Energy & Fuels 1991,5, 786-791
786
coal tar maltenes and their aromatic fractions based on the direct integration of FT-IR spectra. For the fractions of phenolic compounds, the determination of new integral absorptivities based on a much larger set of samples than in the present work is needed. Conclusions From the results discussed in this work following conclusions can be drawn: 1. The combination of extrography and complexation chromatography provides well-separated compound classes of coal tar. Fractions of saturates, aromatics, and polars were developed from four coal tar maltenes. 2. The quantitative evaluation of FT-IR spectra was performed on the base of the determination of the integral
absorptivities for aliphatic and aromatic hydrogen. The aliphatic integral absorptivities rapidly drop from saturates to polars, i.e., with increasing polarity of molecules, as the absorptivities depend simultaneously on the structure of aliphatic moieties and on the dipole moments of aliphatic C-H bonds. 3. On comparing the quantitative evaluation of FT-IR and lH NMR spectra, very good agreement was obtained for maltenes and their aromatic fractions by using Solomon's integral absorptivities. However, they were not suitable for the analysis of polar fractions when the direct integration of spectral peaks was used. Acknowledgment. The author thanks J. Buchtele for providing the coal tars, and I. Lang and H. Pavlikovi for NMR measurements.
Moisture Determination of Argonne Premium Coal Extracts by 31PNMR Spectroscopy A. E. Wroblewski,t K. Reinartz, and J. G. Verkade* Department of Chemistry and Ames Laboratory, Iowa State University, Ames, Iowa 5001 1-31 11 Received May 10, 1991. Revised Manuscript Received August 30, 1991
A method for the determination of moisture in coals by derivatizing pyridine-extracted moisture with a 31PNMR tagging agent has been developed. Candidate derivatizing reagents which formed anhydride products (R2POPRz)possessing 31Pchemical shifts that did not overlap with derivatized I phenols and carboxylic acids in the coal extract included CIPOCHzCHzO(l),ClPOCMe2CMe20(2), CIPSCHzCHzS (3), CIPPhz (9), and C1(0)PPhz (5). Because of interesting but bothersome side reactions encountered with 1-3 and 9, reagent 5 was finally selected as the reagent of choice for determining moisture contents in six Argonne Premium Coals. Advantages of reagent 5 include its clean and instantaneous reaction under very mild conditions to form Ph2(0)POP(0)Ph2(7) which contains two 31Pnuclei for NMR integration for each molecule of water reacted.
.
b
b
1
i
Introduction The determination of moisture in coals has long been an active field of investigation, since water content is one of the most important factors determining the quality and utility of coals. Drying coals at temperatures of 105-110 "C, as for example in the ASTM D3302 method,' is a generally accepted method for moisture determination. A problem with this type of method is that different coals show varying sensitivities to thermal decomposition. In low-rank coals, decomposition already begins well below 100 "C." The possibility of coal oxidation, especially with low-rank coals, is another disadvantage of oven-drying because the process is usually carried out in air.2 Finally, it has been shown that low-rank coals retain water even after drying at 100 0C.6,6 The advantages of oven-drying methods are that they are easily performed (since no sophisticated equipment is necessary), they are fast, and they are quite reproducible. Other methods for moisture determination have also been elaborated. The one most widely employed is the azeotropic distillation with an immiscible organic solvent 'On leave of absence from Technical University, Lodz, Poland.
such as toluene or xylene. This approach works especially well with high-moisture-content coals,' although it can be used for coals with any water content. If a relatively high boiling solvent such as xylene is used as a solvent, however, higher moisture contents are usually estimated owing to thermal decomposition of the coal.8 The Karl Fischer titration method does not appear to have any significant advantages over drying.2 Several new methods for moisture determination have been described recently which rely on '80 isotope dilution? microwave absorptionlOJ1and transmission," IR spec(1) I988 Annual Book of ASTM Standards; 1988,Vol. 05.05,D3302, pp 331-337.
(2)Allardice, D. J.; Evans, D. G. Anal. Meth. Coal Coal Prod. 1978, 1, 247.
(3)Allardice, D. J.; Evans, D. G . Fuel 1971,50,219. (4)Swann, P.D.; Harris, J. A.; Sieman, S.R.; Evans, D. G. Fuel 1973, 52,154. (5)Hippo, E. J.; Neavel, R. C.; Smith, S. E.; Lang, R. J.; Miller, R. N. Prepr. Pap.-Am. Chem. SOC., Diu. Fuel Chem. 1987,32,179. (6) Schafer, H. N. S.Fuel 1980,59,295. (7) B.ainbridge, J. R.; Scanlan, P. G.; Belyea, I. Fuel 1949,28, 88. (8)Simek, B. G.; Ludmilla, J. Fuel 1947,26,132. (9)(a) Olsen, E. S.;Diehl, J. W. Prepr. Pap.-Am. Chem. SOC., Diu. Fuel Chem. 1988,33,415.(b)Finseth,D. Prepr. Pap.-Am. Chem. SOC., Diu. Fuel Chem. 1987,32,260. (10)De, K.S.Fuel 1988,67,1020.
0887-0624/ 91/2505-0786$02.50/ 0 0 1991 American Chemical Society
Energy & Fuels, Vol. 5, No. 6,1991 787
Moisture Determination of Coal Extracts
Table I. Argonne Premium Coal Samples Analyzed with Reagent 5 -100 mesh -20 mesh coal identificn no. sealing date identificn no. sealing date North Dakota Beulah-Zap Seam Illinois No. 6 Blind Canyon Seam Pittsburgh No. 8 Pennsylvania Upper Freeport Pocahontas No. 3
lignite -
801
01410
13/04/87
801
00300
2/13/81
high-volatile bituminous high-volatile bituminous bituminous medium volatile bituminous low-voltaile, bituminous
301 601 401 101
02476 00977 01459 00981
5/12/86 10/13/86 4/29/86 1/31/85
301 601 401 101
00572 00284 00356 02365
4/18/86 10/23/86 4/22/86 1/31/85
501
01117
7/08/86
500
00297
6/23/86
troscopy,l2y-ray ba~kscattering,'~ and heating by microwave energy with continuous weighing.14 Except for the '80 dilution technique, these approaches are designed as rapid commercial methods to monitor moisture contents with reasonable accuracy. Although l80isotope dilution is time consuming, it allows the determination of the total exchangeable oxygen content. Although NMR spectroscopy has become an important tool in the study of coal s t r u c t ~ r ethere , ~ ~ have been few published reports that employ this technique for moisture determination. These techniques primarily involve solidstate NMR studies of relaxation times,ls-lgalthough lowresolution NMR has also been used.20 We have recently utilized high-resolution 31P NMR spectroscopy for the quantitativez1 and qualitativezz~z3 analysis of phenols in coal-derived materials after derivatization with reagents based on the 2-chloro-1,3,2-diheterophospholanes structure, namely, compounds 1, 2, and 3. In the course of these studies we always observed C'-PC0-J 0
cl-p?*;; 0
CP -I]; CH3
1
3
2
the formation of a 31PNMR signal that could be assigned to respective anhydrides depicted as 4 in reaction 1. We 2(1,2,3) + H20
-
R--,x:P r-O-P
