UOP 779-2008 CHLORIDE IN PETROLEUM DISTILLATES BY MICROCOULOMETRY.pdf

1、 IT IS THE USERS RESPONSIBILITY TO ESTABLISH APPROPRIATE PRECAUTIONARY PRACTICES AND TO DETERMINE THE APPLICABILITY OF REGULATORY LIMITATIONS PRIOR TO USE. EFFECTIVE HEALTH AND SAFETY PRACTICES ARE TO BE FOLLOWED WHEN UTILIZING THIS PROCEDURE. FAILURE TO UTILIZE THIS PROCEDURE IN THE MANNER PRESCRIB

2、ED HEREIN CAN BE HAZARDOUS. MATERIAL SAFETY DATA SHEETS (MSDS) OR EXPERIMENTAL MATERIAL SAFETY DATA SHEETS (EMSDS) FOR ALL OF THE MATERIALS USED IN THIS PROCEDURE SHOULD BE REVIEWED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTION EQUIPMENT (PPE). COPYRIGHT 1977, 1992, 2008 UOP LLC. All rights r

3、eserved. 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, 610.832.9555 FAX, or

4、610.832.9585 PHONE. Chloride in Petroleum Distillates by Microcoulometry UOP Method 779-08 Scope This method is for determining chloride in liquid hydrocarbons at concentrations ranging from approximately 0.3 to 1000 ppm. Higher concentrations can be determined with appropriate sample dilution. The

5、method determines the total organic chloride. Some inorganic chloride present as salts is not included (see Note 1). Except for fluoride, other halogens that may be present in the sample are determined as chloride. Both nitrogen and sulfur compounds interfere at concentrations greater than approxima

6、tely 0.1%. Reference ASTM Method D 4052, Density and Relative Density of Liquids by Digital Density Meter, www.astm.org UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org Outline of Method A commercial microcoulometer is set up and calibrated with liquid standards. Two modes of samp

7、le introduction are permitted, direct injection into the combustion tube or boat inlet. Using the direct injection technique, the sample is injected at a controlled rate into the combustion tube. Using the boat inlet technique, a measured volume of sample is injected, either manually or with an auto

8、sampler, into an argon purged quartz boat. After the volatile components of the sample have evolved, the boat is moved into a heated zone of the pyrolysis tube, which contains oxygen blended with argon. The combustion products are sparged through a sulfuric acid dryer and into a cell where the halog

9、ens are automatically titrated to a coulometric endpoint. The number of halide equivalents are calculated automatically (as chloride ions) and then reported in the concentration units selected. Apparatus References to catalog numbers and suppliers are included as a convenience to the method user. Ot

10、her suppliers may be used. Balance, readability 0.1-mg 2 of 9 779-08 Beakers, borosilicate glass, 50-, 100-, and 250-mL, Fisher Scientific, Cat. Nos. 02-539-G, -H, and -K, respectively Bottles, washing, low density polyethylene, 125-, 250- and 500-mL, Fisher Scientific, Cat. Nos. 03-409-10AA, -10BB

11、and -10CC, respectively Flasks, volumetric, Class A, borosilicate glass, 25-, 50-, 100-, 250- and 1000-mL, Fisher Scientific, Cat. Nos. 10-210-8A, -8B, -8C, -8E and -8G, respectively Flowmeter, digital, gas, operating range 0.5 to 500 mL/min, Fisher Scientific, Cat. No. 11-164-45 Microcoulometer, wi

12、th attached furnace, cell, autosampler, controls and computer, Model TCL-100, Dia Instruments Co., Ltd., available from COSA Instrument. Microcoulometers from other manufacturers such as Thermo ECS-3000, Analytik Jena Multi EA 3100, or Dohrmann MCTS-120 (no longer manufactured), are also available,

13、but have not been tested. Follow the manufacturers recommendations for maintaining a supply of spare parts and consumables. Pipet filler, Fisher Scientific, Cat. No. 13-681-102A Pipet, transfer, disposable plastic, 152-mm length, Fisher Scientific, Cat. No. 13-711-5A Pipet, volumetric, Class A, 2-,

14、5- and 10-mL, Fisher Scientific, Cat. No. 13-650-2C, -2F and -2L, respectively Refrigerator, flammable storage or explosion proof, Fisher Scientific, Cat. Nos. 97-938-1 or 97-950-1 Regulator, argon, single-stage, with stainless steel diaphragm, Matheson Gas Products, Cat. No. 3231. This regulator is

15、 installed downstream of the two-stage regulator to provide better flow control. Regulator, argon, two-stage, with stainless steel diaphragm, Matheson Gas Products, Cat. No. 3104-580 Regulator, oxygen, single-stage, with stainless steel diaphragm, Matheson Gas Products, Cat. No. 3231. This regulator

16、 is installed downstream of the two-stage regulator to provide better flow control. Regulator, oxygen, two-stage, with stainless steel diaphragm, Matheson Gas Products, Cat. No. 3104-540 Syringes, liquid, 10-, 25-, 50- and 100-L, Hamilton 1700 Series, Alltech, Cat. Nos. 80000, 80200, 80900 and 81000

17、 respectively (if an autosampler is not used) Reagents and Materials References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. References to water mean deionized or distilled water. The following items are required to perform the anal

18、ysis. Additional reagents and materials may be required depending on the specific microcoulometer utilized. Where different reagents are specified in the instrument manual, follow the manufacturer recommendations. Acetic acid, glacial, Fisher Scientific, Cat. No. A38 Ammonium hydroxide, concentrated

19、 Fisher Scientific, Cat. No. A669 Argon, compressed gas, 99.99% minimum purity. 3 of 9 779-08 Chlorobenzene, CHROMASOLV 99.9% minimum purity, Aldrich Chemical, Cat. No. 270644-100ML 1-Chlorobutane, CHROMASOLV 99.8% purity, Aldrich Chemical, Cat. No. 34958-100ML Inorganic chloride standard (NaCl or

20、HCl Solution), as recommended by the microcoulometer manufacturer Oxygen, compressed gas, 99.98% minimum purity Quartz wool, high purity, Alltech Associates, Cat. No. 4033 Sodium bicarbonate, Aldrich Chemical, Cat. No. 34,094-4 Sulfuric acid, concentrated, Aldrich Chemical, Cat. No. 32,050-1 Isoocta

21、ne (2,2,4-Trimethylpentane), chloride free, Mallinckrodt Baker, Cat. No. 9335. Verify that the isooctane is chloride free by analysis on the microcoulometer. Procedure The analyst is expected to be familiar with general laboratory practices, with the technique of microcoulometry, and with the equipm

22、ent being used. This procedure is written for the Dia Instruments microcoulometer listed in Apparatus. If a different microcoulometer is used, modify the procedure as needed. Preparation of Standards 1-Chlorobutane or chlorobenzene, diluted in isooctane is used in this procedure as an example of how

23、 a standard solution is made. Other standards, such as 2,4,5-trichlorophenol in HPLC grade methanol, may be used provided that the solvent is chloride free and that equivalent results can be obtained as from the chlorobenzene. For a 1-chlorobutane standard, prepare a nominally 10,000-g Cl/mL stock s

24、olution as follows: 1. Weigh approximately 2.611 g of 1-chlorobutane to the nearest 0.1 mg into a tared, 100-mL volumetric flask that is chloride free. 2. Dilute to the mark with isooctane Store the stock solution in the volumetric flask in a refrigerator. When stored in a refrigerator, the stock so

25、lution is stable for one month. Prepare fresh solution monthly, or as needed, and store in a refrigerator. If the stock solution is not stored in a refrigerator, prepare fresh solutions daily when the analysis is performed. 3. Calculate the concentration of chloride in the 1-chlorobutane stock solut

26、ion using Equation 1: Chloride, g/mL = 57.9245.35M10000 (1) where: M = mass of 1-chlorobutane weighed into flask, g 35.45 = atomic weight of chlorine 92.57 = molecular weight of 1-chlorobutane 10000 = factor to convert to g/mL 4. Prepare working solutions containing nominally 1000-, 100-, 10- and 1-

27、g Cl/mL by dilution of the stock solution with isooctane in chloride-free volumetric flasks. 4 of 9 779-08 Remove the stock solution from the refrigerator and allow it to come to room temperature before performing the dilutions. Return the stock solution to the refrigerator immediately thereafter. O

28、ther working solutions may be prepared if needed. Use volumetric pipets and volumetric flasks to keep concentration as g Cl/mL. When stored in a refrigerator, the working solutions are stable for one week. Prepare fresh working solutions weekly, or as needed, and store in a refrigerator. If the work

29、ing solutions are not stored in a refrigerator, prepare fresh working solutions daily when the analysis is performed. For a chlorobenzene standard, prepare a nominally 10,000-g Cl/mL stock solution as follows: 1. Weigh approximately 3.174 g of chlorobenzene to the nearest 0.1 mg into a tared, 100-mL

30、 volumetric flask that is chloride free. 2. Dilute to the mark with isooctane and reweigh. Store the stock solution in the volumetric flask in a refrigerator. When stored in a refrigerator, the stock solution is stable for one month. Prepare fresh stock solution monthly, or as needed, and store in a

31、 refrigerator. If the stock solution is not stored in a refrigerator, prepare fresh stock solutions daily when the analysis is performed. 3. Calculate the concentration of chloride in the chlorobenzene stock solution using Equation 2: Chloride, g/mL = 56.11245.35N10000 (2) where: N = mass of chlorob

32、enzene weighed into flask, g 35.45 = atomic weight of chlorine 112.56 = molecular weight of chlorobenzene 10000 = factor to convert to g/mL 4. Prepare working solutions containing nominally 1000-, 100-, 10- and 1-g Cl/mL by dilution of the stock solution with isooctane in chloride-free volumetric fl

33、asks. Remove the stock solution from the refrigerator and allow it to come to room temperature before performing the dilutions. Return the stock solution to the refrigerator immediately thereafter. Other working solutions may be prepared if needed. Use volumetric pipets and volumetric flasks to keep

34、 concentration as g Cl/mL. When stored in a refrigerator, the working solutions are stable for one week. Prepare fresh working solutions weekly, or as needed, and store in a refrigerator. If the stock solution is not stored in a refrigerator, prepare fresh working solutions daily when the analysis i

35、s performed. Preparation of Apparatus 1. Set up the microcoulometer in accordance with the instructions of the manufacturer. If desired, a chart recorder can be connected to the instrument. 2. Polish the electrodes as directed by the manufacturer. Clean the coulometric cell and fill the cell with th

36、e appropriate electrolyte solution. Fill the sulfuric acid scrubber and assemble the instrument according to manufacturer directions. Pack the boat with quartz wool, if a boat inlet autosampler is used. The quartz wool is packed into the quartz boat so that it remains in the boat throughout the anal

37、ysis. 3. Set the furnace temperature(s) and establish gas flows at the manufacturers suggested rates. Verify that the gas flow rates are correct using the digital flowmeter. Adjust the flow rates if necessary. 5 of 9 779-08 4. Enter the appropriate operation parameters into the instrument computer.

38、These instrument parameters are selected by either using the manufacturers suggestions or based on the operators prior experience. One or more of these parameters may need to be modified as more experience is gained and as different sample matrices are analyzed. 5. Condition the electrodes according

39、 to the manufacturs specifications by direct injection of the inorganic chloride solution into the cell followed by titration to a stable baseline. The baseline stability is determined by inspection of the onscreen or chart recorder trace. Calibration of Apparatus 1. Select appropriate chloride stan

40、dards for a linear calibration. It is recommended to include at least 3 standards (and a solvent blank for samples 10 ppm). Follow instrument manufacturers guidelines to determine maximum injectable volume. The linear calibration can be made from injections of the same volume of standards of differe

41、nt concentrations or of different volumes of a single standard concentration. It is recommended that an autosampler is used with the instrument. Instruments with direct autosampler introduction into the combustion tube can analyze larger sample volumes than boat inlet instruments. Boat inlet instrum

42、ents will require separate introduction programs depending on the volatility of the sample. 2. Create a calibration program sequence in the instrument control software. The solvent blank and the lowest standard on the calibration should be analyzed in duplicate. 3. Initialize the coulometer accordin

43、g to the manufacturers instructions. The coulometer must be started prior to any injection so that a true baseline can be used and to make certain that any volatile halides are not lost. This is done automatically when a computer controlled autosampler is used 4. For a direct injection instrument, t

44、he standard is slowly injected directly into the combustion tube. The use of an autosampler is recommended for control of the injection rate. If the combustion tube, sulfuric acid scrubber, or coulometric cell become coked during the injection, they must be removed and cleaned appropriately. Coking

45、can be minimized by slowing the rate at which the sample is introduced into the furnace. 5. For a boat inlet instrument, the standard is injected into the quartz wool contained in the boat making certain that the entire sample is contained by the boat and none of the sample spatters. The boat positi

46、on is programmed for proper volatilization and combustion of the sample matrix. The rate at which the boat is moved into the furnace will depend on the volume of the injection and the boiling range of the standards components. The boat should be moved into the furnace in such a manner so as to preve

47、nt the sample from flash combusting and forming coke in the pyrolysis tube. If the combustion tube, sulfuric acid scrubber, or coulometric cell become coked during the injection, they must be removed and cleaned appropriately. Coking can be minimized by slowing the rate at which the sample is introd

48、uced into the furnace. 6. Retract the combustion boat from the furnace upon completion of the coulometric titration and allow the boat to cool to ambient temperature before starting the next analysis. 7. Record the amount of chloride titrated and verify that the titration was performed properly by e

49、xamining the titration profile onscreen or on the chart recorder. The profile should be examined for, but not limited to, excessive tailing, overshoot; insufficient integration time, excessive integration time, and unstable baseline. If any of these problems occur, the appropriate corrective action must be taken before proceeding. 6 of 9 779-08 Most instruments will record the titration data and calculate the results automatically. 8. Repeat the analysis of the remaining standards and create a linear calibrat