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 1965, 1982, 2007, 2008, 2017 UOP LLC. All rights reserved.
3、 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, 610.832.9555 FAX, or
4、610.832.9585 PHONE. Diene Value by Maleic Anhydride Addition Reaction UOP Method 326-17 Scope This method is for determining maleic anhydride reactivity with a wide variety of oils, ranging from debutanized light hydrocarbon distillates to heavy drying oils, using titration. The method gives a measu
5、re of the conjugated diolefin content of the sample. The determination is somewhat empirical since some conjugated diolefins may not react completely, while certain compounds other than conjugated diolefins also may be reactive. For example, anthracene, along with many of its homologs and correspond
6、ing alkylated compounds, as well as certain vinyl aromatics, react as dienes with maleic anhydride. Therefore, the results obtained by this method must be carefully interpreted in the light of these specified limitations. The range of quantitation for diene value is from 1.2 to over 100. A modified
7、procedure can be used to estimate diene values less than 1.2. If the average molecular weight of the conjugated diolefins is known or can be estimated, the mass-% concentration of conjugated diolefins can be calculated. References AOCS Official Method Th 1a-64, “Diene Value,” www.aocs.org Ellis, B.
8、A. and Jones, R. A., Analyst 61, 812 (1936) McKinney, R. S., Hallbrook, N. J., and Rose, W. G., Oil and Soap 19, 141-143 (1942) Norton, J. A., Chem. Rev. 31, 319 (1942) UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org Outline of Method Maleic anhydride is refluxed with the sample
9、in boiling toluene for 3 hours. The unreacted maleic anhydride is hydrolyzed to maleic acid, extracted from the reaction mixture, and titrated with sodium hydroxide. A blank is run using the same amount of maleic anhydride as charged to the reaction flask. The amount reported as having reacted with
10、the sample is the net volume obtained by potentiometric titration difference, and from this data the diene value and/or the percent dienes can be calculated. An alternative titration technique, using a manual (colorimetric) procedure, is described in the Appendix. Additional information regarding th
11、is technique is provided in References. 2 of 11 326-17 Definition Diene value, the number of grams of iodine equivalent to the amount of maleic anhydride that reacts with 100 g of sample (based on 2 atoms of iodine per mole of maleic anhydride) under the specified reaction conditions. Apparatus Refe
12、rences to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Balance, readability 0.01 g Beaker, 250-mL, tall, without spout, borosilicate glass, Reliance Glass, Cat. No. G-9906-002, three required Bottle, polyethylene, 1000- mL, Fisher Scien
13、tific Co., Cat. No. 03-313-5D Condenser, Liebig, with Ts 24/40 ground-glass joint, Fisher Scientific, Cat. No. 07-721C, at least two required Crucible, high form, 10- mL, porcelain, Fisher Scientific, Cat. No. FB965C, with cover, Fisher Scientific, Cat. No. FB965S Cylinders, graduated, 10- and 25- m
14、L, Class B, Fisher Scientific, Cat. Nos. 08-549-5B and -5C, respectively Desiccator, 150- mm ID, and porcelain plate, Fisher Scientific, Cat. Nos. 12-141-433 and 08-641A, respectively Electrode, iEcotrode Plus, combination glass, with sleeve diaphragm, double junction, Metrohm AG, Cat. No. 6.0280.30
15、0. Store in water when not in use. Flask, Erlenmeyer, 250- mL, Fisher Scientific Co., Cat. No. 10-040F Flask, Erlenmeyer, 250- mL, with Ts 24/40 ground-glass joint, Fisher Scientific, Cat. No. 10-047C, at least two required Flask, Erlenmeyer, 500- mL, borosilicate glass, heavy walled, with side arm,
16、 Fisher Scientific, Cat. No. 10-180K, optional, see Standardization of Sodium Hydroxide Flask, volumetric, 1000- mL, Class A, Fisher Scientific, Cat. No. 10-210-5G Funnel, filter, Fisher Scientific, Cat. No. 10-326-2C Funnel, separatory, 250- mL, Fisher Scientific, Cat. No. 10-437-5C Hot plate, Thom
17、as Scientific, Cat. No. 5983C06 Magnetic stir bar, Fisher Scientific, Cat. No. 14-511-64, three required Mortar, porcelain, 130- mm OD, with pestle, porcelain, Fisher Scientific, Cat. Nos. FB961E and FB961O, respectively Oven, drying, capable of operation at 120C, Fisher Scientific, Cat. No. 15-103-
18、0508 Pipet filler, Fisher Scientific, Cat. No. 13-681-102A Pipet, Mohr, 25- mL, Fisher Scientific, Cat. Nos. 13-665-100F Pipets, volumetric transfer, 2-, 3-, 5-, 10-, and 20- mL, Class A, Fisher Scientific, Cat. Nos. 13-650-2C, -2D, -2F, -2L, and -2N, respectively 3 of 11 326-17 Regulator, nitrogen,
19、 two-stage, high purity, delivery pressure range 15-200 kPa (2-30psig), Matheson Gas Products, Model 3121-580 Ring stands and clamps, to hold apparatus, local supply Stirrer, magnetic, Fisher Scientific, Cat. No. 14-493-120S Stirring rod, glass, Fisher Scientific, Cat. No. 11-380D Titrator, potentio
20、metric, recording, 2000- mV range, 1- mV resolution, capable of reducing the titration rate to a minimum in the vicinity of the endpoint, with dispenser having a volume readout of 0.00 - 99.99 mL, 0.0001 of the buret volume resolution, Metrohm Model 905 Titrando system with 801 Stirrer, Metrohm AG T
21、ongs, stainless steel, crucible, Fisher Scientific, Cat. No. 15-186 Tubing, thick walled, rubber, for vacuum use, Fisher Scientific, Cat. No. 14-173D, optional, see Standardization of Sodium Hydroxide Vacuum pump, Precision Model No. DD-20, Fisher Scientific, Cat. No. 01-182, optional, see Standardi
22、zation of Sodium Hydroxide 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 water. Absorbent, carbon dioxide, Ascarite II, 20 to 30-mesh, Fisher Scientific, Cat. No. A1
23、84-500 Boiling chips, silicon carbide, Fisher Scientific, Cat. No. NC9063828 Desiccant, 8 mesh, indicating, Fisher Scientific, Cat. No. 07-578-3A Electrolyte, 3 mol/L potassium chloride, Fisher Scientific, Cat. No. 01-917-103 Filter paper, qualitative, medium, acid-free, non acid-washed, Whatman No.
24、 1, Fisher Scientific, Cat. No. 09-805F 1,3 Cyclohexadiene, with 0.05% BHT (Butylated Hydroxy Toluene) as inhibitor, Purity 97%, Sigma Aldrich Cat. No C100005 Maleic anhydride 108-31-6, 99%, mp 52-55C, Acros Organics, Fisher Scientific, Cat. No. AC125240010 Maleic anhydride in toluene. Dissolve 60 g
25、 of maleic anhydride in warm toluene. Cool, transfer to a one-liter volumetric flask, and dilute to the mark with toluene. Allow the solution to stand at least one day, and filter through a qualitative-grade filter paper before using. Methyl-tert-butyl ether 1634-04-4, (MTBE), or tert-butyl methyl e
26、ther, 3 degree boiling range, Fisher Scientific Co., Cat. No. E127-4, or equivalent 1,3 Cyclohexadiene reference standard solution Standard A (for DV more than 1.2). Weigh to the nearest 0.1 mg, 2 g of 1,3 Cyclohexadiene into a 250- ml volumetric flask, tared to nearest 0.01 g. Dilute the mark with
27、Toluene, mix well and re-weigh. Record the total weight. Calculate Theoretical Diene value by Equation 2. Store the solution in refrigerator (stable for six months). 1,3 Cyclohexadiene reference standard solution Standard B ( for DV less than 1.2).Weigh to the nearest 0.01 g, 50 g of 1,3 Cyclohexadi
28、ene reference standard (for DV more than 1.2) into a 250- ml volumetric flask, tared to nearest 0.01g. Record the weight. Dilute to the mark with Toluene, mix 4 of 11 326-17 well and re-weigh. Record the total weight. Calculate the Theoretical Diene value by Equation 3. Store the solution in refrige
29、rator (stable for six months). Nitrogen, 99.999% minimum purity PTFE Sleeve, ST/NS 24/40, Sigma Aldrich, Cat No. Z104884 or Pencil, soft lead, local supply, source of graphite lubricant Phenolphthalein indicator solution, 1% w/v, Fisher Scientific, Cat. No. SP62-500 Potassium hydrogen phthalate, pri
30、mary standard, Fisher Scientific, Cat. No. P243-100 Sodium hydroxide, 0.1M, Certified, Fisher Scientific, Cat. No. SS276-1, for low diene value analysis only Sodium hydroxide, 1.0M, Certified, Fisher Scientific, Cat. No. SS266-1 Toluene, 99.8%, HPLC grade, Fisher Scientific, Cat. No. T290-1 Water, c
31、arbon dioxide free, see Standardization of Sodium Hydroxide Water, deionized Procedure The analyst is expected to be familiar with general laboratory practices, the technique of potentiometric titration, and with the equipment being used. Standardization of Sodium Hydroxide 1. Assemble and operate t
32、he titrator and electrodes as per the manufacturers instructions. 2. Fill the dispenser reservoir of the titrator with the 1.0 M sodium hydroxide solution. If a diene value less than 1.2 is to be determined, standardize the 0.1 M sodium hydroxide solution in the same manner. The solution must be pro
33、tected from atmospheric carbon dioxide by attaching a guard tube containing an absorbent, such as Ascarite, to the dispenser reservoir. 3. Crush approximately 3 g of potassium hydrogen phthalate using a mortar and pestle. 4. Transfer the potassium hydrogen phthalate to a clean crucible and dry at 12
34、0C for 2 hours in a drying oven. 5. Remove the crucible from the oven using tongs, place it in a desiccator, cover it, and allow it to cool to ambient temperature. 6. Place a stirring bar into each of three 250- mL beakers. The standardization is performed in triplicate. 7. Weigh approximately 0.5 g
35、 of dried potassium hydrogen phthalate, to the nearest 0.1 mg, into each of the three 250- mL beakers and record the masses in each beaker. If the 0.1-M sodium hydroxide solution is being standardized, weigh in approximately 0.1 g of the dried potassium hydrogen phthalate, to the nearest 0.1 mg. 8.
36、Add, by graduated cylinder, 100 mL of carbon dioxide free water to each beaker. The water must be carbon dioxide free. Prepare immediately before use by boiling deionized water for approximately 10 minutes to expel carbon dioxide and then cooling while purging with nitrogen, or by placing the water
37、under vacuum for sufficient time to degas. For example, 500 mL of water requires approximately 90 minutes under vacuum to fully degas. 5 of 11 326-17 9. Place one of the beakers on the titration stand, immerse the electrodes and buret tip, start a slow flow of nitrogen to the headspace of the beaker
38、 to expel air, and stir. Adjust the stirring speed to create a vortex in the solvent such that bubbles do not develop at its center. Obtain a stable reading before proceeding to the next step. 10. Adjust the titration parameters so that the initial titration rate in the plateau region is 0.3 mL/min
39、and the titration rate in the region of the endpoint is reduced to 0.1 mL/min. Titrate the potassium hydrogen phthalate solution with the 1.0M sodium hydroxide. Record, to the nearest 0.001 mL, the volume of titrant used to reach the endpoint of the titration. The endpoint is the midpoint of the inf
40、lection; the point at which the curve changes from concave to convex. 11. Titrate the contents of the other two beakers in the same manner. 12. For each titration, calculate the molarity of the sodium hydroxide to three decimal places, using Equation 1: B2.204A10M 3 )1( where: A = mass of potassium
41、hydrogen phthalate weighed into beaker, g B = volume of sodium hydroxide solution used to reach the endpoint, mL M = molarity of the 1.0M sodium hydroxide, moles/L 204.2 = molecular mass of potassium hydrogen phthalate, g/mole 103 = factor to convert moles/mL to moles/L 13. Average the results of th
42、e three determinations to three decimal places. Results from each of the triplicate runs should not deviate by more than 0.001 M. If greater deviations occur, make certain that there are no problems with the equipment or the procedure; then repeat the procedure until the required repeatability is ob
43、tained on three consecutive runs. The sodium hydroxide solution must be standardized at least weekly to detect changes in molarity. A reference quality assurance sample may be run daily to confirm the stability of the titrant between standardizations. Standardization with 1,3 Cyclohexadiene 1. Calcu
44、late the theoretical Diene value (Standard A) reference standard to one decimal place using Equation 2. Theoretical Diene Value = )T13.80( )(XP)8.253(2) where: 253.8 = Molecular Mass of Iodine X = Mass of 1,3 Cyclohexadiene, g P = percentage Purity of 1,3 Cyclohexadiene 80.13 = Molecular Mass of 1,3
45、 Cyclohexadiene T = Total Mass of 1,3 Cyclohexadiene plus Toluene diluent, g 2. Calculate the theoretical Diene Value (Standard B) reference standard to two decimal place using Equation (3) Theoretical Diene Value = 1T ) (Y )2m e q n ( V a lu e fro (3) where: Y = Mass of 1,3 Cyclohexadiene reference
46、 standard in Toluene, g T1 = Total Weight of Y plus Toluene diluent, g 6 of 11 326-17 For more than 1.2 DV, take aliquot size between 5-10 g and for less than 1.2 DV take aliquot of 20 g. For rest of procedure follow from step 2 in “Sample Analysis” section. If determined Diene value is not within 1
47、0% of calculated theoretical Diene Value, then re-standardize Sodium Hydroxide solution and verify critical process step like reflux and Maleic acid recovery stage. Sample Analysis 1. Weigh a sample of appropriate size, usually 5-20 g, into the dry 250- mL Erlenmeyer flask with a ground glass joint.
48、 If a diene value greater than 1 is expected, use 5-10 g; if a diene value less than 1 is expected use 20 g. 2. Using a volumetric pipet, add 20 mL of the filtered maleic anhydride-toluene solution and a few boiling chips to prevent bumping. If the measured diene value of the sample was previously d
49、etermined to be less than 1.2, and an estimate of the value below 1.2 is desired, pipet only 2 mL of the filtered maleic anhydride-toluene solution into the flask containing 20 g of the sample. With a Mohr pipet (or individual volumetric pipets), add 18 mL of toluene and a few boiling chips to prevent bumping. 3. Pipet the same amount of filtered maleic anhydride-toluene solution used for the samples to an empty 250- mL Erlenmeyer flask with a ground glass joint. This will be the blank, and should be treated in the same manner as the samples.
