Phenylacetaldehyde derivative, preparation method and application thereof, and method for detecting content of aniline compound

Abstract

The invention provides a phenylacetaldehyde derivative as shown in a formula (1). The invention also provides a preparation method of the phenylacetaldehyde derivative and application of the phenylacetaldehyde derivative as a color developing agent for detecting aniline compounds. The invention further provides a method for detecting the content of aniline compounds and a method for monitoring waste brine discharge in the isocyanate production process. The phenylacetaldehyde derivative provided by the invention has relatively strong color development capability, and even if the content of aniline compounds is extremely low, the phenylacetaldehyde derivative can quickly react and show obvious change of chromaticity. The detection method provided by the invention is simple and convenient to operate, does not need expensive detection instruments, is accurate and reliable in detection result and low in detection limit, and can realize online detection and analysis. According to the monitoring method provided by the invention, data of different emission sites can be collected in real time, and the process operation condition can be judged in time, so that abnormal working conditions can be handled in time, downstream accidents are avoided, the production safety is improved, and environmental protection is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of chemical analysis and detection, and in particular to a phenylacetaldehyde derivative and a preparation method thereof and use thereof as a color developer. The present invention also relates to a method for detecting the content of aniline compounds. The present invention further relates to a method for monitoring the discharge of waste brine in an isocyanate production process. Background Art

[0002] Isocyanate is an important raw material for polyurethane (PU) materials. It is obtained by condensing aniline substances with formaldehyde under acidic conditions, and then undergoing a series of refining processes to obtain the amine corresponding to isocyanate (i.e., polymethylene polyphenyl polyamine, referred to as polyamine), which is then subjected to 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] Since the condensation reaction liquid contains a large amount of acid, alkaline solutions such as sodium hydroxide are usually added during the refining process for neutralization, resulting in waste brine containing a large amount of polyamines. After the waste brine is treated by the deamine process, there are many treatment methods such as external discharge, chlor-alkali recycling, and biochemical bacterial decomposition. Aniline substances are biologically toxic and have a destructive effect on chlor-alkali electrolytic membranes. Regardless of which of the above treatment methods is adopted, specific content control requirements for aniline substances are required. Therefore, strictly controlling the effect of the deamine process to prevent the aniline substances in the final brine from exceeding the standard is of great significance to downstream brine treatment and system stability.

[0006] At present, the determination of aniline compounds is divided into two categories: spectroscopic method and chromatographic method; the spectroscopic method is mainly based on the national standard "Water Quality-Determination of Aniline Compounds-N-(1-Naphthyl)ethylenediamine Azo Spectrophotometric Method" (GB 11889-89), while the chromatographic method is based on the national standard "Water Quality-Determination of Aniline Compounds-Gas Chromatography-Mass Spectrometry"

[0007] (HJ 822-2017), in addition to liquid chromatography, fluorescence spectroscopy and other determination methods. However, these methods are all offline laboratory determinations, requiring manual sample delivery and professional analysis. The time from device sampling to laboratory analysis results generally takes more than 2 hours, and it cannot immediately characterize the device status at the moment of sampling, delaying the time for troubleshooting. In addition, the spectroscopic method has simple instrument requirements, but it still requires the preparation of diazotization reagents, color developers, reducing agents and other reagents in advance, and the color development process is cumbersome, requiring manual adjustment of reaction conditions, and high technical requirements for personnel; the chromatographic method requires expensive chromatographic instruments, high analysis costs, and poor tolerance to high-salt samples. The instrument itself requires professional maintenance.

[0008] A Chinese patent (CN 112161972B) discloses a test paper set for rapid graded quantitative detection of the content of primary aromatic amines in an acidic solution and its application, which adopts a test paper visual method and uses a color developer p-dimethylaminobenzaldehyde to estimate the primary aromatic amines in an acidic system. However, the detection method provided by the patent is only applicable to the content interval estimation of aniline compound solutions above 0.01%, and the test accuracy is poor. For waste brine after amine removal treatment, the content of aniline compounds (in terms of aniline) is <0.001%, generally <0.0003%), and the detection method provided by the patent is difficult to apply. There may be two main reasons: first, the color developer p-dimethylaminobenzaldehyde solution used is yellow because the amine group is easily oxidized, which is easy to interfere with the test results at low content; second, the color change is not strong at the low content (<0.001%) level, and the precision of visual estimation is poor.

[0009] In summary, there is an urgent need to develop a detection method suitable for detecting low levels of aniline compounds in waste brine, so as to achieve online analysis and detection with high detection sensitivity and to monitor the discharge of waste brine in real time. Summary of the invention

[0010] To remedy the deficiencies in the prior art, an object of the present invention is to provide a phenylacetaldehyde derivative which can be used as a new color developer for detecting aniline compounds, and is particularly suitable for samples with very low aniline compound content, such as waste brine produced by steps such as amine removal during the production of isocyanate.

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

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

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

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

[0015]

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

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

[0018] In some preferred embodiments, R1, R2 and R3 can each independently be a C1-C4 straight chain or branched alkyl group (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc. alkyl group). In some more preferred embodiments, R1, R2 and R3 can each independently be a methyl or ethyl group.

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

[0020] S1: an alkylchlorosilane as shown in formula (2) reacts with 4-bromothioanisole as shown in formula (3) to prepare an intermediate A as shown in formula (4);

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

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

[0023] Wherein, R1, R2 and R3 are each independently as defined in the above technical solution;

[0024]

[0025] In the preparation method provided by the present invention, each raw material or reagent can be a commercial product, or can be prepared by itself with reference to the existing technology.

[0026] In the preparation method provided by the present invention, in the step S1, the alkylchlorosilane and 4-bromothioanisole can react 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, such as n-butyl lithium. The first catalyst can be added in the form of a pure substance, or dissolved in a solvent to form a solution. For example, it can be added to the reaction system in the form of a n-hexane solution of n-butyl lithium.

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

[0029] In some preferred embodiments, the molar ratio of the alkylchlorosilane, 4-bromothioanisole, triethylenediamine and the first catalyst may 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-bromothioanisole, triethylenediamine and the first catalyst may 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 may be -20 to 20°C, and the reaction time may be 1 to 5 hours. In some more preferred embodiments, the reaction temperature in step S1 may be -5 to 5°C (e.g., 0°C), and the reaction time may be 2 to 3 hours.

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

[0032] In the preparation method provided by the present invention, in the step S2, the intermediate A and N,N-dimethylformamide can react 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 may be 60-120° C., and the reaction time may be 0.5-5 h. In some more preferred embodiments, the reaction temperature in step S2 may be 75-85° C. (e.g., 80° C.), and the reaction time may be 2-4 h.

[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, that is, intermediate B. The pH value can be adjusted using an alkali solution, such as an aqueous solution of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate and the like.

[0036] In the preparation method provided by the present invention, in the step S3, the intermediate B and ethyl monochloroacetate can react 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 of pH <3 to obtain the phenylacetaldehyde derivative.

[0037] In some preferred embodiments, the second catalyst may be an alkylammonium halide catalyst, such as tetrabutylammonium bromide.

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

[0039] In some preferred embodiments, the second organic solvent may 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 may 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 may be 1:1-1.2:0.08-0.12.

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

[0042] In some preferred embodiments, in step S3, an acid-containing alcohol solution with a pH of 2 to 3 may be used for adjustment to achieve an acidic condition of pH < 3. In some more preferred embodiments, the acid-containing alcohol solution is a methanol solution of sulfuric acid.

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

[0044] In some preferred embodiments, after the hydrolysis process is completed, an alkali solution (such as an aqueous solution of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, etc.) can be used to adjust the pH to neutral (such as about 7), and an organic solvent (such as dichloromethane) can be used for extraction. After the extract is dried (such as dried over anhydrous sodium sulfate), the organic solvent is removed to obtain the target product, i.e., the phenylacetaldehyde derivative.

[0045] The third aspect of the present invention provides the use of the phenylacetaldehyde derivative described in any one of the above technical solutions as a color developer for detecting aniline compounds.

[0046] The phenylacetaldehyde derivatives of the present invention can react rapidly with aniline compounds under acidic conditions (taking aniline as an example, the reaction formula is shown below), and can show obvious chromaticity changes even at extremely low concentrations, so they are very suitable for use as color developers for detecting aniline compounds.

[0047]

[0048] The aniline compounds described in the present invention are a general term for aniline and a class of compounds containing aniline structural fragments, and their content is usually referred to as aniline content. For example, the content of aniline compounds measured in GB / T 11889-1989 is referred to as aniline content.

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

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

[0051] T2: The content of aniline compounds in the sample to be tested is obtained from the chromaticity value obtained in step T1 by using a pre-established working curve of chromaticity value and aniline compound content.

[0052] In some preferred embodiments, the sample to be tested may be waste brine discharged during the production of isocyanate, wherein the content of aniline compounds in the sample to be tested is no more than 0.001 wt.% calculated as aniline. In some more preferred embodiments, the content of aniline compounds in the sample to be tested is no more than 0.0005 wt.%, for example, no more than 0.0003 wt.%, calculated as aniline.

[0053] In some preferred embodiments, the sample to be tested may be treated at a constant temperature of 20 to 40° C. for 10 to 30 minutes before the color development reaction.

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

[0055] In some preferred embodiments, the volume ratio of the sample to be tested to the developer solution may be 30 to 300: 1. In some more preferred embodiments, the volume ratio of the sample to be tested to the developer solution may be 70 to 130:1.

[0056] In some preferred embodiments, the reaction temperature of the color development reaction may be 20 to 40° C., preferably the same as the temperature during the constant temperature treatment, and the reaction time of the color development reaction may be 20 to 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 not exceeding 0.00005wt.% (preferably not exceeding 0.00003wt.%), adding different amounts of aniline thereto, forming 15 to 25 (for example, 20) samples with a content gradient distribution within the range of 0.00002 to 0.001wt.% (preferably 0.00005 to 0.0005wt.%), and using N-(1-naphthyl)ethylenediamineazo spectrophotometry to determine the aniline compound content in each sample; testing the chromaticity value of each sample by the method of step T1, and correlating the chromaticity value with the aniline compound content to obtain the working curve. In some more preferred embodiments, a working curve of chromaticity value and aniline compound content can be established by partial least squares regression.

[0058] In some preferred embodiments, a colorimeter can be used to detect the chromaticity value described in step T1. The colorimeter is respectively connected to a sample buffer tank for containing the sample to be tested and a color developer storage tank for containing the color developer solution. The sample buffer tank can also be used to perform constant temperature treatment on the sample to be tested.

[0059] In some preferred embodiments, the color development reaction is carried out in the measuring cell of the colorimeter, the sample to be tested is sent from the sample buffer tank into the measuring cell of the colorimeter, and the developer solution is sent from the developer storage tank into the measuring cell of the colorimeter, and the two undergo a color development reaction therein. A light source and a detector are arranged outside the measuring cell, and the light path runs through the measuring cell. In some more preferred embodiments, the light path length can be 100 to 200 mm.

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

[0061] In some preferred embodiments, the colorimeter is connected to the sample buffer tank and the developer storage tank via electromagnetic valves, respectively.

[0062] In some preferred embodiments, the colorimeter and the sample buffer tank are also connected to a waste liquid tank respectively, and the reaction liquid after the color development reaction and the remaining sample to be tested 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 achieved by using an online colorimeter, and the colorimetric value can be transmitted to the analysis system through an optical cable. The working curve of the colorimetric value and the content of the aniline compound can be pre-stored in the analysis system, and automatic analysis can be achieved according to the colorimetric value, thereby obtaining the detection value. The analysis system can be a PC host, which can be set in a control room far away from the detection site. One analysis system can also be used for multiple different detection sites at the same time.

[0064] The fifth aspect of the present invention provides a method for monitoring the discharge of waste brine during the production of isocyanate. The content data of aniline compounds in the waste brine is collected at regular intervals using the detection method described in any one of the above technical solutions, and the obtained content data is compared with the preset maximum limit content of aniline compounds, thereby monitoring whether the discharge of the waste brine meets the standards.

[0065] In some preferred embodiments, the interval time of data collection may be 60 to 90 minutes, and may also be set according to actual working conditions.

[0066] In some preferred embodiments, the maximum content limit of the aniline compound is 0.0003 wt.% to ensure that the emission standards are met.

[0067] In the monitoring method provided by the present invention, the content data of the monitored location can be transmitted to the DCS screen of the control room by wired or wireless means through the PC host, and the DCS high limit alarm can be set at the same time.

[0068] The monitoring method provided by the present invention can timely monitor the removal effect of aniline compounds in the production process, and can enable operators to respond quickly when indicators in the discharged waste brine are abnormal, thereby avoiding the occurrence of biochemical system collapse, environmental protection indicator abnormalities and the like in the downstream.

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

[0070] (1) The phenylacetaldehyde derivative provided by the present invention has a novel structure. Through the optimization and adjustment of the functional groups, the color development ability is greatly improved. Even at extremely low content of aniline compounds, it can react quickly and show obvious changes in color. Therefore, it can be used as a new and efficient color developer for the detection of aniline compounds.

[0071] (2) The phenylacetaldehyde derivatives provided by the present invention have a simple preparation process, cheap and readily available raw materials, mild reaction conditions, and no need for a complicated purification process, and are therefore very suitable for industrial-scale production and application.

[0072] (3) The detection method provided by the present invention is easy to operate, has a fast detection speed, does not require expensive instruments and equipment, and has accurate and reliable detection results, and has a lower detection limit. In addition, compared with conventional laboratory offline analysis detection methods, the detection method provided by the present invention can achieve on-site sampling and color development, online analysis of colorimetric values ​​and corresponding detection results, so it does not need to be completed entirely in the laboratory, has good timeliness and avoids a large amount of manpower loss.

[0073] (4) The monitoring method provided by the present invention can collect data from different waste brine discharge locations in real time and promptly judge the process operation status, which is convenient for timely handling of abnormal operating conditions, avoiding the occurrence of downstream accidents, improving production safety, and is also beneficial to environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 It is a schematic structural diagram of the on-site detection device for aniline compounds in Example 2;

[0075] The accompanying drawings are marked as follows: 1. sampling pump; 2. sample buffer tank; 3. color developer storage tank; 4. sample addition solenoid valve; 5. color developer addition solenoid valve; 6. light source; 7. detector; 8. measuring cell; 9. optical path; 10. waste liquid tank.

[0076] Figure 2 This is a correlation curve between the actual content of aniline compounds in the waste brine sample in Example 3 and the content tested by laboratory analysis.

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

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

[0079] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments.

[0080] Unless otherwise specified, the raw materials or reagents used in the examples of the present invention are commercially available products.

[0081] The percentages used in the embodiments of the present invention are all by mass unless otherwise specified.

[0082] The "laboratory analysis test method" used in the embodiments of the present invention is the national standard GB / T11889-1989, namely "Water quality - Determination of aniline compounds - N-(1-naphthyl)ethylenediamine azo spectrophotometry", to determine the content of aniline compounds in waste brine, and the analytical instrument used is the Cary 100 UV-visible spectrophotometer from Agilent, USA.

[0083] Example 1 Preparation of developer

[0084] (1) Synthesis of intermediate A

[0085] Weigh 0.2 mol trimethylsilyl chloride, 0.2 mol 4-bromothioanisole and 0.2 mol triethylenediamine, dissolve in 350 mL tetrahydrofuran, add 80 mL 2.5 M n-butyl lithium n-hexane solution, control the temperature to 0°C, react for 2 hours, add water to quench and terminate the reaction; extract the precipitate with n-hexane for 3 times, then dry with anhydrous sodium sulfate, remove n-hexane by vacuum rotary evaporation, and obtain intermediate A, with a reaction conversion rate of 87%. The reaction formula is as follows:

[0086]

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

[0088] (2) Synthesis of intermediate B

[0089] Weigh 0.15 mol of intermediate A, 0.15 mol of N,N-dimethylformamide and 0.15 mol of phosphorus oxychloride, react at 80°C for 3 hours, add sodium hydroxide aqueous solution (NaOH concentration is 10 wt.%) dropwise to adjust the pH to 4, rinse the precipitate with pure water and filter it three times, filter and dry it to obtain intermediate B, and the reaction conversion rate is 90%. The reaction formula is as follows:

[0090]

[0091] 1 H NMR (DMSO-d6, 300MHz): 0.21 (s, 9H), 2.12 (s, 2H), 7.57 (d, J = 14.4Hz, 2H), 7.75 (d, J = 14.4Hz, 2H), 9.89 (s, 1H).

[0092] (3) Synthesis of color developer from intermediate B

[0093] Weigh 0.1mol of intermediate B, 0.1mol of ethyl monochloroacetate and 0.01mol of tetrabutylammonium bromide, add 100mL of anhydrous tetrahydrofuran to dilute, add 0.01mol of potassium carbonate, and react at room temperature for 30h; after the reaction is completed, add sulfuric acid methanol solution with pH=2-3 to the reaction system to adjust the pH to <3.0, heat reflux and hydrolyze for 2h, add 10wt.% sodium hydroxide solution after the hydrolysis is completed to adjust the pH to neutral, extract the reaction system with 45mL of dichloromethane three times, remove moisture with anhydrous sodium sulfate, and vacuum rotary evaporation 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, 300MHz): 0.21 (s, 9H), 2.12 (s, 2H), 7.28 (d, J = 14.4Hz, 2H), 7.34 (d, J = 14.4Hz, 2H), 3.66 (d, J = 6.5Hz, 2H), 9.72 (t, J = 6.5Hz, 1H).

[0096] Example 2

[0097] The on-site detection device used in this embodiment is as follows Figure 1 As shown, a sampling pump 1 is connected to a sample buffer tank 2 for conveying a sample to be tested; the sample buffer tank 2 and a color developer storage tank 3 are respectively connected to a measuring cell 8 of an online colorimeter (model: Optek C4000-AF26-VB-PV, including a light source 6, a detector 7 and an optical path 9 formed therebetween) through a sample addition solenoid valve 4 and a color developer addition solenoid valve 5, for conveying the sample to be tested and the color developer solution to the colorimeter, respectively, and determining the content of aniline compounds (in terms of aniline) in the sample to be tested by causing the color of the test solution to change due to the reaction between the sample to be tested and the color developer; the colorimeter is connected to a waste liquid tank 10 for discharging waste liquid after detection; the waste liquid 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 liquid tank 10.

[0098] The test steps are as follows:

[0099] (1) Adding a prepared developer solution to the developer storage tank 3 in advance, the developer solution is prepared by adding 1 g of the developer prepared in Example 1 to 100 mL of 37% hydrochloric acid solution and 900 mL of tetrahydrofuran, and stirring until uniform;

[0100] (2) Introducing the sample to be tested into the sample buffer tank 2 through the sampling pump 1, and maintaining it at a constant temperature of 30° C. for 20 min;

[0101] (3) After the sample is kept at a constant temperature, the connecting pipeline between the measuring cell 8 and the sample buffer tank 2 is opened through the sample addition solenoid valve 4, and the connecting pipeline between the measuring cell 8 and the developer storage tank 3 is opened through the developer addition solenoid valve 5, and 50 mL of the sample and 0.5 mL of the developer solution are accurately transferred into the quartz glass measuring cell 8. The developer reacts with the aniline compound in the sample to be tested, causing the chromaticity of the test solution to increase. After the reaction is kept at a constant temperature of 30°C for 30 minutes, the chromaticity value of the test solution after the reaction is detected by a colorimeter, and then the chromaticity value and the aniline compound content are determined by the pre-selected working curve (such as the working curve of Example 3). Figure 3 The content of aniline compounds in the sample to be tested can be determined.

[0102] Example 3

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

[0104] (1) Collect 20 waste brine samples from different locations and at different times, analyze the content of aniline compounds in the samples using laboratory analysis and testing methods, determine the waste brine sample with the lowest aniline compound content (wherein the aniline compound content is 0.000028wt.%), artificially add different amounts of aniline to the sample, the added aniline content is 0-0.0005%, respectively, in an arithmetic progression distribution, and obtain a group of 20 samples containing different aniline compound contents. Use laboratory analysis and testing methods to determine the laboratory analysis content of aniline compounds in the group of samples. The linear relationship curve between the actual content of aniline compounds in the sample and the laboratory analysis content is shown in the figure below: Figure 2 As shown, the correlation coefficient R 2 =0.9977, which shows that the laboratory analysis test results can characterize the actual content of aniline compounds in the waste brine samples.

[0105] (2) The 20 waste brine samples to which aniline was added in (1) were subjected to colorimetric measurement using an on-site detection device. The detection device and test steps were consistent with those in Example 2.

[0106] (3) The actual content of aniline compounds in the 20 waste brine samples to which aniline was added in (1) was correlated with the chromaticity value detected by the on-site detection device, and the partial least squares regression method was used to establish a working curve for the content of aniline compounds in the waste brine samples, such as Figure 3 As shown, the correlation coefficient R 2 =0.9944, it can be seen that the chromaticity value can accurately reflect the content of aniline compounds in the waste brine.

[0107] In addition, using the working curve established above, the detection device and test steps of Example 2 were used to analyze the content of aniline compounds in the remaining 19 waste brine samples in (1), and compared with the content of aniline compounds obtained by the laboratory analysis test method in (1). The correlation curves of the two analysis methods are as follows: Figure 4 As shown, the correlation coefficient R 2 =0.9888, indicating that the analytical value determined by the detection method of the present invention has high accuracy and can meet actual needs.

[0108] Example 4

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

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

[0111] (2) The chromaticity values ​​of the post-reaction measuring pool collected at each point are transmitted to a PC host, which uses the data and the working curve established in Example 3 to analyze and calculate the content of aniline compounds in the sample. The analysis results are transmitted to the DCS screen in the control room. The test interval is 60 minutes (or longer), and the measurement can also be manually controlled;

[0112] (3) When the analyzed aniline compound content is higher than the set alarm value (the set alarm value is 0.0003%), the DCS will issue an alarm, and the operator must promptly switch the waste brine with high aniline compound content to the unqualified waste brine tank, and immediately check whether the upstream operating conditions fluctuate. The operator can only switch it back to the qualified waste brine tank after the analysis value returns to normal.

[0113] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

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

Claims

1. A phenylacetaldehyde derivative represented by formula (1), in, R1, R2 and R3 are each independently a C1-C6 alkyl group, preferably a C1-C4 straight-chain or branched alkyl group, and more preferably a methyl group or an ethyl group.

2. The method for preparing the phenylacetaldehyde derivative according to claim 1, characterized in that: The following steps are involved: S1: The alkylchlorosilane represented by formula (2) reacts with 4-bromothioanisole represented by formula (3) to obtain an intermediate A represented by formula (4); S2: the intermediate A reacts with N,N-dimethylformamide to obtain the intermediate B as shown in formula (5); and S3: the intermediate B reacts with ethyl monochloroacetate to obtain an intermediate C as shown in formula (6), and the intermediate C is hydrolyzed to obtain the phenylacetaldehyde derivative; wherein R1, R2 and R3 are each independently as defined in claim 1; 3. The preparation method according to claim 2, characterized in that: In the step S1, the alkylchlorosilane reacts with 4-bromothioanisole in the presence of triethylenediamine and a first catalyst in a first organic solvent to obtain the intermediate A; Preferably, the first catalyst is an alkyl lithium catalyst, more preferably n-butyl lithium; Preferably, the first organic solvent is one or more of tetrahydrofuran, dichloromethane, and n-hexane; Preferably, the molar ratio of the alkylchlorosilane, 4-bromothioanisole, triethylenediamine and the first catalyst is 1:0.8-1.2:0.8-1.2:0.8-1.2; Preferably, the reaction temperature in step S1 is -20 to 20°C, more preferably -5 to 5°C, and the reaction time is 1 to 5 hours.

4. The preparation method according to claim 2 or 3, characterized in that: In the step S2, the intermediate A reacts with N,N-dimethylformamide in the presence of phosphorus oxychloride to obtain the intermediate B; Preferably, the molar ratio of the intermediate A, N,N-dimethylformamide and phosphorus oxychloride is 1:0.9-1.5:0.8-1.5, more preferably 1:1-1.3:1-1.4; Preferably, the reaction temperature in step S2 is 60-120° C., more preferably 75-85° C.; and the reaction time is 0.5-5 h.

5. The preparation method according to any one of claims 2 to 4, characterized in that: In the step S3, the intermediate B reacts 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 an acidic condition of pH <3 to obtain the phenylacetaldehyde derivative; Preferably, the second catalyst is an alkylammonium halide catalyst, more preferably tetrabutylammonium bromide; Preferably, the acid binding agent is one or more of sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide; Preferably, the second organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and dichloromethane; Preferably, the molar ratio of the intermediate, ethyl monochloroacetate and the second catalyst is 1:1-2:0.01-0.15, more preferably 1:1-1.2:0.08-0.12; Preferably, the reaction temperature in step S3 is 15 to 45° C., more preferably 20 to 30° C., and the reaction time is 10 to 70 hours, more preferably 20 to 40 hours; Preferably, an acidic alcohol solution with a pH of 2 to 3 is used for adjustment to achieve an acidic condition of pH < 3; more preferably, the acidic alcohol solution is a methanol solution of sulfuric acid; Preferably, the hydrolysis is carried out under reflux for 0.5 to 3 h.

6. Use of the phenylacetaldehyde derivative according to claim 1 as a color developing agent for detecting aniline compounds.

7. A method for detecting the content of aniline compounds, characterized in that: The following steps are involved: T1: subjecting the sample to be tested to a color reaction with a color developer solution, and determining the colorimetric value after the reaction, wherein the color developer solution contains the phenylacetaldehyde derivative according to claim 1 as a color developer; as well as T2: using a pre-established working curve of chromaticity value and aniline compound content, the chromaticity value obtained in step T1 is used to calculate the content of aniline compounds in the sample to be tested; Preferably, the sample to be tested is waste brine discharged during the production of isocyanate, wherein the content of aniline compounds calculated as aniline is no more than 0.001 wt.%, preferably no more than 0.0005 wt.%.

8. The method according to claim 7, characterized in that The sample to be tested is treated at a constant temperature of 20 to 40° C. for 10 to 30 minutes before the color development reaction; and / or The developer solution comprises a third organic solvent, an inorganic acid and the developer; preferably, the third organic solvent is tetrahydrofuran; the inorganic acid is hydrochloric acid, sulfuric acid or phosphoric acid, and its volume content is 2-20%, preferably 8-12%; the content of the developer is 0.05-1wt.%, preferably 0.07-0.1wt.%; and / or The volume ratio of the sample to be tested to the developer solution is 30 to 300:1, more preferably 70 to 130:1; and / or The reaction temperature of the color development reaction is 20-40°C, and the reaction time is 20-40min; Preferably, the working curve is established by the following process: A sample to be tested with an aniline compound content not exceeding 0.00005wt.% is taken, and different amounts of aniline are added thereto to form 15 to 25 samples with a content gradient distribution within a range of 0.00002 to 0.001wt.% (preferably 0.00005 to 0.0005wt.%), and the content of the aniline compound in each sample is determined by N-(1-naphthyl)ethylenediamineazo spectrophotometry; the chromaticity value of each sample is tested by the method of step T1, and the chromaticity value and the content of the aniline compound are correlated to obtain the working curve.

9. The method according to claim 7 or 8, characterized in that: Using a colorimeter to detect the chromaticity value, the colorimeter is respectively connected to a sample buffer tank for containing the sample to be tested and a developer storage tank for containing the developer solution; Preferably, the color development reaction is carried out in a measuring cell of the colorimeter, and the optical path length of the measuring cell is 100 to 200 mm; Preferably, the material of the measuring cell is one or more of quartz glass, silicate glass, and crystal; Preferably, the colorimeter is connected to the sample buffer tank and the developer storage tank respectively through electromagnetic valves; Preferably, the colorimeter and the sample buffer tank are also connected to a waste liquid tank respectively; Preferably, the colorimeter is an online colorimeter.

10. A method for monitoring the discharge of waste brine in an isocyanate production process, characterized in that: Collecting the content data of aniline compounds in the waste brine at regular intervals using the method described in any one of claims 7 to 9, and comparing the obtained content data with the preset maximum limit content of aniline compounds, thereby monitoring whether the discharge of the waste brine meets the standards; Preferably, the interval time is 60 to 90 minutes; and / or Preferably, the maximum limit content of the aniline compound is 0.0003 wt.%.

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