SH/T 0245-1992 Determination of aromatic hydrocarbon content in solvent naphtha (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 title / English name / replacement relationship

• Standard number: SH/T 0245-92 (confirmed in 2004)
• Chinese title: Determination of aromatic hydrocarbon content in solvent naphtha (chromatographic method)
• English title: not provided in the available source
• Replacement relationship: replaces SY 2307-82
• First issued: 1978
• Technical administration: under the technical administration of the Research Institute of Petroleum Processing
• Drafting: drafted under the responsibility of Jinzhou Refinery
• Approval/implementation: approved by China Petrochemical Corporation in 1992-05-20, implemented in 1992-05-20

2. Scope of application and non-applicability

• Applicable to solvent naphtha of the 145～200℃ fraction.
• Not applicable: not provided in the available source.

3. Method principle

Use a polar chromatographic column, detect by backflush with a flame ionization detector, then calculate the aromatic hydrocarbon content by the external standard area method.

4. Reagents and materials (purity / preparation)

4.1 Reagents

• N,N- bis(β- cyanoethyl)formamide: chromatographic stationary liquid.
• Trichloromethane: analytical reagent.
• Standard n-heptane.
• 1,3,5- trimethylbenzene: used for preparation of the external standard sample (accurate to 0.0002g).
• Aromatic-free C₅～C₇ alkanes: used for dilution (the carbon-number range is unclear in the source transcription and remains unverified).

4.2 Materials

• 6201 support: 60～80 mesh.
• Hydrogen: purity greater than 98%.
• Air: compressed air.

4.3 Preparation of external standard sample (5.2)

Weigh a certain amount of 1,3,5- trimethylbenzene (accurate to 0.0002g) in a stoppered conical flask, dilute with standard n-heptane or aromatic-free C₅～C₇ alkanes to a mass percentage concentration close to the aromatic hydrocarbon content of the test sample, then weigh (accurate to 0.0002g). Calculate its exact concentration, then inject into an ampoule for storage.

5. Instruments and equipment

• Chromatograph: a gas chromatograph equipped with a flame ionization detector. Overall sensitivity requirement: when injecting 2μL of a n-heptane solution containing 0.1%(m/m) toluene, the toluene peak height shall be not less than 4mm.
• Chromatographic column: stainless steel, length 2m, internal diameter 4mm.
• Recorder: 0～10mV; full-scale response time below 2s, and the recording paper width shall be not less than 250mm.
• Four-way backflush valve.
• Microsyringe: 10μL.
• Stoppered conical flask: 125mL.
• Beaker: 500mL.
• Enamel tray.

6. Recommended operating conditions

Typical operating conditions (6.1):

• Pre-column pressure: 68.6kPa (0.7kgf/cm²)
• Carrier gas flow rate: 55mL/min
• Air flow rate: 800mL/min
• Chromatographic column temperature: 110℃
• Detector temperature: 150℃
• Vaporization chamber temperature: 250℃

Determination of chromatographic column resolution (5.4): under the specified conditions, inject with a microsyringe a n-heptane solution containing 1%(V/V) each of toluene and decalin; the measured resolution between toluene and decalin shall be not less than 1.0.

7. Sampling and test sample preparation

• Preparation of chromatographic column (5.1): weigh N,N- bis(α- cyanoethyl)formamide 38g, place in a 500mL beaker, add trichloromethane 100mL, after complete dissolution, slowly add 100g 6201 support into the solution in the beaker with constant stirring, after thorough mixing, pour it into an enamel tray, place in a fume hood to air-dry naturally until there is no solvent odor. Pack the above-prepared stationary phase into the chromatographic column, plug it with copper gauze, install it on the chromatograph, introduce carrier gas, and keep it strictly leak-free.
• Backflush valve gas circuit is shown in Figure 1 (1— chromatographic column; 2— four-way valve).
• Test sample preparation: not provided in the available source.

8. Analysis procedure

6.1 Start the instrument; after the baseline is stable, analysis can be carried out. 6.2 First, use a clean 10μL microsyringe to draw 2μL of the external standard sample, and accurately inject all of it into the injection port; after observing on the recording paper that the non-aromatic hydrocarbon chromatographic peaks have completely emerged and the baseline has recovered, immediately turn the “backflush valve” until the aromatic hydrocarbon chromatographic peaks have completely emerged. Adjust the “attenuation” according to the size of the aromatic hydrocarbon chromatographic peak so that the aromatic hydrocarbon peak height is not less than 2mV. 6.3 Use a clean 10μL microsyringe to draw 2μL of the test sample, carry out the determination of aromatic hydrocarbon content in the test sample according to clause 6.2, and after the aromatic hydrocarbon chromatographic peaks have completely emerged, turn off the recorder switch. A typical chromatogram is shown in Figure 2 (1— non-aromatic hydrocarbons; 2— aromatic hydrocarbons).

9. Qualitative and quantitative determination and calculation formula

The aromatic hydrocarbon content x [%(m/m)] in the test sample is calculated according to the following formula:

x = (A₁ / A) × P

Where:

• A₁ — the aromatic hydrocarbon chromatographic peak area of the test sample;
• A — the aromatic hydrocarbon chromatographic peak area in the external standard sample;
• P — the aromatic hydrocarbon content in the external standard sample, %(m/m).

10. Precision

Repeatability: the difference between two results of repeated determinations by the same operator shall not exceed the following values.

11. Report

Take the arithmetic mean of the two results of repeated determinations as the aromatic hydrocarbon content of the test sample.

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 reference