1、TRACE METALLIC IMPURITIES IN FRESH CATALYSTSBY ICP-AESUOP Method 927-92SCOPEThis method is for determining trace levels of iron, sodium, calcium, magnesium, titanium, molybdenumand silicon in fresh alumina supported catalysts of known composition by Inductively Coupled Plasma-Atomic Emission Spectro
2、metry (ICP-AES). All these elements except silicon can also be determined infresh silica-alumina supported catalysts. The method is sufficiently flexible to permit the determination ofother metals at trace levels if they can be brought into solution using the sample preparation proceduredescribed. C
3、oncentration ranges covered are listed in Table 1. Catalysts containing alpha- or theta-aluminaphases cannot be analyzed by this method.OUTLINE OF METHODAlumina supported catalysts are dissolved using sulfuric acid, while silica-alumina supported catalystsare dissolved in sulfuric and hydrofluoric a
4、cids. The resulting sample solution is aspirated into an ICP-AESinstrument and the concentration of each element is determined by comparison to matrix-matched standardsolutions. Sample results are reported on an as-received basis.APPARATUSReferences to catalog numbers and suppliers are included as a
5、 convenience to the method user. Othersuppliers may be used.Balance, readability 0.1-mgBeaker, Teflon, 250-mLBeaker, borosilicate glass, one-liter, used for warm water bathBottles, polypropylene, 125-mL and one-liter, Fisher Scientific, Cat. Nos. 02-925C and 925F,respectivelyCylinder, graduated, pol
6、ypropylene, 10-, 25- and 50-mLIS THE USERS RESPONSIBILITY TO ESTABLISH APPROPRIATE PRECAUTIONARY PRACTICES AND TODETERMINE THE APPLICABILITY OF REGULATORY LIMITATIONS PRIOR TO USE. EFFECTIVE HEALTH ANDSAFETY PRACTICES ARE TO BE FOLLOWED WHEN UTILIZING THIS PROCEDURE. FAILURE TO UTILIZE THISPROCEDURE
7、 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 REVIEWED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTIONEQUIPMENT (PPE). COPYRIGHT 1992 UOP LLCALL RI
8、GHTS 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 website, www.astm.org, or by contacting Customer Service atserviceastm.org, 610.832.9555 FAX, or 610.832.
9、9585 PHONE.2 of 7927-92Flasks, volumetric, polypropylene, 100-, 200- and 1000-mLFunnel, disposable, 55-mm diameter, Fisher Scientific, Cat. No. 10-320AGloves, polyethyleneHot plate, variable heat to at least 400CInductively Coupled Plasma-Atomic Emission Spectrometer, computer controlled, having a b
10、andpass of0.010 nm (FWHM) or better, and covering the wavelength range specified in Table 1. The instrumentmust have the ability to use internal standards and perform background corrections, and must measurethe internal standard response concurrently with each element response. A Perkin-Elmer Plasma
11、 2000spectrometer, or its equivalent, is required. A corrosion resistant sample introduction system isrecommended.Pipets, total volume, Class A, 5-, 10-, 15-, 20-, 25-, 30- and 50-mL, several of each requiredRegulator, argon, two-stage, high purity, Matheson Gas Products, Model 3104-580Regulator, ni
12、trogen, two-stage, high purity, Matheson Gas Products, Model 3104-580Thermometer, 0 to 100C, for use with warm water bath, Fisher Scientific, Cat. No. 15-077CThermometer, electronic, with surface temperature probe, Omega Engineering, Cat. Nos. HH81 and88108K, respectivelyWatch glass, Teflon, 75-mmWa
13、ter purification system, to provide 18.3 megohm/cm, Type 1 Reagent Grade water, Fisher Scientific,Cat. No. 09-050-256REAGENTS AND MATERIALSAll reagents shall conform to the specifications established by the Committee on Analytical Reagents ofthe American Chemical Society, when such specifications ar
14、e available, unless otherwise specified.References to water mean 18.3 megohm/cm, Type 1 Reagent Grade water.References to catalog numbers and suppliers are included as a convenience to the method user. Othersuppliers may be used.Aluminum metal, shot, 99.9999% minimum purity, Johnson Matthey, Alfa Pr
15、oducts, Cat. No. 10574Argon, 99.995% minimum purity, ICP feed gasHydrochloric acid, concentrated, high purity, Baker Ultrex gradeHydrofluoric acid, 48%Hydrogen peroxide, 30%Mercury metal, 99.99999% purity, SPEX Industries, Cat. No. HG05-50Nitrogen, 99.99% minimum purity, water/oil free, ICP optics p
16、urge gasScandium solution, 1000-g/mL, Inorganic Ventures, Cat. No. CGSC1-53 of 7927-92Standard solutions of metals, Fe, Na, Ca, Mg, Ti, Mo and Si solutions of 1000-g/mL concentrations,Inorganic Ventures, Cat. Nos. CGFE1-5, CGNA1-5, CGCA1-5, CGMG1-5, CGTI1-5, CGMO1-5 andCGSI1-5, respectivelySulfuric
17、acid, concentrated, high purity, Baker Ultrex GradeSulfuric acid, 80%. Mix four parts concentrated sulfuric acid with one part water, adding the acid to thewater slowly to avoid spattering.Yttrium solution, 1000-g/mL, Inorganic Ventures, Cat, No. CGY1-5. Not required if the spectrometerspecified in
18、APPARATUS is used (see Note 1).PROCEDUREAll subsequent steps involving handling and heating of concentrated acids or acid solutions must beperformed in a fume hood.Preparation of 10,000-g/mL Aluminum Solution1. Weigh 10.0 0.1 g of pure aluminum metal to the nearest 0.1 mg, and transfer to a one-lite
19、rpolypropylene bottle.2. Add one drop of mercury metal and 50 mL of concentrated high purity hydrochloric acid to the bottle.3. Cap the bottle, but leave the cap loose to allow pressure release.4. Place the bottle in a warm water bath (40 to 50C) to start the reaction, and adjust the reaction rate t
20、omaintain an approximate 25-mm layer of bubbles (foam) above the liquid. If the layer exceeds thislevel, control by adding a little water to the bottle. As it decreases, add hydrochloric acid dropwiseuntil a total of 100 mL (50 mL from Step 2 plus 50 mL additional) has been added. The dissolutiontak
21、es several hours.5. Transfer the solution to a one-liter polypropylene volumetric flask, quantitatively with water, using afunnel, after dissolution is complete. The remaining mercury is also transferred to the bottle. After the aluminum solution has been consumed,dispose of the mercury by following
22、 appropriate statutory guidelines.6. Cool to ambient temperature and dilute to volume. Cap and invert several times to mix thoroughly.Store in a one-liter polypropylene bottle.Preparation of Calibration Standards1. Prepare standards at the concentrations shown in Table 1 by appropriate dilution of t
23、he 1000-g/mLstandard metal solutions, using the high purity hydrochloric acid. Silicon is not added to Standard 2when determining impurities in silica-alumina supported catalysts. Two standards are used for Ca to cover two different concentration ranges using two differentwavelengths. The standards
24、are prepared in the same matrix as the samples, matching the acid and aluminum levels inthe final sample dilution, see Sample Preparation. If a spectrometer other than that specified in APPARATUS is used, yttrium can be substituted as theinternal standard (see Note 1).4 of 7927-922. Prepare a calibr
25、ation blank having the same matrix as the samples. Due to the linear response of the ICP instrument, multiple standards are not required. A single standardand calibration blank are sufficient to define the calibration line slope and intercept for each element.Table 1Elements Sought, Recommended Wave
26、lengths,Concentration Ranges Covered and Recommended Standard ConcentrationsConcentration Concentration, g/mLElement , nm Range, mass-% Std. 1 Std. 2Fe 238.204 0.005 - 1.0 50.0Na 589.592 0.003 - 1.0 50.0Ca 393.366 0.001 - 0.10 5.0Ca 422.673 0.10 - 1.0 50.0Mg 285.213 0.001 - 0.50 25.0Ti 323.452 0.002
27、 - 1.0 50.0Mo 202.030 0.005 - 0.50 25.0Si* 252.611 0.005 - 0.20 10.0Al Matrix Element - Concentration to Match SampleSc Internal Standard (see Note 1) 50.0 50.0*see Note 2Sample PreparationTo avoid contamination, whole pill samples are dissolved in high purity acids, and plasticware is usedthroughou
28、t the preparation scheme. Use of gloves is also highly recommended. Clean labware must be usedthroughout this procedure. Previously cleaned beakers that are stored in drawers must be rinsed with dilutehydrochloric acid, followed by several rinses with water, just prior to starting the procedure belo
29、w.1. Weigh, to the nearest 0.1 mg, 1.0 g of whole pill catalyst into a 250-mL Teflon beaker. Ground samples can be analyzed, but contamination from the grinding procedure is likely.2. Add, with a polypropylene graduated cylinder, 25 mL of water to the beaker to wet the catalyst.3. Add to the beaker,
30、 with a polypropylene graduated cylinder, 12 mL of 80% sulfuric acid, and swirl tomix the contents. If the catalyst support is alumina only, proceed to Step 5. Add the acid slowly to avoid spattering.4. Add to the beaker, with a polypropylene graduated cylinder, 10 mL of concentrated hydrofluoric ac
31、id,if the sample is a silica-alumina supported catalyst. Appropriate safety precautions must be taken when handling hydrofluoric acid.5. Place the beaker on a hot plate and adjust the heat to achieve mild boiling.6. Cover the beaker with a Teflon watch glass, if the sample is alumina only (no HF add
32、ed), and heatuntil the sample is completely dissolved, then proceed to Step 8.7. Continue heating while slowly increasing the temperature until the evolution of thick white fumescharacteristic of sulfuric acid, if the sample is silica-alumina.5 of 7927-92 This will volatilize the silicon as the tetr
33、afluoride and remove any residual HF. The hot plate temperature must not exceed 300C, as measured with a surface probe, or the Teflon beakerwill deform and/or melt.8. Remove the beaker from the hot plate and allow it to cool.9. Add 40 mL of water and 10 mL of concentrated hydrochloric acid to the be
34、aker and cover with aTeflon watch glass. If the sample contains platinum, also add 3 drops of hydrogen peroxide to the beaker to redissolve theplatinum.10. Return the beaker to the hot plate and bring to a boil.11. Remove the beaker from the hot plate and allow it to cool.12. Transfer the contents o
35、f the beaker, quantitatively using a funnel, to a 200-mL polypropylenevolumetric flask.13. Pipet 10 mL of 1000-g/mL scandium solution into the flask as an internal standard. If a spectrometer other than that listed in APPARATUS is used, yttrium can be substituted as the internalstandard (see Note 1)
36、.14. Allow the flask to cool to ambient temperature. Then dilute to volume with water. Cap and invert theflask several times to mix thoroughly.15. Prepare the matched standard solutions and a calibration blank as described in Preparation ofCalibration Standards. The preparation of Standard 2 and the
37、 analysis of the samples must be completed the same day as thesamples are diluted to final volume. The solutions are not stable overnight (silica will precipitate). Standard1 and the calibration blank are stable for 3 months.Sample AnalysisSet up the ICP-AES instrument in accordance with the instrum
38、ent manufacturers guidelines, allowingthe system to equilibrate for at least 30 minutes after the plasma is ignited prior to starting the analysis.Table 1 lists recommended wavelengths for each element. Other wavelengths may be used if it can beshown that precision is not adversely affected (see PRE
39、CISION). If the recommended spectrometer is used,Myers-Tracy signal compensation must be used. Use of a corrosion resistant sample introduction system isrecommended.1. Standardize the instrument by aspirating the blank, followed by Standards 1 and 2. Allow sufficientwash-out time between aspirations
40、. Wash-out times are dependent on instrument conditions such as pump rate, and on concentration levelsbeing measured, and can vary between 30 and 120 seconds.2. Aspirate the samples, after first entering the dilution factors into the computer. Allow sufficient wash-out time between aspirations.3. As
41、pirate the standards, treating them as samples with no dilution factors, as calibration checks asoften as recommended by the instrument manufacturer, but at the very least following aspiration ofthe final sample. Any calibration checks and the final standard readings should return the concentrations
42、 of the elements inthe standards within 5% relative. If not, recalibrate and reaspirate the samples.6 of 7927-92CALCULATIONSIf the dilution factor for the sample is entered into the instrument computer, the concentrations of theelements in the original sample in mass-ppm, on an as-received (AR) basi
43、s, are calculated by the computer.Divide the mass-ppm values by 10,000 to convert to mass-%. Below 0.10 mass-%, report to two significantfigures; at and above 0.10 mass-%, report to three significant figures.NOTES1. The choice of an internal standard is dictated by the instrument requirements and th
44、e composition ofthe samples to be analyzed. Some instruments require a specific element (i.e., scandium). Other elementsthat are commonly used include yttrium, bismuth and rhodium. One requirement is that the internal standardelement not be present in the sample at levels above a few mass-ppm. A ful
45、l discussion of internalstandardization is not possible here. For this method, the use of Sc or Y is recommended.The concentration of the internal standard to be used is dependent on instrument response, wavelengthand the concentrations of other elements being ratioed to the internal standard. Use t
46、he instrumentmanufacturers recommendations, or a compromise concentration of 50 mass-ppm of either Sc or Y, whichis mid-range in concentration, versus the other elements being determined by this method.When using internal standards, a sequential ICP-AES instrument measures element emission intensiti
47、es instep-wise fashion, moving from one element wavelength to the next. If the internal standard is also read inthis way, there will be a time interval between the reading of the internal standard intensity and thesubsequent element intensities. During this interval, instrument drift can occur that
48、will lead to error in theanalysis. To avoid this, the method specifies use of a sequential instrument that reads the internal standardemission intensity at the same time each element intensity is read; this compensates for any drift in theinstrument.In the case of a simultaneous instrument, the inte
49、rnal standard is read concurrently with all elements ofinterest, therefore, drift is not a factor. An additional benefit of an internal standard in either case is tocompensate for slight differences in matrix conditions between the samples and standards that can arisefrom small variations in levels of matrix components such as the aluminum and acids (these generally causeslight viscosity and/or nebulization differences).2. The maximum solubility for silicon in the acid matrix used in this method is 60 mass-ppm in solution,or 1.2 mass-% on the cataly
