UOP 163-2010 Hydrogen Sulfide and Mercaptan Sulfur in Liquid Hydrocarbons by Potentiometric Titration.pdf
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1、 uop 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 PRES
2、CRIBED 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 1964, 1967, 1987, 1989, 2005, 2010
3、 UOP LLC. All rights reserved. Nonconfidential UOP Methods are available from ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. The UOP Methods may be obtained through the ASTM website, www.astm.org, or by contacting Customer Service at servicea
4、stm.org, 610.832.9555 FAX, or 610.832.9585 PHONE. Hydrogen Sulfide and Mercaptan Sulfur in Liquid Hydrocarbons by Potentiometric Titration UOP Method 163-10 Scope This method is for determining hydrogen sulfide and mercaptan sulfur in hydrocarbons by potentiometric titration. Typical samples include
5、 gasoline, naphtha, light cycle oils and similar distillates that are liquid at ambient temperature and pressure. The lower limit of quantitation is 0.2 mass-ppm mercaptan (as sulfur) and 1.0 mass-ppm hydrogen sulfide (as sulfur). References UOP Method 41, “Doctor Test for Petroleum Distillates,” ww
6、w.astm.org UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org Outline of Method The liquid hydrocarbon sample is weighed into 2-propanol containing a small amount of ammonium hydroxide. The solution is titrated potentiometrically with alcoholic silver nitrate using a glass reference
7、 and silver-silver sulfide indicating electrode system. Hydrogen sulfide and mercaptan sulfur concentrations are calculated as mass-ppm. Free sulfur complicates the potentiometric curve, and instructions are given for interpreting the curve when free sulfur is present. Apparatus References to catalo
8、g numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Balance, readability 0.1-mg Beaker, Berzelius, tall form, 400-mL, Fisher Scientific, Cat. No. 10-310-9 Beakers, electrolytic, 250-mL, Brinkmann Instruments, Cat. No. 020212209, available from Metro
9、hm USA, two or more required Cleaning pad, synthetic, mildly abrasive, Scotch-Brite, Runco Office Supply, Cat. No. MMM-96 Cylinder, graduated, 100-mL, Class B, VWR, Cat. No. 89000-270 2 of 7 163-10 Desiccator, 160-mm ID, and porcelain plate, VWR, Cat. Nos. 25035-005 and 89038-068, respectively Elect
10、rode, combination silver/glass Titrode, 6.0430.100, Brinkmann Instruments, Cat. No. 020948507, available from Metrohm USA. The electrode should be dedicated to sulfur analysis. Flasks, volumetric, Class A, 500-mL, VWR, Cat. No. 89090-748, two required Pipets, volumetric transfer, Class A, 1-, 8-, an
11、d 50-mL, VWR, Cat. Nos. 89045-056, -070, and -086, respectively Regulator, nitrogen, two-stage, high-purity, delivery pressure range 15-200 kPa (2-30 psi), Matheson Tri-Gas, Model 3121-580 Rubber bulb-type pipet filler, VWR, Cat. No. 53502-205 Titrator, potentiometric, recording, 2000-mV range, 1-mV
12、 resolution, capable of reducing the titration rate to a minimum in the vicinity of the endpoint, with dispenser having a volume readout of 0.00 - 99.99 mL, 0.0001 of the buret volume resolution, Metrohm Model 836 Titrando system with optional sample changer, and two 20-mL burets, Brinkmann Instrume
13、nts, Metrohm USA Automatic titration using the titrator is recommended. However, titration can be performed manually using the following equipment. Buret, 50-mL, Class A, with PTFE stopcock, VWR, Cat. No. 89001-624 pH meter, digital, Mettler Toledo, Model S20K, VWR, Cat. No. 11238-592 Stirrer, magne
14、tic, with stir bar, VWR, Cat. No. 12365-380 Reagents and Materials References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Unqualified references to solutions mean aqueous solutions. Ammonium hydroxide, 28.0-30.0 mass-% NH3, Certifie
15、d ACS Plus grade, Fisher Scientific, Cat. No. A669-212 Desiccant, 8-mesh, indicating, Drierite, VWR, Cat. No. 22891-028 Detergent, LiquiNox, VWR, Cat. No. 21837-005 Nitrogen, high purity, 99.99% Paper, test, lead acetate, strips in vials, VWR, Cat. No. 60792-009 2-Propanol, Certified ACS grade, VWR,
16、 Cat. No. VW5520-3. Purge with nitrogen for 10 to 15 minutes before using. Silver nitrate, 0.1000-N solution, VWR, Cat. No. VW3214-2 Silver nitrate, alcoholic solution, 0.0100-N. Prepare a 0.0100-N alcoholic silver nitrate solution by pipetting 50 mL of the standardized 0.1000-N solution into a 500-
17、mL volumetric flask. Dilute to the mark with 2-propanol, cap and invert several times to mix thoroughly. This solution is stable for two months, after which a new solution is prepared. Silver nitrate, alcoholic solution, 0.0010-N. Prepare a 0.0010-N alcoholic silver nitrate solution by pipetting 50
18、mL of the standardized 0.0100-N solution into a 500-mL volumetric flask. Dilute to 3 of 7 163-10 the mark with 2-propanol, cap and invert several times to mix thoroughly. This solution is stable for two months, after which a new solution is prepared. Sodium sulfide nonahydrate, VWR, Cat. No. EM-SX07
19、70-1 Sodium sulfide nonahydrate, 1% solution. Dissolve 1.0 g 1.0 mg of sodium sulfide in 100 mL of water. Toluene, 99.8% minimum purity, VWR, Cat. No. AA43061-K2. Purge with nitrogen for 10 to 15 minutes before using. Water, deionized or distilled Wipers, Kimwipes Ex-L, VWR, Cat. No. 21905-026 Proce
20、dure The analyst is expected to be familiar with general laboratory practices, the technique of titration, and with the equipment being used. Electrode Preparation 1. Prepare the silver electrode by cleaning the surface of the silver band on the electrode with a mild detergent. Prepare this electrod
21、e fresh daily or as required. Proper electrode preparation is essential to obtain reproducible and noise-free titration curves having good distinguishable endpoints. 2. Rinse the electrode with water and wipe dry with a wiper. 3. Polish the surface of the electrode gently with a cleaning pad until t
22、he surface is smooth to the touch. 4. Rinse the electrode with water again and wipe dry with a wiper. 5. Immerse the electrode in a solution consisting of 1 mL of concentrated ammonium hydroxide, 96 mL of 2-propanol and 8 mL of 1% aqueous sodium sulfide solution. Add slowly from a buret over a perio
23、d of about 10 minutes, with stirring, approximately 10 mL of 0.0100-N alcoholic silver nitrate solution. A film of silver sulfide will be deposited on the silver. Wipe off the excess silver sulfide on the electrode with a wiper. The automatic titrator may be used instead of the buret, titrating a mi
24、nimum of 10 mL of titrant. During the titration of samples containing sulfide, the electrode will be coated with AgS. It is necessary to repeat the electrode preparation when the coating begins to peel, becomes rough and uneven, or if the titration curves become noisy. To remove any residue from pre
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