ASTM_D_4926_-_06_2011.pdf

Designation:D492606(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 adoption 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 transition 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 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.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 approximate 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 relative 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 the 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 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 exhibit 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 slits(for example,3 and 0.15,respectively),goniometer speed of 0.5/min or equivalent,chart speed of about 0.5 cm/min or equivalent,and scale orgain factors to provide conveniently measurable peaks.Com-puterized data acquisition equipment may also be used.NOTE1For diffractometers employing step 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 catalyst sample for 3 h at 500C.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 the 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 1,2011.Published April 2011.Originallyapproved in 1989.Last previous edition 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.4 Measure the height of the 67 2u peak above back-ground for the sample and the reference material to giveH(sample)and H(reference),respectively.NOTE2Reference material may be prepared by calcining a high-purity sample of fine-particle boehmite for 3 h at 550C.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 equa