(694b) Growth of Tetrahydrofuran (THF) Clathrate Hydrates: A Molecular Dynamics Study

The growth of tetrahydrofuran (THF) clathrate hydrates and methane-THF clathrate hydrate were calculated by Molecular dynamic (MD) simulations.  The melting points of THF hydrate determined from MD simulations were 277.5K at 1atm and 270K at 1000atm, in good agreement with the experimental data (277.6K at 1atm and 274K at 1000atm). The melting point of THF hydrate was found to correlate strongly with the solubility of THF in water. The solubility of THF in water may decrease from completely miscible to less than 0.01 (mol THF/mol solution) at 298K and 1atm by changing the interaction parameters between THF and water.  In the latter case, the melting point of THF clathrate hydrate decreased to less than 260K at 1atm.  The occupancy of THF in the 5¹²6⁴ cages strongly stabilized the structure II hydrate. In the growth process, the all 5¹²6⁴ cages are filled with THF (occupancy is 1). The promoting effect of THF on CH₄ clathrate hydrates was successfully simulated. With the adding THF in the system, the melting temperature of CH₄ clathrate hydrate increased about 50 K.