[MIS16-P01] N2、O2およびArハイドレートの解離熱測定
キーワード：ガスハイドレート、解離熱、水和数、熱量測定
Gas hydrates are crystalline clathrate compounds composed of gas and water molecules, and stable under low temperature and high pressure conditions. Dissociation heats (enthalpies) of gas hydrates have been obtained from their phase diagrams using the Clapeyron equation; however, the application has also been difficult due to low quality of the phase data. Dissociation heat of N2 hydrate was reported by Kang et al. (2001), but the value is thought to be overestimated because it is larger than that of methane hydrate. Dissociation heat of O2 and Ar hydrates have not reported yet. In this study, we applied calorimetric technique to determine their dissociation heat.
The samples of gas hydrates were synthesized from fine ice powder and guest gases at 273.2 K and the pressure condition of 20MPa (N2) and 16MPa (O2 and Ar). The ice powder started to melt and formed these gas hydrates. Approximately 1 g of each hydrate sample was set in a pressure cell specially designed for a Tian-Calvet type heat-flow calorimeter, and its dissociation monitored. The experimental setup and technique were the same as the one that was used previously by Hachikubo et al. (2009; 2012).
Dissociation heats of N2, O2, and Ar hydrates from hydrate to gas and ice are 12.8±0.2 [kJ mol-1], 12.6±0.1[kJ mol-1], and 13.2±0.1[kJ mol-1], respectively. Yoon et al. (2003) reported that dissociation heats of N2 and O2 hydrates are 12.18 [kJ mol-1] and 11.52 [kJ mol-1], respectively, using the Clausius-Clapeyron equation. Therefore, our data are several percent smaller than the previous report.
References
Kang S-P, Lee H (2001) Enthalpies of dissociation of clathrate hydrates of carbon dioxide, nitrogen, (carbon dioxide + nitrogen), and (carbon dioxide + nitrogen + tetrahydrofuran). J Chem Thermodyn 33: 513-521.
Hachikubo A, Kida M, Okuda M, Sakagami H, Shoji H (2009) Dissociation heat of mixed-gas hydrate composed of methane and ethane. Seppyo 71(5): 341-351.
Hachikubo A, Khlystov O, Kida M, Sakagami H, Minami H, Yamashita S, Takahashi N, Shoji H, Kalmychkov G, Poort J (2012) Raman spectroscopic and calorimetric observations on natural gas hydrates with cubic structures I and II obtained from Lake Baikal. Geo-Mar Lett 32: 419-426.
Yoon J-H, Yamamoto Y, Komai T, Haneda H, Kawamura T (2003) Rigorous approach to the prediction of the heat of dissociation of gas hydrates. Ind Eng Chem Res 42: 1111-1114.
The samples of gas hydrates were synthesized from fine ice powder and guest gases at 273.2 K and the pressure condition of 20MPa (N2) and 16MPa (O2 and Ar). The ice powder started to melt and formed these gas hydrates. Approximately 1 g of each hydrate sample was set in a pressure cell specially designed for a Tian-Calvet type heat-flow calorimeter, and its dissociation monitored. The experimental setup and technique were the same as the one that was used previously by Hachikubo et al. (2009; 2012).
Dissociation heats of N2, O2, and Ar hydrates from hydrate to gas and ice are 12.8±0.2 [kJ mol-1], 12.6±0.1[kJ mol-1], and 13.2±0.1[kJ mol-1], respectively. Yoon et al. (2003) reported that dissociation heats of N2 and O2 hydrates are 12.18 [kJ mol-1] and 11.52 [kJ mol-1], respectively, using the Clausius-Clapeyron equation. Therefore, our data are several percent smaller than the previous report.
References
Kang S-P, Lee H (2001) Enthalpies of dissociation of clathrate hydrates of carbon dioxide, nitrogen, (carbon dioxide + nitrogen), and (carbon dioxide + nitrogen + tetrahydrofuran). J Chem Thermodyn 33: 513-521.
Hachikubo A, Kida M, Okuda M, Sakagami H, Shoji H (2009) Dissociation heat of mixed-gas hydrate composed of methane and ethane. Seppyo 71(5): 341-351.
Hachikubo A, Khlystov O, Kida M, Sakagami H, Minami H, Yamashita S, Takahashi N, Shoji H, Kalmychkov G, Poort J (2012) Raman spectroscopic and calorimetric observations on natural gas hydrates with cubic structures I and II obtained from Lake Baikal. Geo-Mar Lett 32: 419-426.
Yoon J-H, Yamamoto Y, Komai T, Haneda H, Kawamura T (2003) Rigorous approach to the prediction of the heat of dissociation of gas hydrates. Ind Eng Chem Res 42: 1111-1114.