ASTM_D_4780_-_12.pdf

Designation:D478012Standard Test Method forDetermination of Low Surface Area of Catalysts andCatalyst Carriers by Multipoint Krypton Adsorption1This standard is issued under the fixed designation D4780;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 the specificsurface area of catalysts and catalyst carriers in the range from0.05 to 10 m2/g.A volumetric measuring system is used toobtain at least three data points which fall within the linear BETregion.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:2D3663 Test Method for Surface Area of Catalysts andCatalyst CarriersD3766 Terminology Relating to Catalysts and CatalysisE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 DefinitionsConsult Terminology D3766.3.2 Symbols:PH1=initial helium pressure,torr.PH2=helium pressure after equilibration,torr.TH1=temperature of manifold at initial heliumpressure,C.TH2=temperature of manifold after equilibration,C.P1=initial Kr pressure,torr.T1=manifold temperature at initial Kr pressure,K.T1=manifold temperature at initial Kr pressure,C.P2=Kr pressure after equilibration,torr.T2=manifold temperature at P2,K.T2=manifold temperature at P2,C.Po,N=liquid nitrogen vapor pressure,torr.Po,krypton=calculated krypton vapor pressure,torr.Ts=liquid nitrogen temperature,K.X=relative pressure,P2/Po,krypton.Vd=volume of manifold,cm3.Vs=the apparent dead-space volume,cm3.Ws=weight of sample,g.W1=tare weight of sample tube,g.W2=weight of sample plus tare weight of tube,g.Vds=volume of krypton in the dead space,cm.3V1=See 11.3.5.V2=See 11.3.6.Vt=See 11.3.7.Va=See 11.3.9.Vm=See 11.6.4.Summary of Test Method4.1 A catalyst or catalyst carrier sample is degassed byheating in vacuum to remove absorbed vapors from thesurface.The quantity of krypton adsorbed at various lowpressure levels is determined by measuring pressure differen-tials after introduction of a fixed volume of krypton to thesample at liquid nitrogen temperature.The specific surface areais then calculated from the sample weight and adsorption datausing the BET equation.5.Significance and Use5.1 This test method has been found useful for the determi-nation of the specific surface area of catalysts and catalystcarriers in the range from 0.05 to 10 m2/g for materialsspecification,manufacturing control,and research and devel-opment in the evaluation of catalysts.The determination ofsurface area of catalysts and catalyst carriers above 10 m2/g isaddressed in Test Method D3663.1This 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 May 1,2012.Published July 2012.Originally approvedin 1988.Last previous edition approved in 2007 as D478095(2007).DOI:10.1520/D4780-12.2For 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.Apparatus6.1 Aschematic diagram of the apparatus is shown in Fig.1.It may be constructed of glass or of metal and may operatemanually or automatically.It has the following features:6.1.1 Vacuum System,capable of attaining pressures below10-4torr(1 torr=133.3 Pa).This will include a vacuum gage(not shown in Fig.1).Access to the distribution manifold isthrough the valve V.6.1.2 Distribution Manifold,having a volume between 5and 40 cm3(Vd)known to the nearest 0.01 cm3.This volumeis defined as the volume between the stopcocks or valves andit includes the volume within the pressure gage.6.1.3 Constant Volume Gages,capable of measuring 1 to 10torr to the nearest 0.001 torr and 0 to 1000 torr to the nearesttorr(1 torr=133.3 Pa).6.1.4 Valve(H),from the helium supply to the distributionmanifold.6.1.5 Valve(K),from the krypton supply to the distributionmanifold.6.1.6 Sample Tube(s),with volume between 5 cm3and 25cm3,depending on the application.The sample tube(s)may beconnected to the distribution