Thermodynamic Stability, Spectroscopic Identification, and Gas Storage Capacity of CO2–CH4–N2 Mixture Gas Hydrates: Implications for Landfill Gas Hydrates

• Published in: Environmental science & technology Vol. 46; no. 7; pp. 4184 - 4190
• Main Authors: Lee, Hyeong-Hoon, Ahn, Sook-Hyun, Nam, Byong-Uk, Kim, Byeong-Soo, Lee, Gang-Woo, Moon, Donghyun, Shin, Hyung Joon, Han, Kyu Won, Yoon, Ji-Ho
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 03.04.2012
• Subjects: Carbon - analysis; Carbon Dioxide - analysis; Kinetics; Magnetic Resonance Spectroscopy; Methane - analysis; Nitrogen - analysis; Pressure; Refuse Disposal; Spectrum Analysis, Raman - methods; Thermodynamics; Water - chemistry; X-Ray Diffraction
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es203389k

Landfill gas (LFG), which is primarily composed of CH4, CO2, and N2, is produced from the anaerobic digestion of organic materials. To investigate the feasibility of the storage and transportation of LFG via the formation of hydrate, we observed the phase equilibrium behavior of CO2–CH4–N2 mixture hydrates. When the specific molar ratio of CO2/CH4 was 40/55, the equilibrium dissociation pressures were gradually shifted to higher pressures and lower temperatures as the mole fraction of N2 increased. X-ray diffraction revealed that the CO2–CH4–N2 mixture hydrate prepared from the CO2/CH4/N2 (40/55/5) gas mixture formed a structure I clathrate hydrate. A combination of Raman and solid-state 13C NMR measurements provided detailed information regarding the cage occupancy of gas molecules trapped in the hydrate frameworks. The gas storage capacity of LFG hydrates was estimated from the experimental results for the hydrate formations under two-phase equilibrium conditions. We also confirmed that trace amounts of nonmethane organic compounds do not affect the cage occupancy of gas molecules or the thermodynamic stability of LFG hydrates.