Thermodynamic and spectroscopic analysis of multi-guest mixed hydrate

Abstract

Various low molecular weight gases like a methane, ethane and carbon dioxide etc. react with water molecules and make clathrate hydrates in a specific temperature and pressure conditions. Clathrate hydrates, called gas hydrates, have tree structures, sI, sII and sH. After discovery of gas hydrates, there are several efforts to apply it in the industrial fields. Especially, as a new energy source, natural gas hydrates which containing natural gases as a guest molecules are attracted research attention. In connection with the recovery of natural gases in the natural gas hydrates, carbon dioxide sequestration in the layer of natural gas hydrates has been studied. In this study, firstly I have analyzed the natural gas hydrate samples from KIGAM and KORDI by using spectrometers. And then, methane hydrates which prepared in laboratory were replaced by mixed gases containing carbon dioxide and nitrogen. Methane-ethane sII hydrates were also prepared, and replaced by carbon dioxide. The results of analysis of natural gas hydrates show sI hydrate containing methane as a guest molecule. Using NMR spectrometer, hydration number and cage occupancies were identified. Two samples show same properties. After the concept which is swapping carbon dioxide for natural gas in the natural gas hydrate is presented, many researchers are trying to concrete this technology. In this study, laboratory-made methane hydrate was replaced by mixed gas of carbon dioxide and nitrogen. The reacted gas hydrate was dissociated and analyzed by GC. The GC results confirmed nitrogen, methane and carbon dioxide peaks. It shows that replacement reaction clearly occurred. Using Raman spectrometer, methane in the small cages were replaced by nitrogen, and methane in the large cages were replaced by carbon dioxide. NMR spectrometer and GC result confirmed that over all 80 % of methane could be replaced by mixed gas of carbon dioxide and nitrogen. The methane and ethane mixed hydrate was prepared. By the ...