Energy & Fuels 2008, 22, 2419–2421
2419
Isolation and Identification of Fatty Acid Amides from Shengli Coal Ming-Jie Ding,†,‡ Zhi-Min Zong,† Ying Zong,† Xiao-Dong Ou-Yang,† Yao-Guo Huang,† Lei Zhou,† Feng Wang,† Jiang-Pei Cao,† and Xian-Yong Wei*,†,§ School of Chemical Engineering, China UniVersity of Mining and Technology, Xuzhou 221008, Jiangsu, China, Department of Light Industry, Luohe Vocational Technology College, Luohe 462002, Henan, China, Key Laboratory of Coal ConVersion and New Carbon Materials, Hubei ProVince, Wuhan UniVersity of Science and Technology, Wuhan 430081, Hubei, China ReceiVed August 18, 2007. ReVised Manuscript ReceiVed March 24, 2008
Shengli coal, a Chinese brown coal, was extracted with carbon disulfide and the extract was gradiently eluted with n-hexane and ethyl acetate (EA)/n-hexane mixed solvents with different concentrations of EA in a silica gel-filled column. A series of fatty acid amides, including fourteen alkanaimdes (C15-C28) and three alkenamides (C18 and C22), were isolated from the coal by this method and analyzed with a gas chromatography/ mass spectrometry.
Introduction Molecular characterization of organic nitrogen species (ONSs) in coals is of considerable significance, since almost all the nitrogen species exist in organic matter of coals and are converted to NOx and N2O during combustion, causing severe environmental pollution, including acid rain, photochemical smog, the greenhouse effect, and ozone layer depletion.1–4 Inseparable techniques, such as 15N NMR,5 X-ray photoelectron spectroscopy,6 and X-ray adsorption near-edge structure spectroscopy, 7 are usually used to provide insight into the structure of ONSs in coals. However, using such methods, one cannot obtain information on molecular composition of ONSs in coals because of the complexity of ONSs in molecular composition and very low concentration of ONSs in coals. ONSs in coals have been reported to be pyridinic, amino, nitrile, pyrrolic, pyridonic, pyrrolidonic, quaternary, and N-oxide types4 according to investigations by inseparable techniques, but such results are far from determination of molecular composition of ONSs in coals. In addition, other types of nitrogen, such as amides, in coals have rarely been identified. The extraction of coals8–14 and their reaction mixtures8,13,14 with a carbon disulfide (CS2)/N-methyl-2-pyrrolidinone (NMP) * Corresponding author. E-mail:
[email protected]. † China University of Mining and Technology. ‡ Luohe Vocational Technology College. § Wuhan University of Science and Technology. (1) Kambara, S.; Takarada, T.; Toyoshima, M.; Kato, K. Fuel 1995, 74 (9), 1247–1253. (2) Ohshima, Y.; Wang, Y.; Tsubouchi, N.; Ohtsuka, Y. Prepr. Pap.sAm. Chem. Soc., DiV. Fuel Chem. 2000, 45, 335. (3) Tomita, A. Fuel Process. Technol. 2001, 71 (1-3), 53–70. (4) Stan´czyk, K. Energy Fuels 2004, 18 (2), 405–409. (5) Solum, M. S.; Pugmire, R. J.; Grant, D. M.; Kelemen, S. R.; Gorbaty, M. L.; Wind, R. A. Energy Fuels 1997, 11 (2), 491–494. (6) Kelemen, S. R.; Gorbaty, M. L.; Kwiatek, P. J. Energy Fuels 1994, 8 (4), 896–906. (7) Mitra-Kirtley, S.; Mullins, O. C.; van Elp, J.; Cramer, S. P. Fuel 1993, 72 (1), 133–135. (8) Wei, X. Y.; Shen, J. L.; Takanohashi, T.; Iino, M. Energy Fuels 1989, 3 (5), 575–579. (9) Qin, Z. H.; Zong, Z. M.; Liu, J. Z.; Ma, H. M.; Yang, M. J.; Wei, X. Y. J. Fuel Chem. Technol. 1997, 25 (6), 549–553. (10) Qin, Z. H.; Yuan, X. H.; Zong, Z. M.; Wang, C.; Yu, B.; Wei, X. Y. J. Fuel Chem. Technol. 1998, 26 (3), 275–279.
mixed solvent (1:1 by volume) have been extensively investigated since Iino et al. reported their finding that CS2 has a significant synergic effect with NMP on coal extraction.15 The results of thermal reaction of CS2 with NMP suggest that strong π-π interaction between CS2 and NMP could be responsible for the significant synergic effect.16 A subsequent investigation shows that similar reaction of CS2 with a series of amides can also proceed, implying the presence of strong π-π interaction between CS2 and the amides,17 and such a π-π interaction could be a tool to understand the composition of amides in coals. The possiblity was first confirmed by our group in a recent report:18 a fatty acid amide (FAA), i.e., tetradecanamide, was detected in CS2-extractable fraction of inertinite-rich samples from two Chinese bituminous coals with a gas chromatography/mass spectrometry (GC/MS). These results propmt us to find other aimdes from other coals. In the present study, Shengli coal, a Chinese bituminous coal, was extracted with CS2 and the extract was subject to further separation using column chromatography to concentrate FAAs possibly present in the coal. Experimental Section Coal Sample and Solvents. The coal sample was collected from Shengli coal field in Inner Mongolia, China. It was pulverized to pass through a 200-mesh sieve (
