AC Analytical controls reformulyser M4 expands its capabilities on gasoline analysis ASTM D6839-21 and ISO 22854

The AC Reformulyser is one of the most used analysers worldwide to determine the total aromatic, total olefin, benzene, oxygen content, and oxygenates in finished gasoline, with an active global installed base of over 500 instruments. Many international fuel specifications refer to the Reformulyser-compliant methods ISO 22854 or ASTM D6839.

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Article Summary

Refineries in the United States are subjected to Environment Protection Agency (EPA) regulations that specify single parameter analysis methods for total aromatics, total olefin, and benzene content as measured by ASTM D1319, D3606, D5580, D4815, D5599, and D5769.

To extend the versatility of the AC Reformulyser, AC Analytical Controls expanded its already extensive analytical measurement range for oxygen content, specific oxygenates, and specific aromatics, as future changes in gasoline composition are expected. The Reformulyser now also includes correlations to the traditional EPA ASTM methods in the ASTM D6839.

As part of its research and development process to expand the Reformulyser capabilities, AC analytical Controls applied the outcome of two studies:
- Interlaboratory Study (ILS) organised by PAC which included over 60 participating laboratories worldwide to extend the concentration range of selected oxygenates, benzene, and toluene.
- Method comparison study of ASTM D6839 versus D3606, D5769, D5580, D1319, and D6550 based on real-life samples from the ASTM Proficiency Test Program from 2004 to 2019.

Interlaboratory study - Extending the measurement range
Governments around the world are setting tighter legislation on greenhouse gas emissions. To comply with these new laws, the automotive industry is focused on reducing their car and truck emissions. One of their research programs, in collaboration with the petroleum industry, investigates how fuel composition can be changed to meet future greenhouse gas specifications while maintaining a superior driving experience.

Overall, the trend is to blend higher concentrations of various oxygenates like (bio) ethanol, (bio) methanol, MTBE, ETBE, TAME and TAEE into a finished gasoline.

Recognising these changes in fuel composition, AC Analytical Controls began preparing an ILS in 2019 to add, update and extended the concentration range for oxygen content and selected oxygenates and aromatics in ASTM D6839 and ISO 22854. The ILS samples were measured by more than 60 laboratories worldwide in 2020 and the statistical outcome of the ILS permitted us to update the concentration range for the listed components and oxygen content shown in table 1.

The updated concentration range in ASTM D6839 was accepted in April 2021. The official release of the updated ASTM D6839 will follow shortly. The ISO 22854 is expected to follow later in 2021.

ASTM PTP comparison study - Correlations
United States refiners must comply with and report according to EPA (Environment Protection Agency) regulation methods. The EPA’s Performance Based Monitoring System (PBMS) allows the use of results from alternative methods that are correlated with the EPA referee methods with the main requirement that the correlations are made in accordance with ASTM D6708.

The Reformulyser method ASTM D6839 is considered an alternative method. Correlations with the EPA method and other typical gasoline property methods would be a great addition to the use of the Reformulyser application for gasoline testing.

Real-life results from the ASTM Proficiency Test Program from 2004 to 2019 were used to compare the results between the Reformulyser (D6839) and other ASTM test methods D3606, D5580, D5769, D1319 & D6550.

The method used for this comparison is ASTM D6708 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material. By following this statistical method, a statement about the expected difference in results of the two test methods can be made. If there is a difference or bias between the two test methods a correction or correlation can be applied and is accepted in the industry.

The statistical study resulted in relations for benzene, total aromatics, and total olefins between the Reformulyser (D6839) and other ASTM methods (D1319, D3606, D5580, D5769 and/or D6550).

The ASTM balloting process for adding these additional correlations in the Reformulyser method is completed. The correlations for benzene, total aromatics, and total olefins between the Reformulyser (D6839) and other ASTM methods (D1319, D3606, D5580, D5769 and/or D6550) are accepted and will be part of the next version of the D6839 method.

Overall, the results from the Reformulyser show no or only very small bias between methods. Most noticeable is the benzene content, where there is no bias between D6839 and D5769 as well as D5580. This shows how well the Reformulyser correlates as a full PIONA gasoline composition analyser to other single parameter methods. See table 3 for the overview of added correlations.

EPA fuel regulation
As of January 1st, 2021, the EPA regulation for reformulated gasoline has been streamlined to only four parameters that need reporting:
- Reid Vapour Pressure (D5191)
- Oxygen Content (D5599)
- Sulphur Content (D7039)
- Benzene Content (D5769)

Until 2021, the referee procedure for measuring benzene content was D3606 but has been changed to D5769. The benzene content in reformulated gasoline should have an average concentration of 0.62 vol%, with a maximum average concentration of 1.30 vol%.

This is excellent news for United States customers, as the correlation for D5769 is included in the D6839 with a measurement range of 0.52 — 1.67 vol%. Following EPA’s Performance-based Measurement System (PBMS), the Reformulyser can now be used as an alternative method to report benzene content to the EPA.

The correlation equation is ASTM D6839 = ASTM D5769 meaning no bias correction is required.

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