ASTM_D_1658_-_80_scan.pdf

7009276 0023735 2ZO+m 4CTb LSTANDAAD3 ANSI/ASTM D 1658-80 AMERICAN SOCIETY FOR TESTING AND MATERIALS 1916 Race St.,Philadelphia,Pa.19103 Reprinted from the Annual Book of ASTM Standards,Copyright ASTM If not listed in the current combined index,will appear in the next edition.Standard Test Method for CARBON NUMBER DISTRIBUTION OF AROMATIC COMPOUNDS IN NAPHTHAS BY MASS SPECTROMETRY This standard is issued under the fixed designation D 1658;the number immediately following the designation indicates the year of original adoption or.in the case of revision.the year of last revision.A number in parentheses indicates the year of last reapproval.1.scope 1.1 This method covers the determination by mass spectrometry of the carbon number distribution of aromatic compounds in naph-thas boiling up to 350F(177C).Erroneous results may be obtained if the method is applied to narrow boiling fractions or to samples having an isomer distribution different from that used in calibration.2.Summary of Method 2.i Samples are analyzed by mass spectrom-etry,using the parent masses of the aromatic compounds according to carbon number.Sat-urates and olefins have negligible contribution to these masses.Results are expressed in per-cent by liquid volume.3.Significance and Use 3.1 A knowledge of the concentration of aromatic compounds by carbon number is use-ful in assessing the performance of motor gas-oline and aromatics reformers and their asso-ciated fractionation and extraction units.Such data can also be used to advantage in the blending of motor fuels and in the manufacture of solvents.4.Apparatus 4.1 Mass Spectrometer-Any mass spec-trometer capable of passing the performance test described in Section 6.4.2 Sample Inlet System-Any sample inlet system permitting the introduction of the test mixture(see 6.2)without loss,contamination,or change in com osition.4.3 Microburet or Constant-Volume Pipet.r 5.Reference Standards 5.1 Samples of the following hydrocarbons will be required:benzene.toluene,ethylben-zene,p-,m-,and o-xylene,isopropylbenzene,n-propylbenzene,I-methyl-2-ethylbenzene,1-methyl-3-ethylbenzene,I-methyl-4-ethylben-zene,1,2,3-trimethylbenzene,1,2,4-trimethyl-benzene,and 1,2,5-trimethylbenzene.(Dan-ger-Benzene is a poison,carcinogen and is extremely flammable,see Annex Al.l.Other liquids are flammable,see Annex A1.2.)NOTE-Only American Petroleum institute pure hydrocarbons,National Bureau of Standards stan-dard hydrocarbon samples,Phillips Petroleum Co.research grade hydrocarbons,or other hydrocarbons of equal purity should be used.6.Performance Test 6.1 Calibration:6.I.1 Calibrate the instrument in accordance with the manufacturers instructions for the compounds listed under reference standards(Section 5)making duplicate runs and using the same manipulative technique as in 7.2.Rerun any compound whose coefficient on its parent mass differs by more than 10.5%from the average value.The C8 and C9 compounds may either be run separately or combined in the proportions shown in Table 2 and run as mixtures.This method is under the jurisdiction of ASTM Com-mittee D-2 on Petroleum Products and Lubricants.Current edition approved Aug.29,1980.Published Oc-tober 1980.Originally published as D 1658-59 T.Last pre-vious edition D 1658-63(1979).Satisfactory microburets are described by Taylor,R.C.,and Young,W.S.,“Application to Spectrometer Calibration and to Preparation of Known Mixtures,”Analytical Chemis-“y,Vol 17,ANCHA,1945,p 811 814,and Purdy,K.M.,and Hams,R.J.,;b i d.,Vol f2,i950,pp.1337-1338.NOTICE:This standard has either been superseded and replaced by a new version or discontinued.Contact ASTM International(www.astm.org)for the latest information.W 9009276 0023736 l b 7 6.1.2 Read the peak heights from the records of each compound corresponding to m/e+(mass/charge)ratios of 78,92,106,and 120.Calculate the weighted average of each peak height for the Cn and Cg aromatics,using the isomer distribution of the sample to be ana-lyzed if it is known.Otherwise,calculate the weighted average of each peak height for the Cn and Cg aromatics by multiplying by the liquid fractions shown in Table 2 and summing the products.6.1.3 Express the calibration coefficients in units of peak height per unit of liquid at con-stant sensitivity.Arrange the coefficients for calculations by any convenient method.One arrangement of coefficients for the direct method of solution is to tabulate the data in columns according to descending number of m/e+and rows of descending carbon number.6.2 Test Mixture-Prepare a synthetic test mixture containing equal volumes of benzene,toluene,and Cs and C9 aromatics,with the Cs and Cs aromatics having the isomer distribu-tion shown in Table 2.(Danger-Benzene is a poison,carcinogen and is extremely flammable;see Annex Al.1.Other liquids are extremely.Flammable,see Annex A 1.2.)Record the mass spectrum of the test mixture from m/e+78 to 120,using the same manipulative technique as in 7.2.The calculated composition must agre