UOP 269-2010 Nitrogen Bases in Hydrocarbons by Titration.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 1970, 1990, 2010 UOP LLC. All rights r

3、eserved. Nonconfidential 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

4、610.832.9585 PHONE. Nitrogen Bases in Hydrocarbons by Titration UOP Method 269-10 Scope This method is for determining basic organic nitrogen in petroleum distillates using potentiometric titration. This method may be applied to both clear and colored samples. The range of quantitation for petroleum

5、 distillates is from 0.0005 to 1.0 mass-% nitrogen, while for viscous materials, such as heavy oils, the range is 0.001 to 5.00 mass-% nitrogen. This method may give erroneous results for materials containing bases other than nitrogen compounds (e.g., caustic-washed distillates containing sodium soa

6、ps, or crude oil containing inorganic bases). Clear or very lightly colored samples may be analyzed down to a lower limit of quantitation of 0.5 mass-ppm (0.00005 mass-%) using the color indicator titration technique described in the Appendix. Reference UOP Method 999, “Precision Statements in UOP M

7、ethods,” www.astm.org Outline of Method Organic bases are titrated potentiometrically using a pH electrode, a perchloric acid in acetic acid titrant, and an acetic acid titration solvent. Apparatus References to catalog numbers and suppliers are included as a convenience to the method user. Other su

8、ppliers may be used. Balance, readability 0.1-mg Beaker, 250-mL, tall, without spout, borosilicate glass, Brinkmann Instruments, Cat. No. 020212209, Metrohm USA Cylinder, graduated, 100-mL, Fisher Scientific, Cat. No. 08-548D Desiccator, with porcelain plate, Fisher Scientific, Cat. No. 08-615A Elec

9、trode, Ecotrode combination Long Life pH, Metrohm USA, Cat. No. 020.912.146 2 of 10 269-10 Flasks, Class A, volumetric, 100-, 250-, and 1000-mL, Fisher Scientific, Cat. Nos. 10-210-5C, -5E, and -5G, respectively Hot plate, Fisher Scientific, Cat. No. 11-100-16H Oven, drying, capable of operation at

10、110C Pipets, 10-, 20-, 25-, and 50-mL, Class A, Fisher Scientific, Cat. Nos. 13-650-2L, -2N, -2P, and -2S, respectively Rubber bulb-type pipet filler, Fisher Scientific, Cat. No. 13-681-51 Titrator, potentiometric, recording, 2000-mV range, 1-mV resolution, capable of following a maximum allowable d

11、rift throughout a titration and/or reducing the titration rate to a minimum in the vicinity of the equivalence point, with dispenser having a volume readout of 0.001-99.999 mL with a resolution of 0.0001 of the buret volume, Metrohm Model 835 TitrandoTM system with optional Model 814 sample changer,

12、 and 20-mL buret Reagents and Materials References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. References to water mean deionized or distilled. Acetic acid, glacial, less than 0.10% water, Fisher Scientific, Cat. No. A38 Acetone, 99

13、.5% minimum purity, Fisher Scientific, Cat. No. A18 Dessicant, indicating, Fisher Scientific, Cat. No. 07-578-3B Perchloric acid, approximately 1-N, Fisher Scientific, Cat. No. SP339-500 Perchloric acid, approximately 0.02-N. Pipet 20 mL of the 1-N perchloric acid solution into a one-liter volumetri

14、c flask. Dilute to the mark with glacial acetic acid and mix well. Standardize this solution against THAM solution as described under Standardization. This solution is stable for two months, after which a new solution is prepared. Potassium chloride solution, 3 mol/L, Metrohm USA, Cat. No. 6.2308.02

15、0 THAM, tris(hydroxymethyl)aminomethane, primary standard, Fisher Scientific, Cat. No. T395 THAM solution. Dry THAM in an oven at 110C for 2 hours; cool in a desiccator. Weigh, to the nearest 0.1 mg, between 0.5 and 0.6 g of dried THAM into a 100-mL volumetric flask. Dilute to the mark with glacial

16、acetic acid and mix well. The prepared solution is stable for 2 weeks. Toluene, 99.5% minimum purity, Fisher Scientific, Cat. No. T324 Water, deionized or distilled Procedure The analyst is expected to be familiar with general laboratory practices, the technique of titration, and the equipment being

17、 used. Standardization 1. Assemble and operate the titrator and electrode according to the manufacturers instructions. 2. Fill the dispenser reservoir of the titrator with the 0.02-N perchloric acid solution. 3. Pipet 10 mL of THAM solution into a clean, dry 250-mL beaker. 3 of 10 269-10 4. Add, by

18、graduated cylinder, 100 mL of glacial acetic acid to the beaker. 5. Place the beaker containing the diluted standard on the titration stand, stir and titrate the standard with the 0.02-N perchloric acid under the following conditions: Adjust the titrator parameters so that the initial titration rate

19、 in the plateau region is 0.5 mL/min while the titration rate in the region of the endpoint is reduced to 0.1 mL/min. The standardization is performed in triplicate. 6. Record the volume of titrant required to reach the endpoint of the titration. The end point is the midpoint of the inflection, that

20、 point at which the curve changes from concave to convex, see Figure. 7. Add, by graduated cylinder, 100 mL of glacial acetic acid to another 250-mL beaker, for use as a blank. 8. Titrate the blank using the 0.02-N perchloric acid in duplicate as described above. If the blanks do not repeat within 0

21、.02 mL, check the equipment and procedures, and repeat the blank titrations. 9. Calculate the normality of the perchloric acid to the fourth decimal place using Equation 1: Normality of perchloric acid = GB FWA2549.8(1) where: A = volume of dilute THAM solution titrated, mL B = volume of perchloric

22、acid solution used to reach the endpoint of the dilute THAM solution, mL F = volume to which THAM solution was diluted, mL G = volume of perchloric acid used to reach the endpoint of the acetic acid blank, mL W = mass of THAM, weighed into flask, g 8.2549 = 14.1211000 (1a) where: 121.14 = molecular

23、weight of THAM, g/mole 1000 = factor to convert liters to milliliters 10. Average the results of the three determinations. Results from each of the triplicate runs should not deviate by more than 0.001-N. If greater deviations occur, make certain that there are no problems with the equipment or the

24、procedure; then repeat the procedure until the required repeatability is obtained on three consecutive runs. The perchloric acid solution must be standardized at least weekly to detect changes in normality. A reference quality assurance sample may be run daily to confirm the stability of the titrant

25、 between standardizations. Part A Samples Soluble in Glacial Acetic Acid 1. Add, by graduated cylinder, 100 mL of glacial acetic acid into a clean dry 250-mL beaker. 4 of 10 269-10 2. Add the sample, weighed to the nearest 0.1 mg, to the glacial acetic acid. The sample amount depends on the concentr

26、ation of basic nitrogen present. Use Table 1 as a guide to choose the appropriate sample mass. Table 1 Guide to Choose the Appropriate Sample Mass Estimated Basic N, mass-% Approximate Sample Mass, g 0.0015 100 0.0015 to 0.025 25 0.025 to 0.070 15 0.070 to 0.15 5 0.15 to 1.0 1 3. Place the beaker co

27、ntaining the weighed sample in position for titration, stir and titrate the sample with the 0.02-N perchloric acid using the parameters established in the section on Standardization, Step 5. 4. Record the volume of titrant required to reach the endpoint of the titration, see Standardization, Step 6.

28、 The Figure shows several typical titration curves. Figure Nitrogen Base Determination, Typical Titration Curves 5. Prepare a blank containing 100 mL of glacial acetic acid and analyze it in the same manner as the sample. Part B Samples Insoluble in Glacial Acetic Acid (Heavy Oils) 1. Warm the sampl

29、e on a hot plate and shake it to make sure it is homogeneous. 5 of 10 269-10 2. Weigh, to the nearest 0.1 mg, a representative aliquot of the sample into a 250-mL beaker. See Table 2 for the amount to weigh, based upon the expected concentration of nitrogen in the sample. 3. Dissolve a weighed sampl

30、e in toluene; the amount of sample and toluene will vary. Use Table 2 as a guide. If the sample does not dissolve readily in toluene, warm again. Table 2 Guide to Choose the Appropriate Amount of Toluene to Use Estimated Basic N, mass-% Approximate Sample Mass, g Toluene, mL 0.01 25 50 0.010 to 0.03

31、5 10 50 0.035 to 1.0 1 25 1.0 to 5.0 0.3 25 4. Using a graduated cylinder, add glacial acetic acid slowly. If no precipitate forms, add a total of 75 mL of glacial acetic acid. If a precipitate forms, add an amount of glacial acetic acid equal to the total amount of sample-plus-toluene used. In some

32、 heavy oil samples a precipitate will form as soon as any glacial acetic acid is added. Ignore the precipitate formed. 5. Place the beaker containing the weighed sample in position for titration, stir and titrate the sample with the 0.02-N perchloric acid using the parameters established in the sect

33、ion on Standardization, Step 5. 6. Record the volume of titrant required to reach the endpoint of the titration, see Standardization, Step 6. The Figure shows several typical titration curves. 7. Prepare a blank containing the same amount of toluene and glacial acetic acid as used for the sample, an

34、d analyze it in the same manner as the sample. Calculations Calculate the mass-% basic nitrogen in the sample to three significant figures as follows: Basic nitrogen, mass-% = ( )S NDC4.1 (2) where: C = volume of perchloric acid used to reach the endpoint of the sample titration, mL D = volume of pe

35、rchloric acid used to reach the endpoint of the blank titration, mL N = normality of perchloric acid solution, from Equation 1 S = sample mass, g 1.4 = ( ) ( )100010014 (2a) where: 14 = molecular weight of nitrogen, g/mole 100 = factor to convert g/g to mass-% 1000 = factor to convert liters to mill

36、iliters 6 of 10 269-10 Precision Precision statements were determined using UOP Method 999. Repeatability and Site Precision A nested design was carried out for determining basic nitrogen on three samples with two analysts in one laboratory. Each analyst carried out tests on two separate days, perfo

37、rming two tests on each sample each day. The total number of tests was 24. The precision data are summarized in Table 3. Two tests performed by the same analyst on the same day should not differ by more than the repeatability allowable difference with 95% confidence. Two tests performed in one labor

38、atory by different analysts on different days should not differ by more than the site precision allowable difference with 95% confidence. Table 3 Repeatability and Site Precision, basic nitrogen, mass-% Repeatability Site Precision Sample Mean Within- Day esd Allowable Difference Within- Lab esd All

39、owable Difference Part A, 1 0.0006 0.00004 0.0002 0.00019 0.0012 Part A, 2 0.7673 0.01083 0.0425 0.01104 0.0434 Part B, 3 0.0017 0.00011 0.0005 0.00019 0.0009 The data in Table 3 are a short-term estimate of repeatability. When the test is run routinely, a control standard and chart should be used t

40、o develop a better estimate of the long-term repeatability. Reproducibility There is insufficient data to calculate reproducibility of the test at this time. Time for Analysis The elapsed time and labor requirement are identical, 0.5 hour for Part A, and 1.0 hour for Part B. Suggested Supplier Fishe

41、r Scientific, 711 Forbes Ave., Pittsburgh, PA 15219-4785 (412-490-8300) Metrohm USA, 6555 Pelican Creek Circle, Riverview, FL 33578 (813-316-4700) 7 of 10 269-10 Appendix Nitrogen Bases in Petroleum Distillates by Color Indicator Titration Scope This method is for determining basic organic nitroge

42、n in clear or very light-colored distillates using a visual indicator titration. It is applicable over the range 0.5 to 100 mass-ppm as nitrogen, but is especially useful from 0.5 to 5.0 mass-ppm. Colored samples interfere with the observation of the color indicator and, therefore, cannot be accurat

43、ely analyzed by this method. Colored samples can be analyzed over a wide concentration range by potentiometric titration as described in the body of the method. Reference ASTM Method D4052, “Density and Relative Density of Liquids by Digital Density Meter,” www.astm.org Outline of Method Samples are

44、 titrated colorimetrically with a perchloric acid in acetic acid titrant, using crystal violet as a visual indicator. Apparatus The following apparatus are an addition or substitution to that listed in the body of the method. References to catalog numbers and suppliers are included as a convenience

45、to the method user. Other suppliers may be used. Beakers, 400-mL, tall, without spout, borosilicate glass, Fisher Scientific, Cat. No. 10-310-9 Bottle, dropping, with ground glass stopper/pipet, 125-mL, Fisher Scientific, Cat. No. 02-9863 Buret, micro, 10-mL, 0.02-mL subdivisions, Class A, with Tefl

46、on stopcock, Fisher Scientific, Cat. No. 20-105B Buret, 50-mL, 0.1-mL subdivisions, Class A, with PTFE stopcock, Fisher Scientific, Cat. No. 03-700-22C Magnetic stirrer, with stir bar, Fisher Scientific, Cat. Nos. 14-493-120M and 14-511-64, respectively Pipets, volumetric, 5- and 100-mL, Class A, Fi

47、sher Scientific, Cat. Nos. 13-650-2F and -2U, respectively Reagents and Materials The following reagents and materials are an addition or substitution to that listed in the body of the method. References to catalog numbers and suppliers are included as a convenience to the method user. Other supplie

48、rs may be used. References to water mean deionized or distilled. Crystal violet, Fisher Scientific, Cat. No. C581 Crystal violet indicator solution. In the dropping bottle, dissolve approximately 0.1 g of crystal 8 of 10 269-10 violet in 100 mL of glacial acetic acid. Perchloric acid, approximately

49、0.01-N. Pipet 10 mL of 1-N perchloric acid solution into a one-liter volumetric flask. Dilute to the mark with glacial acetic acid and mix well. Standardize this solution against THAM solution as described under Standardization. Procedure Standardization Standardize the 0.01-N perchloric acid solution as follows: 1. Prepare and fill the 10- or 50-mL buret, for low (0.5 5 mass-ppm nitrogen expected) or high (5 100 mass-ppm nitrogen expected) nitrogen concentrations, respectively, with the 0.01-N perchloric acid in g