UOP 690-2013 C8 and Lower Boiling Paraffins and Naphthenes in Low-Olefin Hydrocarbons by GC.pdf

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4、0.832.9585 PHONE. C8 and Lower Boiling Paraffins and Naphthenes in Low-Olefin Hydrocarbons by GC UOP Method 690-13 Scope This gas chromatographic method is for determining C8 and lower boiling paraffins and naphthenes in hydrocarbons containing less than 2 mass-% olefins (see Note 1) having a maximu

5、m final boiling point of 260C. Benzene and toluene are also determined. Certain non-aromatic components of interest are reported as composites and C8 aromatics are not determined (see Note 2). The quantitation limit for any reported component is 0.01 mass-%. References ASTM Method D4307, “Preparatio

6、n of Liquid Blends for Use as Analytical Standards,” www.astm.org ASTM Method D6839, “Hydrocarbon Types, Oxygenated Compounds, and Benzene in Spark Ignition Engine Fuels by Gas Chromatography,” www.astm.org Scanlon, J. T. and Willis, D. E., Journal of Chromatographic Science, 23, 333-340 (1985) UOP

7、Method 304, “Bromine Number and Bromine Index of Hydrocarbons by Potentiometric Titration,” www.astm.org UOP Method 744, “Aromatics in Hydrocarbons by GC,” www.astm.org Outline of Method Two gas chromatographic analyses using the same column are required to determine the greatest number of resolved

8、non-aromatic components. Based on the degree of resolution required, either Analysis A alone, or both Analyses A and B may be used. In both analyses, a sample is injected into a gas chromatograph that is equipped with a fused silica capillary column and a flame ionization detector (FID). A separate

9、set of operating conditions is used for each analysis. The mass-% composition of the sample is obtained by the internal normalization technique of quantitation, wherein component peak areas for the entire sample are first corrected for differences in response and then normalized to 100%. Some unreso

10、lved non-aromatic components from Analysis A can then be resolved and calculated using data obtained from Analysis B (see Note 3). 2 of 14 690-13 Apparatus References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Balance, readable to

11、0.0001 g Chromatographic column, 50 m of 0.20-mm ID fused silica capillary, internally coated to a film thickness of 0.5-m with cross-linked methyl silicone, Agilent Technologies, Cat. No. 19091S-001. Use of this specific column is recommended. The same column is used for Analysis A and Analysis B.

12、Data system, or electronic integrator, for obtaining peak areas. This device must integrate areas at a sufficiently fast rate so that narrow peaks typically resulting from use of a capillary column can be accurately measured. Agilent Technologies, ChemStation Gas chromatograph, capable of multiple t

13、emperature ramping and capable of cryogenic operation at 32C, built for capillary column chromatography utilizing a split injection system, having a glass injection port insert, and equipped with a flame ionization detector that will give a minimum peak height response of 5 times the background nois

14、e for 0.01 mass-% of benzene when operated at the recommended conditions. Electronic pressure control (EPC) is recommended. Agilent Technologies, Model 7890 Gas purifier, to remove oxygen from the hydrogen carrier gas, VICI Mat/Sen, Cat. No. P-200-1 Leak detector, gas, Grace Davison, Cat. No. 21-250

15、 Refrigerator, explosion-proof or flammable storage, VWR, Cat. No. 55700-340 Regulator, air, two-stage, high purity, delivery pressure range 30-700 kPa (4-100 psi), Matheson Tri-Gas, Model 3122-590 Regulator, hydrogen, two-stage, high purity, delivery pressure range 30-700 kPa (4-100 psi), Matheson

16、Tri-Gas, Model 3122-350 Regulator, nitrogen, two-stage, high purity, delivery pressure range 30-700 kPa (4-100 psi), Matheson Tri-Gas, Model 3122-580 Sample injector, any syringe or injector capable of injecting a 0.5-L volume of sample. An automatic injection device is recommended. Agilent Technolo

17、gies, Model 7683 Reagents and Materials References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Air, zero gas, total hydrocarbons less than 2.0 ppm as methane Benzene, 99.9% minimum purity, Sigma-Aldrich, Cat. No. 270709 Carbon dioxi

18、de, liquid, if necessary for cryogenic cooling of the GC column oven to 32C n-Hexane, 99% minimum purity, Sigma-Aldrich Chemical, Cat. No. 139386 Hydrogen, zero gas, 99.95% minimum purity, total hydrocarbons less than 0.5 ppm as methane Nitrogen, zero gas, 99.99% minimum purity, total hydrocarbons l

19、ess than 0.5 ppm as methane Syringe, for sample injector, 10-L, Agilent Technologies, Cat. No. 5181-1273 Toluene, 99% minimum purity, Sigma-Aldrich, Cat. No. 179965 3 of 14 690-13 p-Xylene, 99% minimum purity, Sigma-Aldrich, Cat. No. 134449 Procedure The analyst is expected to be familiar with gener

20、al laboratory practices, the technique of gas chromatography, and the equipment being used. Dispose of used reagents, materials, and samples in an environmentally safe manner according to local regulations. Chromatographic Technique 1. Install the gas purifiers in the supply lines between the gas so

21、urces and the gas inlets on the gas chromatograph. Column and FID life may be significantly reduced if the gas purifiers are not used. 2. Install the fused silica capillary column in the gas chromatograph. CAUTION: Hydrogen carrier gas leakage into a confined volume of the column oven can cause a vi

22、olent explosion. It is, therefore, mandatory to test for leaks each time a connection is made and periodically thereafter. 3. Establish the recommended operating conditions as given in Table 1, Analysis A. Other conditions may be used provided they produce the required sensitivity and chromatographi

23、c separations equivalent to those shown in the Typical Chromatogram (Figures 1 and 2). Table 1 Recommended Operating Conditions Analysis A Analysis B Carrier gas hydrogen hydrogen Column head pressure 32C 140 kPa (20 psig) 140 kPa (20 psig) Equivalent flow 1.1 mL/min 1.1 mL/min Equivalent linear vel

24、ocity 33 cm/sec 33 cm/sec Split flow 215 mL/min 215 mL/min Injection port temperature 230C 230C Column temperature program Initial temperature 32C 60C Initial time 6 min 8 min Programming rate 1 5C/min 5C/min Intermediate temperature 52C 90C Intermediate time 14 min 0 min Programming rate 2 20C/min

25、20C/min Final temperature 250C 250C Final time 9 min 10 min Detector FID FID Temperature 250C 250C Hydrogen flow rate* 30 mL/min 30 mL/min Air flow rate* 400 mL/min 400 mL/min Makeup nitrogen flow rate* 30 mL/min 30 mL/min Sample size 0.5 L 0.5 L *Consult the manufacturers instrument manual for sugg

26、ested flow rates. 4. Program the column oven to 250C and maintain this temperature until a stable baseline has been obtained at the required sensitivity. 5. Cool the column oven to 32C. 4 of 14 690-13 6. Inject 0.5 L of sample and start the integrator and the column temperature programming sequence.

27、 The use of an autoinjector or autosampler automates the injection of the sample into the GC, starts the data system, and the GC oven program simultaneously. 7. Identify the components by comparing the resultant chromatogram to the Typical Chromatogram shown in Figures 1 and 2. If necessary, confirm

28、 the sites of the aromatic components by comparison with the calibration blend (see Calibration). 8. Establish the recommended operating conditions as given in Table 1, Analysis B, if resolution of the co-eluting components in Analysis A is required, and proceed to Steps 9 and 10. Other conditions m

29、ay be used provided they produce the required sensitivity and chromatographic separations equivalent to those shown in the Typical Chromatogram (Figures 3 and 4). 9. Inject 0.5 L of sample and start the integrator and the column temperature programming sequence. 10. Identify the components by compar

30、ing the chromatogram obtained to the Typical Chromatogram shown in Figures 3 and 4. If necessary, confirm the sites of the aromatic components by comparison with the calibration blend (see Calibration). Calibration This analysis uses internal normalization of the entire sample to quantitate the C8 m

31、inus components. In order to accurately analyze the entire sample, C6 through C8 aromatic components must be identified and response factors determined for them. This is necessary because C6 through C8 aromatic components do not have the same detector response as the non-aromatic components. The non

32、-aromatic components all have essentially the same detector response. Calibrate whenever chromatographic conditions have changed and periodically thereafter. 1. Prepare a calibration blend as described in ASTM Method D 4307, “Preparation of Liquid Blends for Use as Analytical Standards,” to contain

33、approximately equal masses of n-hexane, benzene, toluene and p-xylene. This blend is stable for six months if refrigerated. 2. Analyze the blend in triplicate as described under Chromatographic Technique, Analysis A. 3. Identify the peaks and obtain the peak areas for each component from the triplic

34、ate runs. 4. Determine the relative response factor for each component in each run to three decimal places, using n-hexane as reference and Equation 1. CDAB F = (1) where: A = component in the blend, mass-% B = peak area of n-hexane C = n-hexane, mass-% D = peak area of component F = relative respon

35、se factor for each component Relative response factors from each of the triplicate runs should not deviate from the average by more than 2% of the value. If greater deviations occur, make certain that there are no problems with the equipment, then make additional runs until the required repeatabilit

36、y is obtained on three consecutive runs. 5 of 14 690-13 5. Average the relative response factors for each component from the three runs. Use these averages as J in Equation 2. Use the relative response factor for n-hexane for all the non-aromatic (see Table 3) and C9+ (the unidentified peaks eluting

37、 after methylcyclohexane in Figure 1) components in the sample. Use the relative response factor of p-xylene for ethylbenzene, m-xylene, p-xylene and o-xylene. Calculated relative response factors should be similar to the theoretical relative response factors shown in Table 2. The theoretical relati

38、ve response factors were calculated using the effective carbon number (ECN) concept as described by Scanlon and Willis. If the determined relative response factors differ by more than 5% from those shown in Table 2, recheck the apparatus, operating conditions, and blend preparation procedures. Table

39、 2 Theoretical Relative Response Factors n-Hexane 1.000 Benzene 0.906 Toluene 0.916 p-Xylene 0.924 If the C9+ components are known to be primarily aromatics, use the response factor for p-xylene instead of the response factor for n-hexane for the C9+ components. Calculations Calculate the concentrat

40、ion of each C8 and lighter component in the sample for Analysis A, and, if applicable, Analysis B, to the nearest 0.01 mass-% using Eq. 2. TPJ 100 %-mass Component, = (2) where: J = average relative response factor of individual component P = peak area of individual component T = sum of the products

41、, PJ, of all recorded peaks 100 = factor to convert to mass-% When Analysis B is used, peaks 30A, 31A, 40A, 40B, 56A, 56B, 56C, 60A, 60B, 62A and 62B (see Tables 3 and 4) are resolved and the concentrations calculated directly from Analysis B, using Equations 1 and 2. Composite peaks 40, 56 and 60,

42、Analysis A, are fully resolved in Analysis B. The Analysis B individual concentrations require re-normalization to conform to the composite concentration totals in Analysis A. This is accomplished by use of Equation 3. YWX %-mass component, Individual = (3) where: W = component amount, Analysis B X

43、= composite amount, Analysis A Y = sum of component concentrations from Analysis B, in Analysis A composite Additionally, determine the concentrations for 1-cis-2-dimethylcyclopentane, 2,2-dimethylhexane and 3-ethylhexane, which are unresolved in Analysis A, from the Analysis A and B data Equations

44、4, 5, and 6. 1-cis-2-Dimethylcyclopentane, mass-% = LG (4) where: 6 of 14 690-13 G = methylcyclohexane, from Analysis B L = methy1cyclohexane + 1-cis-2-dimethycyclopentane, from Analysis A 2,2-Dimethylhexane, mass-% = NH (5) where: H = 1,1,3-trimethylcyclopentane, from Analysis B N = 1,1,3-trimethyl

45、cyclopentane + 2,2-dimethylhexane, from Analysis A 3-Ethylhexane, mass-% = RS (6) where: R = 3-ethylhexane + l-cis-3-dimethylcyclohexane + 1-cis-2-trans-3-trimethylcyclopentane, from Analysis A S = 1-cis-3-dimethylcyclohexane + 1-cis-2-trans-3-trimethylcyclopentane, from Analysis B If, after all the

46、 calculations above, the sum of all components (resolved and unresolved) does not total 100 mass-%, renormalize the data to 100 mass-%. Report each component to the nearest 0.01 mass-% below one mass-%, and to three significant figures at or above one mass-%. Table 3 Retention Times of Identified Co

47、mponents, Analysis A Peak numbers with letter designations refer to co-eluting peaks, i.e.; 30A and 30B co-elute. If some separation of these peaks does occur, it should not be inferred that A elutes before B. Typical Retention Time, Min Peak No. Component Identification 2.10 2.35 2.54 2.71 2.79 3.3

48、3 3.67 4.32 5.00 5.04 5.16 5.60 6.23 7.19 7.28 7.45 7.67 8.29 8.56 8.72 9.16 9.23 9.35 9.58 9.86 9.99 10.06 * 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Ethane site Propane Isobutane n-Butane 2,2-Dimethylpropane Isopentane n-Pentane 2,2-Dimethylbutane Cyclopentane 2,3-Dimet

49、hylbutane 2-Methylpentane 3-Methylpentane n-Hexane 2,2-Dimethylpentane Methylcyclopentane 2,4-Dimethylpentane 2,2,3-Trimethylbutane Benzene 3,3-Dimethylpentane Cyclohexane 2-Methylhexane 2,3-Dimethylpentane 1,1-Dimethylcyclopentane 3-Methylhexane 1-cis-3-Dimethylcyclopentane 1-trans-3-Dimethylcyclopentane 3-Ethylpentane 7 of 14 690-13 Typical Retention Time, Min Peak No. Component Identification 10.13 10.46 10.82 11.93 12.08 12.61 12.70 12.82 13.20 13.30 13.71 13.93 14.22 14.78 14.86 15.29 15.41 15.53 15.74 15.94 16.03 16.20 16.68 17.03 17.23 1