ASTM_D_3246_-_15.pdf

Designation:D324615Standard Test Method forSulfur in Petroleum Gas by Oxidative Microcoulometry1This standard is issued under the fixed designation D3246;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.Scope*1.1 This test method covers determination of sulfur in therange from 1.5 to 100 mg/kg(ppm by mass)by weight inhydrocarbon products that are gaseous at normal room tem-perature and pressure.NOTE1The test method has been tested cooperatively only onhigh-purity ethylene gas.Precision data have not been developed for otherproducts.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:2D1265 Practice for Sampling Liquefied Petroleum(LP)Gases,Manual MethodD1193 Specification for Reagent WaterD3120 Test Method for Trace Quantities of Sulfur in LightLiquid Petroleum Hydrocarbons by Oxidative Microcou-lometryD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceF307 Practice for Sampling Pressurized Gas for Gas Analy-sis2.2 Other Standards:Compressed GasAssociation Booklets G-4 and G-4-1 on theUse of Oxygen33.Summary of Test Method3.1 A sample is injected into a combustion tube maintainedat about 800C having a flowing stream of gas containingabout 80%oxygen and 20%inert gas(for example,nitrogen,argon,etc.).Oxidative pyrolysis converts the sulfur to sulfurdioxide which then flows into a titration cell where it reactswith triiodide ion present in the electrolyte.The triiodide thusconsumed,is coulometrically replaced and the total currentrequired to replace it is a measure of the sulfur present in thesample injected.3.2 The reaction occurring in the titration cell as sulfurdioxide enters is:I321SO21H2OSO313I212H1(1)The triiodide ion consumed in the above reaction is gener-ated coulometrically thus:3I2I3212e2(2)3.3 These microequivalents of triiodide(iodine)are equal tothe number of microequivalents of titratable sample ion enter-ing the titration cell.3.4 A liquid blend containing a known amount of sulfur isused for calibration.4.Significance and Use4.1 Trace quantities of sulfur compounds in hydrocarbonproducts can be harmful to many catalytic chemical processesin which these products are used.Maximum permissible levelsof total sulfur are normally included in specifications for suchhydrocarbons.It is recommended that this test method be usedto provide a basis for agreement between two laboratorieswhen the determination of sulfur in hydrocarbon gases isimportant.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.03 on Elemental Analysis.Current edition approved Jan.1,2015.Published January 2015.Originallyapproved in 1973.Last previous edition approved in 2014 as D3246 14.DOI:10.1520/D3246-15.2For 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.3Available from Compressed Gas Association,1235 Jefferson Davis Hwy.,Arlington,VA 22202.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.2 On liquefied petroleum gas,total volatile sulfur ismeasured on an injected gas sample.For such material a liquidsample must be used to measure total sulfur.5.Interferences5.1 This test method is applicable in the presence of totalhalide concentrations of up to 10 times the sulfur level and totalnitrogen content of up to 1.0%.Free nitrogen does notinterfere.5.2 This test method is not applicable in the presence oftotal heavy metal concentrations(for example,Ni,V,Pb,etc.)in excess of 500 mg/kg.NOTE2To attain the quantitative detectability that the method iscapable of,stringent techniques should be employed and all possiblesources of sulfur contamination must be eliminated.6.Apparatus4,56.1 Pyrolysis FurnaceThe sample should be pyrolyzed inan electric furnace having at least two separate and indepen-dently controlled temperature zones,the first being an inletsection that can maintain a temperature sufficient to volatilizeall the organic sample.The second zone shall be a pyrolysissection that can maintain a tempera