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3、All rights reserved. Nonconfidential UOP Methods are available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, USA. The UOP Methods may be obtained through the ASTM website, www.astm.org, or by contacting Customer Service at serviceastm.org, 610.832.9
4、555 FAX, or 610.832.9585 PHONE. Total, Inorganic, and Organic Chloride in Hydrocarbons UOP Method 588-12 Scope This potentiometric method is for determining total and inorganic chloride, and calculating organic chloride, in hydrocarbons. The method is applicable to samples with chloride concentratio
5、ns of 1 mass-ppm or higher. For lower levels of chloride use UOP Method 991 “Chloride, Fluoride, and Bromide in Liquid Organics by Combustion Ion Chromatography (CIC).” Iodide and/or bromide, if present, are calculated as chloride. Samples that are polymerized by sodium biphenyl (such as styrene) ca
6、nnot be analyzed by this method. Results for samples containing ammonia and/or amines may be biased high (see Note 1). Reference UOP Method 991, “Chloride, Fluoride, and Bromide in Liquid Organics by Combustion Ion Chromatography (CIC),” www.astm.org UOP Method 999, “Precision Statements in UOP Meth
7、ods,” www.astm.org Outline of Method To determine total chloride, the hydrocarbon sample is weighed and transferred to a separatory funnel containing toluene. Sodium biphenyl reagent is added to promote rapid conversion of the organic chloride into inorganic chloride. Excess reagent is decomposed wi
8、th alcohol and water, and the phases are separated. The chloride containing aqueous phase is acidified, concentrated, acetone is added, and the solution titrated potentiometrically. Inorganic chloride determination is identical to total chloride except that the addition of sodium biphenyl reagent is
9、 omitted. Organic chloride is then calculated as the difference between the total chloride and inorganic chloride determinations. Apparatus References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Balance, readable to 0.0001 g Balance
10、, readable to 0.01 g 2 of 9 588-12 Beaker, 250-mL, tall, without spout, borosilicate glass, Wilmad-LabGlass, Cat. No. G-9906-002 Boiling chips, Fisher Scientific, Cat. No. 09-191-12 Bottles, glass, 60-mL, Fisher Scientific, Cat. No. 02-911-787 Cylinders, graduated, Class B, 10-, 25-, 50-, and 100-mL
11、, Fisher Scientific, Cat. Nos. 08-550B, C, D, and E, respectively Desiccator, with plate, Fisher Scientific, Cat. No. 08-615B Electrode, combination silver/glass Titrode Model 6.0430.100, Metrohm USA, Cat. No. 020948507 Flask, volumetric, Class A, 500-mL, Fisher Scientific, Cat. No. 10-208K Funnel,
12、separatory, 250-mL, Fisher Scientific, Cat. No. 10-437-5C Hot plate, electric, capable of maintaining 150C, Fisher Scientific, Cat. No. 11-100-49H Oven, drying, capable of operation at 110C, Fisher Scientific, Cat. No. 13-247-725G Pipet, volumetric, Class A, 50-mL, Fisher Scientific, Cat. No. 13-650
13、-2S Pipet filler, Fisher Scientific, Cat. No. 13-681-102A Stirring bars, Teflon-coated, Fisher Scientific, Cat. No. 14-512-148 Titrator, potentiometric, recording, 2000-mV range, 1-mV resolution, with dispenser having a volume readout of 0.00 to 99.9 mL and 0.01% resolution, Titrando Model 904, Metr
14、ohm USA Tongs, beaker, Fisher Scientific, Cat. No. 02-622 Tray, for ice bath, polypropylene, Fisher Scientific, Cat. No. 13-361-10 Reagents and Materials References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Unless otherwise specif
15、ied references to water mean deionized or distilled water. Acetone, 99.9% minimum purity, Fisher Scientific, Cat. No. A18-4 Cleaning pad, synthetic, mildly abrasive, Scotch-Brite, Runco Office Supply, Cat. No. MMM-96 Congo red paper, VWR, Cat. No. 60791-006 Detergent, cleaning compound, Liqui-Nox, F
16、isher Scientific, Cat. No. 04-322-15B Desiccant, Drierite, indicating, 10- to 20-mesh, Fisher Scientific, Cat. No. 07-578-4A Gloves, nitrile, Fisher Scientific, Cat. No. 11-395-19C Ice, water Isooctane, 99.9% minimum purity, Fisher Scientific, Cat. No. O301-4 Isopropyl alcohol, 99.9% minimum purity,
17、 Fisher Scientific, Cat. No. A416-4 Nitric acid, concentrated, Certified ACS Plus, Fisher Scientific, Cat. No. A200-212 Nitric acid, approximately 5N. Add 160 mL of concentrated nitric acid slowly to approximately 200 mL of water in a 500-mL volumetric flask. Dilute to the mark with water, cap and i
18、nvert several times to mix thoroughly. 3 of 9 588-12 Pipet, disposable, LDPE, Fisher Scientific, Cat. No. 13-711-9AM Potassium chloride, 99.995% minimum purity, Alfa Aesar, Cat. No. 87626, VWR. Oven dry an aliquot before each use at 105C for 2.5 hours, and cool in a desiccator. Silver nitrate, 0.1N
19、solution, Fisher Scientific, Cat. No. SS72-4, see Silver Nitrate Standardization Silver nitrate, 0.01N standard aqueous solution. Prepare by diluting the 0.1N solution, see Silver Nitrate Standardization. Sodium biphenyl reagent, commercially obtainable under the name of “Organic Halogen Reagent” fr
20、om GFS Chemicals. The reagent is packed in 18-mL bottles (hereafter referred to as “vials”). One vial contains 13 to 15 milli-equivalents of active sodium. The reagent cannot be used after the expiration date stated on the package (see Note 2). Toluene, 99.9% minimum purity, Fisher Scientific, Cat.
21、No. T324-4 Water, deionized or distilled Wipers, Kimwipes, lint free, Fisher Scientific, Cat. No. 06-666A Procedure The analyst is expected to be familiar with general laboratory practices, the technique of titration, and the equipment being used. Dispose of used reagents, materials, and samples in
22、an environmentally safe manner according to local regulations. SilverSilver Chloride Electrode Preparation and Reconditioning Proper electrode preparation is essential to obtain reproducible and noise-free titration curves having good endpoints. An electrode should be dedicated to chloride analysis.
23、 Prepare and recondition the silver-silver chloride electrode as follows: 1. Clean the silver surface with a Scotch-Brite pad. Rinse with water and dry. 2. Weigh approximately 0.1 g of potassium chloride and place in a beaker. Using a graduated cylinder, add 20 mL of 5N nitric acid and 80 mL of wate
24、r to the beaker. Immerse the electrode; and titrate to the endpoint with 0.1N silver nitrate. 3. Remove the electrode from the solution and rinse with water. 4. Wipe the excess silver chloride from the electrode with a wiper. The electrode should be cleaned after each titration by rinsing with water
25、. The freshly coated silver-silver chloride electrode may be stored in water or carefully dried using wipers and stored for future use. It is necessary to repeat the electrode preparation when the AgCl begins to peel from the surface. Silver Nitrate Standardization The 0.1N silver nitrate solution m
26、ay be purchased at a certified concentration. Alternatively, the solution may be standardized as follows. 1. Weigh 0.10 0.01 g of dried potassium chloride to the nearest 0.0001 g into a clean, dry 250-mL electrolytic beaker. 2. Using a graduated cylinder, add 100 mL of water and a stirring bar to th
27、e beaker. Add a few drops of 5N nitric acid to acidify. 4 of 9 588-12 3. Titrate the potassium chloride solution, while stirring, with the nominally 0.1N silver nitrate solution. 4. Calculate the normality of the silver nitrate solution to 3 significant figures using Equation 1. AgNO3, N = B07455.0
28、A (1) where: A = mass of potassium chloride weighed into beaker, g B = volume of silver nitrate solution used in titration, mL N = calculated normality of AgNO3, moles/liter 0.07455 = molecular mass of the potassium chloride, g/mole, multiplied by 0.001, the factor to convert mL to liter 5. Repeat S
29、teps 1 through 4 two more times, average the three values and record the average normality thus obtained. 6. Prepare a 0.01N silver nitrate solution by pipeting 50 mL of the standardized 0.1N solution into a 500-mL volumetric flask. Dilute to the mark with water, cap and invert several times to mix
30、thoroughly. Calculate and record the normality of this solution to three decimal places; the average of the three replicates of N from Equation 1 divided by 10. Sample Preparation Caution: This method cannot be used on samples that polymerize with sodium biphenyl, such as styrene, since a violent re
31、action may occur. Extreme care must be used to prevent contamination. All glassware should be exclusively reserved for this analysis. Clean glassware using detergent, rinse with water followed by acetone. Determine a blank for each group of samples using all the reagents, including as many vials of
32、the sodium biphenyl reagent as used in the samples. Follow all the steps of the analysis, except omit the sample itself. 1. Proceed to Step 1 under Total Chloride Determination for chloride estimates below 10 mass-%, or Step 1 under Sample Dilution for chloride estimates at or above 10 mass-%, if no
33、 heavy oils or solids are to be analyzed. 2. Heat viscous heavy oils or solids in the 110C oven until fluid. Loosen caps or lids to allow expansion of the samples during heating. 3. Remove the sample from the oven using gloves or tongs and shake well to homogenize the sample. 4. Proceed immediately
34、to the next step: either Step 1 under Sample Dilution for samples with chloride estimates at 10 mass-% or higher, or Step 1 under Total Chloride Determination for samples with chloride estimates below 10 mass-%. Sample Dilution 1. Tare a 60-mL capped bottle on the four-place balance. 2. Add 30 mL of
35、 toluene to the bottle using a graduated cylinder. 3. Cap the bottle and reweigh. Record the mass of toluene to four decimal places. 5 of 9 588-12 4. Tare the bottle again and add, dropwise, 5 g of sample to the bottle containing the toluene. Record the sample mass added to four decimal places. 5. C
36、ap the bottle and shake well to thoroughly mix the contents. 6. Repeat Steps 1 through 3 with a second 60-mL bottle. 7. Tare the second bottle containing toluene and add dropwise 5 g of the diluted sample from the first bottle. Record the diluted sample mass added to four decimal places. 8. Cap the
37、second bottle and shake well to thoroughly mix the contents. 9. Use 18 to 20 g of this second dilution (see Table 1) for the sample size in Step 1 under Total Chloride Determination. Table 1 Expected Halide Concentration Sample Size, g Normality of Silver Nitrate 1-5 mass-ppm 50-100 0.01 5-10 mass-p
38、pm 25-35 0.01 0.5-10 mass-% 3-5 0.1 10-50 mass-% 18-20* 0.1 * See Sample Dilution, Step 9. 10. Calculate the dilution factor using Equation 2: Z = ( ) ( )VY YXVU + (2) where: U = toluene mass used in first dilution, g V = sample mass used in first dilution, g X = toluene mass used in second dilution
39、, g Y = first dilution sample mass used in second dilution, g Z = dilution factor Total Chloride Determination 1. Place 50 mL of toluene in a 250-mL seperatory funnel. Weigh the container plus sample (or dilution) to four significant figures, and add the appropriate amount of sample to the separator
40、y funnel using Table 1 as a reference. 2. Reweigh the sample container and remaining contents to determine the exact mass of sample transferred to at least four significant figures. 3. Add the contents of two vials of sodium biphenyl reagent to the separatory funnel. 4. Stopper the separatory funnel
41、 and swirl to mix the contents thoroughly, invert and vent frequently through the stopcock. 5. Add one additional vial of sodium biphenyl reagent if the solution or suspension resulting from Steps 3 and 4 is not blue-green in color; otherwise proceed to Step 6 (see Note 3). If, after addition of the
42、 third vial of sodium biphenyl reagent, the solution or suspension is still not blue-green in color, discontinue the procedure and begin again using less sample. 6. Allow 10 minutes after repeated mixing for the reaction to reach completion. 6 of 9 588-12 7. Add 5 mL of isopropyl alcohol to the sepa
43、ratory funnel, stopper and shake. Invert and vent frequently. This destroys excess reagent (the blue-green color changes to clear, water-white). The solution temperature will rise during the reaction. 8. Add 20 mL of water, stopper the funnel again and rock it gently for approximately one minute. In
44、vert and vent pressure frequently through the stopcock. Allow the contents to return to room temperature before proceeding to Step 9 (about 15 minutes). 9. Add 10 mL of 5N nitric acid, stopper and shake gently for one minute, releasing pressure frequently through the stopcock. 10. Drain the aqueous
45、phase into a second separatory funnel containing 50 mL of isooctane, stopper and shake well, venting frequently. 11. Drain the aqueous phase from Step 10 into a 250-mL electrolytic beaker. 12. Extract the sample in the first separatory funnel a second time with 20 mL of water acidified with 6 drops
46、of 5N nitric acid. 13. Stopper and shake the first separatory funnel well, venting frequently, and then drain the aqueous phase into the second separatory funnel containing the isooctane. 14. Stopper and shake the second separatory funnel well, venting frequently, and then drain the aqueous phase in
47、to the electrolytic beaker containing the first aqueous extract. 15. Test the aqueous extract in the beaker with Congo red paper. If the paper does not turn blue, add dropwise 5N nitric acid until the blue color is obtained. 16. Add a few boiling chips to the beaker and evaporate the solution on a h
48、ot plate, kept just below the boiling point of the liquid, until 25 to 30 mL remains. Do not allow the solution to boil. Loss of chloride can occur if the sample is boiled or evaporated to a volume of less than 25 mL. 17. Cool the solution to ambient temperature in an ice bath, and then add 100 mL o
49、f acetone. 18. Titrate the solution potentiometrically with standardized 0.1N or 0.01N silver nitrate, see Table 1, using the conditioned combination silver/glass electrode. The blank is titrated with the 0.01N silver nitrate. 19. Determine and record the volume of titrant used to reach the chloride endpoint. The Figure shows a typical titration curve with the chloride endpoint noted. If more than one halide is present, the chloride endpoint is determined by the potential as shown in the Figure. Blanks exhibiting more than one endpoint are an indication of contami
