1、Designation: D 4926 06Standard Test Method forGamma Alumina Content in Catalysts Containing Silica andAlumina by X-ray Powder Diffraction1This standard is issued under the fixed designation D 4926; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of revision, the year of last revision. 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 gammaalumina and related transition aluminas
3、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 as thestandard. The values given in parentheses are for informationonly.1
4、.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. Referenced Do
5、cuments2.1 ASTM Standards:2E 691 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 approximate rang
6、e 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 relative amount
7、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 the literature
8、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 well asalumi
9、num-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 exhibit strongX
10、-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 slits (for e
11、xample, 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 step scanning,
12、 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 catalyst sam
13、ple for3hat500C.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 Obtain diffraction patterns for three samples over theapproximate range from 52 to 76 2u, using th
14、e conditionsdescribed in 5.1.1This 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, 2006. Published April 2006. Originallyapproved in 1989. Last previous e
15、dition approved in 2001 as D 492689(2001).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.1Copyright ASTM Int
16、ernational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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 material may be prepared by calcining
17、 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!5Hsample!Href!3Wsample!Wref!3Gref!Gs
18、ample!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 thesample to the gain factor used
19、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 the catalystif the measured sa
20、mple 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 secondary reference material c
21、an 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 relative X-ray powder diffraction inte
22、nsity 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 factor just determined above (IR1
23、/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 E 691, the within-laboratory repeatability was
24、 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 aluminacontent; X-ray powder diffractionA
25、STM 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 expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are
26、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 revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standard
27、sand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committe
28、e 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).3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D32-1027.D4926062
