Water-Soluble Structure H Clathrate Hydrate Formers

Abstract

Hexamethyleneimine, 1-methylpiperidine, 2-methylpiperidine, 3-methylpiperidine, and 4-methylpiperidine as isomers of C6H13N were revealed as new sH clathrate hydrate forming molecules. They show fully soluble characteristics to water, whereas already known sH formers such as methylcyclohexane and 2,2-dimethylbutane (neohexane) are immiscible or very slightly soluble to water. The L–H–V equilibrium P–T behavior of these new sH clathrate hydrates shows a tendency to shift to much milder conditions than already known ones. We particularly note that 1-methylpiperidine appears to be the best for promotion. To verify the distribution of CH4 molecules and crystal structure of clathrate hydrates, 600 MHz solid-state NMR, Raman spectroscopy, and XRD pattern analysis were conducted. These noticeable properties of new formers are expected to open new research fields to the hydrate community and contribute to hydrate-based technological applications with high energy efficiency.

The structure of coronene cluster ions inferred from H2 uptake in the gas phase

“…The model is classical; it neglects delocalization and zero point energies which have been shown to have significant consequences for the adsorption of helium, hydrogen, and neon on coronene 30,37-41 and other carbonaceous systems. [49][50][51] Even so, we expect that the classical structures discussed here will have some bearing on the spatial probability distribution of the actual quantum mechanical system. It has been shown, for example, that a classical description of (neutral or cationic) He 32 C 60 which has a commensurate solvation shell captures essential features of more rigorous quantum mechanical descriptions [49][50][51] although discrepancies become more significant for incomplete and incommensurate shells.…”

The effect of time step, thermostat, and strain rate on ReaxFF simulations of mechanical failure in diamond, graphene, and carbon nanotube

“…[36] ReaxFF has also been used to investigate fracture properties of materials such as silicon, [30,37] graphyne, [38,39] graphene, [22,29] and Fe/Ni/Al. [40] While ReaxFF has been shown to accurately reproduce fracture properties of some materials, it is unclear if the most recent C/H/O parameter set of Chenoweth et al [17] (henceforth referred to as the Chenoweth C/H/O parameter set) is appropriate for simulating fracture behavior in carbon-based systems. Because of the complex nature of fracture and the relative novelty of ReaxFF, specific modeling details and simulation parameters for predicting crack initiation and growth in carbon-based materials have not been fully explored.…”

Thermodynamic inhibition of 4-methylmorpholine while forming sH hydrate with methane

“…More experimental data would be required for hydrate equilibrium conditions of 4-mMPL, but it can be concluded that 4-mMPL might be used to inhibit the hydrate formation. On the basis of several studies on phase stability (Lee et al, 2010;Shin et al, 2011;Jin et al, 2013), most binary sH hydrate systems require milder conditions to form gas hydrate compared with the pure CH 4 hydrate. The phase stability of gas hydrates is known to be affected by the molecular size and shape of the LMGS as well as guest-host interactions.…”

“…A large number of studies have been carried out to identify phase equilibrium conditions, formation kinetics, and structural characteristics (Lee et al, 2010;Seo et al, 2010). Moreover, new LMGSs enclosed in sH hydrates with CH 4 gas are being explored for gas storage application and separation media, since sH hydrates commonly have superior storage capacity and thermodynamic stability compared to sI and sII hydrates (Shin et al, 2011;Jin et al, 2013;Strobel et al, 2008). Recently, the gas hydrate has become one of the major issues in flow assurance, as it may block flowlines during the production and transportation of petroleum fluids (Sloan, 2005).…”