X-ray photoelectron spectroscopy (XPS) was used to investigate changes in nitrogen functionalities present in Chinese Huadian (HD), Maoming (MM) and Yaojie (YJ) oil shales during pyrolysis. Throughout the process (T ≤ 600 °C), most of the nitrogen contained in raw oil shale samples was retained in their semi-cokes. Five peaks of nitrogen functionalities (N 1s) appeared in the XPS spectra of raw HD, MM and YJ oil shale samples and their semi-cokes: N-6 (pyridine), N-A (amino), N-5 (pyridone), N-Q (quaternary nitrogen) and N-X1 (pyridine N-oxide). To obtain an acceptable fit, an additional peak at 404 (±0.5) eV (N-X2) was required in the N 1s spectra of the samples. N-5 could either represent pyridone or a mixture of pyridone and pyrrolic nitrogen forms, the most abundant ones in all samples. At a relatively low temperature (300 °C) the desorption reaction occurred and the amount of chemisorbed oxygen associated nitrogen (N-X2) decreased significantly. As the pyrolysis temperature increased from 300 to 500 °C, pyridine N-oxide was converted to pyridone, and, simultaneously, the latter was converted to pyridine and pyridine structures associated with oxygen – quaternary nitrogen. In the semi-cokes of Huadian and Maoming oil shale samples at 600 °C, most of the pyridone was converted into pyridine and quaternary nitrogen. At this temperature, especially the condensation reaction of pyridine into quaternary nitrogen occurred in the semi-coke of Yaojie oil shale sample, while quaternary nitrogen represented the nitrogen atoms in the interior of precursors of the graphene layers.
1. Qian, J. L., Wang, J. Q., Li, S. Y. World’s oil shale available retorting technologies and the forecast of shale oil production. In: Proceedings of the 18th International Offshore and Polar Engineering Conference, Vancouver, British Columbia, Canada, July 6–11, 2008, I, 19–20.
2. Bunger, J. W., Crawford, P. M., Johnson, H. R. Hussert revisited – 5: Is oil shale America's answer to peak-oil challenge. Oil Gas. J., 2004, 102(30), 16–24.
3. Barkia, H., Belkbir, L., Jayaweera, S. A. A. Thermal analysis studies of oil shale residual carbon. J. Therm. Anal. Calorim., 2004, 76(2), 615–622.
https://doi.org/10.1023/B:JTAN.0000028040.16844.40
4. Sklarew, D. S., Hayes, D. J. Trace nitrogen-containing species in the offgas from two oil shale retorting processes. Environ. Sci. Technol., 1984, 18(8), 600–603.
https://doi.org/10.1021/es00126a006
5. Mushrush, G. W., Beal, E. J., Hardy, D. R., Hughes, J. M. Nitrogen compound distribution in middle distillate fuels derived from petroleum, oil shale, and tar sand sources. Fuel Process. Technol., 1999, 61(3), 197–210.
https://doi.org/10.1016/S0378-3820(99)00056-9
6. Jiang, X. M., Yang, L. J., Yan, C., Hang, X. X., Yang, H. L. Experimental investigation of SO2 and NOx emissions from Huadian oil shale during circulating fluidized-bed combustion. Oil Shale, 2004, 21(3), 249–257.
7. Akash, B. A., Jaber, J. O. Characterization of shale oil as compared to crude oil and some refined petroleum products. Energ. Source., 2003, 25(12), 1171–1182.
https://doi.org/10.1080/00908310390233612
8. Bai, J. R., Xu, W., Pan, S., Zhang, B. X. Oil shale retorting process characteristic orthogonal carbon analysis. J. Northeast Dianli Univ., 2015, 35(5), 46–50 (in Chinese).
9. Pels, J. R., Wójtowicz, M. A., Moulijn, J. A. Rank dependence of N2O emission in fluidized-bed combustion of coal. Fuel, 1993, 72(3), 373–379.
https://doi.org/10.1016/0016-2361(93)90056-8
10. Kelemen, S. R., Gorbaty, M. L., Kwiatek, P. J. Quantification of nitrogen forms in Argonne premium coals. Energ. Fuel., 1994, 8(4), 896–906.
https://doi.org/10.1021/ef00046a013
11. Kelemen, S. R., Afeworki, M., Gorbaty, M. L., Kwiatek, P. J., Solum, M. S., Hu, J. Z., Pugmire, R. J. XPS and 15N NMR study of nitrogen forms in carbonaceous solids. Energ. Fuel., 2002, 16(6), 1507–1515.
https://doi.org/10.1021/ef0200828
12. Kelemen, S. R., Freund, H., Gorbaty, M. L., Kwiatek, P. J. Thermal chemistry of nitrogen in kerogen and low-rank coal. Energ. Fuel., 1999, 13(2), 529–538.
https://doi.org/10.1021/ef9802126
13. Liu, Y. H., Che, D. F., Li, Y. T., Hui, S. E., Xu, T. M. X-ray photoelectron spectroscopy determination of the forms of nitrogen in Tongchuan coal and its chars. J. Xi’an Jiaotong Univ., 2001, 35(7), 661–665 (in Chinese).
14. Mullins, O. C., Mitra-Kirtley, S., Van Elp, J., Cramer, S. P. Molecular structure of nitrogen in coal from XANES spectroscopy. Appl. Spectrosc., 1993, 47(8), 1268–1275.
https://doi.org/10.1366/0003702934067991
15. Mitra-Kirtley, S., Mullins, O. C., van Elp, J., George, S. J., Chen, J., Cramer, S. P. Determination of the nitrogen chemical structures in petroleum asphaltenes using XANES spectroscopy. J. Am. Chem. Soc., 1993, 115(1), 252–258.
https://doi.org/10.1021/ja00054a036
16. Mitra-Kirtley, S., Mullins, O. C., van Elp, J., Cramer, S. P. Nitrogen chemical structure in petroleum asphaltene and coal by X-ray absorption spectroscopy. Fuel, 1993, 72(1), 133–135.
https://doi.org/10.1016/0016-2361(93)90388-I
17. Kelemen, S. R., Gorbaty, M. L., Kwiatek, P. J., Fletcher, T. H., Watt, M., Solum, M. S., Pugmire, R. J. Nitrogen transformations in coal during pyrolysis. Energ. Fuel., 1998, 12(1), 159–173.
https://doi.org/10.1021/ef9701246
18. Stańczyk, K., Dziembaj, R., Piwowarska, Z., Witkowski, S. Transformation of nitrogen structures in carbonization of model compounds determined by XPS. Carbon, 1995, 33(10), 1383–1392.
https://doi.org/10.1016/0008-6223(95)00084-Q
19. Pels, J. R., Kapteijn, F., Moulijn, J. A., Zhu, Q., Thomas, K. M. Evolution of nitrogen functionalities in carbonaceous materials during pyrolysis. Carbon, 1995, 33(11), 1641–1653.
https://doi.org/10.1016/0008-6223(95)00154-6
20. Wang, Q., Xu, X. C., Chi, M. S., Zhang, H. X., Cui, D., Bai, J. R. FT-IR study on composition of oil shale kerogen and its pyrolysis oil generation characteristics. J. Fuel Chem. Technol., 2015, 43(10), 1158–1166 (in Chinese).
21. Heistand, R. N. The Fischer Assay: Standard for the oil shale industry. Energ. Source., 1976, 2(4), 397–405.
https://doi.org/10.1080/00908317608945962
22. Kelemen, S. R., Afeworki, M., Gorbaty, M. L., Sansone, M., Kwiatek, P. J., Walters, C. C., Freund, H., Siskin, M., Bence, A. E., Curry, D. J., Solum, M., Pugmire, R. J., Vandenbroucke, M., Leblond, M., Behar, F. Direct characterization of kerogen by X-ray and solid-state 13C nuclear magnetic resonance methods. Energ. Fuel., 2007, 21(3), 1548–1561.
https://doi.org/10.1021/ef060321h
23. Pietrzak, R., Wachowska, H. The influence of oxidation with HNO3 on the surface composition of high-sulphur coals: XPS study. Fuel Process. Technol., 2006, 87(11), 1021–1029.
https://doi.org/10.1016/j.fuproc.2006.08.001
24. Buckley, A. N. Nitrogen functionality in coals and coal-tar pitch determined by X-ray photoelectron spectroscopy. Fuel Process. Technol., 1994, 38(3), 165–179.
https://doi.org/10.1016/0378-3820(94)90046-9
25. Liao, H. Q., Li, B. Q., Zhang, B. J. Desulfurization and denitrogenation in copyrolysis of coal with hydrogen-rich gases. J. Fuel Chem. Technol., 1999, 27(3), 268–272 (in Chinese).
26. Wang, Q., Sun, B. Z., Hu, A. J., Bai, J. R., Li, S. H. Pyrolysis characteristics of Huadian oil shales. Oil Shale, 2007, 24(2), 147–157.
27. Williams, P. T., Ahmad, N. Influence of process conditions on the pyrolysis of Pakistani oil shales. Fuel, 1999, 78(6), 653–662.
https://doi.org/10.1016/S0016-2361(98)00190-2
28. Jaber, J. O., Probert, S. D. Non-isothermal thermogravimetry and decomposition kinetics of two Jordanian oil shales under different processing conditions. Fuel Process. Technol., 2000, 63(1), 57–70.
https://doi.org/10.1016/S0378-3820(99)00064-8
29. Qin, K. Z., Guo, S. H. The structure research of Fu Shun and Mao Ming oil shale. 4. The content and composition of minerals. J. Fuel Chem. Technol., 1987, 15(1), 1–8 (in Chinese).
30. Baughman, G. L. Synthetic Fuels Data Handbook, 2nd edition. Cameron Engineers Inc, Denver, USA, 1978.
31. Gong, B., Buckley, A. N., Lamb, R. N., Nelson, P. F. XPS determination of the forms of nitrogen in coal pyrolysis chars. Surf. Interface Anal., 1999, 28(1), 126–130.
https://doi.org/10.1002/(SICI)1096-9918(199908)28:1<126::AID-SIA633>3.0.CO;2-V
