Method for determining aldehyde compounds in epoxypropane

Abstract

The invention discloses a method for determining aldehyde compounds in epoxypropane, which belongs to the field of liquid chromatography detection, and is characterized by comprising the following four steps: step 1, equipment selection: a high performance liquid chromatograph is provided with a UV detector, step 2, standard curve drawing: (formaldehyde, acetaldehyde and propionaldehyde), step 3, formaldehyde, acetaldehyde and propionaldehyde content determination in a sample, and step 4, aldehyde compound content determination. And 4, taking the to-be-detected solution and the blank solution epoxypropane as important chemical raw materials, solving the problems of low response, incomplete analysis types and low formaldehyde gas chromatography accuracy of the existing gas chromatography for detecting aldehydes, and being mainly applied to the aspect of detecting aldehyde compounds in epoxypropane.

Description

Technical Field

[0001] The invention relates to the field of analysis and detection, and in particular to a method for determining aldehyde compounds in propylene oxide. Background Art

[0002] As an important propylene derivative, propylene oxide plays an important role in industrial production. About 7% of propylene is used in the production of propylene oxide each year. Its production processes mainly include chlorohydrinization, co-oxidation (also known as indirect oxidation) and direct oxidation.

[0003] In today's world, the main industrial production methods of propylene oxide are chlorohydrinization and co-oxidation. The co-oxidation method can be further divided into ethylbenzene co-oxidation and isobutane co-oxidation. It is worth mentioning that in recent years, the cumene oxidation method and the direct oxidation method with hydrogen peroxide have been successfully developed and gradually realized industrial production, and the direct oxidation method using oxygen as the oxidant is also in the process of development.

[0004] The direct hydrogen peroxide oxidation method (HPPO method) is a new process for preparing propylene oxide by catalyzing the epoxidation of propylene with hydrogen peroxide (hydrogen peroxide). In this production process, only propylene oxide and water are generated, which has the advantages of simple process flow and high product yield, and no other related products are produced, which basically does not cause pollution. Our company uses the direct hydrogen peroxide oxidation method (HPPO method) as a process technology, however, formaldehyde, acetaldehyde, propionaldehyde, methylal and other by-products will be produced during the chain reaction.

[0005] Total aldehyde content is a key indicator of propylene oxide product specifications. In the production process of polyether, a downstream product of propylene oxide, if the total aldehyde content is too high, it will not only have a significant inhibitory effect on the reaction, but also cause the color of the polyether to darken and be accompanied by a foul odor. At the same time, it will also increase the toxicity of the polyether and reduce the strength of the polyurethane resin, a downstream product of the polyether. In recent years, with the continuous development of high-grade polyether, a downstream product of propylene oxide, users' quality requirements for propylene oxide have also been further improved, which is mainly reflected in the total aldehyde mass fraction in propylene oxide must be less than 0.005%. Summary of the invention

[0006] Purpose of the invention: At present, the gas chromatography method specified by the national standard has many shortcomings in the determination of aldehydes. On the one hand, its response value is low, and on the other hand, the types of aldehydes that can be analyzed are not comprehensive, especially when determining formaldehyde, the accuracy of gas chromatography is poor. In view of this, in order to accurately determine the aldehyde substances in propylene oxide, we have conducted improved research on the analysis method of propylene oxide aldehydes based on a large amount of relevant information, and are committed to developing a new analysis method that needs to have high accuracy and good repeatability.

[0007] To achieve the above object, the present invention adopts the following technical scheme: the liquid chromatography detection method of aldehydes in propylene oxide comprises reacting a set of standard solutions of formaldehyde, acetaldehyde and propionaldehyde and a sample to be tested with p-nitrobenzyloxyamine (PNBA) to form corresponding oxime derivatives. The oxime derivatives in the test solution are analyzed by high performance liquid chromatography using a 280nm UV detector. The technical problem of determining aldehyde substances in propylene oxide is achieved.

[0008] The specific technical solutions of the present invention are as follows:

[0009] A method for determining aldehyde compounds in propylene oxide, characterized in that it comprises the following steps:

[0010] Step 1: Equipment selection: High performance liquid chromatograph equipped with UV detector.

[0011] Instrument parameters: See the table below:

[0012]

[0013]

[0014] Step 2: Drawing of standard curve: (formaldehyde, acetaldehyde, propionaldehyde)

[0015] ① Standard stock solution 1# of each standard:

[0016] Weigh known amounts of formaldehyde, acetaldehyde, and propionaldehyde to an accuracy of 0.1 mg and add them to water to obtain a standard solution of each component at 1000 mg / L.

[0017] ②Standard stock solution 2# of each standard:

[0018] Dilute the 1000 mg / L standard solution 10 times to obtain a 100 mg / L standard solution.

[0019] ③Pipette standard stock solution 2# separately:

[0020] 0mL, 1mL, 10mL, 20mL, and 50mL were placed in 6 100mL volumetric flasks respectively, and diluted to the scale with pure water to prepare standard working solutions containing 0mg / L, 1mg / L, 10mg / L, 20mg / L, and 50mg / L of aldehyde respectively.

[0021] ④ Use a pipette to transfer 5 mL of PNBA solution and 1 mL of 10 mg / L standard solution into a 10 mL brown screw-cap sample bottle. Seal the bottle and mix well using ultrasonic oscillation.

[0022] ⑤ Place the above samples at room temperature for half an hour before testing.

[0023] ⑥ 0mg / L, 1mg / L, 20mg / L, 50mg / L and other standard solutions are prepared in the same way as steps ④ and ⑤ and tested.

[0024] ⑦ The above standard samples were filtered through membrane filters (0.45 μm) and tested according to the standard operating procedures, operating conditions and instrument parameters of the HPLC instrument. The signal peak areas of different concentrations were obtained from the chromatographic results.

[0025] Step 3: Determination of formaldehyde, acetaldehyde, and propionaldehyde content in the sample: Pipette 5 mL of PNBA solution and 1 mL of the test object into a 10 mL brown screw-cap sample bottle, seal it, and mix it evenly with ultrasonic oscillation to use as the test solution. The solution is placed at room temperature for more than half an hour before measurement. Blank sample: Pipette 5 mL of PNBA solution and 1 mL of pure water into a 10 mL brown screw-cap sample bottle, seal it, and mix it evenly with ultrasonic oscillation to use as the blank sample.

[0026] Step 4: Filter the test solution and blank solution with a filter membrane (0.45 μm) and perform the test according to the standard operating procedures of the HPLC instrument and the operating conditions according to the instrument parameters. The signal peak areas of different concentrations are obtained from the spectrum results.

[0027] The present invention has the following beneficial effects:

[0028] In the process of high performance liquid chromatography detecting aldehyde compounds of propylene oxide, the corresponding oxime derivatives are formed by the reaction of aldehyde compounds with p-nitrobenzyloxyamine (PNBA). For example, formaldehyde reacts with (PNBA) to generate oxime derivatives with ultraviolet absorption, and a 280nm UV detector is used to analyze the oxime derivatives in the test solution, which significantly improves the accuracy and reliability of the detection. However, when analyzing low-concentration formaldehyde in gas chromatography, the response value of formaldehyde in the F ID detector is low, and it is difficult to accurately detect the results. In summary, liquid chromatography has achieved remarkable beneficial results in detecting propylene oxide aldehyde compounds (especially formaldehyde), providing strong technical support for devices, etc.

[0029] The testing method of the present invention is simple and efficient, suitable for operation in different laboratories, and has good economic effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Draw a calibration curve for the formaldehyde mentioned in the present invention;

[0031] Figure 2 Draw a calibration curve for acetaldehyde mentioned in the present invention;

[0032] Figure 3 Draw a calibration curve for the propionaldehyde mentioned in the present invention;

[0033] Figure 4 The spectrum of formaldehyde, acetaldehyde and propionaldehyde in the sample mentioned in the present invention; DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0035] A method for determining aldehyde compounds in propylene oxide, characterized in that it comprises the following steps:

[0036] Step 1: Equipment selection: High performance liquid chromatograph equipped with UV detector.

[0037] Instrument parameters: See the table below:

[0038]

[0039] Step 2: Drawing of standard curve: (formaldehyde, acetaldehyde, propionaldehyde)

[0040] ① Standard stock solution 1# of each standard:

[0041] Weigh known amounts of formaldehyde, acetaldehyde, and propionaldehyde to an accuracy of 0.1 mg and add them to water to obtain a standard solution of each component at 1000 mg / L.

[0042] ②Standard stock solution 2# of each standard:

[0043] Dilute the 1000 mg / L standard solution 10 times to obtain a 100 mg / L standard solution.

[0044] ③Pipette standard stock solution 2# separately:

[0045] 0mL, 1mL, 10mL, 20mL, and 50mL were placed in 6 100mL volumetric flasks respectively, and diluted to the scale with pure water to prepare standard working solutions containing 0mg / L, 1mg / L, 10mg / L, 20mg / L, and 50mg / L of aldehyde respectively.

[0046] ④ Use a pipette to transfer 5 mL of PNBA solution and 1 mL of 10 mg / L standard solution into a 10 mL brown screw-cap sample bottle. Seal the bottle and mix well using ultrasonic oscillation.

[0047] ⑤ Place the above samples at room temperature for half an hour before testing.

[0048] ⑥ 0mg / L, 1mg / L, 20mg / L, 50mg / L and other standard solutions are prepared in the same way as steps ④ and ⑤ and tested.

[0049] ⑦ The above standard samples were filtered through membrane filters (0.45 μm) and tested according to the standard operating procedures, operating conditions and instrument parameters of the HPLC instrument. The signal peak areas of different concentrations were obtained from the chromatographic results.

[0050] Step 3: Determination of formaldehyde, acetaldehyde, and propionaldehyde content in the sample: Pipette 5 mL of PNBA solution and 1 mL of the test object into a 10 mL brown screw-cap sample bottle, seal it, and mix it evenly with ultrasonic oscillation to use as the test solution. The solution is placed at room temperature for more than half an hour before measurement. Blank sample: Pipette 5 mL of PNBA solution and 1 mL of pure water into a 10 mL brown screw-cap sample bottle, seal it, and mix it evenly with ultrasonic oscillation to use as the blank sample.

[0051] Step 4: Filter the test solution and blank solution with a filter membrane (0.45 μm) and perform the test according to the standard operating procedures of the HPLC instrument and the operating conditions according to the instrument parameters. The signal peak areas of different concentrations are obtained from the spectrum results.

[0052] Example 1

[0053] Example 1 of the present application provides a liquid chromatography detection method for determining aldehydes in propylene oxide.

[0054] Equipment selection: High performance liquid chromatograph equipped with UV detector.

[0055]

[0056] Example 2

[0057] Example 2 of the present application provides a liquid chromatography detection method for determining aldehydes in propylene oxide, and the detection method includes: preparing a standard reserve mother solution, preparing a set of formaldehyde, acetaldehyde, and propionaldehyde standard solutions, establishing a standard curve, and detecting formaldehyde, acetaldehyde, and propionaldehyde.

[0058] The process of preparing a standard stock solution of 1000 mg / L includes: accurately measuring formaldehyde, acetaldehyde, and propionaldehyde, about 0.1 g each, accurate to 0.1 mg, and diluting them into a 100 mL volumetric flask with pure water to obtain a standard solution of 1000 mg / L containing formaldehyde, acetaldehyde, and propionaldehyde.

[0059] The process of preparing the standard stock solution of 100 mg / L includes: accurately pipetting 10 mL of formaldehyde, acetaldehyde, and propionaldehyde containing 1000 mg / L into a 100 mL volumetric flask, diluting with ultrapure water, making up to the mark, and shaking to obtain a standard solution of aldehyde, acetaldehyde, and propionaldehyde with a concentration of 100 mg / L.

[0060] The process of preparing a set of formaldehyde, acetaldehyde and propionaldehyde standard solutions includes: accurately aspirating 0mL, 1mL, 10mL, 20mL and 50mL of 100mg / L standard stock solution into a 100mL volumetric flask, diluting to the scale with ultrapure water, and preparing standard working solutions containing 0mg / L, 1mg / L, 10mg / L, 20mg / L and 50mg / L aldehyde, respectively.

[0061] Use a pipette to take 5 mL of PNBA solution and 1 mL of 0 mg / L, 1 mg / L, 10 mg / L, 20 mg / L, and 50 mg / L standard solutions, respectively, and put them into 10 mL brown screw-cap sample bottles, seal them, and mix them evenly with ultrasonic vibration. Place the above samples at room temperature for half an hour before testing.

[0062] The process of establishing the standard curve includes: filtering the above standard samples with membrane filters (0.45 μm) and injecting them into a high performance liquid chromatograph for analysis, recording the chromatogram, and performing regression analysis on the obtained peak area and the corresponding standard working solution solubility to obtain the standard curves of formaldehyde, acetaldehyde, and propionaldehyde; a set of standard working curves of formaldehyde, acetaldehyde, and propionaldehyde standard solutions are as follows: Figure 1-Figure 3 shown.

[0063] Example 3

[0064] Sample preparation: Determination of formaldehyde, acetaldehyde and propionaldehyde content in samples: Pipette 5mL of PNBA solution and 1mL of sample into a 10mL brown screw-cap sample bottle, seal it and mix it evenly with ultrasonic oscillation to use as the test solution. The solution is left at room temperature for more than half an hour before measurement. Blank sample: Pipette 5mL of PNBA solution and 1mL of pure water into a 10mL brown screw-cap sample bottle, seal it and mix it evenly with ultrasonic oscillation to use as the blank sample. Filter the test solution and blank solution with a filter membrane (0.45μm) respectively, and then inject them into a high performance liquid chromatograph for analysis, record the corresponding peak areas, and use the external standard method to obtain the content of formaldehyde, acetaldehyde and propionaldehyde in the sample respectively. Please refer to Figure 2 .

[0065] Example 4

[0066] This example investigates the methodology of the liquid chromatography detection method for the determination of aldehyde compounds in propylene oxide provided in the present application, including precision and accuracy.

[0067] The precision process includes: using the liquid chromatography detection method for aldehyde compounds of propylene oxide provided in the present application to measure and implement: testing sample A, and testing its formaldehyde, acetaldehyde, and propionaldehyde contents for 6 consecutive times.

[0068] sample Formaldehyde: mg / kg Acetaldehyde: mg / kg Propionaldehyde: mg / kg Sample A: 1.247 14.321 4.265 Sample A: 1.236 14.183 4.196 Sample A: 1.259 14.294 4.315 Sample A: 1.304 14.182 4.142 Sample A: 1.277 14.352 4.178 Sample A: 1.264 14.374 4.166 RSD:% 1.90 0.58 1.58

[0069] Formaldehyde: RSD 1.90% < 5%, acetaldehyde: RSD 0.58% < 2%, propionaldehyde: RSD 1.58% < 2%, indicating good precision.

[0070] The accuracy process includes: using the liquid chromatography detection method for aldehyde compounds of propylene oxide provided by the present application to measure and implement: adding 10 mg / L formaldehyde, acetaldehyde, and propionaldehyde standard solutions to the test sample A, and testing its formaldehyde, acetaldehyde, and propionaldehyde content for 3 consecutive times, and measuring its recovery rate:

[0071]

[0072] The spiked recoveries of formaldehyde, acetaldehyde and propionaldehyde were 98.05%, 94.11% and 102.04%, all of which met the recovery range of 90%-110%, indicating that the spiked recoveries met the requirements.

[0073] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for determining aldehyde compounds in propylene oxide, characterized in that: The following steps are involved: Step 1: Equipment selection: HPLC equipped with UV detector; Step 2: Draw the standard curve: (formaldehyde, acetaldehyde, propionaldehyde); ① Standard stock solution 1# of each standard: weigh known amounts of formaldehyde, acetaldehyde, and propionaldehyde to an accuracy of 0.1 mg, and add them to water to obtain a standard solution of 1000 mg / L of each component; ② Standard stock solution 2# of each standard: dilute the 1000 mg / L standard solution 10 times to obtain a 100 mg / L standard solution; ③ Transfer standard stock solution 2#: 0mL, 1mL, 10mL, 20mL, 50mL into 6 100mL volumetric flasks respectively, dilute to the scale with pure water, and prepare standard working solutions containing 0mg / L, 1mg / L, 10mg / L, 20mg / L, 50mg / L aldehyde respectively; ④ Use a pipette to transfer 5 mL of PNBA solution and 1 mL of 10 mg / L standard solution, put them into a 10 mL brown screw-cap sample bottle, seal it and mix them evenly with ultrasonic vibration; ⑤ Place the above samples at room temperature for half an hour before testing; ⑥ 0mg / L, 1mg / L, 20mg / L, 50mg / L and other standard solutions are prepared in the same way as steps ④ and ⑤ and tested; ⑦ The above standard samples were filtered through membrane filters (0.45 μm) and tested according to the standard operating procedures, operating conditions and instrument parameters of the HPLC instrument. The signal peak areas of different concentrations were obtained from the chromatogram results; Step 3: Determination of formaldehyde, acetaldehyde, and propionaldehyde content in the sample: Pipette 5 mL of PNBA solution and 1 mL of the test substance into a 10 mL brown screw-cap sample bottle, seal it, and mix it evenly with ultrasonic oscillation to use as the test solution. The solution is placed at room temperature for more than half an hour before measurement. Blank sample: Pipette 5 mL of PNBA solution and 1 mL of pure water into a 10 mL brown screw-cap sample bottle, seal it, and mix it evenly with ultrasonic oscillation to use as the blank sample; Step 4: After filtering the test solution and the blank solution with a filter membrane (0.45 μm), the test was performed according to the standard operating procedures of the HPLC instrument and the operating conditions according to the instrument parameters. The signal peak areas of different concentrations were obtained from the chromatogram results.

Images