1、Designation: D 4782 04Standard Test Method forPalladium in Molecular Sieve Catalyst by Wet Chemistry1This standard is issued under the fixed designation D 4782; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 p
3、alladium.1.2 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 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Ref
4、erenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 456 Terminology Relating to Quality and StatisticsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.
5、 Summary of Test 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 p
6、alladium iodide(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
7、at the same time 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. Apparatu
8、s5.1 pH Meter with 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
9、Hot-Plate, with 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. Alternati
10、vely, a petri dish 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,310-mL.5.16 Graduated Cylinders, 5-mL, 10-mL, 25
11、-mL, 100-mL.5.17 Filter Paper, Whatman No. 40, 11 cm.5.18 Funnel, filter.5.19 Desiccator.5.20 Crucible Cover, porcelain.6. Reagents and Materials6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the s
12、pecifications of the Commit-tee on Analytical Reagents of the American Chemical Society,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, 2004. Published April
13、 2004. Originallyapproved in 1988. Last previous edition approved in 1997 as D 478291(1997).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 S
14、ummary page onthe ASTM website.3Alundum or other suitable materials may be used.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.where such specifications are available.4Other grades may beused, provided it is first ascertained that t
15、he reagent is ofsufficiently high purity to permit 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 D 1193.6.3 Desiccant Molecular Sieve, type 4A.6.4 Filte
16、r Paper Pulp.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 NDissolve 1.6989 gof silver nitrate (AgNO3) in distill
17、ed water, dilute to 1000 mL,and mix well.NOTE 1The preparation of the AgNO3standard solution is a criticalstep. If any traces of chloride, organic matter or reducing agents arepresent in the water, more AgNO3will be used in the back-titration and thefinal result will be low. Standardization is recom
18、mended.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 %) to one part water, then cool.6.12 Sulfuric Ac
19、id, 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 conditions for 16 h.7.1.1 For determination of per
20、cent 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 of palladium, transfer approxi-mately 1.6 g o
21、f 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 furnace maintained at1000C and heat for at lea
22、st 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 weight, andF = final sample weight.7.3 Preparat
23、ion 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 remove silicon dioxide (SiO2).7.3.3 Promptly remov
24、e 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 prevent breakage.7.3.4 Add 20 mL of 48 % H2SO4and 1
25、5 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 pulp. Add 5 mL of HF and stirsample a minimum of
26、 5 min to complex the iron present andsolubilize any remaining SiO2.7.3.6 Add exactly 20.00 mL of 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 beaker with distilled water.7.3.8 Filter con
27、tents of beaker through 11 cm size WhatmanNo. 40 filter paper. A Buchner 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 Titration:7.4.1 Perform the potentiometric titr
28、ation 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 titrant in smaller increments of about 0.1
29、 mL,obtaining scale readings after each addition.NOTE 2The 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 point and decrease sharply after the end poi
30、nt. The derivative functioncan also be used.7.4.1.2 Record milliliters of AgNO3and millivolt readingson a graph or on a titration sheet like that shown in Fig. 1, andobtain the end point from the inflection point of the titrationcurve.7.4.2 Determine the titer of the 0.01 N KI solution inaccordance
31、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 bar, and add about 1 mL of 10 % ofNa2SO3solution.7.4.2.2 Titrate potentiometrically with 0.01000 N of AgNO3solution as described in 7.
32、4.1, using a buret.4Reagent 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 for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the Unite
33、d States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D47820428. Calculation of Results8.1 Calculate the weight percent of palladium in the testsample on a 1000C ignited basis as follows:Palladium, weight % 5T 2 V!N 3 0.0532 3 100S 3100 2 % LOI!100!(2)
34、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,N = normality of 0.01000 N AgNO3,S = sample weight, g,% LOI = loss on ignition weight percent, as determined in7.2.4, and0.0532 = milliequivalent weight of palladium.9. Precision and Bias
35、9.1 Test ProgramAn interlaboratory study was conductedin which the weight % palladium (volatile free basis) wasmeasured in one separate test material in twelve separatelaboratories. Practice E 691, modified for non-uniform dataFIG. 1 Titration RecordD4782043sets, was followed for the data reduction.
36、 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 the difference between two testresults, an
37、d S is the appropriate estimate of standard deviation.Definitions and usage are given in Terminology E 456 andE 177, respectively.Test Result(Consensus Mean)weight %95 % RepeatabilityInterval(Within Laboratory)weight %95 % ReproducibilityInterval(Between Laboratories)weight %0.5390 0.004 (0.78 % of
38、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 this standard. Users of this standard are
39、 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 be reviewed every five years andif not r
40、evised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you
41、 may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D4782044
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