ASTM D2425

ASTM D2425 – Standard Test Method for Hydrocarbon Types in Middle Distillates by Mass Spectrometry

Description:

Significance and Use

5.1 A knowledge of the hydrocarbon composition of process streams and petroleum products boiling within the range of 160 °C to 343 °C (320 °F to 650 °F) is useful in following the effect of changes in process variables, diagnosing the source of plant upsets, and in evaluating the effect of changes in composition on product performance properties.

5.2 A test method to determine total cycloparafins and low level aromatic content is necessary to meet specifications for aviation turbine fuel containing synthesized hydrocarbons.

Scope

1.1 This test method covers an analytical scheme using the mass spectrometer to determine the hydrocarbon types present in conventional and synthesized hydrocarbons that have a boiling range of 160 °C to 343 °C (320 °F to 650 °F), 5 % to 95 % by volume  as determined by Test Method D86. Samples with average carbon number value of paraffins between C₁₂ and C₁₆ and containing paraffins from C₁₀ and C₁₈ can be analyzed. Eleven hydrocarbon types are determined. These include: paraffins, noncondensed cycloparaffins, condensed dicycloparaffins, condensed tricycloparaffins, alkylbenzenes, indans or tetralins, or both, C_nH _2n-10 (indenes, etc.), naphthalenes, C_nH_2n-14  (acenaphthenes, etc.), C_nH _2n-16 (acenaphthylenes, etc.), and tricyclic aromatics.

Note 1: This test method was developed on Consolidated Electrodynamics Corporation Type 103 Mass Spectrometers. Operating parameters for users with a Quadrupole Mass Spectrometer are provided.

1.2 This test method is intended for use with full boiling range products that contain no significant olefin content.

Biodiesel (FAME components) could interfere with the separation of the sample and the characteristic mass fragments of FAME compounds are not defined in the procedure.

Hydrocarbons containing tertiary carbon fragments, sometimes found in synthetic aviation fuels, will interfere with the characteristic mass fragments of paraffins and result in a false, elevated cycloparaffin content.

Note 2: “No significant olefin content” for this method means <2.0 % by volume by Test Method D1319.

1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.