UOP 960-2006 Trace Oxygenated Hydrocarbons in Liquid Hydrocarbon Streams 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 1998, 2006 UOP LLC. All rights reserve

3、d. 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 610.83

4、2.9585 PHONE. Trace Oxygenated Hydrocarbons in Liquid Hydrocarbon Streams by GC UOP Method 960-06 Scope This method is for determining trace levels of individual oxygenated hydrocarbons, with boiling points up to 138C, in C4liquefied petroleum gas (LPG), light isomerate and naphtha. Mono-oxygenated

5、hydrocarbons determined include C1through C5alcohols, and C2through C6carbonyls and ethers. Di-oxygenated hydrocarbons determined include C2through C4methyl esters and 1,4-dioxane. The range of quantitation for 2-butanone is 0.2 to 250 mass-ppm (mg/kg). The range of quantitation for other components

6、 may be estimated by multiplying the relative response factor of the component from Table 2 times the above values. Inorganic compounds containing oxygen, such as water, are not determined. Carbon monoxide and carbon dioxide are not determined. Unsaturated oxygenated hydrocarbons may be detected but

7、 are not identified. Oxygenated hydrocarbons containing other heteroatoms such as nitrogen, chlorine or sulfur are not determined. Certain oxygenated hydrocarbons are not separated and are reported as composites. See Table 2 for a list of all identified compounds and composites. Some sulfur and nitr

8、ogen compounds are known to elute in the oxygenate region of the chromatogram; Figures 2A and 2B show elution times of some identified sulfur and nitrogen compounds. References ASTM Method D 1657, “Density or Relative Density of Light Hydrocarbons by Pressure Hydrometer,” www.astm.org ASTM Method D

9、2163, “Analysis of Liquefied Petroleum (LP) Gases and Propene Concentrates by Gas Chromatography,” www.astm.org ASTM Method D 2598, “Calculation of Certain Physical Properties of Liquefied Petroleum (LP) Gases from Compositional Analysis,” www.astm.org ASTM Method D 4052, “Density and Relative Densi

10、ty of Liquids by Digital Density Meter,” www.astm.org ASTM Practice D 4307, “Preparation of Liquid Blends for Use as Analytical Standards,” www.astm.org 2 of 18 960-06 UOP Method 373, “Composition of C2 Through C5 Hydrocarbon Mixtures by Gas Chromatography, www.astm.org UOP Method 999, “Precision St

11、atements in UOP Methods,” www.astm.org Outline of Method A repeatable volume of sample is injected into a specially modified gas chromatograph (GC) that is equipped with two megabore capillary columns operating at different temperatures. The first column, a non-polar column, fractionates interfering

12、 sample components from the system. The second column, a selective CP-Lowox column, separates and analyzes the oxygenates. The non-polar column operates isothermally inside an auxiliary oven, and the CP-Lowox column resides in the main GC oven. Initially, the columns are connected in series, and aft

13、er the elution of components of interest from the non-polar column, the non-polar column is backflushed. The CP-Lowox column is maintained in foreflush and temperature programmed, eluting compounds to a flame ionization detector (FID). Two sample injections (fractionations) may be required. 1. Fract

14、ionation A is used to determine all oxygenates other than methyl ether. 2. Fractionation B is used to determine methyl ether. Quantitative results are obtained by the external standard method of quantitation wherein the peak areas for the components of interest are compared to peak areas of a calibr

15、ation standard. Apparatus References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Balance, readability 0.1-mg Bracket, nut plate assembly, for mounting bulkhead fittings in GC oven, Agilent Technologies, Cat. No. 05890-80660 Chromato

16、graphic column, 10 m of 0.5-mm ID CP-Simdist Ultimetal, Varian, Cat. No. CP7592 Chromatographic column, 10 m of 0.53-mm ID CP-Lowox, Varian, Cat. No. CP8587 Electronic leak detector, Gow-Mac Mini gas leak detector, 115 volt, Restek, Cat. No. 21640 Fittings, CGA, for blend cylinder, CGA No. 510, Math

17、eson Tri-Gas Fittings, internal union, bulkheads for transfer lines, 4 required, VICI Valco Instruments, Cat. No. ZBU1 Fittings, fused silica adapters to connect to bulkheads, 4 required, VICI Valco Instruments, Cat. No. FS1.8-5 Fittings, internal union, for connecting front injection port to 4-port

18、 sampling valve, 1 required, VICI, Cat. No. ZU1T Fused silica tubing, 10 m of 0.53-mm ID, methyl deactivated, Varian, Cat. No. CP4076 Gas chromatograph, capable of temperature ramping, equipped with two electronic pressure controlled injection ports, a separate isothermal heated zone, built for capi

19、llary column chromatography, utilizing a split injection system capable of pressure pulsed injection and equipped with an FID that will give a minimum peak height response of five times the background noise for 0.1 mass-ppm of 2-butanone when operated at the recommended conditions, Agilent Technolog

20、ies, Model 6890 3 of 18 960-06 Integrator, electronic, for obtaining peak areas. This device must be capable of graphically displaying chromatograms and peak integration, Agilent Chemstation or equivalent. Pipet bulb, 1-mL, Fisher Scientific, Cat. No. 13-678-9A Regulator, air, two-stage, high purity

21、, Matheson Tri-Gas, Model 3122-590 Regulator, hydrogen, two-stage, high purity, Matheson Tri-Gas, Model 3122-350 Regulator, methyl ether, Aldrich, Cat. No. Z14,670-6 Regulator, nitrogen, two-stage, high purity, Matheson Tri-Gas, Model 3122-580 Regulator, nitrogen, two-stage, high purity, high pressu

22、re delivery to pressurize LPG sample and blend cylinders, Matheson Tri-Gas, Model 3020-580 Sample injector, syringe or injector capable of injecting a 4-L repeatable volume of sample. An automatic injection system is recommended, Agilent Technologies Model 7683. Syringe, 10-L, for qualitative mixtur

23、e preparation, Hamilton 701NF, 2 required, Restek, Cat. No. 20167 Tubing, 1/16-inch Silcosteel, for transfer lines from valves to GC oven, Restek, Cat. No. 20531 Tubing, Teflon, 1/8-inch for LPG injection, Supelco, Cat. No. 2-0532 Valve, backflush, VICI Valco Instruments, Model C6UWE Valve, LPG inje

24、ction, with actuator, VICI Valco Instruments, Model ACI4UWE2 Valve, vent shut-off, for LPG injection, Swagelok, Cat. No. SS-ORS2 Valve, shut-off, for blend cylinder, Swagelok, Cat. No. SS-1RF4 Valve box (heated with actuator and solenoid), Wasson ECE Reagents and Materials All reagents shall conform

25、 to the specifications established by the Committee on Analytical Reagents of the American Chemical Society, when such specifications are available, unless otherwise specified. References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used.

26、Air, zero-gas, total hydrocarbons less than 2 ppm as methane Blend, LPG, quantitative, certified standard, containing 50 mass-ppm of 2-butanone and 1 mass-ppm of 2-methyl-2-propanol in research grade isobutane, contained in an aluminum Ultra-Line cylinder with a stainless steel valve, Matheson Tri-G

27、as. A 250-psig nitrogen head pressure should be maintained on the LPG blend. Bottle, glass, 500-mL, with cap, for qualitative blend preparation, Fisher Scientific, Cat. No. 03-320-6 Cyclohexane, anhydrous, 99.5+%, Aldrich, Cat. No. 227048. The anhydrous cyclo-hexane is kept under a nitrogen blanket

28、between uses to prevent contamination. Ethyl methyl ether, 90+%, TCI America, Cat. No. M0110 Gas purifier, hydrogen carrier gas purifier, VICI Mat/Sen, Cat. No. P200-1 Gas purifier, air (for detectors), VICI Mat/Sen, Cat. No. P400-1 4 of 18 960-06 Gas purifier, nitrogen, for detector makeup gas, VIC

29、I Mat/Sen, Cat. No. P300-1 Hydrogen, zero-gas, 99.99% minimum purity, total hydrocarbons less than 0.5 ppm as methane Inlet liner, Silcosleeve metal inlet liner with fused silica wool, Restek, Cat. No. 21700-200.1 Nitrogen, zero-gas, 99.99% minimum purity, total hydrocarbons less than 0.5 ppm as met

30、hane Oxygenated hydrocarbons, see Table 2 Toluene, 99.8% purity, Aldrich, Cat. No. 270377 Pipet, Pasteur, disposable, 146-mm, Fisher Scientific, Cat. No. 13-678-20A p-Xylene, 99+%, Aldrich, Cat. No. 240451 Vials, glass, 20-mL, with caps, Fisher Scientific, Cat. No. 03-3386 Procedure Preparation of A

31、pparatus Refer to Fig. 1 when making all tubing and column connections. 1. Install the gas purifiers in the supply line between the instrument gases and the gas chromatograph. Low detection limits are required for the analysis. Purifiers are essential for all gases used, and must be routinely replac

32、ed to be effective. Follow the vendors recommended replacement schedule. 2. Install the 6-port backflush valve in the Wasson valve box onto the Valve 1 actuator. 3. Mount the 4-port LPG injection valve on the external left side of the Wasson valve box. Connect the valve actuator lines to the Valve 2

33、 solenoid connections. Connect 6 inches of Teflon tubing between the sample vent connection of the LPG injection valve and the inlet of the 1/8-inch shut-off valve. The outlet of the 1/8-inch shut-off valve must be directed to a laboratory fume hood. 4. Install bulkheads on brackets inside the oven

34、of the GC. 5. Make valve connections between valves and bulkheads using 1/16-inch Silcosteel tubing. Tubing exiting the valve box must lay flush along the heated channel provided by Wasson ECE. 6. Make connections between the front injection port and the 4-port sampling valve. Cut the carrier flow i

35、nlet line to the front injection port. Connect the carrier flow line from the injection port flow module to the carrier gas port on the 4-port sampling valve. Use 1/16-inch Silcosteel tubing and 1/16-inch internal unions for all connections. All lines should run through the Wasson valve box and lay

36、in the heated channel. 7. Install the Silcosleeve metal inlet liner into the front injection port according to the instrument manufacturer instructions. The Silcosleeve liner has equivalent inertness to glass sleeves but, has greater total volume, allowing the large injections of LPG and volatile li

37、quids to be contained in the injection port. 8. Install the CP-Simdist column in the valve box. The column must rest on the front ledge inside the valve box for the box to close properly. Connect the column to the 6-port backflush valve using the fused silica adapters. 9. Install deactivated fused s

38、ilica tubing between the front injection port, the back injection port, and the associated bulkhead fittings. 5 of 18 960-06 10. Install the remaining deactivated fused silica tubing in the GC oven between the bulkhead and Valve 1, Port 1, and the bulkhead and either the vent or back FID detector, i

39、f present. 11. Install the CP-Lowox column in the GC oven. The inlet end of the column connects to a bulkhead, the outlet end of the column connects to the “front” detector. 12. Check all fittings for leaks using an electronic leak detector. Do not use liquid leak detector on capillary lines. CAUTIO

40、N: Hydrogen gas leakage into the confined volume of the column oven can cause a violent explosion. It is, therefore, mandatory to check for leaks each time a connection is made and periodically thereafter. 13. Establish the operating conditions as given in Table 1. Initially, the injection port shou

41、ld be conditioned for 24 hours at 250C to clean the Silcosteel injection port liner. Then, the injection port temperature should be reduced to operating temperature. Other conditions may be used provided they produce the required sensitivity and chromatographic separations equivalent to those shown

42、in the Typical Chromatogram (Figs. 2A and 2B) . 14. Put the cover on the Wasson ECE valve box, and allow the temperature to equilibrate for a minimum of one hour. 15. Condition the CP-Lowox column according to the manufacturers instructions. Maintain the CP-Lowox column at 200C with carrier gas flow

43、ing when it is not used. 16. Check all fittings in the GC oven for leaks after the CP-Lowox is conditioned. Fractionation Time Determination 1. With the instrument operating at the established conditions, set Valve 1 to the “off” position. See Figure 1. 2. Set up a run table on the GC with Valve 1 “

44、on” at 1.00 minute and Valve 1 “off” at 29.5 minutes. 3. Prepare a qualitative mixture of oxygenates in cyclohexane by the following procedure. This mixture is used to determine retention times of the oxygenates. Fill a 500-mL bottle with 450 mL of cyclohexane Add 1 mL each of toluene and p-xylene A

45、dd 5 L each of the oxygenates in Table 2, mix well Methyl ether is a compressed gas. It should be bubbled into the blend bottle by flowing it through a section of 1/16-inch tubing that is immersed in the cyclohexane, for 3 to 4 seconds. 4. Inject 4 L of the qualitative mixture, start the GC and inte

46、grator and compare to Figures 2A and 2B to identify peaks. The qualitative mixture determines retention times for all possible components and is used to set fractionating cut times. Peak separations and shapes should be similar to chromatograms in Figures 2A and 2B. If the chromatogram is not compar

47、able make appropriate repairs until it is. It is not expected that samples for this analysis will contain all oxygenates found in the qualitative mixture. 5. Reduce the Valve 1 “on” time by 0.05 minute increments until the p-xylene peak is no longer seen on the chromatogram and the 1-pentanol peak d

48、oes not diminish in size (see Figures 2A, 2B and 4). Record this value as the cut time for Fractionation A. 6. Reduce the Valve 1 “on” time further until the toluene peak is no longer seen on the chromatogram and the methyl ether peak does not diminish in size (see Figure 3). Record this value as th

49、e cut time for Fractionation B. 6 of 18 960-06 Table 1 Recommended Operating Conditions Carrier gas hydrogen Front Inlet Temperature 120C isothermal Column head pressure 50C 5.5 kPa gauge (0.8 psig) Equivalent flow 5.0 mL/min Flow mode constant flow Pressure pulse 34.4 kPa gauge (5.0 psig) Pulse time 0.25 min Split ratio 1.0 Split flow 5.0 mL/min Back Inlet Temperature 120C Column head pressure 50C 5.5 kPa gauge (0.8 psig) Equivalent flow 5.0 mL/min Flow mode constant flow Split ratio 5.0 Split flow 25.1 mL/min Auxili