofuran, dichloromethane and n-hexane.

8. The preparation method according to claim 5, characterized in that, The molar ratio of the alkylchlorosilane, 4-bromo-thioanisole, triethylenediamine and the first catalyst is 1:0.8-1.2:0.8-1.2:0.8-1.

2.

9. The preparation method according to claim 5, characterized in that, The reaction temperature in the step S1 is -20-20℃, and the reaction time is 1-5h.

10. The method of claim 9, wherein, The reaction temperature in the step S1 is -5-5℃.

11. The preparation method according to claim 4, characterized in that, In the step S2, the intermediate A is reacted with N, N-dimethylformamide in the presence of phosphorus oxychloride to obtain the intermediate B.

12. The method of claim 11, wherein, The molar ratio of the intermediate A, N, N-dimethylformamide and phosphorus oxychloride is 1:0.9-1.5:0.8-1.

5.

13. The method of claim 12, wherein, The molar ratio of the intermediate A, N, N-dimethylformamide and phosphorus oxychloride is 1:1-1.3:1-1.

4.

14. The method of claim 11, wherein, The reaction temperature in the step S2 is 60-120℃, and the reaction time is 0.5-5h.

15. The method of claim 14, wherein, The reaction temperature in the step S2 is 75-85℃.

16. The method of claim 4, wherein, In the step S3, the intermediate B is reacted with ethyl monochloroacetate in the presence of an acid binding agent and a second catalyst in a second organic solvent to obtain the intermediate C, and the intermediate C is hydrolyzed under acidic conditions with pH < 3 to obtain the phenylacetaldehyde derivative; the second catalyst is an alkyl halide ammonium catalyst.

17. The method of claim 16, wherein the method further comprises, The second catalyst is tetrabutylammonium bromide.

18. The method of claim 16, wherein, The acid binding agent is one or more of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide.

19. The method of claim 16, wherein, The second organic solvent is one or more of N, N-dimethylformamide, N, N-dimethylacetamide, tetrahydrofuran and dichloromethane.

20. The method of claim 16, wherein, The molar ratio of the intermediate, ethyl monochloroacetate and the second catalyst is 1:1-2:0.01-0.

15.

21. The method of claim 20, wherein, The molar ratio of the intermediate, ethyl monochloroacetate and the second catalyst is 1:1-1.2:0.08-0.

12.

22. The method of claim 16, wherein, The reaction temperature in the step S3 is 15-45℃, and the reaction time is 10-70h.

23. The preparation method according to claim 22, characterized in that, The reaction temperature in step S3 is 20-30℃, and the reaction time is 20-40h.

24. The method of claim 16, wherein, The acid-containing alcohol solution with pH=2-3 is used for adjusting to reach the acidic condition with pH<3.

25. The method of claim 24, wherein, The acid-containing alcohol solution is a methanol solution of sulfuric acid.

26. The method of claim 16, wherein, The hydrolysis is carried out under reflux for 0.5-3h.

27. Use of the phenylacetaldehyde derivative according to any one of claims 1-3 as a chromogenic agent for detecting aniline compounds.

28. A method of detecting the content of an aniline compound, characterized by, The method comprises the following steps: T1: performing a chromogenic reaction of a sample to be tested with a chromogenic agent solution, and determining the colorimetric value after the reaction, wherein the chromogenic agent solution comprises the phenylacetaldehyde derivative according to any one of claims 1-3 as a chromogenic agent; and T2: obtaining the content of aniline compounds in the sample to be tested from the colorimetric value obtained in step T1 by a pre-established working curve of colorimetric value and content of aniline compounds.

29. The method of claim 28, wherein, The sample to be tested is waste brine discharged in the production process of isocyanate, wherein the content of aniline compounds is not more than 0.001wt.% in terms of aniline.

30. The method of claim 29, wherein, The sample to be tested is waste brine discharged in the production process of isocyanate, wherein the content of aniline compounds is not more than 0.0005wt.% in terms of aniline.

31. The method of claim 28, wherein, The sample to be tested is treated at constant temperature at 20-40℃ for 10-30min before the chromogenic reaction; and / or The chromogenic agent solution comprises a third organic solvent, an inorganic acid and the chromogenic agent; the third organic solvent is tetrahydrofuran; the inorganic acid is hydrochloric acid, sulfuric acid or phosphoric acid, and the volume content is 2-20%; the content of the chromogenic agent is 0.05-1wt.%; and / or The volume ratio of the sample to be tested to the chromogenic agent solution is 30-300:1; and / or The reaction temperature of the chromogenic reaction is 20-40℃, and the reaction time is 20-40min.

32. The method of claim 31, wherein, The volume content of the inorganic acid is 8-12%.

33. The method of claim 31, wherein, The content of the chromogenic agent is 0.07-0.1wt.%.

34. The method of claim 31, wherein, The volume ratio of the sample to be tested to the chromogenic agent solution is 70-130:

1.

35. The method of claim 31, wherein, The working curve is established by the following process: aniline compounds, 0.00002-0.001wt.% aniline is added to the sample to be tested to form 15-25 samples with content gradient distribution in the range, and the content of aniline compounds in each sample is determined by N-(1-naphthyl)ethylenediamine azo spectrophotometry; the colorimetric value of each sample is tested by the method of step T1, and the working curve is obtained by correlating the colorimetric value and the content of aniline compounds.

36. The method of claim 28, wherein, The colorimetric value is detected by a colorimeter, which is respectively connected with a sample buffer tank for containing the sample to be tested and a chromogenic agent storage tank for containing the chromogenic agent solution.

37. The method of claim 36, wherein, The chromogenic reaction is carried out in a measuring cell of the colorimeter, and the light path length of the measuring cell is 100-200mm.

38. The method of claim 36, wherein, The material of the measuring cell is one or more of quartz glass, silicate glass and crystal.

39. The method of claim 36, wherein, The colorimeter is respectively connected with the sample buffer tank and the chromogenic agent storage tank through electromagnetic valves.

40. The method of claim 36, wherein, The colorimeter and the sample buffer tank are respectively connected with a waste liquid tank.

41. The method of claim 36, wherein, The colorimeter is an online colorimeter.

42. A method of monitoring waste brine discharge in an isocyanate production process, characterized by, The content data of the anilines in the waste brine is collected by using the method of any one of claims 28-41 every certain time interval, and the obtained content data is compared with the preset maximum limit content of the anilines, so as to monitor whether the discharge of the waste brine meets the standard.

43. The monitoring method of claim 42, wherein, The interval time is 60-90 min.

44. The monitoring method of claim 42, wherein, The maximum limit content of the anilines is 0.0003 wt. %. The colorimeter is an online colorimeter. The content data of the anilines in the waste brine is collected by using the method of any one of claims 28-41 every certain time interval, and the obtained content data is compared with the preset maximum limit content of the anilines, so as to monitor whether the discharge of the waste brine meets the standard. The interval time is 60-90 min. The maximum limit content of the anilines is 0.0003 wt. %.

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