1、Designation: D4926 06 (Reapproved 2011)Standard Test Method forGamma Alumina Content in Catalysts Containing Silica andAlumina by X-ray Powder Diffraction1This standard is issued under the fixed designation D4926; the number immediately following the designation indicates the year oforiginal adoptio
2、n or, in the case of revision, the year of last revision. 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 gammaalumina and related trans
3、ition aluminas in catalysts containingsilica and alumina by X-ray powder diffraction, using thediffracted intensity of the peak occurring at about 67 2u whencopper Ka radiation is employed.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in
4、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 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.
5、 Referenced Documents2.1 ASTM Standards:2E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Summary of Test Method3.1 A sample of catalyst is calcined and ground, and anX-ray powder diffraction pattern is obtained under specifiedconditions over the app
6、roximate range from 52 to 76 2u. Thediffracted intensity above background for the peak occurring atabout 67 2u is compared to that of a reference sample, afterappropriate adjustments are made for scale settings and peakhalf-widths.4. Significance and Use4.1 This test method is for estimating the rel
7、ative amount ofgamma alumina in calcined catalyst samples, assuming that theX-ray powder diffraction peak occurring at about 67 2u isattributable to gamma alumina. Gamma alumina is defined asa transition alumina formed after heating in the range from 500to 550C, and may include forms described in th
8、e literature aseta, chi, and gamma aluminas. Delta alumina has a diffractionpeak in the same region, but is formed above 850C, atemperature to which most catalysts of this type are not heated.There are other possible components which may cause someinterference, such as alpha-quartz and zeolite Y, as
9、 well asaluminum-containing spinels formed at elevated temperatures.If the presence of interfering material is suspected, the diffrac-tion pattern should be examined in greater detail. Moresignificant interference may be caused by the presence of largeamounts of heavy metals or rare earths, which ex
10、hibit strongX-ray absorption and scattering. Comparisons between similarmaterials, therefore, may be more appropriate than thosebetween widely varying materials.5. Apparatus5.1 X-ray Powder Diffractometer Unit, with standardsample mount, Cu Ka radiation, monochromator, wide diver-gence and receiving
11、 slits (for example, 3 and 0.15, respec-tively), goniometer speed of 0.5/min or equivalent, chartspeed of about 0.5 cm/min or equivalent, and scale or gainfactors to provide conveniently measurable peaks. Computer-ized data acquisition equipment may also be used.NOTE 1For diffractometers employing s
12、tep scanning, convenientcorresponding conditions include a step size of 0.02 and a counting timeof 2.4 s/step, which is equivalent to a scanning rate of 0.5/min.5.2 Calcination Furnace.5.3 Grinding Equipment, suitable for preparing samples formounting in the sample holder.6. Procedure6.1 Calcine the
13、 catalyst sample for3hat500C.1This test method is under the jurisdiction of ASTM Committee D32 onCatalysts and is the direct responsibility of Subcommittee D32.01 on Physical-Chemical Properties.Current edition approved April 1, 2011. Published April 2011. Originallyapproved in 1989. Last previous e
14、dition approved in 2006 as D492606. DOI:10.1520/D4926-06R11.2For 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 Summary page onthe ASTM website.1
15、Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.2 Grind the sample sufficiently (for example, 200 to 400mesh) to enable it to be packed into a standard X-ray powderdiffractometer sample holder and mounted on the diffractome-ter.6.3
16、Obtain diffraction patterns for three samples over theapproximate range from 52 to 76 2u, using the conditionsdescribed in 5.1.6.4 Measure the height of the 67 2u peak above back-ground for the sample and the reference material to give H(sample) and H (reference), respectively.NOTE 2Reference materi
17、al may be prepared by calcining a high-purity sample of fine-particle boehmite for3hat550C.7. Calculation7.1 The relative X-ray powder diffraction intensity of threesamples, compared to a reference standard and expressed aspercent, is calculated by use of the following equation:100Isample!Iref!5Hsam
18、ple!Href!3Wsample!Wref!3Gref!Gsample!3 100where:H (sample) = defined in 6.4,H (ref) = defined in 6.4,W (sample)/W (ref) = ratio of the peak width at half-heightfor the sample compared to that forthe reference, andG (ref)/G (sample) = ratio of the instrument gain factorused to record the peak for the
19、sample to the gain factor used torecord the peak for the reference.(Gain factor is often defined as theinverse of the product of the diffrac-tometer scale setting and rate multi-plier setting.7.2 The average of the three values calculated in 7.1 can beconsidered a measure of gamma alumina content in
20、 the catalystif the measured sample peak is attributable to gamma alumina,the reference material is essentially pure gamma alumina, andthe sample does not contain large amounts of heavy metals orrare earths. Caution should be observed in comparing resultsfor widely varying materials.7.3 A working or
21、 secondary reference material can be usedas a matter of practical convenience. Should such a secondaryreference material be available, results as calculated in 7.1relative to the first or primary reference material can betransformed to relate to the working reference material. Deter-mine the relativ
22、e X-ray powder diffraction intensity of theprimary reference material relative to the secondary referencematerial, using an equation corresponding to that shown in 7.1and expressing the ratio IR1/IR2in fractional form. Multiply theresult relative to the primary reference material (100 I/IR1)bythe fa
23、ctor just determined above (IR1/IR2) to get the result (100I/IR2) relative to the secondary reference material. Identify thereference materials when reporting the results.8. Precision and Bias38.1 PrecisionBased on the results of a multilaboratory,multisample study and using Practice E691, the withi
24、n-laboratory repeatability was found to be 615 % (2S %) of themeasured value, and the between-laboratory reproducibilitywas found to be 624 % (2S %) of the measured value.8.2 BiasNo estimate of the bias of this test method ispossible.9. Keywords9.1 alumina; catalyst; gamma alumina; gamma aluminacont
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28、ews 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 contact
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