ASTM_D_3908_-_20.pdf

Designation:D390820Standard Test Method forHydrogen Chemisorption on Supported Platinum Catalystsby Volumetric Vacuum Method1This standard is issued under the fixed designation D3908;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 thechemisorption of hydrogen at 298 K(25 C)on supportedplatinum catalysts that have been reduced in flowing hydrogenat 723 K(450 C).It incorporates a static volumetric vacuumtechnique at constant volume.1.2 The test method is intended for use on unused supportedplatinum on alumina catalysts of loadings greater than 0.3weight%.Data on other supports and lower platinum loadingswere not tested.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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D3766 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 Quality and StatisticsSee Terminology E456.3.3 Precision and BiasSee Practice E177.3.4 SymbolsThe following symbols are used:Pc=pressure of gas in calibrated bulb,torrPmc=pressure of gas in calibrated bulb andmanifold,torrPm=pressure in manifold,torrPmd=pressure in manifold and dead space,torrPmx=pressure in manifold prior to expansion intosample tube for X equilibration point,torrPex=equilibrium pressure after expansion for gen-erating X equilibrium point,torrVc=volume of calibrated bulb,cm3Vm=volume of manifold between stopcocks 12and 2 with only 4 and 1 open,cm3Vd=volume of dead space in sample cell contain-ing catalyst(volume between 2 and 3),cm3Vads(STP)x=volume of gas adsorbed at STP,cm3Vads(STP)cx=cumulative volume of gas adsorbed throughX,cm3VS=monolayer volume of gas adsorbed at STP,cm3TmAx=temperature representative of the manifoldprior to expansion into the sample cell,KTmBx=temperature representative of the entire sys-tem after equilibrium pressure(Pex)has beenestablished,KTm=temperature of manifold prior to expansioninto sample cell for dead space determination,KTmD=temperature of entire system after equilibriumpressure has been established for dead spacedetermination,KT=average manifold temperature for a givendose,K=(TmAx+TmBx)/2Wcat=mass of catalyst,gX=weight percent of platinum1This 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 Oct.1,2020.Published November 2020.Originallyapproved in 1980.Last previous edition approved in 2015 as D3908 03(2015).DOI:10.1520/D3908-20.2For 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 StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1%D=percent platinum atoms on the surface4.Significance and Use4.1 This test method sets forth a procedure by whichduplicate catalyst samples can be compared either on aninterlaboratory or intralaboratory basis.It is anticipated thatcatalyst producers and users will find this test method of value.4.2 Discrimination of the samples for which this procedureis recommended must be exercised when considering carrier(support)materials that sorb appreciable quantities of hydrogenor could cause an alteration of the state of the catalyst duringpretreatment,or both,(that is,sintering or metal occlusion).These materials must be identified by the user and experi-mented with to determine the most significant conditions ofmeasurement.4.3 This test method provides a measure of the totalhydroge