Experimental determination and thermodynamic modeling of methane and nitrogen hydrates in the presence of THF, propylene oxide, 1,4-dioxane and acetone

Large pressure depression of methane hydrate by adding 1,1-dimethylcyclohexane

“…tetrahydrofuran (de Deugd et al, 2001;Seo et al, 2001), acetone (Ng and Robinson, 1996;Mainusch et al, 1997;de Deugd et al, 2001;Seo et al, 2001), and 1,4-dioxane (Jager et al, 1999;Seo et al, 2001), generate the structure-II hydrate crystal in the presence of methane and reduce the equilibrium pressure. These additives are, however, unsuitable for our practical object because they are perfectly soluble in water.…”

Study on the kinetics of hydrate formation in a bubble column

“…Because the formation pressure of methane hydrate in pure water is comparatively high, for example, it is 2.603 MPa at 273.15 K, and the induction period is relatively long, THF was added to reduce the hydrate formation pressure and increase the formation rate (Seo et al, 2001). The mole fraction of THF in aqueous solution was fixed at 6%, which is close to the stoichiometric concentration of THF/water whereby THF occupies all the large cages of sII hydrate.…”

Phase Behavior and Structural Characterization of Coexisting Pure and Mixed Clathrate Hydrates

“…As an indirect measure of hydrate formation, the pressure ± temperature (P ± T) trajectory, [1] which represents hydrate nucleation, growth, and dissociation stages, was measured experimentally and the resulting closed loop made by the hydrate formation and dissociation processes is shown in Figure 1 a. The mixed CH 4 THF hydrate started to form directly after going through the three-phase equilibrium boundary, [9] and rapid pressure reduction occurred immediately 13 C NMR spectra of the mixed CH 4 THF hydrate at point B. c) 13 C NMR spectra of the coexisting mixed CH 4 THF and pure CH 4 hydrates at point C.…”

“…Continuum solvent models are incapable of replicating specific solute-solvent interactions, and dynamics methods require considerable computer time to construct and diagonalize the Hessian matrix at each time step. Fourier transform-based methods [8,9] cannot be used with Monte Carlo simulations, give vibrational frequencies but not the associated modes, and/or require longer trajectories to resolve closely spaced vibrational frequencies. [10,11] This contribution demonstrates the capabilities of multivariate statistical analysis [12,13] of quantum MD or QM/MM trajectories to calculate vibrational frequencies for an isolated water molecule, water dimer, and liquid water.…”