1、PALLADIUM IN FRESH AND SPENT ALUMINA CATALYST BYSPECTROPHOTOMETRYUOP Method 917-93SCOPEThis method is for determining palladium in fresh and spent silica-free alumina catalyst over a range ofapproximately 0.2 to 1 mass-%. Components, such as platinum and iridium, that produce colored ions withiodide
2、 and absorb at approximately 408 nm constitute an interference and, therefore, catalysts that containsuch components cannot be analyzed.OUTLINE OF METHODA representative portion of fresh catalyst is ground and appropriately sampled for analysis. Spent catalystmust be dried and ignited at 900C until
3、it is carbon free prior to grinding and sampling. A representativeportion of the ground catalyst is treated with sulfuric, phosphoric, hydrochloric and nitric acids until all ofthe alumina is dissolved and sulfur trioxide, SO3, fumes are observed. Hydrochloric acid and hydrogenperoxide are added to
4、redissolve the palladium.An aliquot of the catalyst solution is reacted with an excess of potassium iodide in a solution containingsodium sulfite to form a stable chromophore. The absorbance is measured at 408 nm and the palladiumconcentration is determined by comparing the absorbance of the sample
5、solution to a standard calibrationcurve prepared from matrix-matched standard palladium solutions. The palladium concentration of freshand spent catalyst is corrected to a volatile-free basis based on a loss on ignition (LOI) according to UOPMethod 275.APPARATUSReferences to catalog numbers and supp
6、liers are included as a convenience to the method user. Othersuppliers may be used.Balance, electronic, readability 0.1-mg, 200-g capacityBalance, electronic, top-loading, readability 0.001-g, 210-g capacityBalance, electronic, top-loading, readability 0.01-g, 2000-g capacityBeakers, Griffin, borosi
7、licate glass, with spout, 50-, 250-, 400- and 2000-mL, Fisher Scientific, Cat. Nos.02-540G, -540K, -540L and -540R, respectivelyIT IS THE USERS RESPONSIBILITY TO ESTABLISH APPROPRIATE PRECAUTIONARY PRACTICES AND TODETERMINE THE APPLICABILITY OF REGULATORY LIMITATIONS PRIOR TO USE. EFFECTIVE HEALTH A
8、NDSAFETY PRACTICES ARE TO BE FOLLOWED WHEN UTILIZING THIS PROCEDURE. FAILURE TO UTILIZE THISPROCEDURE IN THE MANNER PRESCRIBED HEREIN CAN BE HAZARDOUS. MATERIAL SAFETY DATA SHEETS(MSDS) OR EXPERIMENTAL MATERIAL SAFETY DATA SHEETS (EMSDS) FOR ALL OF THE MATERIALS USED INTHIS PROCEDURE SHOULD BE REVIE
9、WED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTIONEQUIPMENT (PPE). COPYRIGHT 1993 UOP LLCALL RIGHTS RESERVEDUOP Methods are available through ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken PA 19428-2959,United States. The Methods may be obtained through the ASTM webs
10、ite, www.astm.org, or by contacting Customer Service atserviceastm.org, 610.832.9555 FAX, or 610.832.9585 PHONE.2 of 11917-93Bottle, narrow-mouth, round, amber glass, 237-mL, with molded plastic conical polyethylene-lined cap,Fisher Scientific, Cat. No. 03-320-6CBottle, polyethylene, right-to-know s
11、afety wash, distilled water, 500-mL, Fisher Scientific, Cat. No. 03-409-11EBulbs, dropper, for Pasteur pipet, Fisher Scientific, Cat. No. 13-678-9ABuret, weighing, 10-mL, Kimble No. 17200F-10, Baxter Scientific Products, Cat. No. B9366-10Calculator, capable of least squares analysisCell, spectrophot
12、ometric, 10-mm path length, near-UV glass, rectangular, universally matched, FisherScientific, Cat. No. 14-385-910A, or a flow cell to fit the spectrophotometer (see Note 1)Crucible, low, wide-form, porcelain, 30-mL, with cover, Fisher Scientific, Cat. Nos. 07-955E and 07-970G, respectivelyCylinders
13、, graduated, borosilicate glass, 10-, 25-, 50-, 100- and 250-mLCylinder, graduated, plastic, polypropylene, 50-mLDesiccator, with plate, Fisher Scientific, Cat. Nos. 08-631B and 08-641C, respectivelyFlask, Kjeldahl, 100-mL, Fisher Scientific, Cat. No. 10-110CFlasks, volumetric, Class A, 100-, 200-,
14、250-, 500- and 1000-mLHot plate, stirring, with Pyroceram glass ceramic top, Fisher Scientific, Cat. No. 11-495-29Pipets, Mohr, Class B, 5-, 10- and 25-mL, Fisher Scientific, Cat Nos. 13-664F, G and H, respectivelyPipet, Pasteur, controlled drop, Fisher Scientific, Cat. No. 13-678-30Pipets, volumetr
15、ic transfer, Class A, 5-, 10-, 15- and 50-mLScoop, weighing, 20-g capacity, nickel alloy, Fisher Scientific, Cat. No. 01-914-38Spatula, ellipso-spoon, 30-cm, Fisher Scientific, Cat. No. 14-375-57Spectrophotometer, minimum spectrophotometric repeatability of 0.0003 at 0.1 Abs, noise less than0.00005
16、Abs (rms) at 0.0 Abs, and 0.0006 Abs (rms) at 2.0 Abs, minimum stability of 0.0003 Abs perhour, readability to 0.0001 Abs, Varian Instrument Group, Cary Model 4 (Note 2)Standards, absorbance, spectrophotometric, certified, glass-filters, 10-30% transmittance, 440- to 635-nmwavelength range, National
17、 Institute of Standards and Technology, Cat. No. SRM-930-DStirrer, magnetic, Fisher Scientific, Cat. No. 11-495-28Stirring bars, magnetic, borosilicate glass, 6-mm OD x 21-mm, and 9.55-mm OD x 25.4-mm, BaxterScientific Products, Cat. Nos. S8313-31 and -33, respectivelyStirring bar, magnetic, quartz,
18、 Alnico magnet, 10-mm OD x 35- to 40-mm, Pyromatics, Cat. No. PI-8789(optional)Stirring rod, borosilicate glass, Baxter Scientific Products, Cat. No. S8205-2Thermometer, surface, with temperature probe, Omega Engineering, Cat. Nos. HH81 and 88108K,respectivelyTongs, beakerWatch glass, borosilicate g
19、lass, ribbed, 100-mm diameter, Fisher Scientific, Cat. No. 02-613B3 of 11917-93REAGENTS AND MATERIALSAll reagents shall conform to the specifications established by the Committee on Analytical Reagents ofthe American Chemical Society, when such specifications are available, unless otherwise specifie
20、d.References to water mean deionized or distilled water, except where noted.References to catalog numbers and suppliers are included as a convenience to the method user. Othersuppliers may be used.Alumina, catalyst support, UOPCatalyst support solution, 4 mass/vol-%. Prepare in a 2-L beaker by disso
21、lving 40 g of catalyst support in400 mL of phosphoric acid, 400 mL of sulfuric acid and 100 mL of water on a hot plate while stirring.Allow to cool to ambient temperature and quantitatively transfer to a 1-L volumetric flask with water.Dilute to the mark with water and mix well. The catalyst support
22、 solution may be stored indefinitely ina well stoppered bottle or flask.Desiccant, indicating Drierite, 8 mesh, Fisher Scientific, Cat. No. 07-578-3AHydrochloric acid, concentrated, 37%Hydrogen peroxide, concentrated, 30%Lens paper, optical, Fisher Scientific, Cat. No. 11-996Nitric acid, concentrate
23、d, 70%Palladium wire, 0.25-mm diameter, high purity 99.997%, Aesar, Cat. No. 10962Phosphoric acid, concentrated, 85%Potassium iodide, free flowing, granular, Fisher Scientific, Cat. No. P410Potassium iodide-sodium sulfite, solution. Dissolve 100 0.01 g of potassium iodide in 100 mL of waterin a 250-
24、mL beaker. Quantitatively transfer to a 200-mL volumetric flask with water. Pipet 10 mL of1.2% sodium sulfite solution into the 200-mL volumetric flask. Fill to the mark with water, stopper andmix well. Prepare daily or each day used.Sodium sulfite, anhydrous, granular, Fisher Scientific, Cat. No. S
25、433Sodium sulfite, approximately 1.2% solution. Dissolve 1.20 0.01 g of sodium sulfite in 50 mL of waterin a 100-mL volumetric flask. Dilute to the mark with water, stopper and mix well. Prepare daily oreach day used.Sulfuric acid, concentrated, 98%Sulfuric acid, 1:1. Carefully, and with ice-cooling
26、, pour 500 mL of concentrated sulfuric acid into 500mL of water, mix and allow to cool. The sulfuric acid may be stored indefinitely in a well stopperedbottle or flask.Test paper, potassium iodide-starch, Fisher Scientific, Cat. No. 14-860STANDARD PREPARATIONAll subsequent steps involving handling a
27、nd heating of concentrated acids or acid solutions must beperformed in a fume hood.1. Weigh 1.0 g of 99.997% palladium wire to the nearest 0.1 mg.4 of 11917-932. Transfer the palladium wire into a 100-mL Kjeldahl flask and add a small borosilicate glass magneticstir bar.3. Add 25 mL of hydrochloric
28、acid and 10 mL of nitric acid to the flask. Place the flask in a 400-mLbeaker. Treatment of the palladium is conducted at ambient temperature until evolution of chlorine has subsided. If allowed to sit overnight, the palladium wire may dissolve without heating.4. Place the flask and beaker on a stir
29、ring hot plate and heat to a gentle boil while stirring slowly.5. Maintain the solution volume at approximately 30 mL by the dropwise addition of concentrated nitricand hydrochloric acid in a ratio of 2 to 5, respectively, until the palladium wire dissolves. Caution must be exercised during the addi
30、tion of the acids to avoid spattering of the palladium solution.6. Evaporate the acid solution slowly to approximately 20 mL by gentle boiling.7. Add 1 to 2 mL of concentrated hydrochloric acid slowly with a Pasteur pipet and then 1 to 2 mL of30% hydrogen peroxide dropwise with a Pasteur pipet to th
31、e stirred, gently boiling solution. Repeatthe additions and the boiling until the evolution of brown oxides of nitrogen ceases. Caution must be exercised during the addition of the hydrochloric acid and hydrogen peroxide to avoidspattering of the palladium solution. The vapor from the boiling acid m
32、ay be checked with water moistened potassium iodide-starch test stripsto verify the removal of nitrate from the sample. Hydrogen peroxide generates chlorine gas when added to the hydrochloric acid. Chlorine gas gives apositive test to potassium iodide-starch test strips. Therefore, allow the hydroge
33、n peroxide to decompose,by waiting a minimum of 2 minutes after the initial reaction has subsided prior to testing the evolved gases.8. Add 30 mL of water and 20 mL of hydrochloric acid to the solution. Swirl to mix.9. Remove the flask and beaker from the hot plate and allow them to cool to ambient
34、temperature.10. Tare a one-liter volumetric flask to the nearest 0.01 g and transfer the palladium solutionquantitatively with water to the flask.11. Add 30 mL of concentrated hydrochloric acid to the solution.12. Dilute with water to a mass that will produce a palladium concentration of exactly 1.0
35、00 mgpalladium per gram of solution, weighed to the nearest 0.01 g. The final mass of the palladium solution is equal to the mass of the palladium wire multiplied by 1000. Forexample, if 1.0034 g of palladium wire were dissolved, the final mass of the palladium solution would be1003.40 g.13. Mix the
36、 solution thoroughly by shaking.14. Subdivide the palladium standard solution without dilution, into separate 237-mL (or smaller) amberglass bottles and seal with polyethylene lined caps. The stability of the solution in an unopened bottle is not known. The working standard in used deteriorateswith
37、time and cannot be used for longer than 4 weeks.5 of 11917-93SAMPLE PREPARATIONObtain a representative sample of fresh or spent catalyst according to UOP Method 918. A total samplemust be obtained allowing no loss of sample to dusting.Spent CatalystCarbon Ignition of Whole PillIgnition of whole pill
38、s, broken pills, fines and dust should be performed according to UOP Method 896.Grinding and Weighing of Fresh and Spent Catalyst1. Grind the fresh or spent catalyst sample as described in UOP Method 918.2. Mix the collected, ground sample thoroughly by randomly shaking it for 5 minutes as described
39、 inUOP Method 918. Once the shaking is complete, the homogenous powder must not be agitated again until after the samplesare taken.3. Scoop sample approximately 2 g of the ground fresh or spent catalyst into a weighing scoop.4. Tare the weighing scoop on the analytical balance to read zero.5. Transf
40、er the catalyst sample carefully, to avoid dusting, into the bottom of a 400-mL beaker. Catalyst dusting must be avoided to prevent loss of sample.6. Place the empty weighing scoop onto the analytical balance and record the differential weight to thenearest 0.1 mg. The sample mass will be read as a
41、minus value on the balance.7. Scoop 2-g portions of fresh or spent catalyst into two tared, pre-ignited ceramic crucibles fordetermination of the LOI by UOP Method 275, for noble metal containing catalyst. Samples for the LOI must be taken at the same time the sample is weighed for the palladiumdete
42、rmination. The two LOIs will be calculated to three significant figures and the results must agree within 5% relativestandard deviation or the entire analysis must be repeated. The procedure as outlined in UOP Method 275 must be followed so as to minimize the formation ofpalladium oxides.PROCEDUREAl
43、l subsequent steps involving handling and heating of concentrated acids or acid solutions must beperformed in a fume hood.Preparation of Standards1. Transfer 50 mL of catalyst support solution using a graduated cylinder, into each of five 400-mLbeakers. Add a borosilicate glass stirring bar to each
44、beaker.6 of 11917-932. Transfer from a weighing buret 4.0-, 6.0-, 7.0- and 8.5-g aliquots (0.3 g) of palladium standard,weighed to the nearest 0.1 mg, into 4 of the 400-mL beakers containing the catalyst support solution.Reserve the fifth beaker for the reagent blank to matrix match the samples.3. R
45、inse the beaker walls with enough water to raise the volume to approximately 125 mL.4. Cover the beakers with a ribbed watch glass and stir the solutions. Ribbed watch glasses are suggested because they speed up sample volume reduction.5. Continue as described in Step 13 under Sample Dissolution.Sam
46、ple Dissolution1. Add a borosilicate glass stirring bar to the beakers containing the catalyst sample. The use of borosilicate glass stirring bars is acceptable because they are easy to obtain, but, it issuggested that the quartz stirring bars be used because they are more robust and less likely to
47、break whilein use, even though quartz is brittle.2. Cover each beaker with a ribbed watch glass and add 40 mL of 1:1 sulfuric acid to each beakerthrough the spout. Swirl to mix. Ribbed watch glasses are suggested because they speed up sample volume reduction.3. Add 20 mL of phosphoric acid, 10 mL of
48、 hydrochloric acid and 5 mL of nitric acid through the spoutof each beaker while stirring on a stirring hot plate without heating. Adjust the stirring rate to prevent the sample from spattering.4. Stop stirring and allow the beaker to stand until the gas evolution subsides.5. Increase the heat slowl
49、y and bring the sample to a boil, while stirring. Adjust the stirring rate to both prevent the sample from bumping, stirring rate too slow; and to prevent thesample from spattering, stirring rate too fast.6. Continue boiling and stirring until the mixture begins to fume at a hot plate temperature of about 400-500C. The surface temperature of the hot plate is monitored with a surface thermometer. If a hot plate temperature of 500C is used instead of 400C, the time required to dissolve the catalyst isreduced.7. Continue to fume until the entire sample has diss
