ASTM D6293
ASTM D6293: Oxygenates and Hydrocarbon Types in Low-Olefin Spark Ignition Engine Fuels by Gas Chromatography
1. Introduction to ASTM D6293
ASTM D6293 is a test method under the jurisdiction of ASTM Committee D02 on Petroleum Products and Lubricants, specifically by Subcommittee D02.04 on Hydrocarbon Analysis. This standard provides a quantitative analysis of oxygenates and hydrocarbon types – paraffin, olefin, naphthene, and aromatic (O-PONA) – in low-olefin spark ignition engine fuels using multidimensional gas chromatography. With the original adoption in 1998 and its latest revision in 2003, it includes the capability to report each hydrocarbon type by carbon number up to C10 (except olefins up to C9) and as a total, with a detection limit as low as 0.05 mass % for a single component.
2. Scope and Applicability
This method covers the quantitative determination of oxygenates, paraffins, olefins, naphthenes, and aromatics in low-olefin spark ignition engine fuels. The precision for olefins ranges from 0.05 to 13 mass %, with specifics on olefin concentrations within certain carbon groups. Although benzene precision was determined in a specific range, this method extends to benzene concentrations up to 5.0 mass %. It's applicable to fuels containing oxygenates and can be adapted for other hydrocarbon streams like naphthas and reformates.
3. Test Method Summary
A representative fuel sample is analyzed using a gas chromatographic system equipped with specific columns, traps, and a hydrogenation catalyst, operating at various temperatures. The system sequentially separates sample portions into different hydrocarbon groups, which are detected by a flame ionization detector. The concentration of each group is then calculated based on the detector's response, normalized to 100%.
4. Significance and Use
Understanding the composition of spark-ignition engine fuels is vital for regulatory compliance, process control, and quality assurance. This test method helps in quantifying olefins and other hydrocarbon types to meet government regulations.
5. Equipment and Reagents
The method requires a computer-controlled gas chromatograph, an automated sample injector, columns, traps, a hydrogenator, and various valves, all with specific requirements detailed in the standard. Helium, hydrogen, and air are used under specified purity conditions, and specific mixtures are employed for system validation and calibration.
6. Sample Preparation and Analysis
A small sample volume is injected into the chromatograph, where it's processed according to a defined sequence of temperature settings and valve operations. The process involves trapping, separating, and hydrogenating (for olefins) different components, which are then quantified based on their flame ionization detector responses.
7. Calculation and Reporting
Results are calculated in mass % and volume % for each hydrocarbon group and oxygenate. The method involves applying response factors to peak areas and normalizing the results. For oxygenates not determined by this method, such as methanol, alternative methods like ASTM D4815 or D5599 are recommended.
6. Precision and Bias
Precision data exists for a range of components, with specific repeatability and reproducibility values. The method outlines no bias information due to the absence of a material with an accepted reference value for hydrocarbon types.
Conclusion
ASTM D6293 offers a detailed framework for analyzing the complex composition of spark ignition engine fuels, providing essential data for compliance and quality control. The precision of this test method and its adaptability to various hydrocarbon streams make it a valuable tool in fuel analysis.