Study on Prompt Methane Hydrate Formation Derived by Addition of Ionic Liquid

Aims: The objective of this study is to establish the fundamental model on methane hydrate formation and to accelerate the rate of methane hydrate formation with a small amount of ionic liquid and to investigate the effect of ionic liquid on hydrate formation. Study Design: Experimental study containing modeling. Place and Duration of Study: The present study was held between April 2010 and February 2012 at Division of Chemical Engineering, Department of Materials Engineering Science, Osaka University. Methodology: Methane hydrate formation was modelized based on the driving force, fugacity difference before and after hydrate formation. BMIM-hexafuorophosphate (BMIMPF6) was adopted as a representative of 1-butyl-3-methylimidazolium (BMIM) salts. The temperature dependence of methane hydrate formation rate was investigated and activation energy of hydrate formation was evaluated for the pure water and BMIM-PF6 aqueous solution systems. Results: An addition of small amount of BMIM-PF6 is able to accelerate the methane hydrate formation. The pseudo-first order reaction model is applicable to the methane hydrate formation in both the pure water and BMIM-PF6 aqueous solution systems. The activation energies of methane hydrate formation are large negative values in the both systems, that is, the methane hydrate formation process is considered to be composed of the precursory hydration and succeeding hydrate formation. A very small amount of BMIMPF6 seems to change the interfacial energy between guest molecules and precursor or initial hydrate particles without the change of the activation energy for overall methane hydrate formation.