Energy & Fuels 1993, 7, 222-226
222
Determination of Total Phenol Concentrations in Coal Liquefaction Resids by 31PNMR Spectroscopy T. Mohan and J. G. Verkade* Department of Chemistry and Ames Laboratory, Iowa State University, Ames, Iowa 50011 Received September 15, 1992. Revised Manuscript Received December 2, 1992
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Fifteen coal liquefaction resids are quantitatively analyzed for phenolics and moisture using the NMR tagging agent ClPOCMe2CMe20. Despite the presence of organic free radicals in these resids, which contributed to the breadth of the derivatized phenolic 31Presonances,excellent agreement with the phenolic contents obtained by FTIR spectroscopy was achieved. The best results were obtained by processing the 31PNMR spectra with an NMRl matched filter apodization program. 3lP
Introduction Coal liquefaction processes require monitoring of process performance. One approach to accomplishing this goal is to selectively quantitate a chemical component such as phenolic OH. With the use of FTIR spectroscopy, the phenolic OH contents in a wide range of coal liquefaction samples were quantitatively assessed by employing THF as a so1vent.laPb Comparison of the FTIR results with those from similar studies using a 19FNMR tagging reagent2 revealed that there was good agreement for many samples but substantial disagreement in samples containing high phenolic contents (ca. 2.0mequiv/g).ld On the other hand, quantitations of phenolic OH contents in a series of H-coal distillates and vacuum bottoms by three NMR tagging techniques P F , 29Si, and 31P)compared fa~orably.~ In that study, Cl(O)PPh2 was concluded to be the reagent of choice because of the stability of its phenolic derivatives (compared with the instability over time of the corresponding derivatives of F3CC(O)C1)and the 100% natural abundance of 31Pcompared with 29Si(4.70 ?4 1. In previous publication^^-^ we have described a variety of NMR spectroscopic tagging reagents for the speciation and quantitation of compounds containing labile hydrogen functional groups, and in particular the potential usefulness of reagents 15!639 and 27-9 in the determination of phenols. Herein, we apply reagent 1 to the determination of the total phenol content in a series of 15 coal liquefaction (1)(a) Robbins, G. A.; Winschel, R. A.; Burke,F. P. Prepr. Pap.-Am. Chem. Soc.,Diu. Fuel Chem. 1985,30,155. (b) Winschel, R. A.; Robbins, G.A,; Burke, F. P. Technical Progress Report, July-Sept. 1985,DOEiPC 70018-13,December, 1985. (c) Burke, F. P.; Winschel, R. A. Technical Report, Oct. 1, 1983-Mar. 31, 1984, DOE Contract No. DE-AC2280PC30027, March, 1985. (d) Robbins, G. A., private communication. (2) (a) Winschel, R. A.; Burke, F. P. "Recycle Slurry Oil Characterization Report: 1011182-3/31/83"; Doe Contract No. DE-AC22-80PC30027, February, 1984. (b) Winschel, R. A. and Burke, F. P. "Recycle Slurry Oil Characterization-SecondAnnual Report"; DOE Contract No. DE-AC2280-PC30027, August, 1983. (3) Dadey, E. J.; Smith, S. L.; Davis, B. H. Energy Fuels 1988,2,326. (4) Schiff, D. E.; Verkade, J. G.; Metzler, R. M.;Squires, T. G.; Venier, C . G. Appl. Spectrosc. 1986, 40, 348. (5) Wroblewski, A. E.; Markuszweski, R.; Verkade, J. G. Prep?. Pap-Am. Chem. Soc., Diu. Fuel Chem. 1987, 32, 302. (6) Wroblewski, A. E.; Lensink, C.; Markuszweski, R.; Verkade, J. G. Energy Fuels, 1988, 2, 765. (7) Lensink, C.; Verkade, J. G. Prepr. Pap.-Am. Chem. Soc., Diu. Fuel Chem. 1988, 33, 906. (8) Lensink, C.; Verkade, J. G. Energy Fuels, 1990,4, 197. (9) Wroblewski, A. E.; Lensink, C.; Verkade, J. G. Energy Fuels 1991, 5, 491.
resids and we compare our results with those obtained for the same samples by FTIR spectroscopy.laSb The FTIR method was chosen as the standard of reference because of its high precision (kO.09 mequiv/g) and low average error (fO.l mequiv/gIb),coupled with the observation that the 19F NMR method is not suitable for coal resids.lcIza We also demonstrate the usefulness of reagent 1 in determining the moisture contents of these liquefaction resids. In the reaction associated with this analysis, the reagent 1 derivatizes water to form the anhydride of 1, namely 3.9 Although 2 provides more than twice the 31P NMR dispersion for phenol^,^-^ reagent 1 was chosen for this study because the peaks were too severely broadened by paramagnetic impurities for reagent 2 to be very useful. Me
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