ASTM D 6730 Detailed Hydrocarbon Analysis

Transcription

1 ASTM D 6730 Detailed Hydrocarbon Analysis Jaap de Zeeuw, Jan Pijpelink and Barry Burger Restek Corporation

2 ASTM D (2006)e1 Determination of Individual Components in Spark Ignition Engine Fuels as well as fuel blends containing oxygenates such as MTBE, ETBE, t-butanol and ethanol Very detailed analysis of of motor fuels 2

3 Biggest Challenges for customers running ASTM D6730 Have good peak shape for alcohols Have sufficient theoretical plates to separate the complex samples Coupling of tuning capillary Analysis time too long, wish for faster methods Reproducibility of column-column quality parameters

4 Why do the refiners run DHA analysis? At the end a certain gasoline must have a certain octane number.. It is very important for the refiner to monitor the blending process carefully to avoid too much yield. Different octane numbers are available Accurate DHA analysis can save a lot of money..

5 Important quality parameter for DHA analysis The column must not only elute hydrocarbons Also need to elute alcohols This is is a big challenge and that s why Rtx-DHA 100 columns are preferred

6 Problem area Ethanol peak shape at 35ºC Supplier 1 Supplier Time (min) Time (min) Restek Time (min)

7 Impact of a taling alcohol peak Supplier 1 type DHA column Oven Oven 5 ºC ºC min., min., 22ºC/min ºC ºC # 24160U 1. ethanol 2. C methyl butene 2 4. t butanol Alcohol Alcohol peaks peaks are are retained by by column column activity activity // adsorption; They They elute elute at at wrong wrong position Time (min) Risk Risk Misidentification and and possible wrong wrong data data

8 Elution of Alcohols on the DHA-type columns ASTM Method D6730 Column Column 100m 100m x x 0.25mm 0.25mm PONA/DHA-type PONA/DHA-type Conditions Conditions acc acc to to ASTM ASTM Concentration Concentration The The SAME SAME amount amount injected injected on on every every column column Rtx-DHA ethanol 2. pentane 3. t-butanol 4. 2-methylbutene-2 Correct positions, Good deactivation Position of of alcohols depend on on the activity of of the surface..

9 ASTM D 6730 specifications Specifications DHA column for AstmD6730 Material fusedsilica Length 100m Internaldiameter 0.25mm Liquidphase methylsilicone Filmthickness 0.50 µm Theoreticalplates,n,pentane at 35 C; to Retentionfactor,k,pentane at 35 C 0.45 to 0.50 Resolution, R,t-butanoland2-methylbutene-2at 35 C3.25 to 5.25 Peak symmetry, t-butanolat 35 C >1.0 to <5.0

10 Front End Slice of the DHA Evaluation mix Column Oven Carrier Rtx-DHA meter x.25mm x 0.5um 35 ºC Isothermal H2, constant 5.0 ml/min. C5 plate number ethanol C5 retention factor 0.48 ethanol t butanol skew/tailing 1.13 Resolution t butanol / 2methylbutene 2 = Time (min) C5 t butanol 2 methylbutene Time (min)

11 ASTM D6730 column specifications C5 theoretical plates C5 retention 35 ºC Resolution, t butanol/2 methylbutene 35 ºC Peak asymmetry, 35 ºC > <5.00 Actual data for the Rtx-1 PONA/ Rtx-DHA 100 C5 theoretical plates C5 retention factor 0.48 Resolution t butanol / 2methylbutene Peak asymmetry, 35 ºC 1.13

12 Standard ASTM-Specs Test for all Restek Rtx- DHA 100 columns ethanol T-butanol pentane 2-methyl-butene-2

13 Specs data is listed on each Rtx-DHA-100 testreport

14 Reproducibility of Rtx-DHA-100 columns Following graphs show the typical performance of the chronological production of 250 Rtx-DHA 100 columns Efficiency /Resolution Retention Inertness Set by ASTM Bleed

15 Efficiency / Resolution Plate number ASTM ASTM spec spec C5 C5 theoretical plates plates Method specs Restek Rtx-DHA columns are are coated with with superior efficiency that s why why they they always separate better.. (data will will be be more accurate)

16 Inertness. Peak asymmetry ASTM ASTM spec spec Asymmetry t-butanol > <5.00 < Method specs Small Small values values for for asymmetry t-butanol guarantee inertness Alcohol Alcohol peaks peaks elute elute where where they they suppose to to elute; elute; Reduced risk risk for for reporting data data with with high high $$ $$ impact impact

17 Retention. Retention factor ASTM ASTM spec spec C5 C5 retention factor ºC ºC Method specs Small Small deviation on on retention factor factor means means similar similar retention times times column column to to column; Convenient to to set set up up & calibrate

18 Resolution. R value ASTM ASTM spec spec Resolution, t-butanol/2 methylbutene ºC ºC Method specs As As the the efficiency and and inertness of of the the Restek Restek column column is is much much higher higher the the resolution is is also also much much better better then then required..

19 Bleed measure in pa at Tmax This This is is not not an an ASTM ASTM spec., spec., but but all all columns are are measured for for bleed bleed Average of of pa pa with with standard deviation of of +/- +/-3 pa. pa. This This will will guarantee a flat flat baseline for for DHA, DHA, allowing accurate detection of of smallest peaks peaks

20 ASTM D6730 column specifications C5 theoretical plates C5 retention 35 ºC Resolution, t butanol/2 methylbutene 35 ºC Peak asymmetry, 35 ºC > <5.00 Actual data for the Rtx-1 PONA / Rtx-DHA-100 C5 theoretical plates C5 retention factor 0.48 Resolution t butanol / 2methylbutene Peak asymmetry, 35 ºC 1.13 v v v v

21 ASTM D 6730 required a tuned column.. ASTM wants general purpose methods Columns from different suppliers will show small differences in selectivity.. By coupling a short piece of Rtx-5, every column can be tuned to fulfill ASTM specs on selectivity.. Tuning pre-column Rtx-5, 2-5 meters Length to to be be determined empirically

22 ASTM 6730 DHA evaluation mix tuning area s Column Column 100m 100m x x 0.25mm 0.25mm Rtx-DHA-100, Rtx-DHA-100, df df = = um um Oven Oven temp. temp. 5 5 ºC,( ºC,( 6.5min.),18ºC/min 6.5min.),18ºC/min 48ºC,( 48ºC,( 30min.), 30min.), 3.5ºC/min 3.5ºC/min ºC 200ºC Carrier Carrier gas gas H2, H2, Flow Flow 5mL/min 5mL/min (Constant (Constant Flow)) Flow)) Peak # 1. ethanol 2. C5 3. t butanol 4. 2 methylbutene ,3 dimethylbutane 6. MTBE 7. C methylcyclopentene 9. Benzene 10. cyclohexane ethylpentane t 2 dimethylcyclopentane 13. C ,2,3 trimethylpentane 15. 2,3,3 trimethylpentane 16. Toluene 17. C8 18. Ethylbenzene 19. P xylene 20. 2,3 DMH 21. C methylnonane 23. 1,2 methylethylbenzene 24. C C ,2,3,5,tetramethylbenzene 27. Naphthalene 28. C methylnaphthalene 30. C Time (min)

23 Focusing on critical areas of resolution (1) Column Column Oven Oven Carrier Carrier 100m 100m x x 0.25mm 0.25mm Rtx-DHA-100, Rtx-DHA-100, df df = = um um m tuning tuning column column C C for for minutes, minutes, than than ramped ramped to to 250C 250C at at 10/minute 10/minute and and held held for for minutes. minutes. H2, H2, 5mL/min, 5mL/min, cm/s cm/s t butanol 4. 2 methylbutene methylcyclopentene 9. Benzene ,3,3 trimethylpentane Toluene > R < min

24 Focusing on critical areas of resolution (2) Column Column Oven Oven Carrier Carrier 100m 100m x x 0.25mm 0.25mm Rtx-DHA-100, Rtx-DHA-100, df df = = um um m tuning tuning column column C C for for minutes, minutes, than than ramped ramped to to 250C 250C at at 10/minute 10/minute and and held held for for minutes. minutes. H2, H2, 5mL/min, 5mL/min, cm/s cm/s 19. p-xylene 20. 2,3 DMH 29. methylnaphthalene 30. C Time (min) Time (min)

25 Coupling the tuning column..

26 Column Cutting Cutting point Slide wafer in ONE direction along the nail..

27 Cutting the fused silica good cut bad cut A flat, 90 square cut will be optimal for all co nnections http//gc.discussing.info/gs/e_columns/cutting.html

28 Press-Tight Application make a sharp cut Dark ring

29 Gasoline, acc to ASTM D6730, Helium as carrier gas n-c4 C3 Column n-c5 n-c6 n-c7 100 x 0.25 mm Rtx-DHA-100, tuned 5%phenyl PDMS Oven 5 C, 10 min -> 50 C, 5 C/min, 54 min, --> 200 C, 1.3 C/min Carrier gas He, 24 cm/s, 39.3 Psi; Injection Split, 1 150; Detection FID; Following the the method Near Near 3 hours hours analysis time; time; Using Using HELIUM n-c9 n-c10 n-c

30 Using Helium and a different program Using the the same column, same GC GC Column 100m x 0.25mm Rtx-DHA-100, df df = µm µm coupled with with 2.6m x 0.25mm Rtx-5DHA tuning column, df df = um um Carrier gas gas He, He, Flow ml/min (Constant Flow), cm/s Oven temp. 5 ºC ºC 15min., 5ºC/min 50ºC, 50min. 8ºC/min 200ºC, min min

31 Using Helium and a different program C13 in 98 minutes

32 Speeding up this application using HYDROGEN Using hydrogen we can operate at at near 2 times the linear velocity as as used for for helium This results in in significant shorter run time To To get the same chromatogram/separation, we need to to adjust the oven temperature program If If we do do not do do this, some peaks will start to to move..

33 Example of separations using different temp program rate at the SAME linear velocity 30 C/min 1-mNap C/min 7 min min m 5 C/min 19 min 2 C/min 1 C/min Some Some components are are very very sensitive for for changes in in 33 min elution elution temperature.. 50 min 0.5 C/min 72 min

34 New methods When using a different gas flow or carrier gas, the conditions must be changed so that the elution temperature of the components remain the same Need to adjust the temperature program rate Use for for this the method translation software developed by by Dr. Blum, Envantage, or or ask your Restek representative

35 Conditions for speeding up this application using HYDROGEN Using the the same column, same GC GC Column 100m x 0.25mm Rtx-DHA-100, df df = µm µm + 2.6m 2.6m x 0.25mm Rtx-5DHA tuning tuning column, df df = µm µm Carrier gas gas H2, H2, Flow 5 ml/min (Constant Flow) Oven temp. 5 ºC ºC 6.5min., 18ºC/min 48ºC, 30min. 3.5ºC/min 200ºC

36 Fast DHA analysis using Hydrogen.. Analysis time time < minutes..

37 Fast DHA using Hydrogen Same GC Same method Same Injection/detection techniques Same column* Neil Johansen No issues with overloading, peak shifts, tailing, high inlet pressures, discrimination and reduced life time.. All All retention data data and and identification is is generated by by Neil Neil Johansen, developer of of the the D6730 D6730 DHA DHA method. Available on on the the Restek Restek website http//

38 Hydrogen safety issues Need to to make sure sure there is is no no accumulation of of H2 H2 possible in in the theoven.. Hydrogen is combustible over a concentration range of 4% to 74% by volume; Diffusion VERY fast; Use of Hydrogen generators limited amount of hydrogen Hydrogen Flow restriction to set with GC inlet (electronic flow setting) Hydrogen detection systems (sniffer) Use MXT type metal capillary columns

39 Rtx-DHA columns Other ASTM methods For ASTM D6733 Rtx-DHA-50 50m x 0.25mm, df = 0.5 µm For ASTM D6729 Rtx-DHA m x 0.25mm, df = 0.5 µm For ASTM D5501 Rtx-DHA m x 0.25mm, df = 1.0 µm

40 Biggest Challenges for customers running ASTM D6730 Have good peak shape for alcohols. Have sufficient theoretical plates... Coupling of tuning capillary... Analysis time too long, wish for faster methods.. Reproducibility of column quality parameters.. V V V V V