Introduction

Individual hydrocarbon components of spark-ignition engine fuels and their mixtures can be determined with well-known detailed hydrocarbon analysis methods such as ASTM D 5134, D 6729 and D 6730. These methods use long (50 to 100 m), narrow bore capillary (250 μm) columns to meet the high resolution specifications of the methods. The analysis time, however, usually exceeds two hours. Improving the speed of DHA analysis is possible with shorter columns having a smaller column internal diameter. By choosing the proper column dimensions, the plate number (i.e. separation performance) is kept constant. Table 1 shows a comparison table of columns with identical plate numbers for different column dimensions.

Table 1: Comparison between column dimensions with identical plate number.

Column ID (mm) Column length (m)Column head pressure (kPa)

0.25 (standard) 100 260

0.15 60 550

0.10 40 800

This application note describes a fast DHA method. By using a 40 m x 0.1 mm x 0.2 μm PONA CB column, the analysis time is reduced, depending on the sample type, by 20 to 40 minutes. This is a factor 3 to 4 shorter analysis time compared to the conventional 100 m column DHA application.

Instrumentation

Technique: DHA Analyzer for fast DHAInjector: 1177 S/SL Split/splitless with full EFC controlDetection: FID with full EFC controlAutosampler: Bruker CP-8400 AutoSampler

Application Note # CA-270368

Detailed Hydrocarbon Analysis of Naphtha

Software:GC Control and Data Handling: Galaxie™ Chromatography softwareDHA Calculations: DHA plug-in software fully integrated into Galaxie

Materials and reagents

Column: PONA CB™, 40 m x 0.1 mm x 0.2 μmSamples: Light naphtha, naphtha Conditions

Carrier Gas: Helium, 95 psiInjector: split 700:1, 250 °CInjection Volume: 1 μLOven: 35 °C (5 min), @ 20 °C/min to 45 °C (6 min), @ 2.5 °C/min to 60 °C (6 min), @ 5 °C/min to 220 °C (2.5 min)Detector: 300 °C

Results and discussion

To validate the performance between a standard DHA and a fast DHA a light naphtha sample is analyzed on both analyzers. Figure 1 shows a fraction of the analysis between the two methods with cyclohexane and toluene as reference components to synchronize both analyses. Note that the time scale for the fast DHA is stretched to match time scale of the standard DHA. In effect the fast DHA fraction is 9 min long while the standard DHA fraction is 28 min. The resolution of both analyses is similar, resulting in an identical separation performance using the fast DHA method. Note that the (relative) elution order for some components of the fast DHA example differs compared to the standard method as result of non-optimized method conditions.

Figure 1: Comparison between standard and fast DHA of a Naphtha sample.

Fast detailed hydrocarbon analysis

0 5 10 15 20 25 30 35 40Min

2

3 8 11 22 26

2335

38

4042

45

53

58

6670

72

80

108

12987

8990

9497

103

Table 2: Peak identification.

Figure 2: Complete analysis of a Naphtha sample by fast DHA.

Identical high separation performance

250µm x 100m upper chromatogram

100µm x 40m lower chromatogram

58

53

5045

42

36

38

40

60

66

9 min

28 min

Synchronized withcyclohexane andtoluene

123456789

10111213141516171819202122232425262728293031323334353637383940414243444546

propeneiso-butanebutanet-2-buteneneo-Pentanec-2-butenecyclobutaneiso-pentane1-penteneiso-Propanolpentanet-2-pentenec-2-pentene2-methyl-2-butene2,2-dimethylbutane4-methyl-1-pentenecyclopentene3-methyl-1-pentenecyclopentaneMTBE2,3-dimethylbutane2-methylpentane3-methylpentane2-methyl-1-pentene1-hexenehexanet-2-hexenet-3-hexene2-methyl-2-pentenet-3-methylcyclopentenet-3-methyl-2-pentene1-hexynec-2-hexene2,2-dimethylpentanemethylcyclopentane2,4-dimethylpentane2,2,3-trimethylbutanebenzene3,3-dimethylpentanecyclohexanet-4-methyl-2-hexene2-methylhexane2,3-dimethylpentane2-methyl-1,5-hexadiene3-methylhexanec-1,3-dimethylcyclopentane

47484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192

1,1-dimethylcyclopentanet-1,3-dimethylcyclopentane3-ethylpentanet-1,2-dimethylcyclopentane1-heptene2,2,4-trimethylpentaneheptanec-3-heptenet-3-methyl-2-hexenet-2-heptenec-1,2-dimethylcyclopentanemethylcyclohexane1,1,3-trimethylcyclopentaneethylcyclopentane2,4-dimethylhexanectc-124-trimethylcyclopentane3,3-dimethylhexane2,3,3-trimethylpentanectc-123-trimethylcyclopentanetoluene3-methyl-3-ethylpentanec-1,3-dimethylcyclohexane3,4-dimethylhexane (D)2-methylheptane4-methylheptane3-methylheptane3-ethylhexane1,1-dimethylcyclohexanet-1,3-ethylmethylcyclopentanet-1,2-ethylmethylcyclopentane1,1-ethylmethylcyclopentanet-1,4-dimethylcyclohexanecycloheptaneoctaneiso-propylcyclopentanec-12-ethylmethylcyclopentanec-1,2-dimethylcyclohexane2,4-dimethylheptane4,4-dimethylheptane2,6-dimethylheptane3,5-dimethylheptane2,5-dimethylheptane3,3-dimethylheptaneethylbenzene2,3,4-trimethylhexanectt-1,2,4-trimethylcyclohexane

93949596979899

100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138

2,3,3-trimethylhexanep-xylene3,4-dimethylheptane(L)2,3-dimethylheptane4-ethylheptane4-methyloctane2-methyloctanectc-124-trimethylcyclohexane3-ethylheptane3-methyloctaneo-xylene1-nonenet-1-methyl-4-ethylcyclohexanec-1-methyl-4-ethylcyclohexanet-1-me-2-n-propylcyclopentanenonanet-1-methyl-2-ethylcyclohexaneiso-propylcyclohexane3,3,5-trimethylheptane2,2-dimethyloctane2,5-dimethyloctanesec-butylcyclopentane2,6-dimethyloctane2,3,6-trimethylheptane3,3-dimethyloctane2-methyl-3-ethylheptanen-propylbenzene1-methyl-3-ethylbenzene1-methyl-4-ethylbenzene2,5,5-trimethylheptane2,3-dimethyloctane4-methylnonane1-methyl-2-ethylbenzene3,3,4-trimethylheptane3-ethyloctaneiso-butylbenzenedecane1,2,3-trimethylbenzene1-methyl-4-isopropylbenzene1-methyl-2-isopropylbenzene1-methyl-3-n-propylbenzene1-methyl-4-n-propylbenzene1-methyl-4-n-propylbenzene1,4-diethylbenzene1,2-diethylbenzeneundecane

per carbon number by weight and volume percent in the PIONA report (table 4). Further summarization of the sample composition results in the sample properties report. The report includes boiling range, MON, RON and density and other sample properties as shown in table 5.

The naphtha sample is analyzed multiple times to demonstrate the systems’ repeatability. A summary of the results is given in table 6, which shows excellent repeatability for both individual components like benzene and toluene, and sample properties like RON, MON and density. Shown also in table 6 are the repeatability results for hexane and heptane, demonstrating that the fast DHA analyzer is capable of measuring components at a higher concentration level. Figure 4a and 4b illustrates that the fast DHA method generates a weight percent repeatability for benzene and toluene that fits perfectly within the repeatability window specified by different DHA methods of ASTM. In order to validate the dynamic range of the Fast DHA analyzer three Naphthas are analyzed that have significant different component concentrations. Figure 5 demonstrates a perfect peak overlap of the components in the C8 region ensuring repeatable identification and quantification of the components.

For the fast detailed hydrocarbon analyzer a standard sample mixture containing n-alkanes is used for calibration. The retention times of the n-alkanes are used to calculate the retention indices of the sample components. These retention indices are compared with a database and peaks are assigned accordingly. Table 2 shows a number of the components in the database, which contains more than 450 components. This approach is very powerful, with virtually all peaks identified. A good example of this is shown in the magnified fraction of the chromatogram (from Figure 2), depicted in Figure 3.

After each analysis, the fast DHA results are converted using the database of the DHA plug-in software. This database contains component information such as density, Motor Octane Number (MON) and Research Octane Number (RON) values, vapor pressure and others. Together with the chromatographic results, the DHA software makes the appropriate calculations and generates associated results. Different reports, depending on the type of information needed, can be generated. In the component identification report, the weight and volume percent for each component is listed (Table 3).

The number of components listed in the report can be over the 450. In order to create a composition overview, similar components mostly isomers, are grouped as paraffins, isoparaffins, olefins, naphthenes, aromatics and oxygenates

Figure 3: Magnified section of a Naphtha sample from neo-pentane up to heptane.

High resolution analysis

3 4 5 6 7 8 9 10Min

5

8 11

1415

19

21

22 23 26

34

35

36 37

38

39

40 42

43

44

45

47

48

53

4950

Table 3: Component identification report.

Table 4: Weight percent profile PIONA report.

FAST DHA Analyzer

Analysis according to FAST DHASample Info N.A.Sample Type SampleAnalyst ADMINISTRATOR Vial 12Data File \Naptha\FastDHA Naptha.DATAMethod \450 Fast DHA\450 Fast DHA Samples\450-GC Fast DHA.dhaDescription FastDHA NapthaInstrument 450-GC 110117Detailed Hydrocarbon Analysis

ID RT CRT Index Name Area Area Percent

Weight Percent

Volume Percent

1 2.642 2.642 300.00 * propane 8.5 0.04 0.06 0.08

2 2.809 2.809 354.91 * iso-butane 144.0 0.72 0.93 1.13

3 2.954 2.954 400.00 butane 931.8 4.67 5.57 6.53

4 3.029 3.029 410.32 neo-Pentane 6.5 0.03 0.04 0.04

5 3.487 3.487 468.31 iso-pentane 1644.7 8.24 9.07 9.93

6 3.778 3.766 500.00 pentane 2451.6 12.29 13.52 14.65

7 4.059 4.059 517.52 2-methyl-2-butene 1.8 0.01 0.01 0.01

8 4.325 4.325 532.37 * 2.2-dimethylbutane 33.2 0.17 0.18 0.18

9 4.901 4.901 561.62 * cyclopentane 212.9 1.07 1.17 1.07

10 4.937 4.937 563.33 * 2.3-dimethylbutane 144.0 0.72 0.79 0.94

11 5.035 5.019 567.18 2-methylpentane 1096.7 5.50 5.80 6.02

12 5.361 5.361 582.60 3-methylpentane 699.0 3.50 3.70 3.77

13 5.798 5.775 600.00 hexane 1905.2 9.55 9.19 9.46

14 6.523 6.523 622.55 * 2.2-dimethylpentane 16.6 0.08 0.08 0.08

15 6.601 6.601 624.75 methylcyclopentane 633.5 3.18 3.20 2.90

16 6.725 6.725 628.19 2.4-dimethylpentane 55.3 0.28 0.28 0.28

17 6.923 6.923 633.56 2.2.3-trimethylbutane 3.6 0.02 0.02 0.02

18 7.452 7.452 647.19 benzene 150.1 0.75 0.62 0.48

19 7.678 7.678 652.72 3.3-dimethylpentane 9.8 0.05 0.05 0.05

20 7.827 7.827 656.28 cyclohexane 379.0 1.90 1.92 1.67

FAST DHA Analyzer

Analysis according to FAST DHASample Info N.A.Sample Type SampleAnalyst ADMINISTRATOR Vial 12Data File \Naptha\FastDHA Naptha.DATAMethod \450 Fast DHA\450 Fast DHA Samples\450-GC Fast DHA.dhaDescription FastDHA NapthaInstrument 450-GC 110117Weight Percent Profile

Saturates Unsaturates

Carbon Cyclic Iso Normal Cyclic N+ Iso Aromatics Oxyg Unknown Total

1

2

3 0.06 0.06

4 0.90 5.46 6.37

5 1.17 9.04 13.44 0.01 23.66

6 5.14 10.48 9.22 0.62 25.46

7 5.06 5.52 5.02 0.16 1.56 0.08 17.39

8 1.49 4.92 3.77 1.55 1.34 13.07

9 1.15 4.61 2.46 0.05 0.88 2.10 11.25

9+ 1.64 0.61 0.18 0.32 2.74

Total 14.01 37.11 40.05 0.22 4.79 3.83 100.00

Conclusion

The Bruker Fast Detailed Hydrocarbon Analyzer is specially designed for analyzing individual hydrocarbon components, as well as oxygenates present in spark ignition fuels and light hydrocarbon streams such as naphtha. The analyzer is equipped with a 40 m x 0.1 mm PONA CB column. The analysis time is significantly reduced compared to conventional DHA while maintaining separation power and ensuring analytical results of high quality. Being able to calculate corrected retention times is a real benefit when using narrow bore columns. The peak shape from components at a higher level in the sample tend to show overloading and thus retention time shifting. The DHA software calculates the corrected retention time based on peak skewing, ensuring correct peak assignment.

The fast DHA analyzer yields all required reports. A detailed hydrocarbon analysis report gives, per component, the content in weight% and volume%, as well as (corrected) retention times and retention index. PIONA reports can be generated, in weight% and or volume%, where sample components are grouped in chemical classes, e.g. iso-, cyclic and normal paraffins and olefins, aromatics and oxygenates. In conclusion, a sample properties report can be generated which gives the MON and RON values, as well as read vapor pressure, density, net heat and gross heat, and a boiling point distribution. The fast DHA analyzer is perfectly capable of analyzing relative light hydrocarbon streams such as naphtha. Peak identification via retention index and comparison with a database proved to be a very powerful methodology.

Table 5: Properties report.

FAST DHA Analyzer

Analysis according to FAST DHASample Info N.A.Sample Type SampleAnalyst ADMINISTRATOR Vial 12Data File \Naptha\FastDHA Naptha.DATAMethod \450 Fast DHA\450 Fast DHA Samples\450-GC Fast DHA.dhaDescription FastDHA NapthInstrument 450-GC 110117

Physical Properties

MON Value 57.6 Net Heat 44.2 kJ/g

RON Value 58.6 Gross Heat 48.0 kJ/g

Reid Vapor P. 14.64 mm Hg Density 0.6903 g/ml

TBP Report

Recovery Percentage

100.0

TBP % OFF D86 % OFF

IBP -0.5

5 % 9.5

10 % 36.1

20 % 36.5

30 % 36.5

40 % 63.3

50 % 71.8

60 % 90.0

70 % 99.2

80 % 119.4

90 % 143.0

95 % 153.5

FBP 176.1

Figure 4a: Repeatability results of Benzene in Naphtha.

Figure 4b: Repeatability results of Toluene in Naphtha.

0.55

0.60

0.65

0.70

0 5 10 15 20

Weight %

Run

Fast DHA Benzene concentrationAverageRepeatability according ASTM D 6730Repeatability according ASTM D 6729Repeatability according ASTM D 5134

1.40

1.50

1.60

1.70

0 5 10 15 20

Weight %

Run

Fast DHA Toluene concentrationAverageRepeatability according ASTM D 6730Repeatability according ASTM D 6729Repeatability according ASTM D 5134

Figure 5: Elution profile of three different Naphthas in the C8 region at different concentration levels.

14 15 16 17 18Min

Naphtha 1 Naphtha 2 Naphtha 3

Table 6: Repeatability results of the naphtha sample.

Naphtha

Run MON RONDensity(g/mL)

HexaneWt%

HeptaneWt%

BenzeneWt%

TolueneWt%

1 57.3 58.2 0.6889 9.20 5.00 0.62 1.55

2 58.4 59.5 0.6886 9.19 5.02 0.62 1.55

3 58.0 59.0 0.6890 9.19 5.01 0.62 1.55

4 58.6 59.8 0.6888 9.22 5.02 0.62 1.55

5 58.6 59.9 0.6897 9.19 5.01 0.62 1.55

6 58.5 59.7 0.6890 9.23 5.03 0.63 1.56

7 58.6 59.8 0.6892 9.19 5.00 0.62 1.55

8 57.6 58.6 0.6903 9.20 5.01 0.62 1.55

9 57.9 59.2 0.6899 9.23 5.04 0.62 1.56

10 58.4 59.6 0.6890 9.20 5.02 0.62 1.55

11 57.5 58.5 0.6893 9.22 5.05 0.62 1.56

12 58.5 59.7 0.6891 9.24 5.03 0.63 1.56

13 58.5 59.8 0.6883 9.25 5.03 0.62 1.56

14 56.7 57.6 0.6897 9.24 5.08 0.62 1.57

15 58.0 59.2 0.6897 9.22 5.04 0.62 1.56

16 58.0 59.2 0.6891 9.22 5.06 0.62 1.57

17 58.5 59.7 0.6890 9.19 4.99 0.62 1.54

18 58.2 59.2 0.6903 9.21 5.02 0.62 1.55

19 57.6 58.8 0.6893 9.13 4.97 0.62 1.54

20 58.8 59.9 0.6880 9.23 5.03 0.62 1.56

Average 58.1 59.2 0.6892 9.2 5.0 0.6 1.6

St.dev. 0.54 0.63 0.0006 0.027 0.025 0.0031 0.0083

RSD% 0.93 1.07 0.09 0.29 0.49 0.50 0.53

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References

ASTM D 5134-98, 2003, “Standard Test Method for Detailed Analysis of Petroleum Naphthas through n-Nonane by Capillary Gas Chromatography,” ASTM International, West Conshohocken, PA, www.astm.org.

ASTM D 6729-04, “Standard Test Method for Determination of Individual Components in Spark Ignition Engine Fuels by 100 Meter Capillary High Resolution Gas Chromatography,” ASTM International, West Conshohocken, PA, www.astm.org.

ASTM D 6730-01, 2006e1, “Standard Test Method for Determination of Individual Components in Spark Ignition Engine Fuels by 100 Meter Capillary (with Pre column) High Resolution Gas Chromatography,” ASTM International, West Conshohocken, PA, www.astm.org.

Keywords

Naphtha

Fast GC analysis

High Resolution Chromatography

Instrumentation & Software

Bruker DHA Analyzer for fast DHA

Galaxie™ Chromatography software

DHA plug-in software

For research use only. Not for use in diagnostic procedures.

Bruker Daltonik GmbH

Bremen · GermanyPhone +49 (0)421-2205-0 Fax +49 (0)421-2205-103 sales@bdal.de

Bruker Daltonics Inc.

Billerica, MA · USAPhone +1 (978) 663-3660 Fax +1 (978) 667-5993 ms-sales@bdal.com

www.bruker.com/chemicalanalysis