A method for measuring trace water content in cumene hydroperoxide solution
By combining indirect iodometric titration and triphenylphosphine reduction with Karl Fischer coulometric method, the problem of measuring trace water content in cumene hydroperoxide solution was solved, ensuring the stability of catalyst performance and lifespan.
Patent Information
- Application Number
- CN202210765764.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-07-01
- Publication Date
- 2026-01-13
- Estimated Expiration
- 2042-07-01
AI Technical Summary
Existing technologies cannot accurately measure the trace water content in cumene hydroperoxide solutions, which affects the performance and lifespan of epoxidation catalysts in subsequent processes. Furthermore, the Karl Fischer coulometric method is not applicable to highly oxidizing cumene hydroperoxide solutions.
The concentration of cumene hydroperoxide was measured by indirect iodometric titration. Its oxidizing property was reduced by triphenylphosphine, and the water content after reduction was measured by Karl Fischer coulometric titration. Finally, the water content of the original solution was calculated.
This method enables accurate measurement of trace water content in cumene hydroperoxide solution, effectively controlling catalyst performance and extending its service life.
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Figure CN115356430B_ABST
Abstract
Description
Technical Field
[0001] This invention provides a method for measuring the trace water content in a cumene hydrogen peroxide solution. Background Technology
[0002] Propylene oxide is an important basic petrochemical raw material and the third largest derivative of propylene after polypropylene and acrylonitrile. It is mainly used in the production of polyether polyols, a raw material for polyurethanes. Currently, the main industrial processes for producing propylene oxide both domestically and internationally include the chlorohydrin process, the co-oxidation process, the cumene hydroperoxide process (CHPPO process), and the hydrogen peroxide oxidation process (HPPO process). With increasing emphasis on environmental protection and the optimization and adjustment of chemical product structures, the chlorohydrin process, the co-oxidation process, and the HPPO process have the following shortcomings: the chlorohydrin process generates large amounts of pollution, the co-oxidation process requires high purity raw materials, and the emerging direct oxidation process is unstable. In comparison, the CHPPO process for producing propylene oxide offers better overall economic benefits.
[0003] In the current industrial production process of propylene oxide (CHPPO process) using cumene, due to the limitations of free radical reaction characteristics, the oxidation of cumene to cumene hydroperoxide in air produces impurities such as α,α-dimethylbenzyl alcohol, organic acids (e.g., formic acid, acetic acid), phenol, and water, in addition to the target product cumene hydroperoxide. Water significantly impacts the performance of the epoxidation catalyst in subsequent stages. It not only causes the decomposition of cumene hydroperoxide and the ring-opening hydrolysis of PO, reducing PO selectivity, but also significantly affects catalyst lifetime. The epoxidation process requires the water content in the cumene hydroperoxide solution participating in the reaction to be below 1000 ppm. Therefore, mastering the method for accurately measuring the water content in the cumene hydroperoxide solution and effectively controlling this index is crucial for improving the lifespan of the epoxidation catalyst in the CHPPO process and enhancing the safety and economy of the process.
[0004] The technology for cumene oxidation to cumene hydroperoxide is relatively mature and is widely used in the phenol-acetone process. In this process, cumene is oxidized in air to produce cumene hydroperoxide, which, after concentration, decomposes under acidic conditions into the target products phenol and acetone. In this process, there are no explicit requirements regarding the water content in cumene hydroperoxide, or it can be assumed that most of the water can be removed through concentration. Therefore, there are few studies analyzing the water content in cumene hydroperoxide. Consequently, there is currently no mature method to accurately measure the trace water content in cumene hydroperoxide solutions.
[0005] In the industry, the moisture content of common organic solvents can be determined according to the method specified in GB / T 6283 "Determination of Moisture Content in Chemical Products - Karl Fischer Method (General Method)". In laboratories, a Karl Fischer moisture analyzer (coulometric method) is typically used to directly measure trace amounts of water in organic solvents, offering accurate and convenient measurement. However, because cumene hydroperoxide has strong oxidizing properties, it will undergo a redox reaction with Karl Fischer reagent, affecting the accuracy of the measurement. Therefore, the Karl Fischer coulometric method is not suitable for measuring the water content in cumene hydroperoxide solutions. Invention Overview
[0006] To address the problems in existing technologies, we propose a method for measuring the water content in a cumene hydroperoxide solution. First, the concentration of cumene hydroperoxide is measured using indirect iodometric titration. Then, excess triphenylphosphine cumene hydroperoxide is added to reduce the oxidizing properties of cumene hydroperoxide, resulting in a reduced solution. The water content of the reduced solution is then measured using the Karl Fischer coulometric method, and finally converted back to the original water content of the cumene hydroperoxide solution.
[0007] The technical solution adopted in this invention includes the following steps:
[0008] Step 1: Sampling and dividing the samples;
[0009] Step 2: Measure the concentration of cumene hydroperoxide in the sample using the indirect iodometric method;
[0010] Step 3: Reduce the cumene hydrogen peroxide solution with excess triphenylphosphine to obtain the reduced solution;
[0011] Step 4: Measure the water content in the reduced solution using the coulometric method;
[0012] Step 5: Convert the water content of the original cumene hydrogen peroxide solution.
[0013] The steps are as follows: Take a certain amount of cumene hydrogen peroxide solution and divide it into sample group (1) and sample group (2).
[0014] The concentration of cumene hydroperoxide solution in sample group (1) was measured using the indirect iodometric method and was C. In sample group (2), a mass of m of cumene hydroperoxide solution was taken as the test sample. To completely react the cumene hydroperoxide in the test sample with mass m and concentration C, an amount greater than [amount missing] needs to be added. Triphenylphosphine was reacted by closed-loop stirring until the amount of solid triphenylphosphine no longer decreased, ensuring that the hydroperoxide in the sample was fully reduced to obtain the reduced test sample.
[0015] The water content of the reduced test sample was measured using the Karl Fischer coulometric method. Repeated analysis was performed on the reduced test sample at least three times, and the average of the data was taken as the water content C1 of the reduced test sample. The total water content in the test sample remained unchanged before and after the addition of triphenylphosphine; therefore, the water content of the test sample was calculated as follows:
[0016] According to the method described in this invention, the trace water content in the cumene hydroperoxide solution can be measured, which is helpful for controlling the quality indicators of cumene hydroperoxide, avoiding the influence of water in the cumene hydroperoxide solution on the performance of the epoxidation catalyst in subsequent processes, and extending the service life of the catalyst. Attached Figure Description
[0017] Figure 1 Schematic diagram of a method for measuring the water content in a cumene hydrogen peroxide solution. Detailed Implementation
[0018] The present invention will be further described below with reference to specific accompanying drawings and embodiments.
[0019] As attached Figure 1 As shown, the analysis and testing consist of five steps:
[0020] Step 1: Sampling and dividing the samples.
[0021] Step 2: Measure the concentration of cumene hydroperoxide in the sample using the indirect iodometric method.
[0022] Step 3: Reduce the cumene hydrogen peroxide solution with an excess of triphenylphosphine to obtain the reduced solution.
[0023] Step 4: Measure the water content in the reduced solution using the coulometric method.
[0024] Step 5: Convert the water content of the original cumene hydrogen peroxide solution.
[0025] Take a certain amount of cumene hydroperoxide solution and divide it into sample group (1) and sample group (2). The separation process should be quick to avoid the solution absorbing water during the separation process. After separation, seal and store the samples.
[0026] The concentration of the cumene hydrogen peroxide solution in sample group (1) was measured using the indirect iodometric method and was C.
[0027] Indirect iodometric method: The concentration of isopropyl hydrogen peroxide is determined by indirect iodometric method: a certain amount of sample is accurately weighed into an Erlenmeyer flask, an equal volume of glacial acetic acid and saturated potassium iodide solution is added, and the mixture is heated and stirred at 60°C for 5 minutes. Then, it is titrated with sodium thiosulfate standard solution until pale yellow, 2 drops of starch indicator are added, and titration is continued until the blue color disappears, which is the endpoint.
[0028] A mass of m of cumene hydrogen peroxide solution was taken as the test sample from sample group (2).
[0029] The reaction of cumene hydroperoxide with triphenylphosphine produces α,α-dimethylbenzyl alcohol and triphenylphosphine oxide, as shown in the following equation:
[0030] C9H 12 O2 + P(C6H5)3 → C9H 12 0+(C6H5)3PO
[0031] To ensure complete reaction of cumene hydroperoxide in a test sample with mass m and concentration C, calculations based on the above reaction equation show that a mass greater than [amount missing] is required. Triphenylphosphine was reacted by closed-loop stirring until the amount of solid triphenylphosphine no longer decreased, ensuring that the hydroperoxide in the sample was fully reduced to obtain the reduced test sample.
[0032] The water content of the reduced test sample was measured using the Karl Fischer coulometric method. Repeated analysis was performed on the reduced test sample for at least three consecutive measurements, and the average of the test data was taken as the water content C1 of the reduced test sample.
[0033] The total water content in the test sample remained unchanged before and after the addition of triphenylphosphine. The water content of the test sample can be calculated as follows:
[0034] Example 1: Step 1, Sampling and Dividing: Take 100 ml of cumene hydroperoxide solution and divide it into sample group (1) and sample group (2). Sample group (1) is used to test the concentration of cumene hydroperoxide solution, and sample group (2) is used to test the water content in cumene hydroperoxide solution. The dividing process should be quick to avoid water absorption by the solution during the dividing process. After dividing, seal and store the samples.
[0035] Step 2: The concentration of cumene hydroperoxide in the sample was measured using the indirect iodometric method: The concentration of the cumene hydroperoxide solution was determined to be 52.1% using the indirect iodometric method.
[0036] Step 3: Reduce the hydrogen peroxide cumene solution with excess triphenylphosphine: Take 5.1g of hydrogen peroxide cumene solution from sample group (2) and put it into a glass stoppered triangular flask, which is recorded as the test sample; add 4.8g of triphenylphosphine to the conical flask, add a dry magnetic stir bar, and stir in a closed manner on a magnetic stirrer until the triphenylphosphine solid no longer decreases, and obtain the reduced test sample.
[0037] Step 4: Measure the water content in the reduced test sample using the Karl Fischer coulometric method: Measure the water content in the reduced test sample using a Karl Fischer coulometric analyzer. The test results are 28 ppm, 21 ppm, 26 ppm, and 31 ppm, respectively. The water content in the reduced test sample is 27 ppm.
[0038] Step 5, convert the water content of the original hydrogen peroxide isopropylbenzene solution: the water content in sample (1) is 51.2 ppm.
[0039] Example 2:
[0040] Step 1, Sampling and Dividing: Take 100ml of cumene hydroperoxide solution and divide it into sample group (1) and sample group (2). Sample group (1) is used to test the concentration of cumene hydroperoxide solution, and sample group (2) is used to test the water content in cumene hydroperoxide solution. The sampling process should be quick to avoid water absorption by the solution during the sampling process. After sampling, seal and store the samples.
[0041] Step 2: The concentration of cumene hydroperoxide in the sample was measured using the indirect iodometric method: The concentration of the cumene hydroperoxide solution was determined to be 50.3% using the indirect iodometric method.
[0042] Step 3: Reduce the cumene hydrogen peroxide solution with excess triphenylphosphine: Take 5.5g of cumene hydrogen peroxide solution from sample group (2) and put it into a glass stoppered Erlenmeyer flask, which is recorded as the test sample. Add 5.0g of triphenylphosphine to the Erlenmeyer flask, add a dry magnetic stir bar, and stir in a closed manner on a magnetic stirrer until the triphenylphosphine solid no longer decreases, and the reduced test sample is obtained.
[0043] Step 4: Measure the water content in the reduced test sample using the Karl Fischer coulometric method: Measure the water content in the reduced test sample using a Karl Fischer coulometric analyzer. The test results are 22 ppm, 28 ppm, 39 ppm, and 18 ppm, respectively. The water content in the reduced test sample is 27 ppm.
[0044] Step 5, convert the water content of the original hydrogen peroxide isopropylbenzene solution: the water content in sample (1) is 49.9 ppm.
[0045] Example 3:
[0046] Step 1, Sampling and Dividing: Take 100ml of cumene hydroperoxide solution and divide it into sample group (1) and sample group (2). Sample group (1) is used to test the concentration of cumene hydroperoxide solution, and sample group (2) is used to test the water content in cumene hydroperoxide solution. The sampling process should be quick to avoid water absorption by the solution during the sampling process. After sampling, seal and store the samples.
[0047] Step 2: The concentration of cumene hydroperoxide in the sample was measured using the indirect iodometric method: The concentration of the cumene hydroperoxide solution was determined to be 55.3% using the indirect iodometric method.
[0048] Step 3: Reduce the cumene hydrogen peroxide solution with excess triphenylphosphine: Take 5.2g of cumene hydrogen peroxide solution from sample group (2) and put it into a glass stoppered Erlenmeyer flask, which is recorded as the test sample. Add 5.1g of triphenylphosphine to the Erlenmeyer flask, add a dry magnetic stir bar, and stir in a closed manner on a magnetic stirrer until the triphenylphosphine solid no longer decreases, and the reduced test sample is obtained.
[0049] Step 4: Measure the water content in the reduced test sample using the Karl Fischer coulometric method: Measure the water content in the reduced test sample using a Karl Fischer coulometric analyzer. The test results are 25 ppm, 35 ppm, 232 ppm, and 33 ppm, respectively. The water content in the reduced test sample is 31 ppm.
[0050] Step 5, convert the water content of the original hydrogen peroxide isopropylbenzene solution: the water content in sample (1) is 61 ppm.
[0051] Example 4:
[0052] Step 1, Sampling and Dividing: Take 100ml of cumene hydroperoxide solution and divide it into sample group (1) and sample group (2). Sample group (1) is used to test the concentration of cumene hydroperoxide solution, and sample group (2) is used to test the water content in cumene hydroperoxide solution. The sampling process should be quick to avoid water absorption by the solution during the sampling process. After sampling, seal and store the samples.
[0053] Step 2: The concentration of cumene hydroperoxide in the sample was measured using the indirect iodometric method: The concentration of the cumene hydroperoxide solution was determined to be 48% using the indirect iodometric method.
[0054] Step 3: Reduce the cumene hydrogen peroxide solution with excess triphenylphosphine: Take 5.5g of cumene hydrogen peroxide solution from sample group (2) and put it into a glass stoppered Erlenmeyer flask, which is recorded as the test sample. Add 4.7g of triphenylphosphine to the Erlenmeyer flask, add a dry magnetic stir bar, and stir in a closed manner on a magnetic stirrer until the triphenylphosphine solid no longer decreases, and the reduced test sample is obtained.
[0055] Step 4: Measure the water content in the reduced test sample using the Karl Fischer coulometric method: Measure the water content in the reduced test sample using a Karl Fischer coulometric analyzer. The test results are 17 ppm, 12 ppm, 15 ppm, and 19 ppm, respectively. The water content in the reduced test sample is 16 ppm.
[0056] Step 5: Convert the water content of the original cumene hydrogen peroxide solution to 28.8 ppm.
[0057] The technical solutions disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the conditions and routes, etc. Although the methods and preparation techniques of this invention have been described through preferred embodiments, those skilled in the art can obviously modify or recombine the methods and technical routes described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technique. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention.
Claims
1. A method for measuring the water content in a cumene hydroperoxide solution, characterized in that: First, the concentration of cumene hydroperoxide solution was measured by indirect iodometric titration. Then, the cumene hydroperoxide solution was reduced by adding excess triphenylphosphine to eliminate the oxidizing property of cumene hydroperoxide and obtain the reduced solution. The water content of the reduced solution was then measured by Karl Fischer coulometric titration and finally converted to the water content of the original cumene hydroperoxide solution. Includes the following steps: Step 1: Sampling and dividing the sample; take a certain amount of cumene hydrogen peroxide solution and divide it into sample group (1) and sample group (2); Step 2: The concentration of cumene hydrogen peroxide solution in the sample was measured using the indirect iodometric method; the concentration of cumene hydrogen peroxide solution in sample group (1) was measured using the indirect iodometric method and was C. A cumene hydrogen peroxide solution with a mass of m was taken as the test sample from sample group (2); Step 3: Reduce the cumene hydrogen peroxide solution with excess triphenylphosphine to obtain the reduced solution; The test sample containing cumene hydroperoxide of mass m and concentration C was mixed with an added mass greater than [amount missing]. The triphenylphosphine was completely reacted by closed-loop stirring until the amount of solid triphenylphosphine no longer decreased, ensuring that the hydroperoxide in the sample was fully reduced to obtain the reduced test sample. Step 4: Measure the water content in the reduced solution using the coulometric method; measure the water content of the reduced test sample using the Karl Fischer coulometric method. Step 5: Convert the water content to the original cumene hydrogen peroxide solution; perform repeated analysis on the reduced test sample in the same group, with no less than three consecutive measurements. The average of the test data is the water content C1 of the reduced test sample; the total water content in the test sample remains unchanged before and after the addition of triphenylphosphine. The water content of the test sample is calculated as follows: