UOP 899-2004 TRACE HYDROCARBONS IN HYDROGEN HYDROCARBON GASES OR LPG BY GC.pdf

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 PRESCRIBE

2、D 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 1988, 1997, 2004 UOP LLC ALL RIGHTS RES

3、ERVED uop and UOP are trademarks and/or service marks of UOP LLC. Marks of other proprietors may appear incidentally in this method for purposes such as product or service identification, but no claim is made to any other proprietors mark used. UOP Methods are available through ASTM International, 1

4、00 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 194428-2959, United States. The Methods may be obtained through the ASTM website, www.astm.org, or by contacting Customer Service at serviceastm.org, 610.832.9555 FAX, or 610.832.9585 PHONE. TRACE HYDROCARBONS IN HYDROGEN, HYDROCARBON GASES, O

5、R LPG BY GC uop Method 899-04 SCOPE This method is for determining individual trace C5minus hydrocarbon impurities in hydrogen or liquefied petroleum gas (LPG), where the specific trace components are sufficiently resolved from the major components, typically propane/propylene or ethane/ethylene. Co

6、mponents eluting after ethyl acetylene are grouped and reported as heavies. The range of quantitation for each component is 2 to 3000 mol- (or mass-) ppm; however, the lower limit of quantitation increases when major components interfere with the resolution of the impurities. REFERENCES ASTM Practic

7、e D 1265, “Sampling Liquefied Petroleum (LP) Gases (Manual Method),” www.astm.org ASTM Practice D 5287, “Automatic Sampling of Gaseous Fuels,” www.astm.org Scanlon, J. T. and Willis, D. E., Journal of Chromatographic Science, 23, 333-340 (1985) UOP Method 516, “Sampling and Handling of Gasolines, Di

8、stillate Fuels, and C3-C4Fractions,” www.astm.org UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org OUTLINE OF METHOD A reproducible volume of gas sample is injected into a gas chromatograph equipped with an alumina PLOT (porous layer open tubular) capillary column, a capillary inj

9、ection port, a flame ionization detector (FID), and a gas or LPG sampling valve. An LPG sample may be expanded and analyzed as a vapor, or analyzed directly in the liquid phase (see NOTE). The concentrations of the hydrocarbon impurities are determined by the external standard method of quantitation

10、 wherein peak areas are compared to the area of a calibration blend containing a known concentration of isobutane. For 2 of 17 899-04 For samples containing C5olefins, a second analysis, under a different column temperature program, is necessary to resolve methyl acetylene from an interfering C5ole

11、fin. APPARATUS References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used except as noted. Chromatographic column, 50 m of 0.53-mm ID PLOT fused silica capillary, internally coated to a film thickness of 9-m with alumina (GS-Alumina), J&

12、W Scientific, Cat. No. 115-3552. Columns from other suppliers, commonly called Al2O3/Na2SO4, provide similar separation but may not be quantitative for diolefins and acetylenes, and their use is not recommended when analysis of these components is necessary. Gas chromatograph, capable of temperature

13、 ramping, equipped with electronic pressure control, built for capillary column chromatography utilizing a split injection system, having a glass injection port insert, a heated valve box, and an FID that will give a minimum peak height response of 5 times the background noise for 2 mol-ppm of isobu

14、tane when operated at the recommended conditions, Agilent Technologies, Model 6890 Injection apparatus, gas, for injection of gas or expanded LPG samples, see Figure 1: Fitting, internal union, for connecting injection port to 6-port sampling valve, Valco Instruments, Cat. No. ZU1T Valve, 6-port, st

15、ainless steel, 1.59-mm (0.0625-inch) fittings, manual with standoff, Valco Instruments, Cat. No. C6UWE Sample loop, stainless steel, 100-L, Valco Instruments, Cat. No. SL100CUW Tubing, stainless steel, 1.6-mm (1/16-inch) OD, 0.76-mm (0.30-inch) ID, Alltech Associates, Cat. No. 300010 Injection appar

16、atus, LPG, for injection of LPG samples in the liquid phase, see Figure 2: Fitting, CGA, for blend cylinder, CGA No. 510, Matheson Gas Products Fitting, internal union, for connecting injection port to 4-port sampling valve, Valco Instruments, Cat. No. ZU1T Fitting, reducing union, 3.2-mm (1/8-inch)

17、 to 1.6-mm (1/16-inch), Swagelok, Cat. No. SS-200-6-1 Tubing, stainless steel, 1.6-mm (1/16-inch) OD, 0.76-mm (0.30-inch) ID, Alltech Associates, Cat. No. 300010 Tubing, translucent, FEP Teflon, 3.2-mm (1/8-inch) OD, 1.6-mm (0.062-inch) ID, 3450 kPa (500 psig), Alltech Associates, Cat. No. 45740 Val

18、ve, 4-port, stainless steel, 0.5-l internal sample volume, 1.59-mm (0.0625-inch) fittings, manual with standoff, Valco Instruments, Cat. No. CI4UWE.5 Valve, vent shut-off, Swagelok, Cat. No. SS-ORS2 3 of 17 899-04 Integrator, or data system, electronic, for obtaining peak areas. This device must int

19、egrate areas at a sufficiently fast rate so that the narrow peaks typically resulting from use of a capillary column can be accurately measured. ChemStation, Agilent Technologies. LPG expansion apparatus, for quantitative expansion of LPG from a liquid to a gas phase, see Figure 3: Fitting, male con

20、nector, stainless steel, 0.25-inch tube fitting to 0.25-inch male NPT, Swagelok, Cat. No. SS-400-1-4. Sample cylinders having an outlet fitting other than 0.25-inch female NPT will require a different fitting. Fitting, port connector, stainless steel, 0.25-inch tube fitting, Swagelok, Cat. No. SS-40

21、1-PC, 2 required Fitting, union tee, stainless steel, 0.25-inch, Swagelok, Cat. No. 400-3 Tubing, stainless steel, Type 304, 0.25-inch OD x 0.210-inch ID, Alltech Associates, Cat. No. 30301 Vacuum pump, capable of achieving a vacuum of 0.1-mm Hg, Fisher Scientific, Cat. No. 01-115-2 Valve, stainless

22、 steel, 0.25-inch, Swagelok, Cat. No. SS-1RS4 LPG expansion cylinder, sample cylinder for containing expanded LPG sample: Cylinder, 4- x 6-inch, 316 stainless steel, 1380 kPa (200 psi) internal pressure, double connection, 0.25-inch pipe hex bored through, Arthur Harris, Cat. No. B-270 Fitting, hex

23、nipple, stainless steel, 0.25-inch NPT, Swagelok, Cat. No. SS-4-HN, 3 required Fitting, tee, stainless steel, 0.25-inch NPT, Swagelok, Cat. No. SS-4-T Gauge, stainless steel, vacuum-pressure, -100 to +200 kPa gauge (-15 to +30.0 psig) range, Matheson Gas Products, Cat. No. 63-2204 Valve, stainless s

24、teel, 0.25-inch NPT inlet, 0.25-inch tube fitting outlet, Whitey, Swagelok, Cat. No. SS-1RM4-S4, 2 required Regulator, air, two-stage, high purity, delivery pressure range up to 690 kPa (100 psi), Matheson Gas Products, Model 3122-590 Regulator, helium, two-stage, high purity, delivery pressure rang

25、e up to 690 kPa (100 psi), Matheson Gas Products, Model 3122-580 Regulator, hydrogen, two-stage, high purity, delivery pressure range up to 690 kPa (100 psi), Matheson Gas Products, Model 3122-350 Regulator, nitrogen, two-stage, high purity, delivery pressure range up to 690 kPa (100 psi), Matheson

26、Gas Products, Model 3122-580 REAGENTS AND MATERIALS References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. 4 of 17 899-04 Air, zero-gas, total hydrocarbons less than 2 ppm as methane Calibration blend, gas, quantitative, primary sta

27、ndard, to contain from 250 to 500 mol-ppm isobutane in helium, Matheson Gas Products Calibration blend, LPG, quantitative, primary standard, to contain from 250 to 500 mass-ppm isobutylene in n-butane, in cylinder with eductor tube, Matheson Gas Products Gas purifier, helium, used to remove oxygen a

28、nd moisture from carrier gas, Mat/Sen, Cat. No. P-100-1 Helium, zero-gas, total hydrocarbons less than 0.5 ppm as methane 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 less than 0.5 ppm as meth

29、ane Tape, Teflon, thread seal, Fisher Scientific, Cat. No. 14-831-300B PROCEDURE Sampling Obtain the sample by following the procedures described in ASTM Practice D 1265, “Sampling Liquified Petroleum (LP) Gases (Manual Method),” ASTM Practice D 5287, “Automatic Sampling of Gaseous Fuels,” UOP Metho

30、d 516, “Sampling and Handling of Gasolines, Distillate Fuels, and C3-C4Fractions,” or other reliable technique. Chromatographic Technique The analyst is expected to be familiar with the technique of gas chromatography and the equipment being used. Quantitative results are based on the injection of a

31、 reproducible volume of both sample and calibration blend. 1. Install the gas purifier in the supply line between the carrier gas source and the carrier gas inlet on the gas chromatograph. Column life is significantly reduced if the gas purifier is not used. 2. For gas phase analysis, install the 6-

32、port gas sampling valve in the valve box of the instrument and the fused silica capillary column as shown in Figure 1. For liquid phase analysis, install the 4-port LPG sampling valve external to the GC near the split injection system. Connect the related apparatus as shown in Figure 2. 3. Establish

33、 the recommended operating conditions as given in Table 1. For samples containing C5olefins, a second analysis, under a different column temperature program, is necessary to resolve methyl acetylene from an interfering C5olefin. Other conditions may be used provided they produce the required sensiti

34、vity and chromatographic separations equivalent to those shown in the Typical Chromatogram, Figure 4. 5 of 17 899-04 Table 1 Recommended Operating Conditions Standard Modified for Conditions Methyl acetylene Carrier gas helium Column head pressure 35C, constant flow mode 70 kPa (10 psig) Equivalent

35、flow 10 mL/min Equivalent linear velocity 59 cm/sec Split flow rate 150 mL/min Injection port temperature 200C Valve box temperature 100C Electronic pressure control constant flow on Column temperature program Initial temperature 35C 100C Initial time 2 min 17 min Programming rate 10C/min 10C/min Fi

36、nal temperature 190C 190C Final time 10 min 19 min Detector FID Detector temperature 200C Hydrogen flow rate* 30 mL/min Air flow rate* 350 mL/min Makeup gas nitrogen Makeup gas flow rate* 30 mL/min Sample size, gas phase 100L repeatable Sample size, liquid phase 0.5L repeatable _ *Consult the manufa

37、cturers instrument manual for suggested flow rates. 4. Condition the column according to the manufacturers instructions. 5. Cool the column oven to a stabilized initial temperature of 35C. 6. Proceed to Step 7 if the sample is in the gas phase. If not, LPG must be carefully expanded into the gas pha

38、se to ensure that a representative sample is analyzed. Proceed to LPG Sampling, gas phase analysis. Alternatively, LPG may be injected as a liquid following the procedure in LPG Sampling, liquid phase analysis. 7. Set the gas sampling valve in the sample purge position. Purge the sample loop with th

39、e sample to be analyzed for approximately one minute. Turn off the sample purge, allow several seconds for the pressure to equilibrate and inject the sample by rotating the gas sampling valve to the inject position. 8. Start the integrator and the column temperature programming sequence. 6 of 17 899

40、04 9. Identify the components of interest by comparing the chromatogram obtained to the Typical Chromatograms (Figures 4 and 5). The PLOT columns will overload easily, which causes retention times to shift, and, depending upon component concentrations, some very large components will mask smaller o

41、nes. Care should be taken when identifying these components. A typical chromatogram of an expanded LPG sample containing some high concentration level components is included for reference (Figure 5). Neopentane elutes between 1-butene and isobutylene. In high concentrations it will interfere with th

42、e 1-butene. A C5olefin, if present, co-elutes at the methyl acetylene site. If C5olefins could be present in the sample, reanalyze the sample for methyl acetylene only using the modified operating conditions listed in Table 1. A typical chromatogram is shown in Figure 6. The instrument must be recal

43、ibrated under these conditions. C5olefins and C6hydrocarbons, if present, may also cause interference at the vinyl acetylene and ethyl acetylene sites. Prepare or purchase qualitative blends containing the relevant compounds, analyze them, and adjust instrument conditions so as to eliminate the inte

44、rferences. 10. Sum the peak areas of the unidentified components eluting after ethyl acetylene to obtain the peak area of the heavies composite. LPG Sampling, for gas phase analysis LPG must be carefully expanded to ensure that a representative sample is analyzed. Various procedures are used to quan

45、titatively expand LPG from a liquid phase into a representative gas phase prior to analysis. The following is the recommended procedure that has been proved to be satisfactory. 1. Assemble the LPG expansion cylinder consisting of a small stainless steel expansion cylinder, a stainless steel gauge wi

46、th a reading range from vacuum to 200 kPa gauge and two stainless steel shut-off valves (see Figure 3). Some expansion cylinders have two valves (C and D) as shown in Fig. 3, some have only one (Valve C). The version shown in Figure 3 is easier to clean, but either may be used. 2. Connect the appara

47、tus to the vacuum system and evacuate the cylinder assembly to 0.013 kPa (0.1-mm Hg). 3. Connect two small pieces of clean stainless steel tubing, a tee and valve B to the evacuated cylinder as shown in Figure 3 (LPG Expansion Apparatus). 4. Place the LPG sample cylinder in a vertical position in a

48、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 (A) to check that no water or sediment is present in the LPG. If water or sediment is determined to be present, discontinue the analysis and obtain a clean sample. LPG samp

49、les are usually contained in a cylinder having valves on both ends or, in some cases, a cylinder where one of the valves is connected to an eductor tube. If the sample cylinder contains an eductor tube, invert the cylinder (both valves on the bottom) and briefly open the valve not connected to the eductor tube to check that no water or sediment is present. 5. Connect the bottom valve or the valve connected to the eductor tube of the LPG sample cylinder with a stainless steel tubing connector to the expansion a