UOP 935-1994 MERCAPTAN TYPES IN KEROSINE BY NMR.pdf

1、MERCAPTAN TYPES IN KEROSINE BY NMRUOP 935-94SCOPEThis method is for determining primary, secondary and tertiary mercaptans (thiols) in kerosines up toseveral thousand mass-ppm, based on the procedure previously suggested by E. Rafii, et al. (1,2). The lowerlimit of detection by 119Sn H decoupled, re

2、focused Insensitive Nucleus Enhancement by PolarizationTransfer (INEPT) Nuclear Magnetic Resonance (NMR) spectroscopy without preconcentration is 40 mass-ppm per mercaptan type in the kerosine. Lower concentrations can be determined using a specifieddistillation procedure. The only known interferenc

3、es are thiophenols and branched alcohols, such asisopropyl and butyl alcohols (see NOTE). The method relies upon the quantitative preparation of soluble tri-n-butyl tin derivatives of all of the thiols present.OUTLINE OF PROCEDUREUOP Method 163 (3) is performed to determine the total mercaptan sulfu

4、r content of the kerosine sample.The mercaptans are derivatized by reaction with bis(tributyltin) oxide (TBTO) to form the correspondingorgano-sulfur-tributyltin compounds. If required, vacuum distillation is performed to concentrate themercaptan-derivatives to greater than 40 mass-ppm for each type

5、 in the kerosine bottoms. The derivatizedsample or concentrate is diluted 50/50 (vol/vol) in a perdeuterobenzene (C6D6)/chromium (III)acetylacetonate solution and analyzed by 119Sn NMR spectroscopy using a proton decoupled, refocusedINEPT procedure. The NMR areas assignable to each mercaptan type ar

6、e determined by a specifiedintegration procedure. The area fraction attributable to each type is then multiplied by the total mercaptansulfur in the sample to determine the concentration of primary, secondary and tertiary thiols.APPARATUSReferences to catalog numbers and suppliers are included as a

7、convenience to the method user. Othersuppliers may be used.Adapter, universal, with gas inlet and 24/40 standard taper joints, Fisher Scientific, Cat. No. K179750-2114Balance, readability 0.01-g, 1800-g capacityIT IS THE USERS RESPONSIBILITY TO ESTABLISH APPROPRIATE PRECAUTIONARY PRACTICES AND TODET

8、ERMINE THE APPLICABILITY OF REGULATORY LIMITATIONS PRIOR TO USE. EFFECTIVE HEALTH ANDSAFETY PRACTICES ARE TO BE FOLLOWED WHEN UTILIZING THIS PROCEDURE. FAILURE TO UTILIZE THISPROCEDURE IN THE MANNER PRESCRIBED HEREIN CAN BE HAZARDOUS. MATERIAL SAFETY DATA SHEETS(MSDS) OR EXPERIMENTAL MATERIAL SAFETY

9、 DATA SHEETS (EMSDS) FOR ALL OF THE MATERIALS USED INTHIS PROCEDURE SHOULD BE REVIEWED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTIONEQUIPMENT (PPE). COPYRIGHT 1994 UOP LLCALL RIGHTS RESERVEDUOP Methods are available through ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoho

10、cken PA 19428-2959,United States. The Methods may be obtained through the ASTM website, www.astm.org, or by contacting Customer Service atserviceastm.org, 610.832.9555 FAX, or 610.832.9585 PHONE.2 of 16935-94Caps, NMR tube, pressure, Wilmad Glass, sized appropriately for the NMR tube (see PROCEDURE,

11、Instrument Specification)Clamps, 3-prong, utility, Fisher Scientific, Cat. No. 05-769Cylinder, graduated, 250-mL, Class A, Fisher Scientific, Cat. No. 08-557EDerivatization apparatus, Dean-Stark, 24/40 standard taper joints, Fisher Scientific, Cat. No. K535800-0000Flask, boiling, round bottom, 500-m

12、L, 24/40 standard taper joint, with thermometer well, FisherScientific, Cat. No. 10-069AFlask, volumetric, Class A, 10-mLHeating mantle, spherical, 500-mL flask size, with cord, Fisher Scientific, Cat. No. 11-472BHeat tape, 610- x 13-mm (2-feet x 1/2-inch), Fisher Scientific, Cat. No. 11-463-54ANucl

13、ear Magnetic Resonance Spectrometer, capable of time-averaged, proton decoupled, refocusedINEPT analysis of 119Sn. See PROCEDURE, Instrument Specification for additional information.Pipet, Mohr, Class B, 1-mLPipet, volumetric transfer, Class A, 5-mLPlug, vortex, glass, Wilmad Glass, sized appropriat

14、ely for NMR tube (see PROCEDURE, InstrumentSpecification)Pump, vacuum, mechanical, Fisher Scientific, Cat. No. 01-182Rotary Evaporator, with reflux condenser and oil bath, Fisher Scientific, Cat. No. 09-548-224Regulator, gas, for supply of nitrogen gas for derivatization, Fisher Scientific, Cat. No.

15、 10-574NRing stand, with rectangular base, 250- x 230-mm with 890-mm rod, Fisher Scientific, Cat. No. 14-679Stirrer, magnetic bar, 32-mm (1.25-inch), Teflon covered, egg-shaped, Fisher Scientific, Cat. No. 14-511-58AStirrer, motor, magnetic, 50/60 Hz, Fisher Scientific, Cat. No. 11-501-4STemperature

16、 controller, stepless, 120 V, 2 required, Fisher Scientific, Cat. No. 13-931-12Thermometer, mercury, 76-mm immersion, calibrated from -5 to 400C, Fisher Scientific, Cat. No. 15-166C3 of 16935-94Thermometer, mercury, 76-mm immersion, 10/30 standard taper, calibrated from -10 to 360C, FisherScientific

17、 Cat. No. 15-002FTrap, vacuum distillation, borosilicate glass, 50/50 standard taper joints, Fisher Scientific, Cat. No. 11-184-1ETube, NMR sample, reusable, Ultra or Royal Imperial Quality Class, Wilmad Glass, sized appropriatelyfor NMR spectrometer (see PROCEDURE, Instrument Specification)Tubing,

18、 vacuum, rubber, red, Fisher Scientific, Cat. No. 14-173DREAGENTS AND MATERIALSUnless otherwise specified, all reagents shall conform to the specifications established by the Committeeon Analytical Reagents of the American Chemical Society, when such specifications are available.References to catalo

19、g numbers and suppliers are included as a convenience to the method user. Othersuppliers may be used.Acetone, free of alcohols, Fisher Scientific, Cat. No. A929-11Bis(tributyltin) oxide, 96% purity, Aldrich, Cat. No. B5,338-3Chromium(III) acetylacetonate, 97% purity, Aldrich, Cat. No. 20-223-1Chromi

20、um(III) acetylacetonate solution, 0.1-M. Weigh 0.349 g chromium(III) acetylacetonate into a 10-mL volumetric flask. Dilute to volume with C6D6. Mix thoroughly to dissolve.Dry iceGrease, high vacuum, silicone, Fisher Scientific, Cat. No. 14-635-5DNitrogen, gas, 99.9% minimum, 2 ppm H2O, Matheson Gas

21、Products, Extra DryPerdeuterobenzene, benzene-d6, C6D6, 99.6 atom-%, Cambridge Isotope Laboratories, Cat. No. DLM-1Pump oil, vacuum, Fisher Scientific, Cat. No. 01-184-150ATetramethyltin, 99+% purity, Aldrich, Cat. No. 14,647.1Tetramethyltin solution, 0.084-M. Weigh 0.15 g tetramethyltin into a 10-m

22、L volumetric flask containingapproximately 5-mL C6D6. Dilute to volume with C6D6. Mix thoroughly.ThreadToluene, 99.8% minimum purity, Fisher Scientific, Cat. No. T291-44 of 16935-94PROCEDUREHandle all reagents in a fume hood using the appropriate safety equipment.Mercaptan Sulfur AnalysisA 50-g samp

23、le is required for analysis by UOP Method 163 to obtain the thiol-sulfur content (totalmercaptan value) of the sample. This value will be used to determine the amount of TBTO to use inPROCEDURE, Preparation of Sample, and in CALCULATIONS.Preparation of Sample1. Clean the 500-mL round bottom flask wi

24、th acetone, follow with a toluene rinse and dry with nitrogengas. If extensive concentration is anticipated, because one or more of the mercaptan types are below 40 mass-ppm, then it is desirable to concentrate more than 200 g of kerosine at a time. If so, then proportionallymore kerosine, toluene,

25、TBTO and a larger flask and heating mantile should be used during derivatization.2. Add the stir bar to the flask and weigh the flask and bar to the nearest 0.01 g.3. Measure approximately 200 g of sample into the tared 500-mL flask using a graduate cylinder, recordthe volume (1 mL) and weigh to the

26、 nearest 0.01 g.4. Calculate to 4 significant figures the millimols of thiol-sulfur present in the sample portion as follows:-310 G MS=32.06(1)where:G = concentration of thiol-sulfur from Mercaptan Sulfur Analysis, mass-ppmM = mass of sample, gS = millimols of thiol-sulfur32.06 = grams of sulfur/mol

27、10-3= factor required to convert from mass-ppm to millimols5. Calculate to the nearest 0.01 g the quantity of TBTO required as follows:T = 1.191 S (2)where:S = previously defined (Eq. 1)T = quantity of TBTO required, g1.191 = factor to convert millimols of thiol-sulfur to grams of TBTO required with

28、 a four-foldmolar excess (2 x 0.59538 g of tin compound per millimol)5 of 16935-946. Add the quantity of TBTO determined in Step 5 to the 500-mL flask, weighing the reagent to thenearest 0.01 g.7. Add 201 g of toluene to the 500-mL flask.8. Cap and swirl the flask to mix the contents.9. Place the 50

29、0-mL flask in a spherical heating mantle, turn on the nitrogen flow and purge thecondenser and the 500-mL flask with nitrogen (see Fig. 1).10. Complete the assembly of the apparatus as indicated in Fig. 1, after purging the apparatus withnitrogen and lubricating the standard taper joints with vacuum

30、 grease. The nitrogen atmosphere in the apparatus should be maintained during the derivatization by continuing thenitrogen flow to prevent air oxidation of mercaptans.11. Clamp the apparatus securely to the ring stand and place the stirring motor under the derivatizationflask.Derivatization of Sampl

31、e1. Turn on the water to the condenser.2. Wrap heating tape around the distillation head (see Fig. 1), plug the tape into a temperature controller,turn on and adjust to maintain the distillation head at a temperature between 170 to 180C. The temperature of the distillation head is set using the stan

32、dard taper immersion thermometer.3. Plug the heating mantle into another temperature controller.4. Turn on the heating mantle temperature controller and adjust to maintain the distillation flaskthermometer temperature at 170 to 180C and hold that temperature for 30 minutes, collecting andmeasuring t

33、he mass (0.01 g) and volume (1 mL) of any distillate produced. The distillation temperature of kerosines vary, depending on the sample. If initial boiling temperatureslower than 170 to 180 C are observed, distill the sample until the boiling point of the sample is in thetarget range and hold for 30

34、minutes. If the initial boiling temperature is higher than 180C, maintain 170 to180C for 30 minutes to complete the derivatization without distillation of the kerosine.5. Turn the temperature controller switches off, remove the heating mantle from the flask and permit theflask to cool to room temper

35、ature, while continuing the nitrogen flow (Fig. 1). If the minimum concentration of each of the mercaptan types is greater than 40 mass-ppm, skip SampleConcentration steps and proceed as indicated in 119Sn NMR Analysis. If the minimum concentration of each of the mercaptan types is unknown, estimate

36、 the approximateconcentration of the mercaptan types by proceeding immediately as indicated in 119Sn NMR Analysis andthen repeat the analysis, concentrating the sample, if appropriate. If concentration is required, estimate the volume of kerosine that must be removed to attain the neededconcentratio

37、n from the volume and mass of overhead collected and the original volume and mass of thesample. Since the organo-sulfur-tributyltin compounds are not volatile, the degree of concentration can bedetermined from the mass of the kerosine bottoms in the derivatization flask and the initial charge.6 of 1

38、6935-946. Transfer the sample to an appropriately sized nitrogen purged glass bottle and seal with a polysealscrew cap. If desired, the derivatization flask used above may also be used for the vacuum distillation after removal ofthe thermometer and the stir bar. If this is to be done, then this step

39、 should be skipped. If desired, the sample may be stored indefinitely at room temperature under nitrogen until the NMRanalysis is performed. Traces of precipitates or haze may be observed in some samples, particularly concentrated samples, dueto the presence of heavy hydrocarbons. Therefore, the sam

40、ple should be mixed well before transferring tothe glass bottle to ensure representative sampling.Sample Concentration1. Mark the receiver flask at the liquid level of distillate to be removed, place the sample in the vacuumdistillation flask and assemble the rotary evaporator as indicated in Fig. 2

41、 and according to themanufacturers instructions. Any convenient marker may be used to calibrate the receiver, and the calibration need only be accurate towithin several mL. If desired, the derivatization flask used in Derivatization of Sample may be used for the vacuum distillationafter removal of t

42、he thermometer and the stir bar.2. Turn on the rotary evaporator, adjust the rotation speed, establish a vacuum and heat the vacuumdistillation flask to distill sufficient kerosine from the sample, using either the heating mantle or theoil bath that is part of the rotary evaporator equipment. If ext

43、ensive concentration is required, it is desirable to concentrate more than 200 g of kerosine at a time.In that case, proportionately more kerosine, toluene, TBTO and a larger flask and heating mantle shouldbe used during Derivatization of Sample and an appropriately larger flask should be used here.

44、3. Turn off and remove either the heating mantle or the oil bath once the required concentration has beencompleted and permit the flask to cool to room temperature.4. Remove the flask from the rotary evaporator. If desired, the sample may be transferred to an appropriately sized bottle, capped, purg

45、ed with nitrogenand stored indefinitely at room temperature under nitrogen until the NMR analysis is performed. Traces of precipitates or haze may be observed in some samples, particularly concentrated samples, dueto the presence of heavy hydrocarbons. The hydrocarbon heavies do not affect the analy

46、sis.Instrument SpecificationThe NMR spectrometer must be capable of performing time-averaged fourier transform (FT), protondecoupled, refocused INEPT analysis of 119Sn. The NMR must be sensitive enough to detect primary,secondary and tertiary mercaptan types that have been reacted with TBTO at 40 ma

47、ss-ppm per mercaptantype. Sample volume versus magnetic field considerations make it impractical to consider magnetic fieldsbelow 4.7 Tesla when attempting to achieve the indicated sensitivities. Table 1 shows signal-to-noisemeasurements that were obtained on two spectrometers that had sufficient se

48、nsitivity to perform thisanalysis. In addition, spectrometers equipped with autosamplers are suggested as a means of more efficientoperation.7 of 16935-94Table 1119Sn INEPT Sensitivity (TBTO)Instrument Bruker CXP-200 Bruker ACP-300Signal/Noise 333:1 450:1TBTO Concentration, mass-% 22.4 22.4Pulse Wid

49、th 90 90Sweep Width, ppm 129 125Line Broadening, Hz 4* 1Number of Data Points 8k 8kZero Filled 16k 16kPulse Program INEPT INEPTMagnetic Field Strength, Tesla 4.7 7.05Number of Scans 1 1Sample Tube Diameter, mm 20 10_* Natural Line WidthThe pulse sequence for the INEPT data acquisition is shown below. The pulse program for a BrukerCXP-200 equipped with an ASPECT 3000 computer as well as the automation program for a Bruker ACP-300 equipped with an ASPECT 3000 computer and a B-ACS 60 autosampler is included in the APPENDIX.1H: P90(1H) - 1/4J