scholarly journals Toward an Understanding of the Propensity for Crystalline Hydrate Formation by Molecular Compounds. Part 2

2021 ◽  
Author(s):  
Rana Sanii ◽  
Ewa Patyk-Kaźmierczak ◽  
Carol Hua ◽  
Shaza Darwish ◽  
Tony Pham ◽  
...  
Keyword(s):  
Hydrate Formation ◽  
Crystalline Hydrate ◽  
Molecular Compounds

scholarly journals Towards an understanding of the propensity for crystalline hydrate formation by molecular compounds

IUCrJ ◽  
2016 ◽  
Vol 3 (6) ◽  
pp. 430-439 ◽  
Author(s):  
Alankriti Bajpai ◽  
Hayley S. Scott ◽  
Tony Pham ◽  
Kai-Jie Chen ◽  
Brian Space ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Crystal Packing ◽  
Hydrate Formation ◽  
Crystalline Hydrate ◽  
Strong Hydrogen Bond ◽  
Hydrogen Bond Donor ◽  
Screening Experiments ◽  
Group Form ◽  
Structural Database ◽  
Molecular Compounds

Hydrates are technologically important and ubiquitous yet they remain a poorly understood and understudied class of molecular crystals. In this work, we attempt to rationalize propensity towards hydrate formation through crystallization studies of molecules that lack strong hydrogen-bond donor groups. A Cambridge Structural Database (CSD) survey indicates that the statistical occurrence of hydrates in 124 molecules that contain five- and six-memberedN-heterocyclic aromatic moieties is 18.5%. However, hydrate screening experiments on a library of 11N-heterocyclic aromatic compounds with at least two acceptor moieties and no competing hydrogen-bond donors or acceptors reveals that over 70% of this group form hydrates, suggesting that extrapolation from CSD statistics might, at least in some cases, be deceiving. Slurrying in water and exposure to humidity were found to be the most effective discovery methods. Electrostatic potential maps and/or analysis of the crystal packing in anhydrate structures was used to rationalize why certain molecules did not readily form hydrates.

scholarly journals Experimental investigations of methane hydrate in sediment suspensions

2018 ◽  
Vol 7 (4.5) ◽  
pp. 651
Author(s):  
Ikkurti Radhika ◽  
Pinnelli S. R. Prasad ◽  
Devarasetty Suresh Babu
Keyword(s):  
Methane Hydrate ◽  
Hydrate Formation ◽  
Bulk Water ◽  
Crystalline Hydrate ◽  
Experimental Investigations ◽  
Clay Particles ◽  
Capillary Effects ◽  
Water Suspensions ◽  
Negative Role ◽  
Synthetic Clay

Methane hydrate structural stability and formation, were studied in water suspensions with synthetic clay (44.17nm),SiO2(60.62nm) and zeolite (35.08nm) at different weight percentages (1wt%,10wt%,20wt%) in isochoric method using stirred autoclave. The for- mation kinetics in these sediments greatly differs from those of the bulk hydrate owing to surface and capillary effects in the pores. It has been confirmed that hydrate formation in confined pores is severely restricted due to increased inner capillary pressure. Further- more in principle , the clay particles suspended in water play a negative role in structuring the crystalline hydrate .More specifically, even though the addition of clay enhances the hydrate yield insignificantly, from our results, the addition of sediments did not affect the phase equilibrium much because water exists in excess around clay particles and therefore the hydrate formed in the bulk water phase is much more dominant than that in the pores. 

Does Local Structure Bias How a Crystal Nucleus Evolves?

2018 ◽  
Author(s):  
Kyle Hall ◽  
Zhengcai Zhang ◽  
Christian Burnham ◽  
Guang-Jun Guo ◽  
Sheelagh Carpendale ◽  
...  
Keyword(s):  
Local Structure ◽  
Molecular Level ◽  
Hydrate Formation ◽  
Mixed Gas ◽  
Local Structures ◽  
Surrounding Environment ◽  
Gas Hydrate Formation ◽  
Significant Research ◽  
Crystal Phases ◽  
Recent Experimental Work

<p>The broad scientific and technological importance of crystallization has led to significant research probing and rationalizing crystallization processes, particularly how nascent</p> <p>crystal phases appear. Previous work has generally neglected the possibility of the molecular-level dynamics of individual nuclei coupling to local structures (e.g., that of the nucleus and its</p> <p>surrounding environment). However, recent experimental work has conjectured that this can occur. Therefore, to address a deficiency in scientific understanding of crystallization, we have</p> <p>probed the nucleation of prototypical single and multi-component crystals (specifically, ice and mixed gas hydrates). Here, we establish that local structures can bias the evolution of nascent</p> <p>crystal phases on a nanosecond timescale by, for example, promoting the appearance or disappearance of specific crystal motifs, and thus reveal a new facet of crystallization behaviour.</p> <p>Analysis of the crystallization literature confirms that structural biases are likely present during crystallization processes beyond ice and gas hydrate formation. Moreover, we demonstrate that</p> <p>structurally-biased dynamics are a lens for understanding existing computational and experimental results while pointing to future opportunities.</p>

Does Local Structure Bias How a Crystal Nucleus Evolves?

2018 ◽  
Author(s):  
Kyle Hall ◽  
Zhengcai Zhang ◽  
Christian Burnham ◽  
Guang-Jun Guo ◽  
Sheelagh Carpendale ◽  
...  
Keyword(s):  
Local Structure ◽  
Molecular Level ◽  
Hydrate Formation ◽  
Mixed Gas ◽  
Local Structures ◽  
Surrounding Environment ◽  
Gas Hydrate Formation ◽  
Significant Research ◽  
Crystal Phases ◽  
Recent Experimental Work

<p>The broad scientific and technological importance of crystallization has led to significant research probing and rationalizing crystallization processes, particularly how nascent</p> <p>crystal phases appear. Previous work has generally neglected the possibility of the molecular-level dynamics of individual nuclei coupling to local structures (e.g., that of the nucleus and its</p> <p>surrounding environment). However, recent experimental work has conjectured that this can occur. Therefore, to address a deficiency in scientific understanding of crystallization, we have</p> <p>probed the nucleation of prototypical single and multi-component crystals (specifically, ice and mixed gas hydrates). Here, we establish that local structures can bias the evolution of nascent</p> <p>crystal phases on a nanosecond timescale by, for example, promoting the appearance or disappearance of specific crystal motifs, and thus reveal a new facet of crystallization behaviour.</p> <p>Analysis of the crystallization literature confirms that structural biases are likely present during crystallization processes beyond ice and gas hydrate formation. Moreover, we demonstrate that</p> <p>structurally-biased dynamics are a lens for understanding existing computational and experimental results while pointing to future opportunities.</p>

A Transferable, Polarisable Force Field for Ionic Liquids

2019 ◽  
Author(s):  
Kateryna Goloviznina ◽  
José N. Canongia Lopes ◽  
Margarida Costa Gomes ◽  
Agilio Padua
Keyword(s):  
Ionic Liquids ◽  
Force Field ◽  
Force Fields ◽  
Dipole Moments ◽  
Van Der Waals Interactions ◽  
First Principles Calculations ◽  
Ion Diffusion ◽  
Fixed Integer ◽  
Molecular Compounds ◽  
Induced Dipoles

A general, transferable polarisable force field for molecular simulation of ionic liquids and their mixtures with molecular compounds is developed. This polarisable model is derived from the widely used CL\&P fixed-charge force field that describes most families of ionic liquids, in a form compatible with OPLS-AA, one of the major force fields for organic compounds. Models for ionic liquids with fixed, integer ionic charges lead to pathologically slow dynamics, a problem that is corrected when polarisation effects are included explicitly. In the model proposed here, Drude induced dipoles are used with parameters determined from atomic polarisabilities. The CL\&P force field is modified upon inclusion of the Drude dipoles, to avoid double-counting of polarisation effects. This modification is based on first-principles calculations of the dispersion and induction contributions to the van der Waals interactions, using symmetry-adapted perturbation theory (SAPT) for a set of dimers composed of positive, negative and neutral fragments representative of a wide variety of ionic liquids. The fragment approach provides transferability, allowing the representation of a multitude of cation and anion families, including different functional groups, without need to re-parametrise. Because SAPT calculations are expensive an alternative predictive scheme was devised, requiring only molecular properties with a clear physical meaning, namely dipole moments and atomic polarisabilities. The new polarisable force field, CL\&Pol, describes a broad set set of ionic liquids and their mixtures with molecular compounds, and is validated by comparisons with experimental data on density, ion diffusion coefficients and viscosity. The approaches proposed here can also be applied to the conversion of other fixed-charged force fields into polarisable versions.<br>

The formation of gas hydrates under shock wave impact on the bubble media (two-dimensional case)

2010 ◽  
Vol 7 ◽  
pp. 90-97
Author(s):  
M.N. Galimzianov ◽  
I.A. Chiglintsev ◽  
U.O. Agisheva ◽  
V.A. Buzina
Keyword(s):  
Shock Wave ◽  
Gas Hydrates ◽  
Hydrate Formation ◽  
Dimensional Case ◽  
Two Dimensional ◽  
Wave Impact ◽  
Bubble Liquid ◽  
One Dimensional ◽  
Bubble Media ◽  
Main Factors

Formation of gas hydrates under shock wave impact on bubble media (two-dimensional case) The dynamics of plane one-dimensional shock waves applied to the available experimental data for the water–freon media is studied on the base of the theoretical model of the bubble liquid improved with taking into account possible hydrate formation. The scheme of accounting of the bubble crushing in a shock wave that is one of the main factors in the hydrate formation intensification with increasing shock wave amplitude is proposed.

Mathematical model of multiphase flow propagation for the case of underwater pipeline damage

2019 ◽  
Vol 14 (2) ◽  
pp. 142-147
Author(s):  
S.R. Kildibaeva ◽  
E.T. Dalinskij ◽  
G.R. Kildibaeva
Keyword(s):  
Oil And Gas ◽  
Control Volume ◽  
Hydrate Formation ◽  
Initial Moment ◽  
Hydrate Shell ◽  
Surrounding Water ◽  
Vertical Coordinate ◽  
Associated Gas ◽  
First Case ◽  
Underwater Pipeline

The paper deals with the case of damage to the underwater pipeline through which oil and associated gas are transported. The process of oil and gas migration is described by the flow of a multiphase submerged jet. At the initial moment, the temperature of the incoming hydrocarbons, their initial velocity, the temperature of the surrounding water, the depth of the pipeline is known. The paper considers two cases of different initial parameters of hydrocarbon outflow from the pipeline. In the first case, the thermobaric environmental conditions correspond to the conditions of hydrate formation and stable existence. Such a case corresponds to the conditions of the hydrocarbons flow in the Gulf of Mexico. In the second case, hydrate is not formed. Such flows correspond to the cases of oil transportation through pipelines in the Baltic sea (for example, Nord stream–2). The process of hydrate formation will be characterized by the following dynamics of the bubble: first, it will be completely gas, then a hydrate shell (composite bubble) will begin to form on its surface, then the bubble will become completely hydrate, which will be the final stage. The integral Lagrangian control volume method will be considered for modeling the dynamics of hydrocarbon jet propagation. According to this method, the jet is considered as a sequence of elementary volumes. When modeling the jet flow, the laws of conservation of mass, momentum and energy for the components included in the control volume are taken into account. The equations are used taking into account the possible formation of hydrate. Thermophysical characteristics of hydrocarbons coming from the damaged pipeline for cases of deep-water and shallow-water pipeline laying are obtained. The trajectories of hydrocarbon migration, the dependence of the jet temperature and density on the vertical coordinate are analyzed.

(+)-3-Carene: Valuable Starting Material for Synthesis of Low-molecular Compounds with Olfactory Properties

2014 ◽  
Vol 18 (4) ◽  
pp. 446-458 ◽  
Author(s):  
Daniel Strub ◽  
Lucyna Balcerzak ◽  
Stanislaw Lochynski
Keyword(s):  
Starting Material ◽  
Molecular Compounds
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