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D5443-23 – Standard Test Method Technical Guide
📐 Test Method Scope and Application
This test method covers the determination of paraffins, naphthenes, and aromatics by carbon number in low olefinic hydrocarbon streams having final boiling points of 200 °C or less. Hydrocarbons with boiling points greater than 200 °C and less than 270 °C are reported as a single group. Olefins, if present, are hydrogenated and the resultant saturates included in the paraffin and naphthene distribution. Aromatics boiling at C9 and above are reported as a single aromatic group.
Individual components are determined only for benzene (C6 aromatic), toluene (C7 aromatic), and cyclopentane (C5 naphthene). The lower limit of detection for any single component or group is 0.05 % by mass. The method is applicable to virgin, catalytically converted, thermally converted, alkylated, and blended naphtha. All values are reported in SI units.
⚠️ Safety Note: Specific precautionary statements are given in Section 8 and Table 1 of the standard. Users must establish appropriate safety, health, and environmental practices before use.
⚙️ Instrumentation and Multidimensional Separation
A representative sample is introduced into a gas chromatographic system containing a series of columns and switching valves. The sample first passes through a polar column that retains aromatic compounds, bi-naphthenes, and high boiling (>200 °C) paraffins and naphthenes. The unretained fraction elutes to a platinum column where any olefins are hydrogenated, and then to a molecular sieve column that performs carbon number separation.
The system enables detailed hydrocarbon type analysis by carbon number. The molecular sieve column provides separation based on molecular size, while the platinum column ensures that olefins are converted to saturates for accurate distribution. This multidimensional approach allows for precise quantification of paraffins, naphthenes, and aromatics in petroleum distillates through 200 °C.
📊 Key Measured Properties and Reporting
| 🟦 Parameter | 📏 Specification | 🎯 Details |
|---|---|---|
| Maximum Final Boiling Point | 200 °C | Determination limit for hydrocarbon streams |
| Group Reporting Range | >200 °C to <270 °C | Reported as a single group |
| Lower Detection Limit | 0.05 % by mass | For single component or group |
| Specific Individual Components | Benzene, Toluene, Cyclopentane | Only C6, C7 aromatics and C5 naphthene |
| Olefin Treatment | Hydrogenated | Included in saturate distribution |
| Unit System | SI (coulomb “C”) | Standard unit for all measurements |
Results include paraffin and naphthene distribution by carbon number, with aromatics from C9 and above reported as a single aromatic group. The method is validated for low olefinic streams and provides reproducible type analysis.
✅ Technical Tip: The hydrogenation step is essential for accurate saturate analysis. Ensure the platinum column is properly conditioned to achieve complete hydrogenation of olefins without affecting other components.
❓ Frequently Asked Questions
🔍 What is the primary purpose of this test method?
To determine the paraffin, naphthene, and aromatic content by carbon number in petroleum distillates with final boiling points up to 200 °C, including naphthas from various conversion processes.
💡 How are olefins accounted for in the analysis?
Olefins are hydrogenated over a platinum column and converted to saturates. These saturates are then included in the overall paraffin and naphthene distribution reported by the method.
⚡ What is the detection limit for components?
The lower limit of detection for any single hydrocarbon component or group is 0.05 % by mass, ensuring sensitivity for trace-level analysis.
📌 Which hydrocarbons are reported as individual species?
Only benzene (C6 aromatic), toluene (C7 aromatic), and cyclopentane (C5 naphthene) are reported individually. All other hydrocarbons are grouped by carbon number or boiling point.