UOP 373-2008 Composition of C2 through C5 Hydrocarbon Mixtures by GC.pdf

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1、 IT IS THE USERS RESPONSIBILITY TO ESTABLISH APPROPRIATE PRECAUTIONARY PRACTICES AND TO DETERMINE THE APPLICABILITY OF REGULATORY LIMITATIONS PRIOR TO USE. EFFECTIVE HEALTH AND SAFETY PRACTICES ARE TO BE FOLLOWED WHEN UTILIZING THIS PROCEDURE. FAILURE TO UTILIZE THIS PROCEDURE IN THE MANNER PRESCRIB

2、ED HEREIN CAN BE HAZARDOUS. MATERIAL SAFETY DATA SHEETS (MSDS) OR EXPERIMENTAL MATERIAL SAFETY DATA SHEETS (EMSDS) FOR ALL OF THE MATERIALS USED IN THIS PROCEDURE SHOULD BE REVIEWED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTION EQUIPMENT (PPE). COPYRIGHT 1959, 1983, 2008 UOP LLC. All rights r

3、eserved. Nonconfidential UOP Methods are available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, USA. The UOP Methods may be obtained through the ASTM website, www.astm.org, or by contacting Customer Service at serviceastm.org, 610.832.9555 FAX, or

4、610.832.9585 PHONE. Composition of CB2B through CB5B Hydrocarbon Mixtures Uby GC UOP Method 373-08 Scope This method is for determining individual components in CB2B through CB5B hydrocarbon mixtures. The lower limit of detection for a single component is 0.01 mass-%. CB6B and heavier components, if

5、 present, may not be fully quantitated. Trace concentrations of these components can be determined using U899. References ASTM Practice D1265, “Sampling Liquefied Petroleum (LP) Gases (Manual Method),” www.astm.org Scanlon, J. T. and Willis, D. E., Journal of Chromatographic Science, 23, 333-340 (19

6、85) UOP Method 516, “Sampling and Handling of Gasolines, Distillate Fuels, and CB3B-CB4B Fractions,” www.astm.org UOP Method 899, “Trace Hydrocarbons in Hydrogen or LPG by Gas Chromatography,” www.astm.org UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org Outline of Method The samp

7、le to be analyzed is injected into a gas chromatograph that is equipped with a liquid phase sampling valve, a porous layer open tubular (PLOT) column, and a flame ionization detector (FID). The mass-% or mol-% composition of the sample is obtained by the internal normalization technique, wherein the

8、 peak areas are first corrected for differences in response and then normalized to 100%. Apparatus References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Chromatographic column, 50m x 0.32mm x 5m (length, ID, layer thickness) AlB2BO

9、B3B/KCl, Varian, Cat. No. CP-7515 2 of 11 373-08 Gas chromatograph, temperature programmable, built for capillary column chromatography, utilizing a split injection system, equipped with a glass injection port insert, provision for both gas and liquid sampling valves and a flame ionization detector

10、that will give a minimum peak height response of five times the background noise for 0.01 mass-% n-butane when operated at the recommended conditions, Agilent Technologies, Model 7890. Integrator, or data system, electronic, for obtaining peak areas. This device must integrate areas at a sufficientl

11、y fast rate so that narrow peaks, typically obtained from a capillary column, can be accurately measured. The integrator must have programmable parameters for controlling baseline events, and have graphics capabilities. ChemStation, Agilent Technologies. Reducer, Swagelok, Cat. No. SS-200-R-1 Regula

12、tor, 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 Tri-Gas, Model 3122-350 Regulator, nitrogen, two-stage, high purity, delivery press

13、ure range 30-700 kPa (4-100 psi), Matheson Tri-Gas, Model 3122-580 Regulator, nitrogen or helium, two-stage, high purity, delivery pressure range 70-1700 kPa (10-250 psi), Matheson Tri-Gas, Model 3126-580 Stainless Steel tubing, 1/16” OD x 0.04” ID, Alltech Associates, Cat. No. 30033 Tubing, translu

14、cent, FEP Teflon, 3.2-mm (1/8-inch) OD, 1.6-mm (1/16-inch) ID, 3450 kPa (500 psi), Alltech Associates, Cat. No. 45740 Valve, liquid sampling valve, 4-port rotary, with 0.5-l internal groove, Valco, Cat. No. DCI4UWE.5 Vent Shut-off valve, Swagelok, Cat. No. SS-ORS2 (Shut-off valve for LPG sampling) R

15、eagents 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 Hydrocarbon Blends, for calibration, Matheson Tri-Gas Hydrogen gas purifier, Valco, Cat. No.

16、 P-200 Hydrogen, purified chromatographic grade, typically 99.995% purity Nitrogen, make-up gas, total hydrocarbons less than 0.5 ppm as methane Procedure The analyst is expected to be familiar with general laboratory practices, the technique of gas chromatography, and the equipment being used. Samp

17、ling Obtain the sample by following the procedures described in ASTM Practice D 1265, “Sampling Liquefied Petroleum (LP) Gases (Manual Methods),” UOP Method 516, “Sampling and Handling of 3 of 11 373-08 Gasolines, Distillate Fuels, and C3-C4 Fractions,” or other reliable technique. The specially coa

18、ted cylinders described in UOP Method 516 may be used but are not required for this application. Chromatographic Technique 1. Install the gas purifier in the supply line between the carrier gas source and the carrier gas inlets on the gas chromatograph. Column life is significantly reduced if the ga

19、s purifier is not used. 2. Install the LPG sampling valve (see Figure 1). The injection valve should be mounted so that it maintains ambient temperature at the start of the run to keep liquid from bubbling in the valve or injection lines prior to injection. If it is desired to make gas injections, r

20、eplace the liquid injection valve on the GC with a gas injection valve and refer to the appendix of this method for how to inject a gas sample. 3. Install the fused silica capillary column in the gas chromatograph, according to the column and gas chromatograph manufacturers instructions. 4. Establis

21、h the flow rate and operating temperature specified under Operating Conditions (see Table 1). Caution: Hydrogen leakage into the confined volume of the column compartment can cause a violent explosion. It is, therefore, mandatory to test for leaks each time a connection is made, and periodically the

22、reafter. 5. Program the column oven to 200C. Maintain this temperature until a stable baseline has been obtained at the required sensitivity. 6. If the sample may contain water or sediment, or is of unknown origin, it must be checked for these contaminants before analysis by releasing a small amount

23、 of the sample from the bottom of the cylinder. Place the LPG sample cylinder in a vertical position in a hood or well vented area. If the cylinder has an outage tube, the outage tube must be at the top. Briefly open the bottom valve onto the floor of a hood to check that no water or sediment is pre

24、sent in the LPG. If water or sediment is determined to be present, discontinue the analysis and obtain a clean sample. 7. Pressurize the LPG cylinder containing the sample (or blend) to approximately 1400 to 2000 kPA gauge (200- to 300-psig) with nitrogen or helium. 8. Mount the cylinder in a vertic

25、al position. The LPG sample is delivered to the lab at elevated pressure. Make sure to connect the sample vessel securely so LPG flows into the GC sampling valve prior to opening valves on the sample vessel. If the cylinder has an outage tube, the outage tube fitting must be at the top. Connect the

26、bottom valve to the sample injector valve inlet tubing. If the cylinder is fitted with an eductor tube, connect the eductor tube outlet to the sample injection inlet tubing in such a manner that the eductor tube is sampling liquid LPG. The connecting tubing between the cylinder and the injector valv

27、e must be as short as possible. 9. Place the injection valve in the fill position. 10. Ensure that the vent shut-off valve is closed. 11. Fully open the bottom valve, or eductor valve of the sample cylinder. 12. Partially open the vent shut-off valve to permit LPG flow through the sampling system. 4

28、 of 11 373-08 Table 1 URecommended Operating Conditions Carrier gas hydrogen Mode constant pressure Head pressure 75 kPa gauge (11 psig) Linear velocity 85C 45 cm/sec Equivalent flow 85C 2.4 mL/min Split flow 300 mL/min Injection port temperature 210C Column temperature programPaP Initial temperatur

29、e 85C Initial hold time 2.5 min Programming rate A 2C/min Intermediate 1 temperature 100C Intermediate 1 hold time 0 min Programming rate B 5.3C/min Intermediate 2 temperature 135C Intermediate 2 hold time 0 min Programming rate C 14C/min Final hold temperature 200C Final hold time 24.25 min Detecto

30、r flame ionization Detector temperature 250C Hydrogen flow ratePbP 35 mL/min Air flow ratePbP 350 mL/min Makeup gas nitrogen Makeup gas flow ratePbP 30 mL/min Sample size 0.5 l for LPG Pa PThe column used for this analysis has an upper limit of 200C; do not exceed. Pb PConsult the manufacturers inst

31、rument manual for suggested flow rates. 13. Purge the sample valve with sample, watching the translucent tubing to ensure it is liquid full. Continue the flow until entrained bubbles are no longer observed in the translucent tubing, and inlet lines are adequately flushed of previous sample residuals

32、. CAUTION: Inspect the translucent tubing regularly. Replace at first signs of wear or kinking. Pressure on the translucent tubing must never exceed 2000 kPa (300 psig). 14. Stop the sample flow by closing the vent shut-off valve. 15. Inject the sample immediately by switching the injection valve to

33、 the inject position, and start the integrator and the column temperature programming sequence. The injection valve remains in the inject position for the duration of the sample run. 16. Close the LPG cylinder valve and immediately open the vent shut-off valve to vent the sampling system. 17. Identi

34、fy each component and calculate their concentrations as described in Calculations. The C2 through C5 hydrocarbon separation is complete in less than 18 minutes. Additional time is required for heavier components to elute if present. 5 of 11 373-08 Calibration It has been found that using effective c

35、arbon number factors, sometimes called theoretical factors, provides accurate quantitation. The theoretical relative response factors were calculated using the effective carbon number (ECN) concept as described by Scanlon and Willis. These factors are listed in Table 2 and are used in the Calculatio

36、ns portion of this method. Table 2 UTheoretical Response Factors UComponentU Response Factor, Umass-%, FU Response Factor, U mol-%, GU Ethane 1.050 1.960 Ethylene 1.031 2.063 Propane 1.027 1.307 Cyclopropane 1.014 1.352 Propylene 1.014 1.352 Isobutane 1.015 0.980 n-Butane 1.015 0.980 Cyclobutane 1.0

37、05 1.005 trans-2-Butene 1.005 1.005 1-Butene 1.005 1.005 Isobutene 1.005 1.005 cis-2-Butene 1.005 1.005 Neopentane 1.008 0.784 Isopentane 1.008 0.784 n-Pentane 1.008 0.784 1,3-Butadiene 0.994 1.031 3-Methyl-1-butene 1.000 0.800 trans-2-Pentene 1.000 0.800 2-Methyl-2-butene 1.000 0.800 1-Pentene 1.00

38、0 0.800 2-Methyl-1-butene 1.000 0.800 cis-2-Pentene 1.000 0.800 Purchase a hydrocarbon calibration blend whose composition is similar to the samples to be analyzed. Analyze the blend as a sample to verify instrument calibration. If the results differ by more than 10% relative, check the apparatus, o

39、perating conditions, and the blend composition. Calculations When LPG injections are made, data is typically reported in mass-%, but may be reported in mol-%. Calculate the concentration of each hydrocarbon to the nearest 0.01 mass- or mol-%, using Equation 1 for mass-% or Equation 2 for mol-%: 6 of

40、 11 373-08 Hydrocarbon, mass-% =S100EF(1) where: E = component peak area F = relative response factor, for mass-%, Table 2 S = sum of the products EF for all the recorded peaks 100 = factor to convert to mass-% Hydrocarbon, mol-% =T100EG(2) where: E = component peak area G = relative response factor

41、, for mol-%, Table 2 T = sum of the products EG of all the recorded peaks 100 = factor to convert to mol-% Precision The precision statement was determined using UOP Method 999. The LPG sample loop was purged and filled. The start button was pushed and the GC automatically injected the sample using

42、the installed injection valve. Repeatability and Site Precision A nested design was carried out for determining components in one LPG hydrocarbon sampleS Swith four analysts in one laboratory. Each analyst carried out two tests on two separate days. The total number of tests for each component was 1

43、6. The precision data are summarized in Table 3. Two tests performed by the same analyst on the same day should not differ by more than the repeatability allowable difference with 95% confidence. Two tests performed in one laboratory by different analysts on different days should not differ by more

44、than the site precision allowable difference with 95% confidence. Table 3 URepeatability and Site Precision, mass-% URepeatabilityU USite PrecisionU UComponentU Mean UConc.U Within- UDay esdU Allowable UDifferenceU Within- ULab esdU Allowable UDifferenceU Propane Propylene Isobutane n-Butane trans-2

45、-Butene 1-Butene Isobutene cis-2-Butene Isopentane 1,3-Butadiene 3-Methyl-1-butene 2-Methyl-1-butene 14.05 25.69 16.28 9.53 9.01 8.25 9.34 6.47 0.75 0.24 0.30 0.09 0.03 0.09 0.03 0.06 0.03 0.06 0.02 0.02 0.01 0.01 0.01 0.01 0.10 0.30 0.10 0.20 0.09 0.18 0.06 0.06 0.03 0.02 0.02 0.01 0.04 0.13 0.04 0

46、.06 0.04 0.04 0.02 0.02 0.01 0.01 0.01 0.01 0.14 0.42 0.14 0.21 0.12 0.14 0.08 0.08 0.03 0.02 0.01 0.01 7 of 11 373-08 The data in Table 3 are a short-term estimate of repeatability. When the test is run routinely, a control standard and chart should be used to develop a better estimate of the long-

47、term repeatability. Reproducibility There is insufficient data to calculate reproducibility of the test at this time. Time for Analysis The elapsed time for one analysis is 0.8 hour. The labor requirement is 0.4 hour. Suggested Suppliers Agilent Technologies, 2850 Centerville Road, Wilmington, DE 19

48、808-1610 (302-633-8000) Alltech Associates, 2051 Waukegan Road, Deerfield, IL 60015-1899 (847-948-8600) Chicago Fluid Systems Technologies, 360 Windy Point Drive, Glendale Heights, IL 60139 (630 545 0003) Cole Parmer Instrument Company, 625 East Bunker Court, Vernon Hills, IL 60061-9872 (847 549

49、7600) Matheson Tri-Gas, Inc., 166 Keystone Drive, Montgomery, PA 18936 (215-641-2700) TVarian, Inc., (Chrompack colums), 2700 Mitchell Drive, Walnut Creek, CA94598 (925 945 2360) TVICI Valco Instruments Co. Inc., P.O. Box 55603, Houston, TX 77255 (713-688-8106) 8 of 11 373-08 9 of 11 373-08 10 of 11 373-08 Appendix Scope This appendix describes how to inject a gaseous sample. Apparatus References to catalog numbers and supp