Clathrate hydrates applications

Lunine, J.I., Stephenson, D.J. (1985). Thermodynamics of Clathrate Hydrate at Low and High Pressures with Application to the Outer Solar System. Astrophys. J. Suppl. Ser. 58,493-531. 

In addition to the use of existing hydrates, it has also been suggested that clathrate hydrates could find applications in storage and separation technology. Bardhun showed in 1962 the viable application of hydrates in desalination of sea water, while hydrates have also been investigated as a method for the storage and transport of methane without the use of high-pressure containers. 

Lunine, J. I., Stevenson, D. J. (1985) Thermodynamics of clathrate hydrate at low and high pressures with application to the outer solar system. Astrophys. J. Suppl., 58, 493-531. 

The next four chapters address several applications of MD to water and aqueous solutions. Floris and Tani describe tiie development of force fields for water-water and water-ion interactions in Chapter 10. Balbuena et al. analyze force fields for cation-water systems introducing new descriptions of short-range interactions. Li and Tomkinson assess the estimation of neutron scattering spectra of ice by MD and lattice dynamics simulations in Chapter 12. Tanaka in Chapter 13 discusses the stability and dynamics of ice and clathrate hydrate using Monte Carlo, MD, lattice dynamics simulations, and a statistical mechanical formulation. 

Clathrate hydrates are ice-like materials that belong to the category of inclusion compoimds. They consist of a sohd network of hydrogen bonded water molecules that form cavities encaging various guesf molecules such as methane, carbon dioxide or small hydrocarbon chains. Hydrates have attracted significant industrial and scientific interest as a result of their involvement in a number of important applications [1]. In particular, hydrate formation is a major concern for safety and flow assiuance in gas and oil pipelines, as well as in unit operations where high pressures and moderately low temperature conditions exist, such that hydrate formation is possible. 

The mechanism of clathrate hydrate formation shows similarities to adsorption of molecules at sites on a surface. The assumptions made for the mechanism of Langmuir adsorption are also applicable for hydrate formation [2]. The occupancy of the sites on a surface in the Langmuir adsorption theory is given by a so-called Langmuir isotherm, which can also be developed for the occupancy of the cavities in clathrate hydrates. 

Since the outstanding physical property of clathrate hydrates is the efficient storage of gases, interest continues in applications where this property will be of use. Typically, a volume of gas hydrate can hold 160 volumes of gas at STP, thus, gas storage, especially energy gases such as methane and hydrogen, continues to be actively pursued. 

VII. Application to Thermodynamic Stability of Clathrate Hydrates A. Chemical Potential of Ices and Empty Clathrate Hydrates... 

One of the most interesting topics at high pressures is application of hydrogen containing clathrate hydrates. Since the discovery of hydrogen clathrate hydrate. 

A common thread in all these applications is the need to understand what makes clathrate hydrates stable. This chapter will present some of the evidence that recent computer simulations have contributed to this issue. To provide a context for the simulation results, we begin with a brief description of clathrate hydrates and their experimental properties. This will be followed in Section 3 by a discussion of the current theory of hydrate stability (the cell theory). It is intended that this Section should bring out the main ideas behind the cell theory, as it is these basic principles that have motivated recent simulations for a rigorous derivation of the cell theory the reader is referred to the original work of van der Waals and Platteeuw [2]. The role of computer simulations in elucidating the behaviour of clathrate hydrates will be considered in detail in Section 4. 

Note that the simulations do deal with model systems rather than the real system. However, the model assumptions of the cell theory are very qualitative and general in nature, and they should be valid for any water-like system. Thus it is not necessary for the simulation to invoke an exact description of water rather, it is sufficient that the simulations deal with a water-like system. If the properties of the simulated water are sufficiently close to those of real water, then one can expect the general conclusions from the simulations about the applicability of the cell theory also to be valid for real clathrate hydrates. 

Computational approaches are now becoming powerful complementary methods to experimental techniques and I am particularly pleased that I have been able to persuade five authors to contribute chapters detailing the applications of these methods to calixarenes and their complexes, to clathrate hydrates, to cyclodextrins and their complexes, to crown ether complexes, to zeolites and their complexes, and to endohedral complexes of the intriguing fullerene molecules. 

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