1、Designation:D7457111Designation: D7457 12Standard Test Method forDetermining Chloride in Aromatic Hydrocarbons andRelated Chemicals by Microcoulometry1This standard is issued under the fixed designation D7457; the number immediately following the designation indicates the year oforiginal adoption or
2、, 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.1NOTEResearch Report was added editorially in August 2011.1. Scope1.1 This test method cove
3、rs the measurement of chloride in aromatic hydrocarbons, their derivatives, and related chemicals asdefined by the method. Aromatics typically do not have any source of chlorides other than organic. The presence of metallic orinorganic chlorides is theoretically possible but not likely and this meth
4、od does not purport to address recovery of thosecompounds.1.2 This test method is applicable to samples with chloride concentrations from 0.24 to 5.0 mg/kg. The test method limit ofdetection (LOD) is 0.07 mg/kg.1.3 This test method is preferred over Test Method D5194 for products, such as styrene, t
5、hat are polymerized by the sodiumbiphenyl reagent.1.4 In determining the conformance of the test results using this method to applicable specifications, results shall be roundedoff in accordance with the rounding-off method of Practice E29.1.5 The values stated in SI units are to be regarded as stan
6、dard. No other units of measurement are included in this standard.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the app
7、licability of regulatorylimitations prior to use. For specific hazard statements, see Section 9.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD1555M Test Method for Calculation of Volume and Weight of Industrial Aromatic Hydrocarbons and Cyclohexane MetricD3437 Prac
8、tice for Sampling and Handling Liquid Cyclic ProductsD3505 Test Method for Density or Relative Density of Pure Liquid ChemicalsD4052 Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density MeterD5194 Test Method for Trace Chloride in Liquid Aromatic HydrocarbonsD6809
9、 Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related MaterialsE29 Practice for Using Significant Digits in Test Data to Determine Conformance with SpecificationsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Met
10、hod2.2 Other Document:OSHA Regulations, 29 CFR paragraphs 1910.1000 and 1910.120033. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 calibration factor/recovery factor, nan indication of the efficiency of the measurement computed by dividing themeasured value of a standard by its
11、 theoretical value.1This test method is under the jurisdiction of ASTM Committee D16 on Aromatic Hydrocarbons and Related Chemicals and is the direct responsibility of SubcommitteeD16.04 on Instrumental Analysis.Current edition approved Feb. 1, 2011. Published March 2011. DOI: 10.1520/D745711E01.Cur
12、rent edition approved Jan. 1, 2012. Published February 2012. Originally approved in 2011. Last previous edition approved in 2011 as D7457 - 111. DOI:10.1520/D745712.2For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual B
13、ook of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3Available from U.S. Government Printing Office Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.1This document is not an ASTM
14、standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all
15、cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.2 dehydrating tube or drying vessel, na chamber containing concentrated s
16、ulfuric acid that scrubs the combustion effluentgases to remove water vapor prior to entering the titration cell.3.1.3 endpoint routine/test titration, nprocesses which allow the coulometer to set the endpoint and gain values to be usedfor sample analysis.3.1.4 oxidative pyrolysis, na process in whi
17、ch a sample is evaporated in an inert gas atmosphere and combusted afterwardscompletely in an oxygen-rich atmosphere at high temperature to break down the components of the sample into elemental oxides.3.1.5 reference electrode, nused in conjunction with sensor electrode to measure the potential of
18、the titration cell.3.1.6 sensor electrode, ndetects changes in silver ion concentration.3.1.7 titration cell, nvessel that contains the sensor-reference electrode pair and generator electrode pair along with the cellelectrolyte.3.1.8 titration parameters, nvarious instrumental conditions that can be
19、 changed for different types of analysis and analyzers.3.1.9 working electrode pair (generator electrode), nan electrode pair consisting of an anode and a cathode.4. Summary of Test Method4.1 An aliquot of sample is introduced into a combustion tube maintained at 900 to 1100C having a flowing stream
20、 of oxygencombustion gas and argon inert gas. Oxidative pyrolysis converts the organic and inorganic halides to hydrogen halides that thenflow into a titration cell where it reacts with silver ions present in the electrolyte. The silver ion thus consumed is coulometricallyreplaced and the total elec
21、trical work to replace it is a measure of the amount of organic halides in the specimen, which wasintroduced (see Annex A1).5. Significance and Use5.1 This test method is useful for determining organic as well as inorganic chloride compounds that can prove harmful toequipment and reactions in proces
22、ses involving hydrocarbons. The combination of both the organic and inorganic chloride iscommonly termed “total chloride” and since the inorganic chlorides are partially recovered, the result for total chloride will bebiased low.5.2 Maximum chloride levels are often specified for process streams and
23、 for hydrocarbon products.5.3 Organic chloride species are potentially damaging to refinery processes. Hydrochloric acid can be produced in hydrotreating or reforming reactors and this acid accumulates in condensing regions of the refinery.6. Interferences6.1 Both nitrogen and sulfur interfere at co
24、ncentrations greater than approximately 0.1 %.6.2 Bromides and iodides, if present, will be calculated as chlorides. However, fluorides are not detected by this test method.6.3 Both organic and inorganic chloride in the sample will be measured due to conversion of both species to HCL during theoxida
25、tive pyrolysis process which is commonly termed as total chloride. The results for total chloride will be biased low since themeasurement of total chloride is the sum of both organic and inorganic chloride compounds in the sample and inorganiccompounds (if present) are only partially converted. The
26、measurement of only the “organic chloride” in the sample can bemeasured by water washing the sample prior to analysis to remove the inorganic chloride in the sample. Partial loss of organichalogens which are partially soluble into the water wash, such as chloroacetic acid, may occur. The water washi
27、ng procedure cannot be applied to water soluble samples.7. Apparatus7.1 Pyrolysis Furnace, which can maintain at 900 to 1100C and sufficient to pyrolyze the organic matrix and convert allchlorine present in the sample to hydrogen chloride. Furnace systems with the furnace orientated horizontally or
28、vertically can beused.7.2 Pyrolysis Tube, made of quartz and constructed in a way that the sample can be evaporated in an inert gas stream, and bepyrolyzed afterwards in the presence of oxygen. The inlet end of the tube must have a sample inlet port with a septum throughwhich the sample can be injec
29、ted by syringe. The inlet end must also have side arms for the introduction of oxygen and inert carriergas. The pyrolysis tube must be of ample volume, so that complete pyrolysis of the sample is ensured.7.3 Titration Cell, containing sensor electrode, reference electrode and working electrode pair.
30、 An inlet from the pyrolysis tubeand magnetic stirring is also required. (WarningExcessive stirring speed will decouple the stirring bar and cause it to bouncein the titration cell, possibly damaging the electrodes. A slight vortex in the cell is adequate.)7.4 Microcoulometer, with connections for t
31、he electrodes, capable of measuring the potential of the sensor electrode, andcomparing this potential with a bias potential, and amplifying the difference to the working electrode pair to generate a current.The microcoulometer output voltage signal should be proportional to the generating current.7
32、.5 Controlling Unit, for programming and setting the operating parameters of the instrument and integration of data.7.6 Flow ControlThe apparatus must be quipped with flow controllers capable of maintaining a constant supply and flow ofoxygen and argon gas.7.7 Sample Inlet (Boat Inlet or Direct Inje
33、ction).7.7.1 Boat Inlet Systems (Horizontal Furnace).D7457 1227.7.1.1 Automated Boat Drive (Required), having variable stops, such that the sample boat may be driven into the furnace andstopped at various points as it enters the furnace thereby ensuring the controlled combustion of the sample and pr
34、eventing theformation of soot or coke, both of which indicate incomplete sample combustion. If direct injection is used with a horizontalsystem, the automated boat drive is not required.7.7.1.2 Boat Inlet Cooler (Required)Sample volatility and injection volume require an apparatus capable of cooling
35、 thesample boat prior to sample introduction. Thermoelectric coolers (peltier) or re-circulating refrigerated liquid devices have bothbeen found effective. Other approaches can be used as long as the performance criteria of the method are not affected. If directinjection is used with a horizontal sy
36、stem, the boat inlet cooler is not required.7.7.1.3 Quartz or Ceramic Sample Boats, of sufficient size to hold 90 to 250 L or mg of sample.7.7.2 Direct Injection (Both Horizontal or Vertical Furnace).7.7.2.1 Direct Injection (Required)A sample introduction system capable of directly injecting sample
37、 into the furnace (eithervertical or horizontal) at a controlled rate thereby ensuring the controlled combustion of the sample and preventing the formationof soot or coke, both of which indicate incomplete sample combustion.7.8 Autosampler (Required), capable of accurately delivering 90 to 240 L of
38、sample into the pyrolysis tube or sample boat ifa boat inlet with automated boat drive and inlet system is used.An autosampler is required to ensure the accuracy and performanceof the method is maintained.NOTE 1Multiple rinsing with clean solvent and/or sample between sample injections and/or betwee
39、n sampling from different sample vials isrecommended to minimize carryover contamination. An independent solvent flush from a separate vial and different from the solvent wash therebyproviding a clean, uncontaminated solvent may also be used. These features may be used as long as they do not degrade
40、 the performance and accuracyof the method.7.9 Dehydrating Tube or Drying Vessel, positioned at the outlet of the pyrolysis tube so that effluent gases are bubbled throughconcentrated sulfuric acid. The water vapor formed in the combustion gases are trapped while all other gases including hydrogenha
41、lides are allowed to flow through into the titration cell.7.10 Gas-Tight Sampling Syringe, having a capacity up to 250 L and capable of accurately delivering 90 to 240 L of sample.Syringes of differing sizes (100 or 250 L) are permissible to be used as long as the precision and accuracy of the metho
42、d are notdegraded.7.11 Balance, analytical, with sensitivity to 0.0001 g.7.12 Gas RegulatorsTwo-stage gas regulators must be used for the reactant and carrier gas.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is inte
43、nded that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, wheresuch specifications are available.4Other grades may be used, provided that the reagent is of sufficiently high purity to permit itsuse without lessening the accura
44、cy of the determination.8.2 Purity of WaterUnless otherwise indicated, references to water shall be understood to mean reagent water conforming toSpecification D1193, Type I. Type II can be used as long as the precision and accuracy of the method is not degraded.8.3 SolventThe solvent of choice must
45、 be capable of dissolving the chloride sample. The solvent of choice should have aboiling point similar to the sample being analyzed. Suggested possibilities include, but are not limited to isooctane, toluene,p-xylene and methanol.8.4 Purity of SolventThe blank value of the solvent used must be smal
46、ler than 0.1 g/Kg chlorides. Before using, the blankvalue of the solvent must be checked by carrying out a chlorine determination with the device being used for this analysis.8.5 Acetic AcidGlacial acetic acid (CHRR3COOH), concentration: 97 %.8.6 Cell Electrolyte SolutionSeveral electrolyte solution
47、s based on acetic acid solutions. Please follow instrumentmanufacturers recommendation.NOTE 2Bulk quantities of the electrolyte should be stored in a dark place and dark bottle and is recommended to be prepared fresh at least everytwo weeks.8.7 Inner Electrolyte SolutionPlease follow the instrument
48、manufacturers recommendation.8.8 Outer Electrolyte Solutions Please follow the instrument manufacturers recommendation.8.9 Gases.8.9.1 Argon, 99.996 % minimum purity required as inert and carrier gas.8.9.2 Oxygen, 99.995 % minimum purity is required as the oxidation gas.8.10 Sodium Acetate, anhydrou
49、s, (NaCH3CO2), fine granular.8.11 Sodium Sulfate, (Na2SO4), crystalline and anhydrous.4Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.D7457 1238.12 Sulfuric Acid, (95 to 98 %), (H2SO4) concentrated.8.13 2,4
