Managing hydrogen bonding in the clathrate hydrate of the 1-pentanol guest molecule

Abstract

It remains a difficult task to predict the hydrate structure and conformation of potential guest molecules in one of the three canonical hydrate lattices. 1-pentanol is characteristic of molecules that...

Further Investigation of Solvent Synergists for Improved Performance of Poly(N-vinylcaprolactam)-Based Kinetic Hydrate Inhibitors

“…One possible reason for the solvent synergetic performance could lay in the fact that iHexOl may form structure II hydrates by stabilizing 5 12 6 4 cages. This has been reported to be the case for 1-pentanol with a NH 4 + and F – ion-doped hydrate . Alcohols possess both a hydrophilic part and a hydrophobic part.…”

“…This has been reported to be the case for 1-pentanol with a NH 4 + and F − ion-doped hydrate. 50 Alcohols possess both a hydrophilic part and a hydrophobic part. The hydrophilic part can destabilize the hydrogenbonded water cages while the hydrophobic part can stabilize the host framework.…”

Effect of Methanol Guests on Thermal Properties of NH4F-Doped THF Clathrate Hydrate

“…This molecule strongly hydrogen-bonds with water molecules in the host and breaks the hydrogen bonding between water molecules of the hydrate cages. Additionally, the THF + CH 3 OH clathrate hydrate in this work contains ammonium fluoride and it was reported in our previous studies that strong guest–host interactions between alcohol guests and doped NH 4 F pairs are observed. ,, Therefore, two effectsone is the destabilization of host framework by methanol guest, and another is the strong interactions between methanol and the doped ion pairon the thermal expansion of the H 2 O/NH 4 F clathrate should be investigated.…”

“…Clathrate hydrates are a type of host–guest compound consisting of space-filling stacked ice-like cages. , The canonical clathrate hydrates, also widely known as gas hydrates, are normally stabilized by van der Waals interactions between gases or hydrocarbon molecules as guests and the hydrogen-bonded water network as host framework. Unlike common clathrate hydrates with neutral or nonpolar guest molecules, there are some special species of clathrate hydrates such as ionic clathrate hydrates (tetramethylammonium hydroxide, perchloric acid, or hexafluorophosphoric acid clathrate hydrates), semi-clathrate hydrates with truncated and merged cages (quaternary ammonium salt clathrate hydrates), or ammonium fluoride-doped clathrate hydrates. − These materials, which include strong interactions between hydrophobic cation or anion guests and counterions incorporated into the host framework or between polar guests and ion pairs doped in host cages, sometimes show relatively higher thermodynamic stability of the hydrate phases, unexpected guest encagement, selective cage occupancies, or structural changes in the hydrate phases. − …”

Effect of Ammonium Fluoride Doping on Nitrogen, Oxygen, and Methane Clathrate Hydrates

“…In this NH 4 F–H 2 O clathrate system, methanol is a suitable guest for the small D cage and acts as a helper guest for other large molecules, such as isoamyl alcohol, 2-methyltetrahydrofuran, or tert -butyl methyl ether, to form binary sII or sH clathrates. , Moreover, strong interactions between doped NH 4 F in the lattice and the hydrophilic part of the guest molecule allow the unexpected enclathration of molecules known not to be incorporated in non-doped clathrate phases. For example, 1,2-propanediol that is too hydrophilic to stabilize the hydrate lattice or 1-pentanol that is too long to fit into the T cage form sII clathrate of NH 4 F–H 2 O solid solution in the presence of a methanol helper guest. , A recent study revealed that the strengthened short-range interactions between the nonpolar (with no electrostatic dipole but with a quadrupole) CO 2 guest and doped NH 4 F in the hydrate lattice were observed in the CO 2 clathrate of NH 4 F–H 2 O solid solution and suggested that this crystal engineering approach can be applied to hydrate-based gas separation . In addition, the NH 4 F doping is accompanied by the shrinking of the lattice framework as a result of the slightly shorter hydrogen bond length of NH 4 F ion pairs in the lattice framework compared to those between water molecules. ,, This means that the lattice dimension can also be managed by adjusting the concentration of NH 4 F doped in the host framework; therefore, the “lattice tuning” by NH 4 F should affect the guest preference and composition in the clathrate hydrate phases.…”