UOP 291-2015 Total Chloride in Alumina and Silica-Alumina Catalysts by Microwave Digestion and Potentiometric Titration.pdf

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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. SAFETY DATA SHEETS (SDS) OR EXPERIMENTAL 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 1963, 1965, 1976, 1986, 1989, 2002, 2013, 2015 UOP LLC. A

3、ll 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, 610.832.95

4、55 FAX, or 610.832.9585 PHONE. Total Chloride in Alumina and Silica-Alumina Catalysts by Microwave Digestion and Potentiometric Titration UOP Method 291-15 Scope This method is for determining the total inorganic chloride content of fresh or spent alumina and silica-alumina catalysts or catalyst sup

5、ports. The range of quantitation is 0.01 to 10 mass-%. Reference UOP Method 954, “Loss on Ignition (LOI) for Fresh, Regenerated, Used, and Spent Catalysts, Catalyst Supports, and Adsorbents,” www.astm.org UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org Outline of Method The as-re

6、ceived sample is weighed into a Teflon vessel and 20% sulfuric acid is added. The vessel is placed in a specially configured microwave oven and heated for a pre-determined amount of time. If promoter metals are present, such as Pt, Pd, etc., the metals are reduced with magnesium as described under P

7、rocedure, Sample Analysis, Reduction. Chloride is determined potentiometrically by titration with a silver nitrate solution using a silver-silver chloride indicating electrode system. Apparatus References to catalog numbers and suppliers are included as a convenience to the method user. Other suppli

8、ers may be used. Balance, readable to 0.0001 g Beakers, sample, 250-mL, Metrohm USA, Cat. No. 6.1432.320 Bottle, washing, 500-mL, Nalgene, Fisher Scientific, Cat. No. 03-409-17E Crucible, 30-mL, Fisher Scientific, Cat. No. FB965E Cylinders, graduated, 100- and 250-mL, Fisher Scientific, Cat. No. 08-

9、550E and -550F, respectively Dispenser, bottle-top, 10-50-mL, VWR, Cat. No. 40000-068 Electrode, combination silver/glass Titrode 6.0430.100, Metrohm USA, Cat. No. 6.0430.100 2 of 9 291-15 Flask, volumetric, Class A, 1000-mL, Fisher Scientific, Cat. No. 10-210-5G Microwave, 600 watt, Milestone Ethos

10、 Microwave Digestion System, with Carousel (turntable), 24-position with Teflon vessels, and Pro24 High Throughput Rotors (Pro2425M) Oven, drying, capable of operation at 105C Pipet, volumetric transfer, Class A, 100-mL, Fisher Scientific, Cat. No. 13-650-2U Pipet filler, Fisher Scientific, Cat. No.

11、 13-681-102A Stir bar, magnetic, Fisher Scientific, Cat. No. 14-513-59 Stir plate, Thermo Scientific Super-Nuova Multi-Position Digital Stir Plate, Fisher Scientific, Cat. No. 11-475-32Q Titrator, potentiometric, recording, 2000-mV range, 1-mV, resolution with dispenser having a volume readout of 0.

12、00 to 99.9 mL and 0.01% resolution, Titrando Model 904, Metrohm USA Watch glass, glass, 65 mm diameter, Fisher Scientific, Cat. No. 02-610B 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

13、water mean distilled water, except where noted. Cleaning pad, synthetic, mildly abrasive, Scotch-Brite, Runco Office Supply, Cat. No. MMM-96 Filter aid, Whatman ashless clippings, Fisher Scientific, Cat. No. 09924542 Magnesium, metal turnings, Sigma-Aldrich, Cat. No. 200905-500G Potassium chloride,

14、primary standard, oven dried at 105C for 2.5 hours, Fisher Scientific, Cat. No. P217-500 Potassium chloride solution, saturated, Fisher Scientific, Cat. No. SP138-500 Silver nitrate, 0.1N standard aqueous solution, Fisher Scientific, Cat. No. SS72-4 Silver nitrate, 0.01N standard aqueous solution. P

15、ipet 100 mL of the 0.1N aqueous solution into a 1000-mL flask and dilute to volume with distilled water. The exact normality is one-tenth that of the certified or standardized value of the nominally 0.1N silver nitrate standard solution. Sulfuric acid, 20%(v/v), Reagent Grade, Fisher Scientific, Cat

16、. No. 816532 Water, distilled Wiper, Kimwipes, Fisher Scientific, Cat. No. 06-666A Procedure The analyst is expected to be familiar with general laboratory practices, the techniques of microwave digestion and potentiometric titration, and the equipment being used. Dispose of used reagents, materials

17、, and samples in 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 c

18、hloride analysis. Prepare and recondition the silver-silver chloride electrode as follows: 3 of 9 291-15 1. Clean the silver surface with a Scotch-Brite pad. Rinse with distilled water. 2. Weigh approximately 0.1 g of potassium chloride and place in a beaker. Using a graduated cylinder, add 20 mL of

19、 20% sulfuric acid and 80 mL of distilled water 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 distilled water. 4. Wipe the excess silver chloride from the electrode with a wiper. The electrode shou

20、ld be cleaned after each titration by rinsing with distilled water. The freshly coated silver-silver chloride electrode may be stored in distilled water or carefully dried using tissues and stored for future use. It is necessary to repeat the electrode preparation when the AgCl begins to peel from t

21、he surface. Silver Nitrate Standardization The 0.1N silver nitrate solution may 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 beaker. 2. Using a

22、graduated cylinder, add 100 mL of distilled water. Add a stirring bar. Acidify with 20 mL of 20% sulfuric acid. 3. Titrate the potassium chloride solution, while stirring, with 0.1N silver nitrate solution. 4. Calculate the normality of the silver nitrate solution to 3 significant figures using Equa

23、tion 1. N =B07455.0 A(1) where: A = mass of potassium chloride weighed into beaker, g B = volume of silver nitrate solution used in titration, mL N = normality of the silver nitrate solution 0.07455 = molecular weight of the potassium chloride multiplied by 0.001, the factor to convert milliliters t

24、o liters Sample Analysis Sample digestion/reduction can be accomplished by microwave heating, as follows, or by conventional heating (see Note and Appendix). Samples of fresh or spent catalyst that contain promoter metals (usually noble metals) must be reduced as described under Reduction. Catalyst

25、bases do not require reduction. Microwave Digestion of Catalyst 1. Weigh approximately 2 g of the as-received catalyst or catalyst support to the nearest 0.0001 g into a 120-mL Teflon vessel. When results are to be reported on a volatile-free basis, weigh out a separate portion of the sample for the

26、 determination of LOI at 900C as directed in UOP Method 954, “Loss on Ignition (LOI) for Fresh, Regenerated, Used, and Spent Catalysts, Catalyst Supports, and Adsorbents,” at the same time the sample is weighed for chloride. 2. Using a graduated cylinder or a bottle-top dispenser, add 30 mL of 20% s

27、ulfuric acid to the Teflon vessel. 4 of 9 291-15 3. Cap and place the vessel in the holder and place on the carousel. 4. Secure and tighten the vessel as per the manufacturers instructions. 5. Repeat the above procedure with additional samples until the carousel contains up to 24 sample vessels. 6.

28、Place the carousel in the microwave oven. 7. Set the power and time program for the appropriate number of samples as suggested by the manufacturer and include at the end of the timing sequence a 20-minute period at 0% power for cooling. Ramp temperature from ambient to 170C at approximately 10C per

29、minute. Hold at 170C for a minimum of 20 minutes. Cool for 20 minutes at 0% power. 8. Remove the carousel from the microwave oven. Remove the vessel from the carousel and make certain the vessel is cool before releasing any pressure. 9. Remove the cap. Carefully rinse the cap with water, catching th

30、e rinsings in a 250-ml sample beaker. 10. Quantitatively transfer the solution in the vessel into a 250-mL sample beaker. Rinse the vessel several times with 10-15 mL of distilled water, being careful not to cause any splashing. If any aluminum sulfate crystals form in the sample solution, warm slig

31、htly on a hot plate or in an oven to dissolve. Reduction Catalyst bases do not require reduction. 1. Add an additional 15 mL of 20% sulfuric acid into the sample beaker to assist with the digestion of the magnesium turnings. 2. Add a stirring bar to each beaker and start the magnetic stirrer. 3. Add

32、 approximately 0.3 g of magnesium turnings and cover with a watch glass. When the magnesium has completely dissolved, add an additional 0.3 g of magnesium turnings to ensure complete reduction. 4. When the magnesium has completely dissolved, rinse the watch glass with distilled water, catching the r

33、insings in the sample beaker. 5. Continue the sample analysis as described under Titration. Titration 1. Assemble and operate the titrator and the electrode according to the manufacturers instructions. 2. Condition the electrode as needed prior to running samples as described in SilverSilver Chlorid

34、e Electrode Preparation and Reconditioning. 3. Prior to titration, add sufficient distilled water to ensure complete electrode immersion, typically to about 100-mL total volume. 4. Add a small amount (0.2 g) of filter aid to assist in keeping the electrode clean and free from silver chloride precipi

35、tate. 5 of 9 291-15 5. Titrate the sample with 0.1N silver nitrate at a titration rate of about 2.5 mL/min using a moderately fast stirring rate (no vortex or splashing). As the endpoint is approached, reduce the titration rate to approximately 0.1 mL/min. For chloride levels below 0.05 mass-%, titr

36、ate with 0.01N silver nitrate. The endpoint of the titration corresponds to that volume of titrant at which the rate of change of potential, EMF/ mL, reaches a maximum. Observe inflections and record the corresponding volume of titrant dispensed. 6. Clean the electrodes after each titration by rinsi

37、ng with distilled water. Calculations Calculate the chloride content of the sample to the nearest 0.01 % as follows: A) As-received basis: Chloride, mass-% =W NC545.3(2) B) Volatile-free basis: Chloride, mass-% = 100V100WNC545.3 (3) where: C = volume of silver nitrate to reach the chloride endpoint,

38、 mL N = normality of silver nitrate V = loss on ignition determined by UOP Method 954, mass-% W = sample mass, g 3.545 = 0.03545 times 100, factor combining the millimolar weight of chlorine and the factor to convert mass fraction to mass-% 100 = 100% Note An alternative digestion procedure using ac

39、orn condensers is described in the Appendix. Data from a comparative study has shown that microwave or hot plate heating produce equivalent results. Precision The precision statements were determined using UOP Method 999. Repeatability and Site Precision A nested design was carried out for determini

40、ng chloride in two reduced catalysts with two analysts in one laboratory. Each analyst carried out tests on two separate days, performing two tests each day per sample. The total number of tests performed was 16. Using a stepwise analysis of variance procedure, the within-day and within-lab estimate

41、d standard deviations (esd) were calculated at the concentration means listed in Table 1. Two tests performed by the same analyst on the same day should not differ by more than the repeatability allowable difference with 95% confidence. Two tests performed in one laboratory by different analysts on

42、different days should not differ by more than the site precision allowable difference with 95% confidence. 6 of 9 291-15 Table 1 Repeatability and Site Precision, mass-% Repeatability Site Precision Catalyst Sample Chloride Concentration Within- Day esd Allowable Difference Within- Lab esd Allowable

43、 Difference Reduced 0.85 0.004 0.01 0.007 0.02 Reduced 0.95 0.006 0.02 0.008 0.02 The data in Table 1 are a short-term estimate of repeatability. When the test is run routinely, a control standard and chart should be used to develop a better estimate of the long-term repeatability. Reproducibility T

44、here is insufficient data to calculate the reproducibility of the test at this time. Time for Analysis The total elapsed time for a set of 12 samples is 7 hours. The labor requirement per analysis is 1.6 hours when done singly or 0.8 hour when done in groups of 6 or more. Suggested Suppliers Fisher

45、Scientific Co., 711 Forbes Ave., Pittsburgh, PA 15219-4785, USA, 1-412-490-8300, Lab Line Instruments, 1999 N 15th and Bloomingdale Avenue, Melrose Park, Il 60160, USA, 1-708-450-2600 Metrohm USA, 6555 Pelican Creek Circle, Riverview, FL 33578, USA, 1-813-316-4700, Milestone Inc. 25 Controls Dr. S

46、helton, CT 06484, USA, 1-866-995-5100, Runco Office Supply, 1655 Elmhurst Road, Elk Grove Village, IL 60007, USA, 1-847-437-4300, Sigma-Aldrich, Milwaukee, WI 53201, USA, 1-414-438-3850, www.sigma- Wilmad/Lab-Glass, 1002 Harding Hwy., Buena, NJ 08310, USA, 1-856-697-3000, www.wilmad- 7 of 9 291-15

47、 Appendix Acorn Condenser Digestion of Catalyst Scope This appendix describes an alternative catalyst digestion procedure using an acorn condenser heating technique. Data from a comparative study has shown that conventional or microwave heating produce equivalent results. Outline of Method The as-re

48、ceived sample is weighed into a sample beaker and digested with hot dilute sulfuric acid. Promoter metals, if present, are reduced with aluminum pellets. The sample is then titrated as described in the body of the method. Apparatus References to catalog numbers and suppliers are included as a conven

49、ience to the method user. Other suppliers may be used. The following apparatus is in addition to or a substitution of those listed in the body of the method: Condenser, acorn type (see Figure), Wilmad LabGlass, Custom order Forceps, stainless steel, Fisher Scientific, Cat. No. 13-812-38 Hood, laboratory Hot plate, stirring, Fisher Scientific, Cat. No. 11-300-49SHP Stir bar, magnetic, 38-mm length, Fisher Scientific, Cat. No. 14-513-60 Tubing, Tygon,