UOP 603-2013 Trace CO and CO2 in Hydrogen and Light Gaseous Hydrocarbons 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 1971, 1988, 2012, 2013 UOP LLC. All ri

3、ghts reserved. Nonconfidential UOP Methods are available from ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. The UOP Methods may be obtained through the ASTM website, www.astm.org, or by contacting Customer Service at serviceastm.org, 610.832

4、.9555 FAX, or 610.832.9585 PHONE. Trace CO and CO2 in Hydrogen and Light Gaseous Hydrocarbons by GC UOP Method 603-13 Scope This method is for determining low concentrations (0.2 to 500 mol-ppm) of carbon monoxide (CO) and carbon dioxide (CO2) in high purity hydrogen, methane and other gas-phase sam

5、ples. The lower limit of quantitation for CO and CO2 in samples containing high concentrations of hydrogen, nitrogen, and other gases, is 0.2 mol-ppm. For samples containing high methane concentrations, an analysis under a different valve configuration is necessary to resolve carbon dioxide from int

6、erfering methane. References Analyzer manufacturers operating manual UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org Outline of Method A repeatable volume of sample is introduced through the gas sampling/backflush valve into a two-column system. After the elution of CO2 from the

7、first column into the second column, the valve is switched to back flush the components remaining in the first column to the vent. For samples containing high methane, the 4-port switching valve is used as a heart cut valve to vent the bulk of methane eluting from the first column. CO, CO2 and metha

8、ne are separated on the second column and converted in the methanizer into methane. A flame ionization detector is used to detect the methane produced. Concentrations of CO and CO2, are calculated using the external standard method of quantitation. Apparatus References to catalog numbers and supplie

9、rs are included as a convenience to the method user. Other suppliers may be used. Analyzer, pre-configured, including a data system, AC Analytical Controls (PAC). A flow diagram of the AC analyzer is shown in Figure 1. Pre-configured analyzers are also available from Agilent Technologies, PerkinElme

10、r Separation Systems, and other supploers. Confirm with the supplier that the analyzer is appropriate for the stream to be analyzed and the analysis required. Instrument gas supply regulators; not all instruments will require all regulators listed below. 2 of 6 603-13 Regulator, air, two-stage, high

11、 purity, delivery pressure range 30-700 kPa (4-100 psi), Matheson Tri-Gas, Model 3122-590 Regulator, helium, two-stage, high purity, delivery pressure range 30-700 kPa (4-100 psi), Matheson Tri-Gas, Model 3122-580 Regulator, hydrogen, two-stage, high purity, delivery pressure range 30-700 kPa (4-100

12、 psi), Matheson Tri-Gas, Model 3122-550 Regulator, nitrogen, two-stage, high purity, delivery pressure range 30-700 kPa (4-100 psi), Matheson Tri-Gas, Model 3122-580 Leak detector, gas, Grace Davison, Cat. No. 60229 Reagents and Materials References to catalog numbers and suppliers are included as a

13、 convenience to the method user. Other suppliers may be used. Columns, replacement, 2 m of 1/16-inch OD x 0.050-inch ID stainless steel tubing, micropacked “Hayesep Q”, two required. These are typical columns used for the analysis. Contact the analyzer manufacturer for specific columns and part numb

14、ers. Instrument gases; not all instruments will require all gases listed below. Air, zero gas, total hydrocarbons less than 2.0 ppm as methane Helium, zero gas, total hydrocarbons less than 0.5 ppm as methane Hydrogen, zero gas, total hydrocarbons less than 0.5 ppm as methane Nitrogen, zero gas, tot

15、al hydrocarbons less than 0.5 ppm as methane Gas calibration blends; purchase only those required for the sample compositions to be analyzed Blend 1, 5 mol-ppm CO, 5 mol-ppm CO2 and 25 mol-ppm methane in hydrogen, Matheson Tri-Gas or local supply Blend 2, 200 mol-ppm CO, 200 mol-ppm CO2 and 200 mol-

16、ppm methane in hydrogen, Matheson Tri-Gas or local supply Blend 3, 5 mol-ppm CO, 5 mol-ppm CO2 in methane, Matheson Tri-Gas or local supply Gas purifiers, for carrier gases, to remove oxygen and moisture, VICI Mat/Sen, Cat. Nos. P100-1 (helium), P200-1 (hydrogen), P300-1 (nitrogen), and (optional) i

17、ndicating oxygen traps, Restek, Cat. No. 22010, as needed for the specific instrument used Methanizer, replacement, nickel catalyst tube. Contact the analyzer manufacturer for specific configuration and part number. Procedure The analyst is expected to be familiar with general laboratory practices,

18、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. Preparation of Apparatus 1. Install the gas purifier in the supply line between the carrier gas source and the carrier

19、 gas inlets on the gas chromatograph. 3 of 6 603-13 Column life is significantly reduced if gas purifiers are not used. Replace the gas purifiers at intervals determined by good laboratory practice. Indicating oxygen traps may be placed downstream of the gas purifiers. When the indicator shows one-h

20、alf used, replace both the gas purifier and the indicating trap. 2. Follow the instrument set-up procedure provided by the manufacturer but do not initially apply heat to the column oven; see Column Conditioning, below. CAUTION: Hydrogen leakage into the confined volume of the column oven can cause

21、a violent explosion. Therefore, it is mandatory to check for leaks each time a connection is made and periodically thereafter. Column Conditioning The columns must be conditioned to remove any traces of solvent or volatile components in the liquid phase and allow the phase to distribute itself evenl

22、y over the surface of the solid support. For porous polymers, conditioning is necessary to remove residual solvents used during polymerization and any compounds adsorbed during storage and handling. This column conditioning is required when the instrument is first installed, and whenever columns are

23、 replaced. Pre-condition the chromatographic columns individually in the chromatograph column oven using the following procedures: 1. Connect the column to the inlet and flush the column with carrier gas to remove air. Do not connect the column to the detector while conditioning: any volatile materi

24、al released from the column may form deposits on the detector. If the carrier gas is hydrogen, connect a piece of tubing to the outlet end of the column and route it outside the column oven to prevent the accumulation of flammable gas within the column oven. 2. Using analytical flow rates, heat the

25、column to 100C, or 50C below the maximum operating temperature, whichever is lower, and maintain for 30 minutes. 3. Heat the column to the final conditioning temperature at a rate of 4C/min or less. Maintain this temperature for at least 4 hours with normal carrier gas flow rates. The final conditio

26、ning temperature should ideally be at least 20C above the analysis temperature, but not higher than 10-15C below the maximum operating temperature for the column. It may be more convenient to condition the columns in a separate GC, if available. 4. When the columns are conditioned, reconnect them to

27、 the valves in the column oven and check for leaks. CAUTION: Hydrogen leakage into the confined volume of the column oven can cause a violent explosion. Therefore, it is mandatory to check for leaks each time a connection is made and periodically thereafter. Chromatographic Technique 1. Connect the

28、sample or calibration blend cylinder to the sample inlet and purge the system with the gas to be analyzed. 2. Flush the inlet tubing and sample loop with the gas for one minute with a flow of approximately 50 mL/min. Stop the sample flow for a few seconds, allowing the contents of the sample loop to

29、 equilibrate to atmospheric pressure. Some instruments are programmed to stop the flow of sample and allow the contents of the sample loop to equilibrate to atmospheric pressure before the sample is injected. In this case, the analysis may be started without manually stopping the sample flow. 3. Sta

30、rt the analysis on the GC. A typical chromatogram is shown in Figure 2. 4 of 6 603-13 For samples containing high methane, the 4-port switching valve is used as a heart cut valve to vent the bulk of methane eluting from the first column. Follow the instructions for high methane containing samples in

31、 the instrument operating manual. Calibration Response factors are required to relate the peak areas of the converted CO and CO2 to mol-ppm. A standard blend containing 5 mol-ppm CO, 5 mol-ppm CO2, and 25 mol-ppm methane in hydrogen is used for calibration of samples containing low concentrations of

32、 CO and/or CO2, while a blend containing 200 mol-ppm CO, 200 mol-ppm CO2, and 200 mol-ppm methane is used for samples containing high concentrations of CO and/or CO2. The methane is included in the blends to monitor separation efficiency of the chromatographic columns and the hydrogenation efficienc

33、y of the methanizer. A standard blend containing 5 mol-ppm CO and 5 mol-ppm CO2 in methane is used for samples containing high concentrations of methane. Analyze the appropriate blend as described under Chromatographic Technique for CO, CO2, and methane. Determine the peak areas of the methane and t

34、he converted CO and CO2. Calculate the response factor relating to the mol-ppm/unit of peak area for each component using Equation 1: K = AP (1) where: A = peak area for converted CO, CO2, or methane K = response factor for converted CO, CO2, or methane P = mol-ppm of CO, CO2, or methane If baseline

35、 resolution is obtained between all three components, the separation efficiency of the chromatographic columns is satisfactory. If the response factors for CO and CO2 are within 5% of the methane factor, the hydrogenation reactor efficiency is satisfactory. Determine response factors as directed abo

36、ve daily when samples are analyzed. Calculations Calculate the mol-ppm of either component of interest in the sample to the nearest 1 mol-ppm using Equation 2: Component, mol-ppm = KS (2) where: K = response factor for the converted component, previously defined S = peak area for the converted compo

37、nent Notes 1. It is necessary to prevent heavier hydrocarbons from passing over the methanizer in order to avoid any buildup of carbon on the surface of the catalyst. This is accomplished by the backflushing of the first column. 2. Samples with high methane concentrations can cause carbon buildup on

38、 the catalyst of the methanizer. To remove this carbon buildup, inject nitrogen multiple times or until the observed CO is less than 0.2 mol-ppm. Precision Precision statements were determined using UOP Method 999, “Precision Statements in UOP Methods.” 5 of 6 603-13 Repeatability and Site Precision

39、 A nested design was carried out for determining impurities in two samples containing primarily hydrogen and two samples containing primarily methane. The four samples were analyzed by two analysts, with each analyst performing analyses on two separate days, performing four analyses each day for a t

40、otal of 64 analyses. Using a stepwise analysis of variance procedure, the within-day and within-lab estimated standard deviations (esd) were calculated at the concentration means listed in Table 3. Two analyses performed in one laboratory by the same analyst on the same day should not differ by more

41、 than the repeatability allowable differences shown in Table 3 with 95% confidence. Two analyses performed in one laboratory by different analysts on different days should not differ by more than the site precision allowable differences shown in Table 3 with 95% confidence. Table 3 Repeatability and

42、 Site Precision, mol-ppm Repeatability Site Precision Sample Mean Within- Day esd Allowable Difference Within- Lab esd Allowable Difference CO in hydrogen 4.9 0.04 0.1 0.06 0.2 CO in hydrogen 200.6 0.17 0.3 0.27 1.0 CO2 in hydrogen 5.1 0.02 0.1 0.03 0.1 CO2 in hydrogen 203.4 0.16 0.5 0.46 2.8 CO in

43、methane 5.0 0.02 0.1 0.02 0.1 CO in methane 200.7 0.23 0.2 0.27 0.7 CO2 in methane 5.1 0.04 0.1 0.04 0.1 CO2 in methane 203.4 0.93 1.2 1.16 4.0 The data in Table 3 represent short-term estimates of the repeatability of the method. When the test is run routinely, use of a control standard and a contr

44、ol chart is recommended to generate an estimate of long-term repeatability. Reproducibility There is insufficient data to calculate the reproducibility of the test at this time. Time for Analysis The elapsed time and labor requirements for one analysis are identical, 0.25 hour. Suggested Suppliers A

45、gilent Technologies, 2850 Centerville Rd., Wilmington, DE 19808-1610, USA, 1-302-633-8000, AC Analytical Controls (PAC), 8824 Fallbrook Dr., Houston, TX 77064, USA, 1-203-925-4602, Grace Davison Discovery Sciences, 2051 Waukegan Rd., Deerfield, IL 60015, USA, 1-847-948-8600, Matheson Tri-Gas, 166

46、 Keystone Dr., Montgomeryville, PA 18936, USA, 1-215-641-2700, PerkinElmer, 940 Winter St., Waltham, MA 02451, USA, 1-203-925-4602, Restek, 110 Benner Circle, Bellefonte, PA 16823, USA, 1-814-353-1300, 6 of 6 603-13 Separation Systems, 100 Nightingale Ln., Gulf Breeze, FL 32561, USA, 1-850-932-1433, VICI Mat/Sen, 7806 Bobbitt, Houston, TX 77055 USA, 1-713-688-9345,