SH/T 0412-1992 Determination of normal paraffin content in liquid paraffin and its feedstock oil (chromatographic method)

AI-translated method card — human verification pending. This is not an official translation of the standard. Unclear source values remain unverified; check the original standard and product certificate before use.

Card type: Test method

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

• Method number: SH/T 0412-92
• Full name: Determination of normal paraffin content in liquid paraffin and its feedstock oil (chromatographic method)
• English name: not provided in the available source
• Replacement relationship: replaces SY 2858-82
• First issued: 1975 year (see additional notes)
• Approval/implementation: approved by China Petrochemical Corporation 1992-05-20, implemented on 1992-05-20

2. Scope of application and non-applicability

• This standard specifies a gas chromatographic method for determining the content of normal paraffins in liquid paraffin and its feedstock oil.
• Applicable to the determination of normal paraffin content in liquid paraffin products produced by molecular sieve dewaxing of kerosene fractions and their feedstock oil (kerosene).
• Not applicable: not provided in the available source.

3. Method principle

Inject the sample into a 5A molecular sieve chromatographic column; normal paraffins are adsorbed; record the chromatographic peaks of non-normal hydrocarbons flowing out; calculate the non-normal hydrocarbon content by external standard quantification; subtract to obtain the normal paraffin content.

4. Reagents and materials (purity / preparation)

• 3.1 nC10—nC15 individual normal paraffins (chromatographic grade). (the normal-paraffin carbon-number range is garbled in the source transcription and requires verification)
• 3.2 pure non-normal hydrocarbons (preparation method attached below).
• 3.3 5A molecular sieve: 40—60 mesh; when the specific pressure is 0.1, the benzene adsorption capacity should be less than 5 mg/g, and the n-hexane adsorption capacity should be greater than 90 mg/g. (The source source-text extraction is “90mg/go”, requires confirmation against the source standard (source-text extraction))
• 3.4 hydrogen: purity 99%(V/V) or above.
• Preparation of standard samples (see Section 5 5.1).

5. Instruments and equipment

• 4.1 chromatograph: when hydrogen is used as carrier gas, the sensitivity to benzene (S) should be greater than (or equal to) 1000 mV. (The source source-text extraction is “1000mvo”, requires confirmation against the source standard (source-text extraction))
• 4.2 recorder: 2—5 mV, scanning time should be less than (or equal to) 1 s. (The source source-text extraction is “Is”, requires confirmation against the source standard (source-text extraction))
• 4.3 chromatographic column: glass, stainless steel or copper U type column, length 20 cm, inner diameter 6—8 mm. (the column inner-diameter range and unit are unclear in the source transcription and require verification)
• 4.4 microsyringe: 10 μL, with quantitative injection device. (The source source-text extraction is “lof'L”, requires confirmation against the source standard (source-text extraction))
• 4.5 reading microscope: magnification 20 times.

6. Recommended operating conditions

• Carrier gas flow rate: 80—100 mL/min. (the carrier-gas flow range and unit are garbled in the source transcription and require verification)
• Column temperature: 160—170 ℃.
• Detection cell: 160—170 ℃. (the detector-cell temperature range is garbled in the source transcription and requires verification)
• Vaporization chamber: 280 ℃±10 ℃.
• Bridge current: turn on the DC power supply and adjust the bridge current to the required milliampere value (the specific milliampere value is not provided in the available source).
• Analysis can be carried out after the baseline is stable.

7. Sampling and sample preparation

• 5.1 Preparation of standard samples
  • 5.1.1 Preparation of primary standard samples
    • 5.1.1.1 According to the individual normal paraffin composition of the sample, prepare a pure normal paraffin standard sample using chromatographic-grade individual normal paraffins.
    • 5.1.1.2 Pass the dewaxed oil (non-normal hydrocarbons) obtained from 5A molecular sieve dewaxing through a 5A molecular sieve adsorption column multiple times at room temperature to remove residual normal paraffins; measure the refractive index of the effluent oil until the measured value is constant; then it can be collected and stored as pure non-normal hydrocarbons.
    • 5.1.1.3 Using the prepared pure normal paraffin standard sample, add a certain amount of pure non-normal hydrocarbons to prepare a primary standard sample, seal it in a small ampoule for later use.
  • 5.1.2 Calibration of secondary standards: select a representative sample from the samples to be analyzed as the secondary standard. Calibrate it on the chromatograph using the corresponding primary standard sample, then seal it in a small ampoule for later use.
• Sample amount for sampling: not provided in the available source.

8. Analysis steps

• 6.1 Preparation of chromatographic column: place 40—60 mesh 5A molecular sieve in a high-temperature furnace at 550 ℃ for activation for 3 h; cool slightly, and quickly pack it into the chromatographic column while hot. It is required to be packed tightly and uniformly; then install it in the chromatograph and activate it with hydrogen at the operating column temperature for 2 h.
• 6.2 Determination of non-normal hydrocarbon content
  • 6.2.1 Analysis conditions: see Section 6.
  • 6.2.2 Turn on the DC power supply and adjust the bridge current to the required milliampere value.
  • 6.2.3 Start the recorder; analysis can be carried out after the baseline is stable.
  • 6.2.4 Using a clean, dry microsyringe, quantitatively inject the secondary standard and the sample separately. (the microsyringe injection procedure is garbled in the source transcription; verify the displayed interpretation before use)

9. Qualitative and quantitative determination and calculation formulas

• 7.1.1 The non-normal hydrocarbon content in the sample is calculated by formula (1):
  • C₁ = (F₁ / F₂) × q
  • Where: C₁—non-normal hydrocarbon content in the sample, %(m/m); F₁—peak area of non-normal hydrocarbons in the sample; F₂—peak area of non-normal hydrocarbons in the standard sample; q— non-normal hydrocarbon content in the standard sample, %(m/m).
  • Note: the source formula (1) source-text extraction is incomplete; the above formula is organized according to the symbols and textual description in the source, requires confirmation against the source standard (source-text extraction).
• 7.1.2 The normal paraffin content in the sample is calculated by formula (2):
  • C₃ = 100 − C₁
  • Where: C₃—normal paraffin content in the sample, %(m/m).
• 7.2 Report the normal paraffin content in the sample as a mass percentage; take the average of repeated determinations to one decimal place.

10. Precision

The difference between two repeated determination results and their average should not exceed the following values:

(the precision-table signs and values are garbled in the source transcription; verify them before applying the displayed limits)

11. Report

Report the normal paraffin content in the sample as a mass percentage; take the average of repeated determinations to one decimal place. (The source does not provide an independent “Report” section; this item is excerpted from 7.2)

12. Referenced documents

not provided in the available source.

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick Q&A