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. SAFETY DATA SHEETS (SDS) OR EXPERIMENTAL SAFETY DATA SHEETS (ESDS) FOR ALL OF THE MATERIALS USED IN THIS PROCEDURE SHOULD BE REVIEWED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTION EQUIPMENT (PPE). COPYRIGHT 1995, 2016 UOP LLC. All rights reserved. Nonconfidential U
3、OP 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 610.832.9585 PHONE. Combin
4、ed Nitrogen in LPG by Chemiluminescence UOP Method 936-16 Scope This method is for determining combined nitrogen in liquefied petroleum gas (LPG). The method determines all nitrogen compounds that are extractable by aqueous acid, including ammonia, amines, nitriles and amides. The method is particul
5、arly useful for LPG samples containing nitrogen species, such as ammonia and amines, which can readily adsorb on stainless steel surfaces in contact with the LPG. The procedure yields quantitative results in the range of 0.2 mass-ppm (mg/kg) to 3 mass%. The method is also used as a preparation step
6、for the analysis of basic nitrogen in LPG by UOP Method 939, “Basic Nitrogen in LPG by Ion Chromatography.” References ASTM Method D4629, “Trace Nitrogen in Liquid Petroleum Hydrocarbons by Syringe/Inlet Oxidative Combustion and Chemiluminescence Detection,” www.astm.org UOP Method 516, “Sampling of
7、 Gasolines, Distillate Fuels and C2-C4 Fractions,” www.astm.org UOP Method 939, “Basic Nitrogen in LPG by Ion Chromatography,” www.astm.org UOP Method 981 “Trace Nitrogen in Liquid Hydrocarbons by Oxidative Combustion with Chemiluminescence Detection,” www.astm.org UOP Method 999, “Precision Stateme
8、nts in UOP Methods,” www.astm.org Outline of Method Nitrogen compounds are quantitatively extracted from an LPG sample using a solution of 2N acetic acid in water. A measured mass of LPG is transferred to a cleaned, silica coated sample extraction cylinder. A known amount of acid solution is added t
9、o a second cylinder, the two vessels are connected and the acid solution is transferred under helium pressure into the sample extraction cylinder. The nitrogen components are extracted into the acid solution by mixing the liquids for several minutes. The LPG and acid extract are allowed to separate.
10、 The acid extract is withdrawn and analyzed for total nitrogen by chemiluminescence, utilizing ASTM Method D4629, “Trace Nitrogen in Liquid Petroleum Hydrocarbons by Syringe/Inlet Oxidative Combustion and Chemiluminescence Detection”. Apparatus References to catalog numbers and suppliers are include
11、d as a convenience to the method user. Other suppliers may be used. 2 of 14 936-16 Adapter, male, 2 required, for charging the acetic acid cylinder, Swagelok, Cat. No. SS-4-TA-1-4 (see also Connector) Balance, readability 0.001 g Balance, readability 0.1 g, capacity 4000 g Beaker, polypropylene, 100
12、-mL, Fisher Scientific, Cat. No. 02-591-27 Clamps, for ring stand and sample cylinders, several required, with holders and cast iron ring, Fisher Scientific, Cat. Nos. 05-769-8Q, 05-754 and 14-050CQ, respectively Connector, stainless steel, used to connect the 300-mL and the 1000-mL cylinders vertic
13、ally together and consisting of a male connector, Swagelok, Cat. No. SS-400-1-4 joined together with one male adapter, Swagelok, Cat. No. SS-4-TA-1-4. Cylinder, collection, for initial sample collection from process stream, stainless steel, Sulfinert coated, 1000-mL, with valve and valve with outage
14、 tube, Restek, Cat. Nos. 24134, 21400, and 21402-038, respectively. Cylinder, extraction, type 304 stainless steel, high pressure, 12,400 kPa gauge (1800 psi) maximum working pressure, 1000-mL capacity, Swagelok, Cat. Nos. 304L-HDF4-1000. Equip the cylinders with two stainless steel valves each, Swa
15、gelok, Cat. No. SS-16DKM4-F4, and two pipe-plugs each, Cajon, quarter-inch P-male-NPT, Swagelok, Cat. No. SS-4-P. Cylinder, acid injection, type 304 stainless steel, high pressure, 12,400 kPa gauge (1800 psi) maximum working pressure, 300-mL capacity, Swagelok, Cat. Nos. 304L-HDF4-300. Equip the cyl
16、inders with two stainless steel valves each, Swagelok, Cat. No. SS-16DKM4-F4, and two pipe-plugs each, Cajon, quarter-inch P-male-NPT, Swagelok, Cat. No. SS-4-P. Cylinders, graduated, borosilicate glass, 50-, 100- and 250-mL, Fisher Scientific, Cat. Nos. 08-556C, D and E, respectively Extractor (opt
17、ional), special construction, see Appendix Flask, Erlenmeyer, 50-mL, Fisher Scientific, Cat. No. FB-500-50 Flasks, volumetric, 100-, 200-, 1000-, and 2000-mL, with caps, Fisher Scientific, Cat. Nos. 10-210-5C, -5D, -5G, and -5H, respectively. Several of each are required, see Reagents and Materials
18、and Procedure. Gage, pressure, 0-20,000 kPa gage (0-3000 psig), 2-inch diameter, ”-inch MNPT, used for testing the pressure of an unknown LPG sample gas cylinder, Matheson Gas Products, Model 63-2233 Hood, laboratory Nitrogen Chemiluminescence Analyzer, with attached furnace, autosampler, vacuum pum
19、p, controls and computer. This method was developed and validated using the Mitsubishi analyzer NSX-2100V, with ND-210 Nitrogen Detector and STC-210 Sample Temperature Controller. The procedure for analysis may be different for other instruments and all other instruments need to be validated before
20、using for this method. The Mitsubishi analyzer must be equipped with the following accessories: Autosampler, Mitsubishi Model ASC-250L, COSA Xentaur Corporation Autosampler syringes, gas tight, 50-L, Mitsubishi, Cat. No. MC18525, COSA Xentaur Corporation Autosampler vials, rinse, Mitsubishi Cat. No.
21、 TX3LSW, COSA Xentaur Corporation 3 of 14 936-16 Cyclone trap, Cat. No. MC 1914, COSA Xentaur Corporation Membrane drier, Perma Pure MD-110-24F-4 or Mitsubishi Tube Dryer, Cat. No. TN6RPC, COSA Xentaur Corporation (see Note 4) Sample Temperature Controller, Mitsubishi Model STC-210, COSA Xentaur Cor
22、poration Vacuum pump, Vacuubrand MD4CNT and Ulvac GLS-050 vacuum pumps meet this requirement; other vacuum pumps must be evaluated before use, COSA Xentaur Corporation (see Note 3) Oven, drying, capable of maintaining 105C Pipet, Mohr, 1-, 5- and 25-mL, Fisher Scientific, Cat. Nos. 13-665-F, -K and
23、-N, respectively Pipet, volumetric, Class A, 50-mL, 20-mL, 10- mL, 4-mL Fisher Scientific, Cat. No. 13-650-2S, 13-650-2N, 13-650-2L, 13-650-2E, respectively. Pipet filler, Fisher Scientific, Cat. No. 13-681-102A Refrigerator, Fisher Scientific, Cat. No. 14-512-526 Regulators, inert gas, two-stage, M
24、atheson Tri-Gas, Models 3810A-580 (used for the nitrogen analyzer) and 3030-580 (used for acetic acid transfer between cylinders) Regulator, oxygen, two-stage, high purity, Matheson Tri-Gas, Model 3810A-540, cleaned for oxygen service by the supplier, used with Nitrogen Analyzer Ring stand, with rec
25、tangular base, 170- x 280-mm base with 910-mm rod, Fisher Scientific, Cat. No. 14670D Tubing, polyethylene, “Poly-Flo”, for charging acetic acid cylinder, 6.4-mm (0.25-inch) OD, Lesman Instruments, Cat. No. 1FRPE4 Tubing, Tygon, R3603, for charging acetic acid cylinder 6.4-mm (1/4”) OD, Fisher Scien
26、tific, Cat. No. 14-169-3C Tubing, vacuum, 6.4-mm (”), Fisher Scientific, Cat. No. 14-173C Vacuum pump, aspirator, Nalgene, Fisher Scientific, Cat. No. 09-960-2, or house vacuum Valve, check, 20,700 kPa gauge (3000 psig), Matheson Tri-Gas, Model 400V Reagents and Materials References to catalog numbe
27、rs and suppliers are included as a convenience to the method user. Other suppliers may be used. References to water mean deionized or distilled water. Acetic acid, glacial, approximately 99.7%, Fisher Certified, Fisher Scientific, Cat. No. A38-212 Acetic acid, approximately 2N. Prepare two liters by
28、 slowly adding 232 mL of glacial acetic acid from a graduated cylinder to approximately 1500 mL of water in a 2000-mL volumetric flask. After the heat of dilution dissipates, dilute to volume with water and mix thoroughly by capping the flask and inverting at least 10 times. Acetone, certified, Burd
29、ick use appropriate personal protection equipment. Usually the acetic acid drains as a milky acid-gas emulsion, which separates easily in a few minutes. Not all the acid needs to be drained, just enough for subsequent analysis. It is preferred to leave some acid in the extraction cylinder, as splash
30、ing may occur when all the acid is drained and LPG begins to come out. 12. Decant a portion of the acid extract from the Erlenmeyer flask into a 15-mL sample vial and analyze the acid extract on the chemiluminescence nitrogen analyzer as directed in ASTM Method D 4629 and according to the following
31、procedure. Preparation of Standard Solutions Pyridine stock solution, 1000 gN/mL Weigh 1.129 0.001g of pyridine to the nearest 0.001g into a clean, dry 200 mL volumetric flask. Dilute to the mark with 2 N acetic acid solution. Cap and mix well. If the pyridine cannot be dispensed with sufficient pre
32、cision to achieve the exact 1.129 g weight, substitute the exact weight added for the 1.129 in Equation 1, and correct the subsequent dilutions. Equation 1 shows the calculation of the concentration of nitrogen in the stock solution: 1000 gN/mL = 200 71.17129.1(1) where: 1.129 = weight of pyridine,
33、g 200 = dilution volume, mL 17.71 = concentration of N in pyridine, % Calibration standard solution, 100 gN/mL Dispense 10 ml of the pyridine stock solution with a volumetric pipette into a clean, dry 100-mL volumetric flask. Dilute to the mark with 2N acetic acid solution. Cap the flask and mix wel
34、l. 8 of 14 936-16 Calibration standard solutions, 10, 5, 1, 0.5, 0.2 gN/mL Prepare a series of 5 working standards by serial dilution of the standard solution with 2N acetic acid solution as follows: 10 gN/mL standard- Dispense 20 mL of the 100 gN/mL standard with a pipet into a clean, dry 200-mL vo
35、lumetric flask. Dilute to the mark with the 2N acetic acid. Cap the flask and mix well. 5 gN/mL standard - Dispense 10 mL of the 100 gN/mL standard with a pipet into a clean, dry 200-mL volumetric flask. Dilute to the mark with the 2N acetic acid. Cap the flask and mix well. 1.0 gN/mL standard - Dis
36、pense 20 mL of the 10 gN/mL standard with a pipet into a clean, dry 200-mL volumetric flask. Dilute to the mark with the 2N acetic acid. Cap the flask and mix well. 0.5 gN/mL standard - Dispense 20 mL of the 5 gN/mL standard with a pipet into a clean, dry 200-mL volumetric flask. Dilute to the mark
37、with 2N acetic acid. Cap the flask and mix well. 0.2 gN/mL standard - Dispense 4 mL of the 10 gN /mL standard with a pipet into a clean, dry 200-mL volumetric flask. Dilute to the mark with 2N acetic acid. Cap the flask and mix well. The stock solution can be retained, if refrigerated, for up to 1 y
38、ear. The standard solutions can be retained, if refrigerated, for 3 months. Instrument Set Up Set up the nitrogen analyzer according to the manufacturers instructions. Connect the cyclone trap to the furnace outlet to prevent water in the gases from overloading the membrane drier. Allow the instrume
39、nt to warm-up and the baseline to stabilize before injecting samples. Establish analysis parameters for the 2 N acetic acid samples. Suggested operating conditions for the Mitsubishi NSX-2100V analyzer are listed in Table 2. If another instrument is used, see that instruments manual for the appropri
40、ate setup instructions. Table 2 Suggested Operating Conditions for NSX-2100 V instrument Upper temperature 600C Lower temperature 800C Argon Main 100 mL/min Oxygen Main 500 mL/min Ozone 200 mL/min Detection start waiting time 0 sec End time 300 sec Sampling/Injection parameters: Fill rate 5 L/sec Po
41、st Fill delay 5 sec Injection rate 0.6 L/sec Post inject delay 10 sec Calibration 1. Fill the rinse bottle with deionized water and pre-fill bottle with methanol. 2. Fill autosampler vials, one each, with the 2N acetic acid (blank) and the 0.2, 0.5, 1, 5, 10 g/mL nitrogen calibration standards. 9 of
42、 14 936-16 3. Before starting to measure calibration standards run a few blanks of 2N acetic acid to condition the instrument and to remove any residual contamination. The response should be stable before proceeding. 4. Run a calibration program with multiple 20 L injections of the solvent blank and
43、 each standard stored in the instrument software. It is recommended to inject each standard or blank at least 4 times. The instrument will average the results of the injections of each standard and the blank. Relative standard deviation (RSD), as calculated by the instrument for the blank, should be
44、 within 25%. The RSD for the standards should be within 15%. 5. Create a regression line using the instrument software using the blank and the five standards. Set the regression line to “y=bx+c”. The calibration method will be saved automatically. 6. Check the calibration curve by analyzing 0.5 gN/m
45、L and 1.0 gN/mL standards as unknowns, (enter “1”, as a density). The standards should be run in triplicate. The instrument will average the results of the triplicate injections. Sample Analysis 1. Enter the sample parameters into the software, this include sample ID, sample volume that is to be inj
46、ected (usually 20L), density (“1” for samples diluted in 2N acetic acid) and appropriate injection program, (the programs are stored under “ASC-250L” and they are established prior to the calibration). Each sample should be injected at least three times to obtain an average result. If the nitrogen c
47、oncentration of the extract exceeds the concentration of the highest standard, the extract must be diluted with 2N acetic acid until the standards span the concentration of the diluted extract. 2. Before starting to measure samples run a few blanks of 2N acetic acid to condition the instrument and t
48、o remove any residual contamination. The response should be stable before proceeding. 3. Fill the autosampler vials with the samples and place the vials onto the autosampler rack according to the saved method. 4. Inject and analyze the samples using the instrument software. Calculations Verify that
49、the acetic acid sample concentration is spanned by the calibration standards. The sample response must be read from the instrument, and the concentration of the extract must be calculated manually using Equation 2, rounding the result to two significant figures at or above 1 mg/kg, and to one significant figure below 1 mg/kg. Concentration of the combined nitrogen in the LPG, mg/kg =LMS(2) where: L = mass of the LPG,
