1. Department of Safety Engineering, Heilongjiang University of Science and Technology, Harbin 150022, China 2. National Central Laboratory of Hydrocarbon Gas Transportation Pipeline Safety, Harbin 150022, China 3. School of Architecture and Civil Engineering，Heilongjiang University of Science and Technology, Harbin 150022, China
Abstract：CH4/C2H6/N2 mixed hydrate formation experiments were performed at 2 ℃ and 5 MPa for three different mine gas concentrations (CH4/C2H6/N2，G1=54∶36∶10，G2=67.5∶22.5∶10，G3=81∶9∶10). Raman spectra for hydration products were obtained by using Microscopic Raman Spectrometer. Hydrate structure is determined by the Raman shift of symmetric C—C stretching vibration mode of C2H6 in the hydrate phase. This work is focused on the cage occupancies and hydration numbers, calculated by the fitting methods of Raman peaks. The results show that structure Ⅰ (sⅠ) hydrate forms in the G1 and G2 gas systems, while structure Ⅱ (sⅡ) hydrate forms in the G3 gas system, concentration variation of C2H6 in the gas samples leads to a change in hydrate structure from sⅠ to sⅡ; the percentages of CH4 and C2H6 in sⅠ hydrate phase are less affected by the concentration of gas samples, the percentages of CH4 are respectively 34.4% and 35.7%, C2H6 are respectively 64.6% and 63.9% for gas systems of G1 and G2, the percentages of CH4 and C2H6 are respectively 73.5% and 22.8% for gas systems of G3, the proportions of object molecules largely depend on the hydrate structure; CH4 and C2H6 molecules occupy 98%, 98% and 92% of the large cages and CH4 molecules occupy 80%, 60% and 84% of the small cages for gas systems of G1, G2 and G3, respectively; additionally, N2 molecules occupy less than 5% of the small cages is due to its weak adsorption ability and the lower partial pressure.
Key words：Gas hydrate;Raman spectroscopy;Cage occupancies;Hydration number
[1] Zhang B Y, Pan C H, Wu Q. Disaster Advances, 2013, 6: 177. [2] LI Dong-liang, DU Jian-wei, HE Song(李栋梁, 杜建伟, 何 松). Scientia Sinica Chimica(中国科学: 化学), 2012, 42(6): 878. [3] Lu H L, Wang J W, Liu C L. Journal of the American Chemical Society，2012, 134: 9160. [4] Grim R G, Kerkar P B, Shebowich M. Journal of Physical Chemistry C，2012, 116: 18557. [5] Cao X X, Su Y, Liu Y. Journal of Physical Chemistry A. 2014, 118: 215. [6] Subramanian S, Kini R A, Dec S F. Chemical Engineering Science, 2000, 55: 1981. [7] Sugahara T, Kobayashi Y, Tani A. Journal of Physical Chemistry A，2012, 116: 2405. [8] Murshed M M, Kuhs W F. Journal of Physical Chemistry B，2009, 113: 5172. [9] MENG Qing-guo, LIU Chang-ling, YE Yu-guang(孟庆国, 刘昌岭, 业渝光). Chinese Journal of Analytical Chemistry(分析化学), 2011, 39(9): 1447. [10] Lee H H, Ahn S H. Environmental Science & Technology，2012, 46: 4184. [11] Qin J F, Kuhs W F. Journal of Chemical & Engineering Data，2014. [12] Sum A K, Burruss R C. Journal of Physical Chemistry B，1997, 101: 7371. [13] Dharmawardhana P B, Parrish W R, Sloan E D. Industrial and Engineering Chemistry Research Fundamentals，1980, 19(4): 410.
