UOP 411-2013 Normal Paraffins by Subtractive 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 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 1966, 1975, 1992, 2013 UOP LLC. All rights reserved. Nonco

3、nfidential 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 610.832.9585 P

4、HONE. Normal Paraffins by Subtractive GC UOP Method 411-13 Scope This method is for determining total normal paraffins (TNP), individual normal paraffins, and total non-normal paraffins in desorbent-free UOP Molex process feed, raffinate, and extract streams. The lower limit of quantitation for an i

5、ndividual normal paraffin is 0.1 mass-%. References ASTM Method D4052, “Density, Relative Density, and API Gravity of Liquids by Digital Density Meter,” www.astm.org ASTM Practice D4307, “Preparation of Liquid Blends for Use as Analytical Standards,” www.astm.org Scanlon, J. T. and Willis, D. E., Jo

6、urnal of Chromatographic Science, 23, 333-340 (1985) UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org Outline of Method Feed and raffinate samples to be analyzed are injected twice into a gas chromatograph that is equipped with a fused silica capillary column internally coated wit

7、h cross-linked methyl silicone, an autosampler, and a flame ionization detector (FID). The first injection is performed with a standard capillary injection port liner; the second injection is performed with a capillary injection port liner packed with molecular sieves that quantitatively remove the

8、normal paraffins from the sample. The total sample chromatogram from injection one is superimposed and aligned with the de-normalized chromatogram from injection two so that the net individual normal paraffin peaks can be measured. The mass-% of each normal paraffin is obtained by the external stand

9、ard calibration technique. An extract sample to be analyzed is injected with the standard capillary injection port liner and the mass-% of each normal paraffin is obtained using the internal normalization calibration technique. Apparatus References to catalog numbers and suppliers are included as a

10、convenience to the method user. Other suppliers may be used. Balance, readable to 0.0001 g Chromatographic column, 30 m of 0.25-mm ID fused silica capillary, internally coated to a film thickness of 0.25 micron cross-linked methyl silicone, RTX-1, Restek, Cat. No. 10123 2 of 11 411-13 Data system, C

11、hemStation, Rev. B.01 or later, Agilent Technologies, for obtaining peak areas. The ChemStation software must have programmable parameters for controlling baseline events, and have signal alignment and subtraction capabilities, no substitution except for the pre-configured systems listed under Gas c

12、hromatograph. Desiccator, VWR, Cat. No. 25035-005, with plate, Cat. No. 89038-068 Gas chromatograph, temperature programmable, built for capillary column chromatography, utilizing a split injection system, equipped with a turn top inlet system, glass injection port inserts, and a flame ionization de

13、tector that will give a minimum peak height response of five times the background noise for 0.01 mass-% n-heptane when operated at the recommended conditions, Agilent Technologies, Model 7890. An autosampler is required. A pre-configured system, complete with gas chromatograph, data system, software

14、, columns, and prepacked injection port liners is available from Separation Systems, with the following catalog numbers: UOP-411-01, UOP 411 GC configuration, single detector/single sided UOP-411-02, UOP 411 GC configuration, double detector/double sided UOP-411-S, SOFTWARE, UOP 411 MOLEX Process so

15、ftware, for distributive and non-distributive mode analysis ss-035-500, LINERS, UOP 411 MOLEX Process liners w/molecular sieves Gas purifier, to remove oxygen from the hydrogen carrier gas, VICI Mat/Sen, Cat. No. P-200-1 Injection port liner, glass, split, focus, SGE Inc., Cat. No. 092002, several r

16、equired, no substitution Leak detector, gas, Grace Davison, Cat. No. 21-250 Puller/inserter tool, Sigma-Aldrich Co., Cat. No. 22406 Regulator, 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, de

17、livery pressure range 30-700 kPa (4-100 psi), Matheson Tri-Gas, Model 3122-350 Regulator, nitrogen or helium, two-stage, high purity, delivery pressure range 30-700 kPa (4-100 psi), Matheson Tri-Gas, Model 3122-580 Sample injector, autosampler, capable of introducing a repeatable 0.5-L volume of sam

18、ple, Agilent Technologies, Model 7693A Tweezers, curved tip, VWR, Cat. No. 63042-964 Reagents 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, local

19、 supply Autosampler vials, glass, 12 x 32 mm, for Agilent autosampler, Fisher Scientific, Cat. No. 03-391-8 Cyclohexane, 99.9% purity, Sigma-Aldrich, Cat. No. 227048-1L Caps, screw, for autosampler vials, open hole with septum, 9 mm, with Tef/Sil/Tef liner, Fisher Scientific, Cat. No. 03-377-2A Desi

20、ccant, indicating, for desiccator, VWR, Cat. No. 22891-028 3 of 11 411-13 Glass wool, Fisher Scientific, Cat. No. 11-390 Hydrogen, zero gas, 99.95% minimum purity, total hydrocarbons less than 0.5 ppm as methane, local supply Molecular sieve, UNISIV-2, 60 to 80 mesh, available prepacked in injection

21、 port liners from Separation Systems, Cat. No. ss-035-500 Pipet bulbs, Fisher Scientific, Cat. No. 13-678-9B Pipets, disposable, Pasteur, Fisher Scientific, Cat. No. 13-678-20A Nitrogen or helium, zero gas, total hydrocarbons less than 0.5 ppm as methane, local supply Normal paraffins, individual ca

22、rbon numbers, typically C8 to C17, 99 mass-% minimum purity, ChemSampCo. Obtain all carbon numbers represented in the feed. Table 1 Normal Paraffins n-Paraffin CAS Number Cat. No. C8 Octane 111-65-9 7056.00 C9 Nonane 111-84-2 6780.00 C10 Decane 124-18-5 0812.55 C11 Undecane 1120-21-4 9479.00 C12 Dod

23、ecane 112-40-3 2269.50 C13 Tridecane 629-50-5 8745.00 C14 Tetradecane 629-59-4 8438.00 C15 Pentadecane 629-62-9 7290.00 C16 Hexadecane 544-76-3 3278.00 C17 Heptadecane 629-78-7 3030.00 Syringe, for sample injector, 10-L, Agilent Technologies, Cat. No. 5181-1273 Vials, 15-mL, with screw cap, Fisher S

24、cientific, Cat. No. 03-339-21J Procedure The analyst is expected to be familiar with general laboratory practices, 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. Chr

25、omatographic 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 gas purifier is not used. 2. Install the fused silica capillary column in the gas chromatograph accord

26、ing to the column and gas chromatograph manufacturers instructions. 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. 3. Install the SGE glass

27、focus injection port liner as received from the manufacturer in the injection port. 4. Establish the recommended operating conditions as given in Table 2. 4 of 11 411-13 Different conditions may be used provided they produce the required sensitivity and chromatographic separations equivalent to thos

28、e shown in the Typical Chromatograms (Figures 1 and 2). Table 2 Recommended Operating Conditions Carrier gas hydrogen Mode constant flow Head pressure 207 kPa gauge (7.7 psig) Linear velocity 35C 37.6 cm/sec Equivalent flow 35C 1.37 mL/min Split flow 65 mL/min Injection port temperature 280C Column

29、temperature program Initial temperature 35C Initial hold time 0 min Programming rate A 5C/min Final hold temperature 275C Final hold time 0 min Detector flame ionization Detector temperature 280C Hydrogen flow rate* 40 mL/min Air flow rate* 400 mL/min Makeup gas nitrogen Makeup gas flow rate* 45 mL/

30、min Sample size 0.5 L *Consult the manufacturers instrument manual for suggested flow rates. 5. Program the column oven to 275C. Maintain this temperature until a stable baseline has been obtained at the required sensitivity. 6. Cool the column oven to a stabilized 35C. 7. Inject 0.5 L of the sample

31、 to be analyzed into the gas chromatograph and start the integrator and column temperature programming sequence. This is the total sample analysis. The use of an autosampler automates the injection of the sample into the GC, starts the data system, and the GC oven program simultaneously. 8. Compare

32、the resultant chromatogram to the typical chromatogram shown in Figure 1 for a feed or raffinate sample and Figure 4 for an extract sample. For extract samples only, proceed to Calculations, Extract Streams. 9. If not using the pre-packed injection port liner, replace the glass wool in an SGE focus

33、injection port liner with molecular sieves by taking the original glass wool out of the liner and packing approximately 0.075 g of 60 to 80 mesh UNISIV-2 in the same location. Use a small amount of glass wool to hold the molecular sieve in place. 10. Remove the as-received glass injection port liner

34、, and install the injection port liner packed with molecular sieves and again establish the recommended operation conditions as given in Table 1. Allow the injection port liner to condition at the stated operating temperature for about one hour. CAUTION: Glass liners are hot when removed. Use tweeze

35、rs or other technique to avoid burns. After initial use, store the liner packed with molecular sieves in a desiccator. The as-received liner may also be stored there for convenience. 5 of 11 411-13 Figure 1 Typical Total Sample Chromatogram, Molex Feed 11. Program the column oven to 275C again. Main

36、tain this temperature until a stable baseline has been obtained at the required sensitivity. 12. Cool the column oven to a stabilized 35C. 13. Inject 0.5 uL of the same feed or raffinate sample to be analyzed into the gas chromatograph and start the integrator and column temperature programming sequ

37、ence. This is the de-normalized analysis. The use of an autosampler automates the injection of the sample into the GC, starts the data system, and the GC oven program simultaneously. 14. Compare the chromatogram obtained to the typical chromatogram shown in Figure 2. Figure 2 Typical De-normalized S

38、ample Chromatogram, Molex Feed g18671g18667g186725 10 15 20 25 30 35 40FID2 B, (2010U411_100610-6SASOL_BLEND.D)Area: 641.866Area: 1025.31Area: 2186.88Area: 5506.3Area: 6624.01Area: 4546.19Area: 3314.22Area: 1949.76Area: 719.703nC9nC10nC11nC12nC13nC14nC15nC16nC175 10 15 20 25 30 35 406 of 11 411-13 I

39、ntegration Technique for Feed and Raffinate Samples The following steps are written for the specified data system. 1. Using Agilent ChemStation software, open a data analysis session and load the data file corresponding to the total sample analysis. Then overlay the data file corresponding to the de

40、-normalized analysis as follows: Under the Graphics menu choose signal options and set the Multi- Chromatogram options as seen below: The chromatograms should then display as the picture below: 2. Click the button. 3. Choose and place two time reference points at the same spot within each chromatogr

41、am, one near the beginning and one near the end of each chromatogram by clicking the button and choosing the points in the chromatogram using the mouse arrow. Be careful to choose the same spot in each chromatogram. 7 of 11 411-13 4. Align the time axis of the signals by clicking the button. 5. Alig

42、n the absorbance axis of the signals by clicking the button. 6. Subtract the de-normalized analysis from the total sample analysis by clicking the button. Click the Yes button to the message shown below: 7. Manually integrate the area under each normal paraffin peak only, making sure that a straight

43、 baseline is drawn consistently under each peak at the same absorbance point on the axis. A baseline hold event initiated at the beginning of the chromatogram where the baseline is flat may aid in determining where the baseline should be drawn. See Figures 3 & 3A. 8. Save the subtracted chromatogram

44、 by going under the File menu and choosing Export File and the AIA File option. Figure 3 Typical Subtracted Chromatogram, Molex Feed 5 10 15 20 25 30 35 40 45Area: 631.58Area: 1309.31Area: 2714.71Area: 5344.22 Area: 6657.15Area: 4678.12Area: 3289.98Area: 1964.09Area: 715.258nC9nC10nC11nC12nC13nC14nC

45、15nC16nC17411-13 Enlarged Typical Subtracted Chromatogram, Molex FeedTypical Chromatogram, Extract0 5 10 150.8711.0771.1351.3761.9122.0662.1532.4242.6893.1923.4004.0295.0335.2335.6115.7615.8945.9936.1206.2856.3336.399 -nC96.5106.5936.7276.7796.8566.9317.0187.1267.2147.3027.4957.5717.6867.8638.0188.0

46、868.2578.3418.4368.5478.6958.8358.9389.236 -nC109.3259.3949.5249.6139.6799.7519.8219.8939.94910.07210.17710.30910.47510.55910.71510.79810.90111.07411.32411.38211.50411.56511.72212.210 -nC1112.36612.47112.54112.61412.71912.87612.93813.03813.16513.30513.47113.57713.69813.87114.00614.11414.32314.961 -n

47、C1215.07915.1418 of 11 Figure 3A Figure 4 20 25 30 3514.11414.32314.961 -nC1215.07915.14115.26115.31615.46615.57915.67615.77315.98016.09616.25616.38416.54616.66316.80616.93517.06917.17517.575 -nC1317.68017.83117.94618.05918.19718.25518.34418.51718.60418.67418.79318.91819.07819.17519.27219.36619.5041

48、9.828 -nC1421.89823.15125.82826.044409 of 11 411-13 Calibration Feed and Raffinate Streams This analysis uses the external standard calculation technique to calculate the sample. 1. Prepare two blends as described in ASTM Practice D4307, “Preparation of Liquid Blends for Use as Analytical Standards,

49、” to contain approximately equal quantities of normal paraffins, C8 through C17 in cyclohexane, with one blend containing the approximate level of total normal paraffins as a typical Molex feed sample, and the other to contain the approximate level of total normal paraffins as a typical Molex raffinate sample. 2. Analyze each blend in triplicate as described under Chromatographic Technique with the as received injection port liner only. The total normal paraffin areas from each of the three runs should not deviate from the average by more t