Tetrahydrofuran Clathrate Hydrate Formation

Abstract

We report on the formation of tetrahydrofuran clathrate hydrate studied by x-ray Raman scattering measurements at the oxygen K edge. A comparison of x-ray Raman spectra measured from water-tetrahydrofuran mixtures and tetrahydrofuran hydrate at different temperatures supports stochastic hydrate formation models rather than models assuming hydrate precursors. This is confirmed by molecular dynamics simulations and density functional theory calculations of x-ray Raman spectra. In addition, changes in the spectra of tetrahydrofuran hydrate with temperatures close to the hydrate's dissociation temperature were observed and may be connected to changes in hydrate's local structure due to the formation of hydrogen bonds between guest and water molecules.

Optical Properties of Tetrahydrofuran Clathrate Hydrates with Polyvinylpyrrolidone (THF + H2O + PVP) Revealed by Terahertz (THz) Time-Domain Spectroscopy

“…If a seed (or stirring) is presented (done) in such a metastable solution, crystallization of THF clathrate hydrates would occur. 18 Otherwise, the metastable state of the solution may continue unless a high degree of supersaturation of solution is provided, where nucleation readily occurs. 4 As shown in Figure 3, the supercooling of the THF solution was clearly observed at 273 K and 268 K, and the hydrate formed between two quartz windows at 263 K. Therefore, we assume that 0.06 mole fraction of the THF aqueous solutions with/without 100w = 3 PVP in a given experimental setting have strong driving force to form clathrate hydrate at 263 K. The temperature of 263 K corresponds to the temperature of the initiating ice crystals for THF hydrates in procedures suggested by O'Reilly et al 19 Unexpectedly, the PVP samples, regardless of their molecular weights, form hydrates at the same temperature (Figure 3b−d).…”

High-resolution nonresonant x-ray Raman scattering study on rare earth phosphate nanoparticles

“…The measurements were conducted at the beamline ID16 of the European Synchrotron Radiation Facility (ESRF) 6 [36]. The samples we used were powders of LaPO 4 , CePO 4 , PrPO 4 , and NdPO 4 nanoparticles with spherelike morphology and 5-nm diameter.…”

“…Non-resonant x-ray Raman scattering (XRS) spectroscopy helps to overcome certain challenges related to XAS in the range of low-energy excitations, since it offers true bulk sensitivity and access to liquids [5,6] and samples contained in complex sample environments such as high-pressure cells [7,8]. XRS is an energy-loss spectroscopy that provides element-specific information similar to XAS but that uses high-energy x-rays (≳8 keV).…”

Investigation of Propane and n- butane Hydrate Formation Condition and Determination of Equilibrium Pressure

“…In this model, the 3-parameter potential of Kihara is used to increase the accuracy rather than the energy of the molecular potential of Lennard Jones. Then the Langmuir constant is calculated and with temperature the hydrate formation pressure is predicted from the van der Waals equation [9,10,11]. Although experimental methods have often been replaced by more advanced thermodynamic methods, the need for and use of manual and experimental calculations in laboratory methods is still unavoidable.…”