1、Designation: D4782 10Standard Test Method forPalladium in Molecular Sieve Catalyst by Wet Chemistry1This standard is issued under the fixed designation D4782; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio
2、n. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of palladiumin molecular sieve-containing fresh catalysts with about 0.5weight % of pall
3、adium.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establis
4、h appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD7442 Practice for Sample Preparation of Fluid CatalyticCracking Catalysts and Zeolites for Elemental Ana
5、lysis byInductively Coupled Plasma Atomic Emission Spectros-copyE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Summary of Te
6、st Method3.1 The test sample is treated with hydrofluoric acid andevaporated to dryness to remove silica; the residue is fusedwith potassium pyrosulfate, and the cooled melt is dissolved in4%H2SO4. A measured excess of 0.01 N potassium iodide(KI) is added to precipitate palladium as palladium iodide
7、(PdI2). The precipitate is filtered and washed, and a smallamount of sodium sulfite is added to the filtrate to reduce anyfree iodine to iodide. The excess iodide is titrated with 0.01 NAgNO3potentiometrically, using a silver electrode versus acalomel electrode. A second sample taken at the same tim
8、e isused to determine loss on ignition.4. Significance and Use4.1 This test method provides a means of determining thepalladium content in fresh catalysts containing molecularsieves.4.2 This test method is not intended to cover samplescontaining metals other than palladium.5. Apparatus5.1 pH Meter w
9、ith Millivolt Scale or automatic recordingtitrator.5.2 Silver-Sulfide Electrode.5.3 Silver-Silver Chloride Double Junction reference elec-trode with 10 % KNO3in the outer chamber.5.4 Fisher Burner.5.5 Low-Temperature Muffle Furnace, 450C.5.6 High-Temperature Muffle Furnace, 1000C.5.7 Hot-Plate, with
10、 sand bath as a preferred option.5.8 Magnetic Stirrer and TFE-Fluorocarbon-Coated Stir-ring Bars.5.9 Burets, 25-mL, with 0.1-mL graduations or an equiva-lent.5.10 Volumetric Flasks, 1000-mL.5.11 High-Silica Beakers, 400-mL, with disposable boro-silicate beakers as an option. Alternatively, a petri d
11、ish can beused for the fusion step, with polypropylene beakers beingused thereafter.5.12 Watch Glasses, preferably ribbed, 87 mm.5.13 Analytical Balance, capable of weighing to nearest 0.1mg.5.14 Weighing Papers.5.15 Porcelain Crucibles, 10-mL.5.16 Graduated Cylinders, 5-mL, 10-mL, 25-mL, 100-mL.5.1
12、7 Filter Paper, Whatman No. 40, 11 cm.5.18 Funnel, filter.5.19 Desiccator.1This test method is under the jurisdiction of ASTM Committee D32 onCatalysts and is the direct responsibility of Subcommittee D32.03 on ChemicalComposition.Current edition approved April 1, 2010. Published May 2010. Originall
13、yapproved in 1988. Last previous edition approved in 2004 as D478204. DOI:10.1520/D4782-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Su
14、mmary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.20 Crucible Cover, porcelain.6. Reagents and Materials6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated
15、, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit
16、its use without lessening theaccuracy of the determination.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Specification D1193.6.3 Desiccant Molecular Sieve, type 4A.6.4 Filter Paper Pulp.NOTE 1Refer to Section 8 on Hazards in
17、Practice D7442 for hazardsassociated with handling of acids.6.5 Hydrofluoric Acid (HF),48%.6.6 Potassium Iodide Solution, 0.01 NDissolve 1.66 g ofpotassium iodide (KI) in distilled water, dilute to 1000 mL, andmix well.6.7 Potassium Pyrosulfate (K2S2O8).6.8 Silver Nitrate Solution, 0.01000 N Dissolv
18、e 1.6989 gof silver nitrate (AgNO3) in distilled water, dilute to 1000 mL,and mix well.NOTE 2The preparation of the AgNO3standard solution is a criticalstep. If any traces of chloride, organic matter or reducing agents arepresent in the water, moreAgNO3will be used in the back-titration and thefinal
19、 result will be low. Standardization is recommended.6.9 Sodium Sulfite Solution, 10 % Dissolve 10 g of anhy-drous sodium sulfite (Na2SO3) in 100 mL of distilled water.6.10 Sulfuric Acid (H2SO4) concentrated, sp gr 1.84.6.11 Sulfuric Acid, 48 % or 9 MAdd slowly, stir one partconcentrated H2SO4(96 %)
20、to one part water, then cool.6.12 Sulfuric Acid, 4 % or 0.72 MDilute 80 mL of 48 %sulfuric acid to 1000 mL.7. Procedure7.1 WeighingPrepare a carefully riffled, finely groundsample of ambient-equilibrated catalyst. For example, thesample could be thinly spread on filter paper and exposed toroom condi
21、tions for 16 h.7.1.1 For determination of percent loss on ignition at1000C, ignite a porcelain crucible at 1000C for at least 30min, place in desiccator to cool, and weigh to nearest 0.1 mg.Transfer approximately 2.0 g of sample to the crucible andweigh to the nearest 0.1 mg.7.1.2 For determination
22、of palladium, transfer approxi-mately 1.6 g of sample, weighed to the nearest 0.1 mg, into a400-mL high-silica beaker.7.2 Loss on Ignition:7.2.1 Place the porcelain crucible containing the test samplein a muffle furnace maintained at 450C and heat for 30 min.7.2.2 Transfer the crucible to a muffle f
23、urnace maintained at1000C and heat for at least 1.5 h to constant weight.7.2.3 Remove the crucible from the furnace, place in des-iccator to cool, and weigh to nearest 0.1 mg.7.2.4 Calculate weight percent loss on ignition at 1000C asfollows:Weight % LOI 5I 2 F!I!3 100 (1)where:I = initial sample we
24、ight, andF = final sample weight.7.3 Preparation of Test Sample for Titration:7.3.1 Cautiously add about 3 mL water to the high-silicabeaker to disperse the test sample.7.3.2 Add 12 mL hydrofluoric acid (HF) to effect dissolu-tion and evaporate to dryness on the cooler areas of the sandbath to remov
25、e silicon dioxide (SiO2).7.3.3 Promptly remove the beaker from the sand bath, coverresidue with9gofpotassium pyrosulfate, and heat gently overa Fisher burner until all excess hydrofluoric acid (HF) is drivenoff. Heat over flame until clear fusion results. Tilt or swirl thebeaker on cooling to preven
26、t breakage.7.3.4 Add 20 mL of 48 % H2SO4and 15 mL of distilledwater, cover and heat to boiling on sand bath to dissolve melt.Remove from the sand bath, dilute to 200 mL with boilingdistilled water, and cool.7.3.5 Place beaker on a magnetic stirrer, insert stirring barand add a small wad of paper pul
27、p. Add 5 mL of HF and stirsample a minimum of 5 min to complex the iron present andsolubilize any remaining SiO2.7.3.6 Add exactly 20.00 mLof 0.01 N KI from a buret whilestirring, and continue stirring for 5 min to coagulate the PdI2.7.3.7 Discontinue stirring, remove stirring bar and rinse intothe
28、beaker with distilled water.7.3.8 Filter contents of beaker through 11 cm size WhatmanNo. 40 filter paper.ABuchner funnel can optionally be used forfiltering. Add about 1 mL of 10 % sodium sulfite solution tofiltrate. Wash the beaker four times and the filter paper fivetimes with 4 % H2SO4.7.4 Titra
29、tion:7.4.1 Perform the potentiometric titration with 0.01000 NAgNO3solution in accordance with the steps as follows:7.4.1.1 Titrate quickly with 0.01000 N AgNO3solution to apredetermined millivolt reading (for example, using 1-mLincrements to an electrode potential reading of about 200 mV),then add
30、titrant in smaller increments of about 0.1 mL,obtaining scale readings after each addition.NOTE 3The point of maximum deflection per increment can bereadily determined during the titration by noting the difference betweenconsecutive scale readings. The difference will increase sharply near theend po
31、int and decrease sharply after the end point. The derivative functioncan also be used.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards fo
32、r LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D4782 1027.4.1.2 Record millilitres of AgNO3and millivolt readingson a graph or on a titration sheet like that shown in Fig. 1, and
33、obtain the end point from the inflection point of the titrationcurve.7.4.2 Determine the titer of the 0.01 N KI solution inaccordance with the following steps:7.4.2.1 Add 5 mL HF to 250 mL of 4 % H2SO4in a 400-mLhigh-silica beaker. Add exactly 20.00 mL of 0.01 N KI from aburet, introduce a stirring
34、bar, and add about 1 mL of 10 % ofNa2SO3solution.7.4.2.2 Titrate potentiometrically with 0.01000 N ofAgNO3solution as described in 7.4.1, using a buret.8. Calculation of Results8.1 Calculate the weight percent of palladium in the testsample on a 1000C ignited basis as follows:Palladium, weight % 5T
35、2 V!N 3 0.0532 3 100S 3100 2 % LOI!100!(2)where:T = 0.01000 N AgNO3, mL, used to titrate 20 mL of0.01 N KI,V = 0.01000 N AgNO3, mL, used to titrate sample,FIG. 1 Titration RecordD4782 103N = normality of 0.01000 N AgNO3,S = sample weight, g,% LOI = loss on ignition weight percent, as determined in7.
36、2.4, and0.0532 = milliequivalent weight of palladium.9. Precision and Bias9.1 Test ProgramAn interlaboratory study was conductedin which the weight % palladium (volatile free basis) wasmeasured in one separate test material in twelve separatelaboratories. Practice E691, modified for non-uniform data
37、sets, was followed for the data reduction. Analysis details arein the research report.9.2 PrecisionPairs of test results obtained by a proceduresimilar to that described in the study are expected to differ inabsolute value by less than 2.772 S, where 2.772 S is the 95 %probability interval limit on
38、the difference between two testresults, and S is the appropriate estimate of standard deviation.Definitions and usage are given in Terminology E456 andE177, respectively.Test Result(Consensus Mean)weight %95 % RepeatabilityInterval(Within Laboratory)weight %95 % ReproducibilityInterval(Between Labor
39、atories)weight %0.5390 0.004 (0.78 % of mean) 0.024 (4.54 % of mean)9.3 BiasThis test method is without known bias.10. Keywords10.1 catalyst; molecular sieve; palladiumASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin t
40、his standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must
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