Analytical Instrumentation 21 Analyser Advantages
Figure 3a and 3b: Concurrent heating of the molecular sieves combines the elution profiles of paraffins (iso and normal) and naphthenes, reducing the analysis time compared to the former method
The independent trap temperature control design, the trap capacity and trap selectivity allows the analyser to optimise the analysis performance. In the case of broad samples ranging from C4 up to C12, a high selectivity demand is required to separate the different groups. By using smart concurrent heating of both molecular sieves, the eluting profile of the paraffins (normal and iso) and the naphthenes is well defined without the overlap of especially light normal paraffins in the iso-paraffin and naphthenes elution area, Figure 2a and 2b illustrate the effect of breakthrough of normal paraffin. This improves analyses interpretation and quantitation [2].
Figure 4. Chromatogram of a commercial standard in fast
Applying concurrent heating also reduces the analysis time significantly since the separate elution profiles of iso-paraffins and naphthenes and the normal paraffins can be combined (Figure 3a and 3b). This solution is also applicable to the olefins reducing the analysis time by 33% for an O-PIONA analysis as illustrated in Figure 4 [3].
Figure 7: Depending on the sample stream, a specific mode of analysis is applicable [5]
PIONA+ Analyser allows customisation of the analysis optimising the separation requirements. By excluding selective traps, i.e. the olefin trap and the Molsieve 5A trap, the analysis is reduced to a PNA (paraffins, naphthenes and aromatics) analysis in the case that iso- and normal paraffins and their olefinic equivalents are grouped per carbon number [5]. This is useful for sample streams that do not need a complete O-PIONA analysis as groups of components are lacking in the sample or are of no interest to be specified separately (Figure 7). By simplifying the analysis method, the analysis time is reduced while the sample interpretation is improved.
The flexibility to in- and exclude traps allows using different modes from PNA up to O-PIONA analysis using one instrument. This is useful when the samples are analysed according to official methods (Figure 8) [4].
Bruker PIONA+ Benefits
Bruker has specifically designed the PIONA+ Analyser to create multi-modal hydrocarbon analysis that is less complicated for the petrochemical analyst. There are many advantages to the instrument, including that it is designed to operate within the parameters set for official methods such as ASTM D-6839, EN 14517, ASTM D 6293, and DIN 5148-1. It is able to operate in multiple-modes to analyse specific groups of compounds including PIONA, PIANO, PINA, PONA, PNA, O-PONA and O-PIONA; and the olefin traps are high capacity (i.e. allow broad range of samples), have high selectivity and a long operating life time. Concurrent heating allows fast analysis with a broader range of samples, for example from C2 to C14. Reporting is undertaken according to standard methods and includes; grouping per hydrocarbon type/per carbon number, weight %, volume %, mol %, TBP, density, Reid Vapor Correlation, RON/MON Correlation, H/C Ratio and Heating Values.
Figure 5:Elution profile of the olefin trap. The high selectivity and capacity ensures a good separation between paraffins and olefins even for broad samples ranging from C3 to C13
Preventing component breakthrough of a trap is also evident to the olefin trap preventing co- elution with its saturated equivalents. Especially high resolution single column detailed hydrocarbon ASTM methods, including ASTM D5134, ASTM D 6729, ASTM D6730 and D6733, refer to a multi-dimensional PONA-type of instrument in case the olefin content exceeds an amount of more than <2%, 25% and 25%, 20% respectively. Utilising an olefin trap with high capacity and selectivity ensures a good separation between the paraffins and olefins (Figure 5).
Conditions: 0.1 µL injection liquid 40°C (3’) 15°C/min 220°C. Conclusion
PIONA analysis is a work-horse methodology and the preferred technique to characterise petroleum streams by hydrocarbon group type by utilising a multi-dimensional GC approach for the refinery laboratory. The PIONA+ Analyser from Bruker has been designed to permit routine PIONA analyses in all refinery laboratories, with a high degree of flexibility in the GC analysis platform to obtain comprehensive characterisation and quantitative information, including hydrocarbon group type, oxygenates and carbon distribution for spark-emission fuels.
References
[1] D6839 – 02 (Reapproved 2007) Standard Test Method for Hydrocarbon Types, Oxygenated Compounds and Benzene in Spark Ignition Engine Fuels by Gas Chromatography. ASTM 2007.
[2] Bruker Application Note # CA-270383. Fast Analysis of Paraffins, iso-Paraffins, Naphthenes and Aromatics in Hydrocarbon Streams.
Figure 6: Weight % report of high olefinic sample of 46 % (highlighted in red)
The high capacity of the olefin trap also allows hydrocarbon fractions such as FCC naphtha with a considerable amount of olefins to be analysed in the standard mode as shown in Figure 6 [4].
In contrast to high resolution single column and GC X GC analysis, the modular design of a
[3] Bruker Application Note # CA-270384. Fast Analysis of Paraffins, iso-Paraffins, Olefins, iso- Olefins, Naphthenes and Aromatics in Hydrocarbon Streams. [4] Bruker PIONA+ Brochure.
[5] Bruker Application Note # CA-270378. Paraffins, Naphthenes and Aromatics (PNA) in Hydrocarbon Streams with the Bruker PIONA+™ Analyser.
Figure 8: The PIONA+ Analyser is highly flexible and can be configured to run a wide variety of methods in the single instrument
April / May 2012 •
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