A method for determining the content of aluminum chloride in thionyl chloride solution by complexometric titration

Abstract

The application discloses a method for determining the content of aluminum in thionyl chloride solution of aluminum trichloride by complexometric titration, and relates to the field of complexometric titration in analytical chemistry. After a sample is hydrolyzed under a closed condition, aluminum ions are combined with an excessive amount of disodium ethylenediaminetetraacetate solution under the condition that the pH value is about 3.0. Then, the excessive amount of disodium ethylenediaminetetraacetate is titrated by using dimethylphenyl orange as an indicator and a zinc chloride standard titration solution under the condition that the pH value is about 6.0. The method has the advantages of convenient sampling safety, simple determination steps, easy mastering, short analysis time and accurate detection result.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry complexometric titration technology, specifically a method for determining the aluminum chloride content in a thionyl chloride solution using complexometric titration. Background Technology

[0002] Aluminum trichloride (AlCl3) is a typical catalyst for the Friedel-Crafts reaction. Anhydrous AlCl3 exhibits high catalytic activity, and it also shows high catalytic activity in the acylation of weakly deactivated aromatic compounds such as chlorobenzene. The presence of AlCl3 plays a decisive role in the Friedel-Crafts acylation reaction. Thionyl chloride is the simplest acyl chloride and is commonly used as a raw material for the sulfonation of aromatic hydrocarbons. In practical applications, to facilitate the use of aluminum trichloride catalysts, aluminum trichloride is dissolved in thionyl chloride and treated before use. The aluminum trichloride content changes before and after treatment. To improve the utilization rate of aluminum trichloride, more accurately calculate the feed amount, and calculate the yield, it is necessary to accurately determine the aluminum chloride content in the prepared thionyl chloride solution. However, the solvent in the aluminum trichloride thionyl chloride solution is volatile, and the solution reacts violently with water, making sampling and dissolution difficult. Therefore, it is urgent to design a convenient and accurate titration method to determine the aluminum chloride content in the thionyl chloride solution. Summary of the Invention

[0003] To address the above problems, the purpose of this invention is to provide a method for determining the aluminum chloride content in a thionyl chloride solution using complexometric titration.

[0004] To achieve the above objectives, the present invention employs the following technical solution: A method for determining the aluminum chloride content in a thionyl chloride solution by complexometric titration includes the following steps: ① Take a sample of m=0.1~0.3 g in an ampoule containing aluminum trichloride thionyl chloride; ② Place the ampoule sampled in step ① into a sealable glass bottle containing deionized water, cover the bottle and shake vigorously to break the ampoule. Let it stand for 10-20 minutes, then shake it for another 1-3 minutes to ensure that all the generated acid mist is absorbed. Use a glass rod to break the capillary. ③ Use a pH meter to measure the absorbent in step ②, add ammonium acetate solution to adjust the pH to 3.0, add an acetate-sodium acetate buffer solution with pH=2.9~3.1, then add EDTA standard solution, boil for 3~5 minutes, and cool to room temperature to obtain the test liquid; ④ Adjust the pH of the test liquid obtained in step ③ to 6.0 by adding ammonia solution, add an acetate-sodium acetate buffer solution with pH=5.9~6.1, add 5~8 drops of xylenol orange indicator, and titrate with zinc chloride standard titration solution until the solution changes from yellow to purple-red as the endpoint; at the same time, perform a blank test; ⑤ Result Calculation The mass fraction ω of aluminum chloride (AlCl3), expressed as a percentage, is calculated using the following formula: ω=(V0- V1)cM÷1000m×100; In the formula: V0 — The numerical value of the volume of zinc chloride standard solution consumed in the titration of the blank test solution, in mL; V1 — The numerical value of the volume of zinc chloride standard solution consumed in the titration of the sample solution, in mL; c — The exact value of the concentration of the zinc chloride standard solution, in mol / L; m — numerical value of sample mass, in grams; M — The numerical value of the molar mass of aluminum chloride, in g / mol.

[0005] Preferably, the molar concentration of the EDTA standard solution is 0.049~0.051 mol / L, and the amount added is 30~50 mL.

[0006] Preferably, the molar concentration of the zinc chloride standard titration solution is 0.049~0.051 mol / L.

[0007] Preferably, the mass concentration of the ammonium acetate solution is 99~101 g / L.

[0008] Preferably, the mass concentration of the ammonia solution is 9-11%.

[0009] Preferably, the ampoule ball has a diameter of 20 mm and the capillary end has a length of 60 mm.

[0010] The present invention has the following advantages over the prior art: The complexometric titration method of this invention for determining the aluminum chloride content in thionyl chloride solution is safe and convenient for sampling, successfully avoiding the loss of volatile thionyl chloride, ensuring accurate weighing, and conducting hydrolysis in a closed environment, making it safe and environmentally friendly. The determination steps are simple and easy to master, with short analysis time and accurate results, providing a new approach for the rapid and accurate determination of aluminum trichloride content in thionyl chloride solution. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of the ampoule ball used in this invention. Detailed Implementation

[0012] The purpose of this invention is to provide a method for determining the aluminum chloride content in a thionyl chloride solution by complexometric titration. The invention will be further described below with reference to specific embodiments.

[0013] The pH meter used was a Mettler FE28-Standard model pH meter, and the electrode used was a Mettler LE438 model pH electrode; the ammonium acetate solution was AR grade; the acetate-sodium acetate buffer solution was AR grade; and the EDTA standard titration solution was AR grade.

[0014] Ammonia solution is AR grade; acetate-sodium acetate buffer solution (pH≈ 6.0) is AR grade; zinc chloride standard titration solution is AR grade; xylenol indicator solution is AR grade, with a mass concentration of 2 g / L according to GB / T 603-2002 Preparation of Preparations and Products Used in Chemical Reagent Test Methods.

[0015] Except for the absence of the sample, the blank test solution uses the same types and amounts of reagents as the sample solution.

[0016] A method for determining the aluminum chloride content in a thionyl chloride solution by complexometric titration includes the following steps: ① Take a clean ampoule (structure as follows) Figure 1 As shown), weigh the sample to an accuracy of 0.0002g. Slightly heat the bulb with a low flame, then insert the capillary end into the sample liquid surface to take a sample of about 0.1~0.3g. Wipe the liquid off the outer wall, seal the capillary with a flame, and weigh it after cooling to an accuracy of 0.0002g.

[0017] ② Place the ampoule into a sealable glass bottle containing 50mL of water, put on the cap, shake vigorously to break the ampoule, let it stand for 10 minutes, and continue to shake for 1 minute to allow all the generated acid mist to be absorbed. Then crush the capillary tube with a glass rod.

[0018] ③ Measure the pH using a pH meter, adjust the pH to 3.0 with ammonium acetate solution, add 10 mL of acetate-sodium acetate buffer solution (pH = 3.0) and 30-50 mL of EDTA standard solution, boil for 5 min, and cool to room temperature to obtain the test liquid; during the test, the molar concentration of EDTA standard solution is 0.049-0.051 mol / L, and the amount added is generally 30-50 mL. If the mass of the sample is small, the volume of EDTA added can be appropriately reduced; if the mass of the sample is large, the volume of EDTA added can be appropriately increased.

[0019] ④ Adjust the pH of the test liquid obtained in step ③ to 6.0 by adding ammonia solution. Add 10 mL of pH 6.0 acetate-sodium acetate buffer solution, add 5-8 drops of xylenol orange indicator solution, and titrate with zinc chloride standard titration solution until the solution changes from yellow to purple-red, which is the endpoint. Perform a blank test at the same time.

[0020] ⑤ Result Calculation The mass fraction ω of aluminum chloride (AlCl3), expressed as a percentage, is calculated using the following formula: ω=(V0- V1)cM÷1000m×100; In the formula: V0—The volume of zinc chloride standard solution consumed in the titration of the blank test solution, in milliliters (mL). V1—The numerical value of the volume of zinc chloride standard solution consumed in the titration of the sample solution, in milliliters (mL). c —The accurate value of the concentration of the zinc chloride standard solution, in moles per liter (mol / L). m —The numerical value of the sample mass, in grams (g); M — The numerical value of the molar mass of aluminum chloride (AlCl3), in grams per mole (g / mol) (M=133.34) Accurately weigh 25.83g of 99.95% pure aluminum trichloride and 100.00g of 99.0% pure thionyl chloride to prepare solution 1; accurately weigh 43.19g of 99.95% pure aluminum trichloride and 100.00g of 99.0% pure thionyl chloride to prepare solution 2; accurately weigh 68.98g of 99.95% pure aluminum trichloride and 100.00g of 99.0% pure thionyl chloride to prepare solution 3. Example 1

[0021] The aluminum chloride content in solution 1 was tested, including the following steps: ① Take a clean ampoule (structure as follows) Figure 1 As shown, the ampoule bulb has a diameter of 20 mm and a capillary end length of 60 mm. Weigh the ampoule; m1 = 0.4536 g. Slightly heat the bulb with a low flame, then insert the capillary end into the sample liquid surface to collect approximately 0.1~0.3 g of sample. Wipe the liquid off the outer wall, seal the capillary with a flame, and after cooling, weigh the sample; m2 = 0.6719 g. Therefore, the mass of the sample is m = m1 - m2 = 0.2183 g.

[0022] ② Place the ampoule into a sealable glass bottle containing 50mL of water, put on the cap, shake vigorously to break the ampoule, let it stand for 10 minutes, and continue to shake for 1 minute to allow all the generated acid mist to be absorbed. Then crush the capillary tube with a glass rod.

[0023] ③ The pH was measured using a pH meter. The pH was adjusted to 3.0 by adding ammonium acetate solution with a mass concentration of 99.5 g / L. 10 mL of acetate-sodium acetate buffer solution (pH=3.0) and 30 mL of EDTA standard solution were added. The mixture was boiled for 5 min and cooled to room temperature to obtain the test liquid. The molar concentration of the EDTA standard solution had been calibrated to 0.05040 mol / L. ④ Adjust the pH of the test liquid obtained in step ③ to 6.0 by adding ammonia solution. Add 10 mL of pH 6.0 acetate-sodium acetate buffer solution, and add 5-8 drops of xylenol orange indicator. Titrate with 0.04920 mol / L zinc chloride standard titration solution until the solution changes from yellow to purple-red, which is the endpoint. The volume of zinc chloride standard solution consumed, V1, is 24.09 mL. Simultaneously, a blank test is performed, consuming 30.73 mL of zinc chloride standard solution, V0.

[0024] ⑤ Result Calculation The mass fraction ω of aluminum chloride (AlCl3), expressed as a percentage, is calculated using the following formula: ω=(V0- V1)cM÷1000m×100; In the formula: V0—The volume of zinc chloride standard solution consumed in the titration of the blank test solution, in milliliters (mL). V1—The numerical value of the volume of zinc chloride standard solution consumed in the titration of the sample solution, in milliliters (mL). c —The accurate value of the concentration of the zinc chloride standard solution, in moles per liter (mol / L). m —The numerical value of the sample mass, in grams (g); M — The numerical value of the molar mass of aluminum chloride (AlCl3), in grams per mole (g / mol) (M=133.34) The mass fraction of aluminum chloride (AlCl3) was ω = 19.95%. Example 2

[0025] The aluminum chloride content in solution 2 was tested, including the following steps: ① Take a clean ampoule (structure as follows) Figure 1 As shown, the ampoule bulb has a diameter of 20 mm and a capillary end length of 60 mm. Weigh the ampoule; m1 = 0.4542 g. Slightly heat the bulb with a low flame, then insert the capillary end into the sample liquid surface to collect approximately 0.1~0.3 g of sample. Wipe the liquid off the outer wall, seal the capillary with a flame, and after cooling, weigh the sample; m2 = 0.6776 g. Therefore, the mass of the sample is m = m1 - m2 = 0.2234 g.

[0026] ② Place the ampoule into a sealable glass bottle containing 50mL of water, put on the cap, shake vigorously to break the ampoule, let it stand for 10 minutes, and continue to shake for 1 minute to allow all the generated acid mist to be absorbed. Then crush the capillary tube with a glass rod.

[0027] ③ The pH was measured using a pH meter. The pH was adjusted to 3.0 by adding ammonium acetate solution with a mass concentration of 99.5 g / L. 10 mL of acetate-sodium acetate buffer solution (pH=3.0) and 30 mL of EDTA standard solution were added. The mixture was boiled for 5 min and cooled to room temperature to obtain the test liquid. The molar concentration of the EDTA standard solution had been calibrated to 0.05040 mol / L. ④ Adjust the pH of the test liquid obtained in step ③ to 6.0 by adding ammonia solution. Add 10 mL of pH 6.0 acetate-sodium acetate buffer solution, and add 5-8 drops of xylenol orange indicator. Titrate with 0.04920 mol / L zinc chloride standard titration solution until the solution changes from yellow to purple-red, which is the endpoint. The volume of zinc chloride standard solution consumed, V1, is 20.29 mL. Simultaneously, a blank test is performed, consuming 30.73 mL of zinc chloride standard solution, V0.

[0028] ⑤ Result Calculation The mass fraction ω of aluminum chloride (AlCl3), expressed as a percentage, is calculated using the following formula: ω=(V0- V1)cM÷1000m×100; In the formula: V0—The volume of zinc chloride standard solution consumed in the titration of the blank test solution, in milliliters (mL). V1—The numerical value of the volume of zinc chloride standard solution consumed in the titration of the sample solution, in milliliters (mL). c —The accurate value of the concentration of the zinc chloride standard solution, in moles per liter (mol / L). m —The numerical value of the sample mass, in grams (g); M — The numerical value of the molar mass of aluminum chloride (AlCl3), in grams per mole (g / mol) (M=133.34) The mass fraction of aluminum chloride (AlCl3) was ω = 30.66%. Example 3

[0029] The aluminum chloride content in solution 3 was tested, including the following steps: ① Take a clean ampoule (structure as follows) Figure 1 As shown, the ampoule bulb has a diameter of 20 mm and a capillary end length of 60 mm. Weigh the ampoule; m1 = 0.4521 g. Slightly heat the bulb with a low flame, then insert the capillary end into the sample liquid surface to collect approximately 0.1~0.3 g of sample. Wipe the liquid off the outer wall, seal the capillary with a flame, and after cooling, weigh the sample; m2 = 0.6506 g. Therefore, the mass of the sample is m = m1 - m2 = 0.1985 g.

[0030] ② Place the ampoule into a sealable glass bottle containing 50mL of water, put on the cap, shake vigorously to break the ampoule, let it stand for 10 minutes, and continue to shake for 1 minute to allow all the generated acid mist to be absorbed. Then crush the capillary tube with a glass rod.

[0031] ③ The pH was measured using a pH meter. The pH was adjusted to 3.0 by adding ammonium acetate solution with a mass concentration of 99.5 g / L. 10 mL of acetate-sodium acetate buffer solution (pH=3.0) and 30 mL of EDTA standard solution were added. The mixture was boiled for 5 min and cooled to room temperature to obtain the test liquid. The molar concentration of the EDTA standard solution had been calibrated to 0.05040 mol / L. ④ Adjust the pH of the test liquid obtained in step ③ to 6.0 by adding ammonia solution. Add 10 mL of pH 6.0 acetate-sodium acetate buffer solution, and add 5-8 drops of xylenol orange indicator. Titrate with 0.04920 mol / L zinc chloride standard titration solution until the solution changes from yellow to purple-red, which is the endpoint. The volume of zinc chloride standard solution consumed, V1, is 18.32 mL. Simultaneously, a blank test is performed, consuming 30.73 mL of zinc chloride standard solution, V0.

[0032] ⑤ Result Calculation The mass fraction ω of aluminum chloride (AlCl3), expressed as a percentage, is calculated using the following formula: ω=(V0- V1)cM÷1000m×100; In the formula: V0—The volume of zinc chloride standard solution consumed in the titration of the blank test solution, in milliliters (mL). V1—The numerical value of the volume of zinc chloride standard solution consumed in the titration of the sample solution, in milliliters (mL). c —The accurate value of the concentration of the zinc chloride standard solution, in moles per liter (mol / L). m —The numerical value of the sample mass, in grams (g); M — The numerical value of the molar mass of aluminum chloride (AlCl3), in grams per mole (g / mol) (M=133.34) The mass fraction of aluminum chloride (AlCl3) was ω = 41.01%.

[0033] The mass fraction of aluminum chloride (AlCl3) in solutions 1, 2, and 3 was determined sequentially using the method described above. Six samples were taken from each solution for parallel testing. The accuracy and precision test results are shown in Table 1. The amount of EDTA added during testing is generally 30-50 mL. If the sample mass is small, the volume of EDTA added can be appropriately reduced; if the sample mass is large, the volume of EDTA added can be appropriately increased.

[0034] Table 1 Analysis Results Solution 1 20.52 19.95，20.44，20.19，21.00，20.68，20.77 20.51 1.88 0.05 Solution 2 30.15 30.66，30.29，29.88，29.70，30.58，30.11 30.20 1.26 0.17 Solution 3 40.80 41.01，39.89，40.37，40.66，41.13，40.52 40.6 1.11 0.49 As can be seen from the results in Table 1, the repeatability RSD of the aluminum chloride content determination results using the test method of the present invention is <2%, and the deviation from the theoretical value is less than 2%, indicating good repeatability and accuracy. This demonstrates that the complexometric titration method of the present invention for determining the aluminum chloride content in thionyl chloride solution is accurate and reliable.

Claims

1. A method for determining the aluminum chloride content in a thionyl chloride solution by complexometric titration, characterized in that: Includes the following steps: ① Take a sample of m=0.1~0.3 g in an ampoule containing aluminum trichloride thionyl chloride; ② Place the ampoule sampled in step ① into a sealable glass bottle containing deionized water, cover the bottle and shake vigorously to break the ampoule. Let it stand for 10-20 minutes, then shake it for another 1-3 minutes to ensure that all the generated acid mist is absorbed. Use a glass rod to break the capillary. ③ Use a pH meter to measure the absorbent in step ②, add ammonium acetate solution to adjust the pH to 3.0, add an acetate-sodium acetate buffer solution with pH=2.9~3.1, then add EDTA standard solution, boil for 3~5 minutes, and cool to room temperature to obtain the test liquid; The EDTA standard solution has a molar concentration of 0.049~0.051 mol / L and is added in a volume of 30~50 mL. ④ Adjust the pH of the test liquid obtained in step ③ to 6.0 by adding ammonia solution, add an acetate-sodium acetate buffer solution with pH=5.9~6.1, add 5~8 drops of xylenol orange indicator, and titrate with zinc chloride standard titration solution until the solution changes from yellow to purple-red as the endpoint; at the same time, perform a blank test; ⑤ Result Calculation The mass fraction ω of aluminum chloride (AlCl3), expressed as a percentage, is calculated using the following formula: ω=(V0- V1)cM÷1000m×100; In the formula: V0 — The numerical value of the volume of zinc chloride standard solution consumed in the titration of the blank test solution, in mL; V1 — The numerical value of the volume of zinc chloride standard solution consumed in the titration of the sample solution, in mL; c — The exact value of the concentration of the zinc chloride standard solution, in mol / L; m — the numerical value of the sample mass, in grams; M — The numerical value of the molar mass of aluminum chloride, in g / mol.

2. The method for determining the aluminum chloride content in a thionyl chloride solution by complexometric titration according to claim 1, characterized in that: The molar concentration of the zinc chloride standard titration solution is 0.049~0.051 mol / L.

3. The method for determining the aluminum chloride content in a thionyl chloride solution by complexometric titration according to claim 1, characterized in that: The mass concentration of the ammonium acetate solution is 99~101 g / L.

4. The method for determining the aluminum chloride content in a thionyl chloride solution by complexometric titration according to claim 1, characterized in that: The mass concentration of the ammonia solution is 9-11%.

5. The method for determining the aluminum chloride content in a thionyl chloride solution by complexometric titration according to claim 1, characterized in that: The ampoule ball has a diameter of 20 mm and a capillary end length of 60 mm.

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