UOP 495-2003 AROMATICS IN MOLEX PROCESS n-PARAFFIN PRODUCTS BY ULTRAVIOLET SPECTROPHOTOMETRY.pdf
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1、 COPYRIGHT 1972, 1975, 2000, 2003 UOP LLC ALL RIGHTS RESERVED uop, UOP, and Molex are trademarks and/or service marks of UOP LLC. Marks of other proprietors may appear incidentally AROMATICS IN MOLEX PROCESS n-PARAFFIN PRODUCTS BY ULTRAVIOLET SPECTROPHOTOMETRY uop Method 495-03 SCOPE This method is
2、for estimating total aromatics in Molex process n-paraffin products. The method determines an average amount of naphthalenes and alkylbenzenes that may be present, provided the concentration of the alkylbenzenes is at least ten times greater than the naphthalenes. In practice, this condition is sati
3、sfied for the specified applications. Other samples with similar compositions may also be suitable for this analysis. The lower limit of detection is 0.0003 mass-%. REFERENCES API Project 44, American Petroleum Institute, 1220 L Street, N.W., Washington, DC 20005 (202-682-8000) www.api.org ASTM Meth
4、od D 4052, “Density and Relative Density of Liquids by Digital Density Meter,” www.astm.org UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org OUTLINE OF METHOD The ultraviolet absorbance spectrum of the sample is measured. Average absorptivities from published spectral data are use
5、d to compute the concentrations of the naphthalenes and alkylbenzenes. Sample complexity does not permit experimental calibration. APPARATUS References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Absorption cells, matched pairs, sil
6、ica, 10-, 5- and 1-cm, Fisher Scientific, Cat. Nos. 14-385-930F, -930E, and -904C, respectively 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 F
7、OLLOWED WHEN UTILIZING THIS PROCEDURE. FAILURE TO UTILIZE THIS PROCEDURE IN THE MANNER PRESCRIBED 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 AP
8、PROPRIATE PERSONAL PROTECTION EQUIPMENT (PPE). 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, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 194428-2959,
9、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. 2 of 8 Balance, readability 0.1-mg Flasks, volumetric, Class A, 25-mL, Fisher Scientific, Cat. No. 10-210-5A, several requ
10、ired Spectrophotometer, capable of scanning and operation in the 360-220-nm region with a spectral bandwidth of 1 nm and capable of 0.5% precision in absorbance measurements at the 1.0 level at this resolution Vacuum source, a water aspirator, Fisher Scientific, Cat. No. 09-960-2, is sufficient REAG
11、ENTS AND MATERIALS References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Isooctane, spectroscopic grade, Fisher Scientific, Cat. No. 0300-4 CALIBRATION Instead of directly calibrating the spectrophotometer with known naphthalenes,
12、the average absorptivities of the C10through C13naphthalenes at 285 nm, 33.7 L/g-cm, and, near 270 nm, 30.0 L/g-cm, are used in this method (see Table 1). Similarly, the average absorptivity of available C10to C20alkylbenzenes near 270 nm, 3.01 L/g-cm, is used (see Table 2). Absorptivities of indivi
13、dual naphthalene and alkylbenzene hydrocarbons at their respective wavelengths are derived from data in the API catalog of ultraviolet spectral data issued by Research Project 44, and are listed in Tables 1 and 2. Table 1 Naphthalene Absorptivities, L/g-cm Compound API Serial Number 285 nm Near 270
14、nm Naphthalene 1-Methylnaphthalene 2-Methylnaphthalene 1,2-Dimethylnaphthalene 1,3-Dimethylnaphthalene 1,4-Dimethylnaphthalene 1,5-Dimethylnaphthalene 1,6-Dimethylnaphthalene 1,7-Dimethylnaphthalene 1,8-Dimethylnaphthalene 2,3-Dimethylnaphthalene 2,6-Dimethylnaphthalene 2,7-Dimethylnaphthalene 1-Iso
15、propylnaphthalene Average 605 539 572 215 216 217 218 219 220 221 222 226 224 203 28.5 32.0 22.9 37.3 36.4 43.5 54.0 36.4 36.0 46.0 22.0 21.3 23.5 31.7 33.7 32.6 32.0 31.8 26.5 26.5 26.0 29.0 35.0 32.5 30.0 30.0 27.5 29.5 31.7 30.0 495-03 3 of 8 Table 2 Alkylbenzene Absorptivities, L/g-cm Compound A
16、PI Serial Number Near 270 nm Tetralin 2-Methyltetralin 5-Methyltetralin 6-Methyltetralin 6-n-heptyltetralin n-Butylbenzene 1,4-Diethylbenzene n-Hexylbenzene 1,4-Diisopropylbenzene n-Octylbenzene n-Undecylbenzene n-Tetradecylbenzene 1,1-Diphenylethane 1,1-Diphenylbutane 1,4-Diphenylbutane Average 133
17、 398 134 135 287 176 188 143 191 144 146 394 199 200 283 4.45 3.83 1.89 5.41 4.96 1.82 3.05 1.40 2.19 1.40 2.50 2.39 2.65 2.72 4.50 3.01 PROCEDURE The size of the cells to be used (10-, 5- or 1-cm) is determined by the concentration expected in the samples. If an estimate is not available, use the 1
18、-cm pair first, and switch to the 5- or 10-cm pair only if greater sensitivity is required. The detection limit for this method is based upon the use of a 10-cm cell for alkylbenzenes. 1. Fill a matched pair of absorption cells with isooctane and place them in their respective beam paths. Perform a
19、background correction by scanning in the region from 360 to 220 nm. 2. Empty the sample cell and dry it using the vacuum. 3. Transfer the sample, as received, into the cell and return it to the spectrophotometer. 4. Obtain the spectrum from 360 to 220 nm. Typical examples are shown in Figures 1 and
20、2. 5. If the absorbance maximum near 270 nm exceeds 1.0, sample dilution is required. (Some instrument manufacturers may recommend a different maximum; follow the manufacturers recommendations.) Proceed to Step 7 if the sample requires dilution. 6. If the sample does not require dilution, obtain the
21、 density of the as received sample using ASTM Method D 4052, Density and Relative Density of Liquids by Digital Density Meter (or equivalent), see NOTE 1. If the absorbance maximum near 270 nm is less than 0.1, proceed to Step 11, otherwise, proceed to Step 12. 7. Dilute sequentially with isooctane
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