NB/SH/T 0741-2010 Determination of hydrocarbon group composition in gasoline Multidimensional gas chromatography

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Card type: Test method

1. Method number / full name / English name / replacement relationship

• Standard number: NB/SH/T 0741—2010
• Chinese name: Determination of hydrocarbon group composition in gasoline Multidimensional gas chromatography
• English name: Standard test method for determination of hydrocarbon types composition in gasoline by multidimensional gas chromatography
• Replacement relationship: replaces SH/T 0741—2004 "Determination of hydrocarbon group composition in gasoline (multidimensional gas chromatography)"
• Issued/implemented: issued on 2010-05-01, implemented on 2010-10-01
• Issuing authority: National Energy Administration
• Previous versions: SH/T 0741—2004
• Main changes compared with the 2004 edition (original foreword): broadened the scope of application and measurement range; enhanced adaptability to finished gasoline containing oxygenates (improvement of the correction method in Annex A); proposed recommended relative mass correction factor values obtained by weighted statistical calculation; added an instrument system verification procedure; precision has changed somewhat
• Annex status: Annex A is a normative annex; Annex B and Annex C are informative annexes

2. Scope of application and non-applicability

• 1.1 specifies the determination of saturated hydrocarbons, olefins, aromatics and benzene in finished gasoline or gasoline blending components by multidimensional gas chromatography.
• 1.2 is applicable to the determination of saturated hydrocarbons, olefins, aromatics and benzene in petroleum fractions with a final boiling point not higher than 210 ℃. Concentration ranges: olefins volume fraction 0.5%~70%, aromatics volume fraction 1%~80%, benzene volume fraction 0.2%~10%. Samples outside these content ranges can also be determined, but precision data are not given. It is also applicable to gasoline products processed from other unconventional crude oils (such as shale or oil sands) that meet the distillation range requirements, or to hydrocarbon fuels synthesized from non-petroleum mineral feedstocks, but precision data are not given.
• 1.3 Gasoline containing ether or alcohol oxygenates: ethers elute with olefins, alcohols elute with non-benzene aromatics, and the hydrocarbon composition results should be corrected according to the type and content of oxygenates determined by relevant test methods (such as SH/T 0663).
• 1.4 is not suitable for determining the content of individual components within each hydrocarbon group other than benzene.
• 1.5 uses International System of Units [SI] units.
• 1.6 does not address all safety issues involved; before use, users must establish appropriate safety protection measures and management systems.

3. Method principle

• 4.1 After the gasoline sample enters the chromatographic system, it first passes through a polar separation column (BCEF column) to separate the aliphatic hydrocarbon components from the aromatic hydrocarbon components. When the aliphatic hydrocarbon components composed of saturated hydrocarbons and olefins pass through the olefin trap, the olefin components are selectively retained, and the saturated hydrocarbons pass through the olefin trap into the flame ionization detector (FID) for detection; after the saturated hydrocarbons have passed through the olefin trap, at which time benzene in the aromatic hydrocarbon components has not yet reached the end of the polar separation column, the olefin trap is temporarily removed from the carrier gas flow path by switching a six-port valve, and benzene enters the detector through a bypass for detection; after benzene has been eluted and detected, another six-port valve is switched to backflush the non-benzene aromatic hydrocarbon components, and the non-benzene aromatics enter the detector for detection; after the non-benzene aromatics have been detected, the olefin trap is placed in the carrier gas flow path again by valve switching, and under appropriate conditions the olefins trapped in the olefin trap are completely desorbed and enter the detector for detection. The detected chromatographic peaks are, in order, saturated hydrocarbons, benzene, non-benzene aromatics and olefins.
• 4.2 The sample requires no pretreatment and is injected directly; a reference sample is used to determine the retention times of the hydrocarbon group components. The chromatographic peak areas of the hydrocarbon group components in the gasoline test sample are measured according to the established procedure, and quantification is performed by the corrected area normalization method to calculate the volume fraction or mass fraction of each hydrocarbon group component in the sample. The chromatographic analysis time for one gasoline sample is about 15 min (the original text has source-text extraction as a doubtful point, written as "about Jamt", requires confirmation against the source standard (source-text extraction)).
• Principle diagrams: Figure 1 (principle diagram), Figure 2 (schematic diagram of system and column connections).

4. Reagents and materials (purity / preparation)

• 8.1 Standard reagents: n-pentane, n-hexane, n-heptane, isooctane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, benzene, toluene, xylene, propylbenzene, isopropylbenzene, trimethylbenzene, etc. Analytical reagent grade or higher purity should be used. Warning: all are flammable or toxic compounds.
• 8.2 Preparation of calibration samples: it is recommended to prepare by mass ratio in order of increasing volatility of the pure substances. It is recommended to first prepare separate mixed components of saturated hydrocarbons, olefins and aromatics, with the weighed content ranges referring to Table 3. Preparation may be carried out according to the actual sample situation so that the calibration sample concentration is close to that of the test sample; Table 4 lists a set of typical calibration sample preparation ratios.
  • Table 3 Preparation contents of each hydrocarbon group component in calibration samples (mass fraction/volume fraction, %): n-pentane 19/20, n-hexane 23/24, n-heptane 17/17, isooctane 17/16, n-octane 11/10, n-nonane 7/7, n-decane 4/4, n-undecane 2/2; 1-pentene 30/32, 1-hexene 26/27, 1-heptene 23/23, 1-octene 10/8, 1-nonene 6/5, 1-decene 3/3, 1-undecene 2/2; toluene 32/32, xylene 30/30, ethylbenzene 10/10, isopropylbenzene 28/28. The totals are all 100/100.
  • Table 3 Note: the volume and mass fractions in the table are not completely consistent corresponding relationships; it is recommended to measure according to the volume fractions listed in the table.
  • Table 4 Preparation of typical calibration samples (serial numbers 1~6, mass fraction and volume fraction of saturated hydrocarbons/olefins/non-benzene aromatics/benzene): serial number 1: 44.7/49.0, 13.7/15.0, 40.5/35.0, 1.17/1.00; serial number 2: 38.6/42.0, 23.0/25.0, 37.3/32.0, 1.18/1.00; serial number 3: 37.0/40.0, 27.8/30.0, 33.4/28.5, 1.78/1.50; serial number 4: 37.4/40.0, 32.9/35.0, 27.9/23.5, 1.80/1.50; serial number 5: 37.9/40.0, 38.0/40.0, 22.2/18.5, 1.82/1.50; serial number 6: 36.3/38.0, 43.1/45.0, 18.8/15.5, 1.84/1.50.
  • Table 4 Note: the volume and mass fractions in the table are not completely consistent corresponding relationships; it is recommended to measure according to the volume fractions listed in the table, then accurately weigh to obtain precise mass fractions.
• 8.3 Compressed air: combustion-supporting gas, purity not less than 99.9%. Warning: high-pressure gas, pay attention to safety.
• 8.4 Hydrogen: fuel gas, purity not less than (the original value is missing, requires confirmation against the source standard (source-text extraction)). Warning: high-pressure gas, extremely flammable.
• 8.5 Both air and hydrogen need to be purified; molecular sieve and activated carbon purifiers are used to remove water and hydrocarbon substances from the gases.
• 8.6 Carrier gas: high-purity nitrogen (original text "high-purity nitrogen", purity value not provided in the available source).
• 8.7 Sample bottles: small glass vials or glass vials with screw caps and rubber septa lined on the outer side with polytetrafluoroethylene.
• 8.8 Quality control check sample: used for routine monitoring of the reliability of the chromatographic system and separation system, monitoring the trapping capacity of the olefin trap, and verifying whether the determination results are within the method precision range by analyzing the quality control check sample. It should be prepared from or purchased as hydrocarbon compounds similar to the test sample, sealed in ampoules and stored at low temperature, and remain unchanged during storage; the calibration sample in Table 4 can be used as a quality control check sample.

5. Instruments and equipment

• 7.1 Gas chromatograph: should at least include a vaporization chamber, a temperature-controlled column oven, a flame ionization detector (FID), a chromatographic workstation and necessary hardware equipment (chromatographic column, olefin trap, balance column, switching valves and corresponding temperature control devices). Any gas chromatograph meeting the performance and parameter requirements may be used. A schematic diagram of the instrument and separation system is shown in Figure 2.
• 7.1 Injection system: capable of introducing about 0.1 μL of gasoline test sample into the vaporization chamber. Both microsyringes and automatic samplers can inject samples.
• 7.2 Carrier gas and detector gas flow control: stable control of carrier gas and detector gas flow rates is very critical for obtaining accurate, reliable and reproducible analytical results.
• 7.3 Flame ionization detector (FID): must meet or exceed the requirements of Table 1.
  • Table 1 Flame ionization detector performance requirements: noise/A typical value 10⁻¹⁴–10⁻¹²; drift/(A/h) typical value 10⁻¹²; detection limit/(g/s) typical value 10⁻¹² (in the table "10–1~10-12" "10-12" "10 ~1 106" are source-text extraction noise, specific values require confirmation against the source standard (source-text extraction)).
• 7.4 Olefin trap: its function is to retain all olefin components and pass all saturated hydrocarbon components when the mixed components of saturated hydrocarbons and olefins separated by the polar column in the sample pass through at a specific temperature. Generally the olefin trapping temperature is 120 ℃~140 ℃; the release temperature is generally 200 ℃~220 ℃, and the specific temperature is determined according to the specific olefins. Note: if olefin breakthrough is found in the olefin trap, it is recommended to adjust the operating conditions up to replacing the olefin trap.
• 7.5 Balance column: has no retention or adsorption for hydrocarbon group components and only serves to balance pressure, so as to ensure a stable baseline during valve switching.
• 7.6 Switching valves: the analysis system should include two two-position six-port valves; valve switching may be manual or automatic, and to ensure accurate valve switching time, automatic switching valves are recommended.
• 7.7 Temperature control of analysis system components: the polar separation column, olefin trap and switching valves should all have independent temperature control systems, and all components contacting the sample should be maintained at a certain temperature to prevent sample condensation. Table 2 lists typical control temperature ranges.
  • Table 2 Temperature control of system components: polar separation column 100–120 ℃ (isothermal); olefin trap 125–210 ℃ (temperature programming 30 ℃/min–50 ℃/min); switching valve 100–160 ℃ (isothermal); sample line 100~160 ℃ (isothermal).
• 7.8 Valve switching drive system: if a pneumatic drive system is used, attention must be paid to ensuring that the air pressure supplied to the pneumatic system meets the drive requirements, so as to achieve rapid valve switching.
• 7.9 Carrier gas purification device: in addition to the molecular sieve, activated carbon and other purifiers conventionally used in gas chromatography to remove water and hydrocarbon impurities from the carrier gas, a dedicated deoxygenation purifier must be installed to ensure that the oxygen content in the carrier gas is below 1 μL/L.
• 7.10 Chromatographic column: polar separation column; any chromatographic column that satisfies complete separation of benzene from aliphatic hydrocarbons using n-dodecane or 1- undecene and complete separation of benzene from toluene, and that leaves suitable valve switching time, may be used. It is recommended to use BCEF as the stationary liquid, with a coating amount of 25%, Chromosorb P (AW) 200 μm~300 μm as the support, with the column tube material being a quartz-lined stainless steel tube or an internally deactivated stainless steel tube, length 5 m, internal diameter 2 mm.
• 7.11 Recording and data processing unit: a chromatography workstation is recommended, and it should have the following functions: 7.11.1 can display the acquired chromatogram; 7.11.2 display the peak area and area percentage data of chromatographic peaks; 7.11.3 calculation and use of correction factors; 7.11.4 have the function of handling noise and ghost peaks; 7.11.5 be capable of necessary manual integration processing; 7.11.6 the determination results are calculated by the corrected area normalization method using chromatographic peak areas or area fractions, the corresponding relative mass correction factors and relevant parameters.

6. Recommended operating conditions

• Table 5 Typical chromatographic operating conditions: separation column temperature control 220 ℃; olefin trapping temperature 110 ℃ (in the original Table 5, "olefin trapping temperature/℃" is inconsistent with the statement in clause 7.4 120–140 ℃, requires confirmation against the source standard (source-text extraction)); olefin release temperature 120–140 ℃ (in the original Table 5, "olefin release temperature/℃" is inconsistent with the statement in clause 7.4 200–220 ℃, requires confirmation against the source standard (source-text extraction)); carrier gas flow rate 25–30 mL/min; detector gas flow rates: hydrogen 300–350 mL/min, air 25–30 mL/min (the corresponding item in the original "25–30" requires confirmation against the source standard (source-text extraction)); injection volume 0.1 μL (the original "0.y" requires confirmation against the source standard (source-text extraction)); valve switching drive pressure 200–300 kPa (the original "2004300" requires confirmation against the source standard (source-text extraction)).
• Table 6 Typical retention times of hydrocarbon group components: saturated hydrocarbons 0.6 min; benzene 3.0 min; non-benzene aromatics 3.0 min (the original "3:0" requires confirmation against the source standard (source-text extraction)); olefins 5.0–9.0 min (the original "5.0–9." requires confirmation against the source standard (source-text extraction)) and 9.0~13.0 min (two sets of numerical values coexist in the original, requires confirmation against the source standard (source-text extraction)).
• Figure 3: chromatogram of a calibration sample containing saturated hydrocarbons, olefins, non-benzene aromatics and benzene.
• Figure 5: typical gasoline chromatogram.

7. Sampling and sample preparation

• 11.1 Sampling and preparation: sample according to method GB/T 4756. If the sample is not analyzed immediately after sampling, to prevent volatilization of light components in the sample, seal it and store it in a refrigerator; before analysis, bring the sample temperature to room temperature.
• 11.2 Analysis system preparation: after turning on the instrument, check whether the parameter settings of the analysis system are accurate; to purify the analysis system, before analyzing samples, run the instrument blank once according to the sample analysis procedure to drive out residual impurities in the chromatographic column and olefin trap.
• 11.3 Take about 0.1 μL (the original "IwL" requires confirmation against the source standard (source-text extraction)) of sample and inject it into the prepared gas chromatography system.

8. Analysis procedure

• 11.3 The sample first passes through the polar separation column, in which the aliphatic hydrocarbon and aromatic hydrocarbon components are completely separated; the mixture of saturated hydrocarbons and olefins separated from the polar separation column enters the olefin trap, in which the olefin components are selectively retained while the saturated hydrocarbons pass through the olefin trap and enter FID for detection (see Figure 2); before benzene elutes from the chromatographic column, switch six-way valve 3B so that the olefin trap is disconnected from the carrier gas flow path and sealed; at this time, the benzene separated from the polar column passes through the balance column and enters FID for detection (see Figure 4a); after benzene has completely eluted, switch another six-way valve 3A so that non-benzene aromatics of C₇ and above (including C₇) are backflushed out of the polar column and enter FID for detection (see Figure 4b). While the non-benzene aromatics are being backflushed, begin to raise the temperature of the olefin trap; after the non-benzene aromatic components have completely eluted, switch six-way valve 3B again so that the olefin trap re-enters the carrier gas flow path; at this time, the olefins are desorbed from the olefin trap and enter FID for detection (see Figure 4c). The resulting chromatogram is processed by the chromatography workstation and corresponding analysis software to calculate the mass fraction or volume fraction of each component.
• Figure 4 Chromatographic operating flow for gasoline composition analysis: a. benzene elution; b. non-benzene aromatic elution; c. olefin elution.
• 9 Instrument system construction and calibration (the original title source-text extraction is "[garbled instrument-system construction and calibration heading]", requires confirmation against the source standard (source-text extraction)):
  • 9.1 System integration (chromatograph and independent temperature control elements) is shown in Figure 2; if a commercial system is used, contact the manufacturer for installation, positioning and system optimization.
  • 9.2 Impurities in the carrier gas may adversely affect the performance of the chromatographic column and olefin trap; therefore, a carrier gas purification system must be installed according to the requirements of clause 7.9 to ensure normal operation of the system.
  • 9.3 Use actual samples, quality control check samples or reference samples to verify the separation effect of the polar column on aliphatic hydrocarbons and aromatic hydrocarbons and the peak elution times of benzene and non-benzene aromatic components, thereby determining the first and second valve switching times; adjust the temperature of the olefin trap through experiments with reference samples or actual samples until the trapping requirements for olefins and ether compounds are met. Typical chromatographic operating conditions are shown in Table 5.
• 10 System verification and calibration (the original title source-text extraction is "system verification and cali[truncated wording]", requires confirmation against the source standard (source-text extraction)):
  • 10.1 Verification of the instrument system: use a calibration sample or an ordinary gasoline sample as the test sample, and carry out the difference between the measured values of non-benzene aromatics in tests with the olefin trap and without the olefin trap (the original source-text extraction is "[truncated trap wording] and bypassing the olefin trap: difference in measured non-benzene aromatics [wording incomplete]", requires confirmation against the source standard (source-text extraction)); compare the peak area values of the non-benzene aromatic measurements in the two tests; if the system is normal, the repeatability of the two tests is required; otherwise, check whether there are problems in the instrument system's tubing connections, six-way valve and carrier gas purity, etc. (this paragraph in the original source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction)).
  • 10.2 Performance check of the olefin trap: the olefin trap is the most critical component in the analysis system of this test method; if the olefin trap fails or does not meet performance requirements, it will directly affect the analysis results. A reference sample with a relatively high olefin content in Table 4 or an actual sample with high olefin content may be used to check the performance of the olefin trap. Under the established test conditions, the olefin trap should allow all saturated hydrocarbon components to pass through and trap all olefin components, as shown in Figure 3. The deviation of the measured results should not exceed the reproducibility requirement for the content level of each component in the calibration sample. Otherwise, the analysis conditions should be adjusted to meet the above requirements, and if necessary, the olefin trap must be replaced.
  • 10.3 Determination of retention times: the retention time ranges of saturated hydrocarbons, benzene, non-benzene aromatics and olefin components may be determined by using a calibration sample or an actual gasoline sample. Table 6 gives the retention times of each hydrocarbon group component through a BCEF column of length 5 m and the olefin trap; Figure 3 is the chromatogram of the sample according to Table 6 (the original is incomplete, requires confirmation against the source standard (source-text extraction)).
• 12 Quality control check: to confirm the reliability of the analysis system, after the instrument has been running for a period of time, two quality control check samples should be analyzed. The analysis procedure for the quality control check samples should be consistent with the gasoline sample analysis procedure. The difference between the results of the two quality control check samples should meet the repeatability requirements specified in the method. If the determination results exceed the requirements, the source of error should be determined and necessary corrections made.

9. Qualitative and quantitative determination and calculation formulas

• 13.1.1 Check the integration status of the integrator or chromatography workstation for the spectrum to determine whether all chromatographic peaks have been reasonably integrated; if not reasonable, the manual integration function of the workstation may be used to correct the baseline and then reintegrate. Note: because the benzene content in gasoline is relatively low, unreasonable baseline cutting and integration will have a relatively large impact on the analysis results.
• 13.1.2 Relative mass correction factors: for gasoline products meeting the distillation range requirements of GB 17930, according to the distribution of components with different carbon numbers in each hydrocarbon group and their response on FID, the relative mass correction factors of each hydrocarbon group component relative to non-benzene aromatics are given in Table 7; for specific gasoline fractions, see Appendix B for the values and calculation. The relative mass correction factors in Table 7 may also be obtained by calculation from standard samples according to formula (1).
  • Table 7 Relative mass correction factors of each hydrocarbon group component: saturated hydrocarbons 1.074; olefins 1.052; non-benzene aromatics 1.000; benzene 0.980.
  • Formula (1): f = (m_A · P_i) / (m_i · P_A)
    • f— relative mass correction factor (with non-benzene aromatic components as reference);
    • m_A— mass fraction of non-benzene aromatics in the standard sample;
    • P_A— peak area fraction of non-benzene aromatics in the standard sample determined by chromatography;
    • m_i— mass fraction of saturated hydrocarbons, olefins or benzene in the standard sample;
    • P_i— peak area fraction of saturated hydrocarbons, olefins or benzene in the standard sample determined by chromatography.
• 13.1.3 The mass fractions of saturated hydrocarbons, olefins, non-benzene aromatic hydrocarbons, and benzene in the sample are calculated according to formula (2): m_i = (f_i · P_i) / (Σ f_i · P_i) × 100 (the original formula source-text extraction is "mi 5×00", requires confirmation against the source standard (source-text extraction))
  • m_i— The mass fraction of a certain component i in the sample, %;
  • f_i—i The relative mass correction factor of the component;
  • P_i—i The peak area fraction of the component determined by chromatography.
• 13.1.4 The volume fractions of saturated hydrocarbons, olefins, non-benzene aromatic hydrocarbons, and benzene in the sample are calculated according to formula (3): V_i = (P_i · f_i / d_i) / (Σ P_i · f_i / d_i) × 100 (the original formula source-text extraction is "V.=zPf/d PH/A x100", requires confirmation against the source standard (source-text extraction))
  • V_i— The volume fraction of a certain component i in the sample, %;
  • f_i—i The relative mass correction factor of the component;
  • P_i—i The peak area fraction of the component determined by chromatography;
  • d_i— The weighted relative density of saturated hydrocarbons, olefins, and non-benzene aromatic hydrocarbons, and the relative density of benzene, see 13.1.5.
• 13.1.5 For gasoline products that meet the distillation range requirements of GB 17930, the weighted relative density values of each hydrocarbon group component are given in Table 8; for specific gasoline fractions, the calculation of weighted relative density is described in Appendix C.
  • Table 8 Weighted relative densities of each hydrocarbon group component in 20 ℃: saturated hydrocarbons 0.6860; olefins 0.6880; non-benzene aromatic hydrocarbons 0.8700; benzene 0.8789.
• 13.1.6 When gasoline contains ether or alcohol compounds, the content of each oxygen-containing compound must first be determined, and then the content of each hydrocarbon group component is calculated according to the method in Appendix A.
• 13.2 Reporting of test results: Report the volume fraction (or mass fraction) of the sum of saturated hydrocarbons, olefins, aromatic hydrocarbons, and benzene in the sample, accurate to 0.1%; the aromatic hydrocarbon content is the sum of non-benzene aromatic hydrocarbon content and benzene content; report the volume fraction (or mass fraction) of benzene, accurate to 0.01%.
• Appendix A (Normative Appendix) Correction of results when oxygen-containing compounds are present:
  • A.1 Overview: Oxygen-containing compounds such as ethers or alcohols can be added to finished gasoline to improve the octane number and emission status of gasoline. When gasoline contains ether or alcohol compounds, when analyzed by this method, the ether compounds in gasoline will peak together with olefin components, and the alcohol compounds will peak together with non-benzene aromatic hydrocarbon components. Therefore, when determining hydrocarbon components in gasoline, the response of oxygen-containing compounds in gasoline must be subtracted from the corresponding hydrocarbon fraction to obtain the true content of hydrocarbon group composition in gasoline after correction. According to the requirements of GB 17930, the content of oxygen-containing compounds in gasoline can be determined by the SH/T 0663 method. Based on the determined mass fractions of each oxygen-containing compound and the apparent peak area results of each hydrocarbon component determined during the test of this method, the mass or volume fractions of each gasoline hydrocarbon group component are obtained according to the following steps.
  • A.2 Correction of peak area fractions:
    • A.2.1 When the sample contains ether compounds, the olefin peak area fraction is corrected according to formula (A.1): A_olef = A_w − Σ(C_i · f_i) (the original formula source-text extraction is "Aint =Aw-2 (G min.)", requires confirmation against the source standard (source-text extraction))
      • A_olef— The area fraction corresponding to the chromatographic peak of the olefin component in the sample after correction, %;
      • A_w— The apparent olefin chromatographic peak area fraction measured by chromatography, %;
      • C_i— The mass fraction of the ith ether compound, %;
      • f_i— The relative mass correction factor corresponding to the ether compound, see Table A.1.
    • A.2.2 When the sample contains alcohol compounds, the non-benzene aromatic hydrocarbon peak area fraction is corrected according to formula (A.2): A_ARO = A_ARO,app − Σ(C_i · f_i) (the original formula source-text extraction is "AARO=", requires confirmation against the source standard (source-text extraction))
      • A_ARO— The area fraction corresponding to the chromatographic peak of the non-benzene aromatic hydrocarbon component in the sample after correction, %;
      • A_ARO,app— The apparent non-benzene aromatic hydrocarbon chromatographic peak area fraction measured by chromatography, %;
      • C_i— The mass fraction of the ith alcohol compound, %;
      • f_i— The relative mass correction factor corresponding to the alcohol compound, see Table A.1.
    • A.2.3 The relative mass correction factors of common oxygen-containing compounds measured on FID relative to non-benzene aromatic hydrocarbons are given in Table A.1.
      • Table A.1 Experimentally determined relative mass correction factors of some oxygen-containing compounds: methyl tert-butyl ether 1.605; ethyl tert-butyl ether 1.58; methyl tert-amyl ether 1.503; ethanol 2.352; tert-butanol 1.495; methanol 4.423.
  • A.3 Calculation of normalized mass and volume fractions of each hydrocarbon group component: After correcting the peak area fractions of olefins and non-benzene aromatic hydrocarbons, the peak area fractions of hydrocarbon components are re-normalized based on the determined area fractions of saturated hydrocarbons and benzene to obtain the normalized area fraction P_i of each hydrocarbon component, and the normalized mass fraction m_i and volume fraction V_i of each hydrocarbon component are calculated according to formula (A.3) and formula (A.4).
    • Formula (A.3): m_i = (P_i · f_i) / (Σ P_i · f_i) × 100
      • m_i— The mass fraction of hydrocarbon group component i in the hydrocarbon components, %;
      • V_i— The volume fraction of hydrocarbon group component i in the hydrocarbon components, %;
      • f_i— The relative mass correction factor of the hydrocarbon group component;
      • P_i— The peak area fraction of component i determined by chromatography after normalization, %;
      • d_i— The weighted relative density of saturated hydrocarbons, olefins, and non-benzene aromatic hydrocarbons, and the relative density of benzene.
    • Formula (A.4): V_i = (P_i · f_i / d_i) / (Σ P_i · f_i / d_i) × 100
  • A.4 Calculation of mass fractions of each hydrocarbon group component in gasoline: Calculate the mass fraction of each hydrocarbon group component in the sample according to formula (A.5).
    • Formula (A.5): m'_i = m_i × (100 − ΣC_oxv) / 100
      • m'_i— The mass fraction of hydrocarbon group component i in gasoline, %;
      • m_i— The mass fraction of hydrocarbon group component i in the hydrocarbon components, %;
      • ΣC_oxv— The sum of mass fractions of all oxygen-containing compounds in the sample, %.
  • A.5 Calculation of volume fractions of each hydrocarbon group component in gasoline: Since the density of hydrocarbon components in gasoline differs from that of oxygen-containing compounds, the influence of density differences on volume fractions should be considered when converting volume fractions.
    • A.5.1 Calculate the relative weighted density of hydrocarbons in the sample d_c according to formula (A.6): d_c = Σ m_i · d_i / 100
      • d_i— The weighted relative density corresponding to the ith hydrocarbon group component (including saturated hydrocarbons, benzene, non-benzene aromatic hydrocarbons, olefins);
      • m_i— The mass fraction of each hydrocarbon group component i in the hydrocarbon components, %.
    • A.5.2 The volume fraction of oxygen-containing compounds in the sample V_oxv is calculated according to formula (A.7): V_oxv = Σ(C_i / d_i) / (Σ(C_i / d_i) + (100 − ΣC_i) / d_c)
      • C_i— The mass fraction of the ith oxygen-containing compound in the sample, %;
      • d_i— The relative density of the ith oxygen-containing compound, values are given in Table A.2;
      • d_c— The weighted relative density of hydrocarbons in gasoline.
      • Table A.2 Relative densities of common oxygen-containing compounds in gasoline (20 ℃): methyl tert-butyl ether (MTBE) 0.7459; ethyl tert-butyl ether (ETBE) 0.7440; methyl tert-amyl ether (TAME) 0.7710; ethanol 0.7967; tert-butanol 0.7910; methanol 0.7963.
    • A.5.3 The volume fraction of each hydrocarbon group component in the sample is calculated according to formula (A.8): V'_i = V_i × (100 − V_oxv) / 100
      • V'_i— The volume fraction of hydrocarbon group component i in the sample, %;
      • V_i— The volume fraction of hydrocarbon group component i in the hydrocarbon components, %;
      • V_oxv— The volume fraction of oxygen-containing compounds in the sample, %.
• Appendix B (Informative Appendix) Calculation of relative mass correction factors for various hydrocarbon compounds:
  • B.1 According to ASTM (original text "ASTM!" requires confirmation against the source standard (source-text extraction)), calculate the mass response factor of different carbon number components of each hydrocarbon group relative to methane on FID according to formula (B.1), see Table B.1.
    • Formula (B.1): f = [(12.011 × C_n) + (1.008 × H_n)] × 0.7487 / (12.011 × C_n)
      • f— The mass response factor of a certain hydrocarbon compound relative to methane;
      • C_n— The number of carbon atoms in a certain hydrocarbon compound;
      • H_n—the number of hydrogen atoms in a certain hydrocarbon compound;
      • 12.011—the relative atomic mass of carbon atoms;
      • 1.008—the relative atomic mass of hydrogen atoms;
      • 0.7487—the correction factor relative to methane.
    • Table B.1 mass response factors relative to methane for different carbon number components of each hydrocarbon family on FID (carbon atom number 5~11+, corresponding values for each carbon number of paraffins P, naphthenes N, olefins O, aromatics A, the source text source-text extraction has severe noise, specific values require confirmation against the source standard (source-text extraction)).
  • B.2 Determination of the composition of components with the same carbon number: use ASTM D6623 or ASTM D6839 to determine the composition of different carbon number components in the hydrocarbon family, see Table B.2.
    • Table B.2 mass fractions of different carbon number components (carbon atom number 4~11+, corresponding mass fractions for each carbon number of paraffins P, naphthenes N, olefins O, aromatics A, the source text source-text extraction has severe noise, specific values require confirmation against the source standard (source-text extraction)).
  • B.3 Calculation of the mass response factors of each hydrocarbon family component relative to methane:
    • B.3.1 The mass response factor of paraffins relative to methane is calculated according to formula (B.2): f_P = Σ(P_i · f_i) / ΣP_i
      • f_P—the mass response factor of total paraffins relative to methane;
      • P_i—the mass fraction of paraffins with different carbon numbers, %;
      • f_i—the mass response factor of paraffins with different carbon numbers relative to methane;
      • ΣP_i—the sum of the mass fractions of paraffins with different carbon numbers, %.
    • B.3.2 The mass response factor of naphthenes relative to methane is calculated according to formula (B.3): f_N = Σ(N_i · f_i) / ΣN_i
      • f_N—the mass response factor of total naphthenes relative to methane;
      • N_i—the mass fraction of naphthenes with different carbon numbers, %;
      • f_i—the mass response factor of naphthenes with different carbon numbers relative to methane;
      • ΣN_i—the sum of the mass fractions of naphthenes with different carbon numbers, %.
    • B.3.3 The mass response factor of saturated hydrocarbons relative to methane is calculated according to formula (B.4): f_S = (ΣP_i · f_P + ΣN_i · f_N) / (ΣP_i + ΣN_i)
      • f_S—the mass response factor of total saturated hydrocarbons relative to methane;
      • f_P—the mass response factor of total paraffins relative to methane;
      • f_N—the mass response factor of total naphthenes relative to methane;
      • ΣP_i—the sum of the mass fractions of paraffins with the same carbon number, %;
      • ΣN_i—the sum of the mass fractions of naphthenes with the same carbon number, %;
      • the mass fraction of saturated hydrocarbons, whose value is the sum of P_i and N_i, %.
    • B.3.4 The mass response factor of olefins relative to methane is calculated according to formula (B.5): f_O = Σ(O_i · f_i) / ΣO_i
      • f_O—the mass response factor of total olefins relative to methane;
      • O_i—the mass fraction of olefins with different carbon numbers, %;
      • f_i—the mass response factor of olefins with different carbon numbers relative to methane;
      • ΣO_i—the sum of the mass fractions of olefins with different carbon numbers, %.
    • B.3.5 The mass response factor of non-benzene aromatics relative to methane is calculated according to formula (B.6): f_A = Σ(A_i · f_i) / ΣA_i
      • f_A—the mass response factor of total non-benzene aromatics relative to methane;
      • A_i—the mass fraction of non-benzene aromatics with different carbon numbers, %;
      • f_i—the mass response factor of non-benzene aromatics with different carbon numbers relative to methane;
      • ΣA_i—the sum of the mass fractions of non-benzene aromatics with different carbon numbers, %.
  • B.4 The calculation of the relative mass correction factors of each hydrocarbon family component relative to non-benzene aromatics is shown in formula (B.7): f_i = f'_i / f_A
    • f_i—the mass correction factors of saturated hydrocarbons, olefins and benzene relative to non-benzene aromatics;
    • f'_i—the mass response factors of saturated hydrocarbons, olefins and benzene relative to methane;
    • f_A—the mass response factor of total non-benzene aromatics relative to methane.
• Appendix C (informative appendix) Calculation of weighted relative density of each hydrocarbon family component:
  • C.1 The relative densities referenced for different carbon number components of each hydrocarbon family are shown in Table C.1.
    • Table C.1 relative densities of different carbon number components (20 ℃): carbon atom number 4~11+, corresponding values for each carbon number of paraffins P, naphthenes N, olefins O, aromatics A (the source text source-text extraction has severe noise, specific values require confirmation against the source standard (source-text extraction)); Note: relative densities are taken from ASTM DS 4A, physical property constants of hydrocarbon compounds.
  • C.2 Determination of the composition of different carbon number components in each hydrocarbon family: use ASTM D6623 or ASTM D6839 to determine the composition of different carbon number components in the hydrocarbon family, see Table C.2.
    • Table C.2 mass fractions of different carbon number components (carbon atom number 4~11+, corresponding mass fractions for each carbon number of paraffins P, naphthenes N, olefins O, aromatics A, the source text source-text extraction has severe noise, specific values require confirmation against the source standard (source-text extraction)).
  • C.3 Calculation of weighted relative density of each hydrocarbon family component:
    • C.3.1 The weighted relative density of paraffins is calculated according to formula (C.1): d_P = Σ(P_i · d_Pi) / ΣP_i
      • d_P—the weighted relative density of paraffins;
      • P_i—the mass fraction of paraffins with different carbon numbers, %;
      • d_Pi—the relative density of paraffins with different carbon numbers;
      • ΣP_i—the sum of the mass fractions of paraffins with different carbon numbers, %.
    • C.3.2 The weighted relative density of naphthenes is calculated according to formula (C.2): d_N = Σ(N_i · d_Ni) / ΣN_i
      • d_N—the weighted relative density of naphthenes;
      • N_i—the mass fraction of naphthenes with different carbon numbers, %;
      • d_Ni—different carbon number naphthenes