ASTM_D_4222_-_03_2015e1.pdf

Designation:D422203(Reapproved 2015)1Standard Test Method forDetermination of Nitrogen Adsorption and DesorptionIsotherms of Catalysts and Catalyst Carriers by StaticVolumetric Measurements1This standard is issued under the fixed designation D4222;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.1NOTEEq 10 in subsection 12.4.7 was corrected editorially in August 2015.1.Scope1.1 This test method covers the determination of nitrogenadsorption and desorption isotherms of catalysts and catalystcarriers at the boiling point of liquid nitrogen.2A staticvolumetric measuring system is used to obtain sufficientequilibrium adsorption points on each branch of the isotherm toadequately define the adsorption and desorption branches ofthe isotherm.Thirty points evenly spread over the isotherm isconsidered to be the minimum number of points that willadequately define the isotherm.1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.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:3D3663 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 DefinitionsSee Terminology D3766.3.2 Symbols:PH1=initial helium pressure,torr.PH2=helium pressure after equilibration,torr.TH1=temperature of manifold at initial helium pressure,C.TH2=temperature of manifold after equilibration,C.P1=initial N2pressure,torr.T1=manifold temperature at initial N2pressure,K.T1=manifold temperature at initial N2pressure,C.P2=pressure after equilibration,torr.T2=manifold temperature after equilibrrium,K.T2=manifold temperature after equilibrium,C.P3=initial N2pressure during desorption,torr.T3=manifold temperature at initial N2pressure,K.T3=manifold temperature at initial N2pressure,C.P4=pressure after equilibration during desorption,torr.T4=manifold temperature after equilibration,K.T4=manifold temperature after equilibration,C.P0=liquid nitrogen vapor pressure,torr.Ts=liquid nitrogen temperature,K.X=relative pressure,P2(4)/P0.Vd=volume of manifold,cm3.Vs=the dead-space volume factor,cm3(STP)/torr.Ws=mass of sample,g.W1=tare of sample tube,g.W2=sample mass+tare of tube after degassing,g.W2=sample mass+tare of tube after adsorption,g.Vds=volume of nitrogen in the dead-space,cm3(STP).V1=see 12.4.3.V2=see 12.4.4.Vt=see 12.4.5.Vad=see 12.4.7.Vde=see 12.5.1This test is under the jurisdiction of ASTM Committee D32 on Catalysts and isthe direct responsibility of Subcommittee D32.01 on Physical-Chemical Properties.Current edition approved April 1,2015.Published August 2015.Originallyapproved in 1983.Last previous edition approved in 2008 as D4222 03(2008).DOI:10.1520/D4222-03R15.2Adamson,A.W.,Physical Chemistry of Surfaces,3rd ed.,John Wiley&Sons,New York,NY,1976,p.532.3For 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 4.Summary of Test Method4.1 The sample is heated and evacuated to remove adsorbedvapors from the surface.The nitrogen adsorption branch of theisotherm is determined by evacuating the sample,cooling thesample to the boiling point of liquid nitrogen(;77.3 K),andsubsequently adding stepwise,known amounts of nitrogen gasto the sample in such amounts that the form of the adsorptionisotherm is adequately defined and the saturation pressure ofnitrogen is reached.Each additional dose of nitrogen isintroduced to the sample only after the foregoing dose ofnitrogen has reached adsorption equilibrium with the sample.By definition,equilibrium is reached if the change in gaspressure is no greater than 0.1 torr/5 min interval.Thedesorption isotherm is determined by desorbing nitrogen fromthe saturated sample in a stepwise mode with the sameprecautions taken to ensure desorption equilibration as appliedunder adsorption conditions.It is essential that the experimen-tal points be distributed over the isotherm in such a manner asto correctly identify and define the isotherm.If the additions orwithdrawals of nitro