Quantitative Determination of Gasoline Blends

Group type analysis of finished gasoline and its blend streams/precursors has become much easier and simpler than before with the introduction of the 4^th generation AC Analytical Controls (AC) Reformulyzer M4.

The Reformulyzer M4 uses capillary/micro-packed columns and traps, causing superior speed of analysis, a very wide analytical range and high precision. It is compliant with methods such as the EN ISO 22854, ASTM D6839 and derived methods.

Based on the product or the sample stream, it is possible to use several analytical modes, ensuring shortest possible runtimes, and data as required for that specific product as seen in Table 1. This article outlines the quantitative determination of hydrocarbon types and oxygenates in Gasoline Blends and Finished Gasoline using the AC Reformulyzer M4.

Table 1. Reformulyzer M4 Analysis Modes vs Product Streams

Analysis Technique

Separation and elution on a series of designed traps and columns helps determine different hydrocarbon types and oxygenates. Figure 1 shows the flow diagram for Reformulyzer M4 and the analysis method used for this method is in Table 2.

The paraffins and naphthenes are separated from the aromatics via the polar column while heavy aromatics and alcohols are retained on the pre-column. Ethers pass through and get trapped on the alcohol or ether trap on the boiling point column.

Naphthenes and paraffins pass the olefin trap where olefinic components are trapped. Further separation of saturates is on the 13X Column resulting in a carbon number distribution. By the use of multiple columns and valves, the polynaphthenes, alcohols and aromatics are studied on a boiling point column in two different Aromatic fractions.

The olefin trap is desorbed in backflush and olefins separated on 13X column between two aromatic fractions. The micropacked columns and traps are arranged on the left side and have separate heater elements for individual temperature programming. This allows simultaneous heating and/or cooling of traps resulting in total analysis runtime of 39mins.

Figure 1. Reformulyzer M4 Flow Diagram

Table 2. Reformulyzer M4 Gasoline method

Using the Reformulyzer M4 in gasoline mode, gravimetric blends and a gasoline N certified reference materials (CRM) were studied.

Typical report outputs from the CRM analysis are shown in Tables 3 and 4 and representative chromatograms are shown below.

Table 3. Reporting Gasoline N Weight%

Table 4. Reporting Gasoline N Volume%

Chromatograms show clear group separations for paraffins, naphthenes, aromatics, olefins and oxygenates, and it is observed that %weight and %volume by carbon numbers are well within specifications for this particular CRM. Reported are compositions in weight% and volume%.

Figure 2. Reference Sample Gravimetric Blend (50.16.512) in Gasoline mode

Figure 3. Gasoline N CRM (00.02.048) in Gasoline mode

The Reformulyzer M4 offers reports group type data in complete compliance with key methods EN ISO 22854 and ASTM D6839.

Weight% and volume% profile reports are generated grouping naphthenes, paraffins, olefins, aromatics and oxygenates by carbon number as well as the totals of the different groups and the totals by carbon number.

Table 5. Reformulyzer M4 Specifications & Ordering Information

Conclusion

By using micropacked and capillary columns and traps the Reformulyzer M4 takes just 39mins to produce reliable results in gasoline mode.

This information has been sourced, reviewed and adapted from materials provided by PAC L.P.

For more information on this source, please visit PAC L.P.