scholarly journals Effect of the THF molecules on the hydrate cavities formation with adding NaCL molecules into the modeling system

2021 ◽  
Vol 2057 (1) ◽  
pp. 012077
Author(s):  
Y Y Bozhko ◽  
R K Zhdanov ◽  
K V Getz ◽  
V R Belosludov
Keyword(s):  
Hydrogen Bonds ◽  
Guest Molecule ◽  
Hydrate Formation ◽  
Water Molecules ◽  
Torsion Angles ◽  
Simulated System ◽  
Thermodynamic Conditions ◽  
Different Temperatures ◽  
Molecular Dynamics Methods ◽  
Simulation Time

Abstract In this work, using molecular dynamics methods by Gromacs package we simulate the hydrate formation in systems containing THF, water, and NACL molecules at different thermodynamic conditions and concentration of THF molecules. The curves of the number of hydrogen bonds are obtained depending on the simulation time at different temperatures. The computer simulations results show that the hydrogen bonds between THF and water molecules are relatively weak, with a maximum number of two water molecules hydrogen bonded to THF, but THF can facilitate water molecules rearrangement to form a pentagonal or hexagonal planar ring that is the part of clathrate cavity. In addition, the THF molecule can significantly increase the likelihood to form clathrate cavities suitable for the second guest molecule. The effect of THF molecules concentration on the hydrate cavities formation with adding NaCL molecules into the modeling system is shown. In this work, data are obtained on the magnitude of torsion angles, the percentage of which increases depending on the simulation time, which allows concluding that labile large and small cavities of sII hydrates are formed. The increase in the THF molecules concentration is shown to lead to a decrease in the hydrogen bonds number of water molecules in the simulated system.

scholarly journals Crystal structures of three halide salts of L-asparagine: an isostructural series

2018 ◽  
Vol 74 (11) ◽  
pp. 1619-1623 ◽  
Author(s):  
Lygia S. de Moraes ◽  
Alan R. Kennedy ◽  
Charlie R. Logan
Keyword(s):  
Hydrogen Bonds ◽  
Acid Amide ◽  
Water Molecules ◽  
Halide Ions ◽  
Carboxylic Acid Amide ◽  
Torsion Angles ◽  
Halide Salt ◽  
Halide Salts ◽  
Salt Forms ◽  
Chloride Monohydrate

The structures of three monohydrated halide salt forms of L-asparagine are presented, viz.L-asparaginium chloride monohydrate, C4H9N2O3 +·Cl−·H2O, (I), L-asparaginium bromide monohydrate, C4H9N2O3 +·Br−·H2O, (II), and L-asparaginium iodide monohydrate, C4H9N2O3 +·I−·H2O, (III). These form an isomorphous and isostructural series. The C—C—C—C backbone of the amino acid adopts a gauche conformation in each case [torsion angles for (I), (II) and (III) = −55.4 (2), −55.6 (5) and −58.3 (7)°, respectively]. Each cation features an intramolecular N—H...O hydrogen bond, which closes an S(6) ring. The extended structures feature chains of cations that propagate parallel to the b-axis direction. These are formed by carboxylic acid/amide complimentary O—H...O + N—H...O hydrogen bonds, which generate R 2 2(8) loops. These chains are linked by further hydrogen bonds mediated by the halide ions and water molecules to give a layered structure with cation and anion layers parallel to the ab plane. Compound (III) was refined as an inversion twin.

scholarly journals A Thermodynamic Study of Methane Hydrates Formation In Glass Beads

2016 ◽  
Vol 16 (1) ◽  
pp. 15
Author(s):  
Tintin Mutiara ◽  
Budhijanto Budhijanto ◽  
I Made Bendiyasa ◽  
Imam Prasetyo
Keyword(s):  
Hydrogen Bonds ◽  
Gas Hydrates ◽  
Methane Hydrate ◽  
Hydrate Formation ◽  
Glass Beads ◽  
Water Molecules ◽  
Equilibrium Pressure ◽  
Natural Gas Hydrates ◽  
System Pressure ◽  
Energy Of Hydrogen Bonds

Natural gas hydrates are non-stoichiometry compounds, in which the molecules of gas are trapped in crystalline cells consisting of water molecules retained by energy of hydrogen bonds. The experiments of Methane hydrate formation are performed at constant temperature in a reactor filled with various sizes of glass beads and water. Methane gas was fed into the reactor at various initial pressures. Equilibrium condition was reached when the system pressure did not change. The experimental results showed that the size of the glass beads gave very small effect on the equilibrium pressure of methane hydrate formation, so the effect could be neglected. In this study, the equation of Langmuir constant was Ci,CH4=(1/RT)exp[A+(B/T)] with the values of A and B for small cages were 6.8465 and 18.0342. The values of A and B for large cages were 7.7598 and 18.0361

scholarly journals Crystal structure and Hirshfeld surface analysis of 2-(1H-indol-3-yl)ethanaminium acetate hemihydrate

2019 ◽  
Vol 75 (4) ◽  
pp. 451-455 ◽  
Author(s):  
Balakrishnan Rajeswari ◽  
Radhakrishnan Santhi ◽  
Palaniyappan Sivajeyanthi ◽  
Kasthuri Balasubramani
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Surface Analysis ◽  
Hirshfeld Surface ◽  
Water Molecules ◽  
Asymmetric Unit ◽  
Torsion Angles ◽  
Hirshfeld Surfaces ◽  
Molecular Salt ◽  
Hirshfeld Surfaces Analysis

The title molecular salt, C10H13N2 +·C2H3O2 −·0.5H2O, crystallized with four 2-(1H-indol-3-yl)ethanaminium cations (A, B, C and D) and four acetate anions in the asymmetric unit, together with two water molecules of crystallization. Each cation is linked to an anion by a C—H...π interaction. The alkylaminium side chains have folded conformations, with N—C—C—C torsion angles of −58.5 (3), 59.5 (3), −64.6 (3) and −56.0 (3)° for cations A, B, C and D, respectively. In the crystal, the cations and anions are liked by N—H...O and C—H...O hydrogen bonds, forming chains propagating along the b-axis direction. The chains are linked by the water molecules via Owater—H...O and N—H...Owater hydrogen bonds, forming layers lying parallel to the bc plane. The overall intermolecular interactions were investigated using Hirshfeld surfaces analysis.

MOLECULAR CHARACTERISTICS OF DISSOCIATED WATER WITH MEMORY EFFECT FROM METHANE HYDRATES

2014 ◽  
Vol 28 (10) ◽  
pp. 1450062 ◽  
Author(s):  
QIBIN LI ◽  
CHAO LIU ◽  
XI CHEN
Keyword(s):  
Melting Temperature ◽  
Memory Effect ◽  
Md Simulations ◽  
Molecular Characteristics ◽  
Water Molecules ◽  
Torsion Angles ◽  
Different Temperatures ◽  
Normal Water ◽  
With Memory ◽  
Oxygen Atoms

The properties of sI methane hydrate dissociation at different temperatures are investigated using molecular dynamics (MD) simulations, focusing on the characteristics of structure of melting water that has memory effect. Upon melting, the clathrate structures of hydrate are damaged. The density of dissolved methane decreases as the melting temperature rises. There is a positive correlation between the density of dissociated water molecules and melting temperature. Most oxygen atoms of dissociated water molecules remain tetrahedrally coordinated whereas the hydrate-like torsion angles ( H – O – O – H ) are like that of normal water. Therefore, the tetrahedrally coordinated oxygen atoms are one of the factors contributing to the memory effect.

scholarly journals 3-(2-Methyl-1,3-benzothiazol-3-ium-3-yl)propane-1-sulfonate monohydrate

2014 ◽  
Vol 70 (6) ◽  
pp. o714-o714 ◽  
Author(s):  
Guo-Cui Zhang ◽  
Ming Kong ◽  
Sheng-Li Li
Keyword(s):  
Hydrogen Bonds ◽  
Side Chain ◽  
Water Molecules ◽  
Torsion Angles

In the title hydrated zwitterion, C11H13NO3S2·H2O, the N—C—C—C and C—C—C—S torsion angles in the side-chain are 171.06 (14) and 173.73 (12)°, respectively. In the crystal, inversion-related molecules are π-stacked with an interplanar separation of 3.3847 (2) Å. O—H...O hydrogen bonds link inversion-related molecules with a pair of water molecules to formR42(8) rings. The closest S...S contact is 3.4051 (15) Å between inversion-related molecules.

The water molecules in CuSO 4 .5H 2 O

1962 ◽  
Vol 266 (1324) ◽  
pp. 95-108 ◽  
Keyword(s):  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Single Crystals ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Neutron Data ◽  
X Ray ◽  
Atomic Nuclei ◽  
Different Temperatures ◽  
Molecular Rotations

Single crystals of fully hydrated copper sulphate have been studied by neutron diffraction and the measurements have been used to construct projections of the neutron-scattering density, due to the atomic nuclei, on the three crystallographic axial planes. These provide full details of the shape and environment of the water molecules and of the hydrogen bonds which link together the atoms in the structure, which was originally proposed by Beevers & Lipson as a result of X -ray diffraction work. It is found that the H—O—H angles for all the water molecules are within a degree or two of the tetrahedral value and the hydrogen bonds have to be bent by up to 26° in order to accommodate them. Corresponding measurements have been made at a series of five different temperatures between 20 and 90°C in order to test a suggestion that molecular rotations of the water molecules occurred before the onset of dehydration: the neutron data refute this suggestion.

Structure of the stoichiometric complex 18-crown-6•H2O•succinic acid

1989 ◽  
Vol 67 (8) ◽  
pp. 1293-1297 ◽  
Author(s):  
Lucie Parenteau ◽  
François Brisse
Keyword(s):  
Hydrogen Bonds ◽  
Succinic Acid ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Gauche Conformation ◽  
Acid Complex ◽  
Centrosymmetric Dimer ◽  
Torsion Angles ◽  
X Ray ◽  
Stoichiometric Complex

Attempts to prepare stoichiometric complexes of the type dicarboxylic acid•18C6•H2O succeeded only with oxalic, succinic, and glutaric acids. The crystal structure of the succinic acid complex was established by X-ray diffraction at 173 K, and was refined to Rw = 0.038 for 3204 observed reflections. The stoichiometry of the complex is 1:1:1 (succinic acid•H2O•18C6). In the solid state there is a dimeric H-bonded association, through a center of symmetry, of two succinic acid molecules. Each diacid is also hydrogen bonded to a water molecule. The water molecules, in turn, form two hydrogen bonds each with the crown ether. The diacid–diacid, diacid–water, and the two water–18C6 hydrogen bonds are 2.657(2), 2.636(2), 2.819(2), and 2.910(2) Å long respectively. They are all nearly linear. The structural units are associated and form the centrosymmetric dimer (18C6–H2O–succinic acid)2. The conformation of the macrocyclic polyether differs significantly from that normally found. Instead of the usual (ttg)6 conformation, that adopted in this complex is (ttgttgstg)2. The two s torsion angles have values of 90.1(3) and 86.9(3)°. In this complex the succinic acid itself is in the gauche conformation. Keywords: macrocycle – succinic acid complex.

scholarly journals Crystal growth of clathrate hydrate formed with H2 + CO2 mixed gas and tetrahydropyran

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Meku Maruyama ◽  
Riku Matsuura ◽  
Ryo Ohmura
Keyword(s):  
Crystal Growth ◽  
Synthesis Gas ◽  
Water System ◽  
Hydrate Formation ◽  
Growth Dynamics ◽  
Operating Conditions ◽  
Mixed Gas ◽  
Thermodynamic Conditions ◽  
The Individual ◽  
And Storage

AbstractHydrate-based gas separation technology is applicable to the CO2 capture and storage from synthesis gas mixture generated through gasification of fuel sources including biomass. This paper reports visual observations of crystal growth dynamics and crystal morphology of hydrate formed in the H2 + CO2 + tetrahydropyran (THP) + water system with a target for developing the hydrate-based CO2 separation process design. Experiments were conducted at a temperature range of 279.5–284.9 K under the pressure of 4.9–5.3 MPa. To simulate the synthesis gas, gas composition in the gas phase was maintained around H2:CO2 = 0.6:0.4 in mole fraction. Hydrate crystals were formed and extended along the THP/water interface. After the complete coverage of the interface to shape a polycrystalline shell, hydrate crystals continued to grow further into the bulk of liquid water. The individual crystals were identified as hexagonal, tetragonal and other polygonal-shaped formations. The crystal growth rate and the crystal size varied depending on thermodynamic conditions. Implications from the obtained results for the arrangement of operating conditions at the hydrate formation-, transportation-, and dissociation processes are discussed.

scholarly journals Hydrogen Inter-Cage Hopping and Cage Occupancies inside Hydrogen Hydrate: Molecular-Dynamics Analysis

2020 ◽  
Vol 11 (1) ◽  
pp. 282
Author(s):  
Yogeshwaran Krishnan ◽  
Mohammad Reza Ghaani ◽  
Arnaud Desmedt ◽  
Niall J. English
Keyword(s):  
Molecular Dynamics ◽  
Energy Barrier ◽  
Guest Molecule ◽  
Arrhenius Equation ◽  
Dynamics Simulation ◽  
Type Ii ◽  
Large Cage ◽  
Guest Molecules ◽  
Simulation Time ◽  
Average Occupancy

The inter-cage hopping in a type II clathrate hydrate with different numbers of H2 and D2 molecules, from 1 to 4 molecules per large cage, was studied using a classical molecular dynamics simulation at temperatures of 80 to 240 K. We present the results for the diffusion of these guest molecules (H2 or D2) at all of the different occupations and temperatures, and we also calculated the activation energy as the energy barrier for the diffusion using the Arrhenius equation. The average occupancy number over the simulation time showed that the structures with double and triple large-cage H2 occupancy appeared to be the most stable, while the small cages remained with only one guest molecule. A Markov model was also calculated based on the number of transitions between the different cage types.

Sign in / Sign up

Export Citation Format

Share Document