ASTM D7974
Guide to ASTM D7974: Analyzing Farnesane, Saturated Hydrocarbons, and Hexahydrofarnesol Content of Synthesized Iso-Paraffins (SIP) Fuel for Blending with Jet Fuel by Gas Chromatography
The ASTM D7974 standard is a crucial protocol for the petrochemical industry, specifically for analyzing synthesized iso-paraffins (SIP) fuel intended for blending with jet fuel. This method, established by the American Society for Testing and Materials (ASTM), provides detailed guidelines for determining the content of farnesane, saturated hydrocarbons, and hexahydrofarnesol in SIP fuel using gas chromatography. Here, we delve into the intricacies of ASTM D7974, highlighting its scope, significance, and the step-by-step procedure it prescribes.
Scope and Purpose
ASTM D7974 targets the precise quantification of farnesane (2,6,10-trimethyldodecane), saturated hydrocarbons, and hexahydrofarnesol in SIP fuel. The method's accuracy ranges are meticulously defined: farnesane from 96% to 99.9% by mass, saturated hydrocarbons (including farnesane) from 97% to 99.9% by mass, and hexahydrofarnesol from 0.02% to 2.0% by mass. While it excels in identifying and quantifying major impurities, it does not encompass the identification of all potential components in SIP fuel. The method is not suitable for substances that boil above 460 °C or fail to elicit a response from a flame ionization detector.
Referenced Documents and Terminology
ASTM D7974 references several ASTM standards crucial for the preparation and analysis of samples, including D4057 for manual sampling, D4307 for liquid blend preparation, and D7566 specifying aviation turbine fuel standards. It also relies on E355 and E594 for definitions and practices related to gas chromatography and flame ionization detection.
Summary of the Test Method
The procedure involves introducing a sample aliquot into a gas chromatograph equipped with a specific capillary column and a flame ionization detector. The sample components are separated based on their chromatographic properties and quantified. The content of farnesane, saturated hydrocarbons, and hexahydrofarnesol is determined through a normalization process of the peak areas in the chromatogram.
Apparatus and Reagents
The test requires a gas chromatograph capable of maintaining specified conditions, a suitable injector, and a flame ionization detector. The column specified is a fused silica open tubular column with a 5% phenyl-methylpolysiloxane bonded phase. High-purity carrier and detector gases, including helium or hydrogen and air, are essential, along with high-purity n-hexane as the solvent.
Procedure
Sampling adheres to Practice D4057, ensuring representative sample collection. The gas chromatograph is prepared and checked for performance, including linearity and column efficiency, following strict guidelines to ensure accuracy and reliability. The analysis involves injecting a measured sample volume and integrating the resultant chromatographic peaks to quantify the SIP fuel components.
Significance and Use
SIP fuels are approved for blending with jet fuel if they meet certain purity specifications. ASTM D7974 offers a methodical approach to determining the purity of farnesane, the principal component, ensuring the fuel blend meets the stringent requirements of Specification D7566. This standard not only facilitates quality control but also supports the development and utilization of alternative fuels in aviation, contributing to the sustainability of the sector.
Precision, Bias, and Reporting
The standard outlines the expected precision for repeatability but notes that reproducibility and bias determinations are pending further interlaboratory studies. Results are reported with precision to the nearest 0.01% mass, highlighting the method's accuracy and reliability.
Conclusion
ASTM D7974 is a vital standard for the petrochemical and aviation fuel industries, providing a rigorous method for analyzing SIP fuel components. Its detailed guidelines ensure the accuracy and reliability of the analysis, contributing to the quality and sustainability of jet fuel blends. As SIP fuels become more prevalent in the aviation industry, adherence to ASTM D7974 will play a critical role in ensuring fuel purity and performance.