UOP690, C₈ and low boiling paraffins and naphthenes in low-olefin hydrocarbons by GC

Introduction

The UOP690 describes the determination method for C8 and lower boiling paraffins and naphthenes in olefin free gasolines (2 mass-%) with a maximum boiling point of 260°C. In this method benzene and toluene are also being determined.

This method contains two procedures using the same column to determine the resolved non-aromatic components. Depending on the degree of resolution required either method A alone, or both method A and B can be used. Method A looks at a broad spectrum of components while method B zooms in on the lighter components and this data can be used to calculate unresolved non-aromatic components from method A.

Figure 1 shows the SCION Instruments 4X6 GC platforms that can be used for UOP690.


Figure 1. SCION Instruments 4X6 GC

Experimental

This analysis can be implemented on the 436-GC and the 456-GC platform. The analysis was performed on the Scion 456-GC analyser equipped with an FID and a 100 positions 8400 autosampler.

The UOP 690 is a perfect and simple method for the determination of the mass-% composition of the sample.

A big advantage of running both methods is the possibility for detailed identification by comparing chromatograms of method A and B. With these methods it is possible to determine the unresolved non-aromatic components from method A.

In table 3 the components that have to be determined by analysis A and B can be found.

Results

All the results were calculated according to the described method in UOP690.

The theoretical relative response factors (TRRF) were determined and showed a deviation from the theoretical value below 3% for the components.

In addition it showed that the three measurements performed for these components had a deviation below 1% amongst the results.  These results were excellent since the deviation against the theoretical values have to be below 5% and the deviation amongst the results no more than 2%.

After establishing the TRRF a gasoline mix was injected to determine the mass-% . This gasoline mix was analysed with method A and method B.

Both methods showed excellent repeatability that are well withing specifications prescribed in the UOP 690.

Table 1. Analytical conditions of method A

Injector  Splitless 200:1, 250 °C
Column SCION-DHA-50
Oven Program 32°C (6.0 min), 5°C/min to 52°C (14.0 min) , 20 °C/min to 250°C (9 min)
Carrier Hydrogen, 1.1 ml/min ( *GC equipped with a H2 sensor bundle)
Detector FID with ceramic jet, 250°C
Air: 300 ml/min, Fuel gas (H2): 30 ml/min, Make up (N2): 30 ml/min
Inj. Volume 0.5 µl
Autosampler 8400
Software Compass CDS

 

Table 2. Analytical conditions of method B

Injector  Splitless 200:1, 250 °C
Column SCION-DHA-50
Oven Program 60°C (8.0 min), 5°C/min to 90°C (0 min) , 20 °C/min to 250°C (10 min)
Carrier  Hydrogen, 1.1 ml/min ( *GC equipped with a H2 sensor bundle)
Detector  FID with ceramic jet, 250°C
Air: 300 ml/min, Fuel gas (H2): 30 ml/min, Make up (N2): 30 ml/min
Inj. Volume 0.5 µl
Autosampler 8400
Software Compass CDS

 

After analysis and calculation of the mass it showed that the sum of  all components (resolved and unresolved) was 99.63 mass-%,  this means that the data had to be renormalized to 100 mass-%.

An example of the chromatograms from method A and B can be found in figure 2.

Table 3: Components determined with analysis A and B, peak number with letters refer to co-eluting peaks.

Peak Nr. A Peak Nr. B Component Peak Nr. A Peak Nr. B Component
1 Propane 36 3.3-Dimethylhexane
2 Isobutane 37 1-trans-2-cis-3-Trimethylcyclopentane
3 n-Butane 38 2.3.4-Trimethylpentane
4 2.2-Dimethylpropane 39A 2.3.3-Trimethylpentane
5 Isopentane 39B Toluene
6 n-Pentane 40A 6 2.3-Dimethylhexane
7 2.2-Dimethylbutane 40B 7 1.1.2-Trimethylcyclopentane
8 Cyclopentane 41 2-Methyl-3-ethylpentane
9 2.3-Dimethylbutane 42 2-Methylheptane
10 2-Methylpentane 43 4-Methylheptane
11 3-Methylpentane 44A 3.4-Dimethylhexane
12 n-Hexane 44B 3-Methyl-3-ethylpentane
13 2.2-Dimethylpentane 45A 1-cis-2-trans-4-Trimethylcyclopentane
14 Methylcyclopentane 45B 8B 1-cis-2-cis-4-Trimethylcyclopentane
15 2.4-Dimethylpentane 46 3-Methylheptane
16 2.2.3-Trimethylbutane 47A 8A 3-Ethylhexane
17 Benzene 47B 9A 1-cis-3-Dimethylcyclohexane
18 3.3-Dimethylpentane 47C 9B 1-cis-2-trans-3-Trimethylcyclopentane
19 Cyclohexane 48 1-trans-4-Dimethylcyclohexane
20 2-Methylhexane 49 1.1-Dimethylcyclohexane
21 2.3-Dimethylpentane 50 1-Methyl-trans-3-ethylcyclopentane
22 1.1-Dimethylcyclopentane 51 1-Methyl-cis-2-ethylcyclopentane
23 3-Methylhexane 52 1-Methyl-trans-2-ethylcyclopentane
24 1-cis-3-Dimethylcyclopentane 53 1-Methyl-1-ethylcyclopentane
25 1-trans-3-Dimethylcyclopentane 54 1-trans-2-Dimethylcyclohexane
26 3-Ethylpentane 55 1-cis-2-cis-3-Trimethylcyclopentane
27 1-trans-2-Dimethylcyclopentane 56A 10 n-Octane
28 2.2.4-Trimethylpentane 56B 11 1-cis-4-Dimethylcyclohexane
29 n-Heptane 56C 12 1-trans-3-Dimethylcyclohexane
30A 2 Methylcyclohexane 57 Isopropylcyclopentane
30B 1A 1-cis-2-Dimethylcyclopentane 58 1-Methyl-cis-2-ethylcyclopentane
31A 3 1.1.3-Trimethhylcyclopentane 59 1-cis-2-Dimethylcyclohexane
31B 1B 2.2-Dimethylhexane 60A 13 n-Propylcyclohexane
32 4A Ethylcyclopentane 60B 14 Ethylcyclohexane
33 2.5-Dimethylhexane 61 Ethylbenzene
34A 5 2.2.3-Trimethylpentane 62A m-Xylene
34B 4B 2.4-Dimethylhexane 62B p-Xylene
35 1-trans-2-cis-4-Trimethylcyclopentane 63 o-Xylene

Figure 2. Example of a chromatogram of an gasoline standard using method A and method B.



Conclusion

The Scion 4X6-GC analyser equipped with a split/spitless injector, Scion Instruments column and FID is capable of performing UOP690 in a way that complies to the method. The C8 and low boiling paraffins and naphthenes are determined on the basis of mass-%, The quantitation limit for any reported component is 0.01 mass-%. The equipment of the 4X6-GC analyser is pre determined, for ordering information or customisation, please contact your local sales representative.

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