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The Role of Molecular Thermodynamics in Developing Industrial Processes and Novel Products That Meet the Needs for a Sustainable Future
Published in I. M. Mujtaba, R. Srinivasan, N. O. Elbashir, The Water–Food–Energy Nexus, 2017
Ioannis G. Economou, Panagiotis Krokidas, Vasileios K. Michalis, Othonas A. Moultos, Ioannis N. Tsimpanogiannis, Niki Vergadou
Clathrate hydrates are crystalline inclusion compounds formed out of water and low molecular weight compounds (Sloan and Koh, 2008). The water molecules through hydrogen bonding form cages around the “guest” molecules whose presence is necessary for the stabilization of the hydrate structure. There are more than 130 known molecules that can play the role of the guest and their size and interactions with water define the type of the hydrate structure. Hydrates structures of type sI, sII, and sH are the most common ones differing mainly in the size and ratio of formed cages. The study of hydrates draws considerable interest given their importance in a number of technological and natural processes. Gas hydrates, in particular, which consist of guest molecules that are components of natural gas (primarily methane) play an important role in the oil and gas industry from a flow assurance point of view as well as a potential energy source due to the fact that methane hydrate is an abundant naturally occurring substance (Hammerschmidt, 1934; Koh, 2002). Additionally, gas hydrates are being studied as a potential environmental risk (Kvenvolden, 1999; Archer et al.,2009) and also for storage and transport applications (Papadimitriou et al.,2010; Khokhar et al.,1998).
Methane from Gas Hydrates
Published in Yatish T. Shah, Water for Energy and Fuel Production, 2014
Clathrate hydrates are solid crystalline “inclusion” compounds, which are formed when water is contacted with small hydrophobic molecules such as methane, ethane, H2S, and CO2 [1–7] (Harrison, 2010, pers. comm.) under certain pressure and temperature conditions. When the inclusion compound is a constituent of natural gas, clathrate hydrates are also referred to as gas hydrates [1–15] (Harrison, 2010, pers. comm.). The gas (or methane) hydrate composition is in general 5.75 mol of water for every molecule of methane, although this number does depend on the cage structure of the water ice. Various molecular structures of gas hydrate and clathrate are illustrated in Figure 12.1 [2]. The average density of methane hydrate is about 0.9 g/cc. Under standard conditions, the volume of methane hydrate will be 164 times less than that of methane gas [1–16] (Harrison, 2010, pers. comm.).
Fluid Properties
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
Gas clathrate hydrates (also known as gas hydrates) are crystalline inclusion compounds composed of hydrogen-bonded water cavities (host) which encage small gas (guest) molecules. Generally, a maximum of one guest molecule occupies each water cavity. Typical guest molecules that form gas hydrates are methane, ethane, carbon dioxide, and propane (see gas hydrate phase equilibria data in Table II). The structural and physical properties of gas hydrates are given in Tables Ia and Ib. Data have been taken from the references indicated.
New environmentally attractive separation technology for flue gas mixture
Published in Molecular Physics, 2018
Olamide H. Animasahun, Muhammad N. Khan, Cornelis J. Peters
Gas hydrate, also known as clathrate hydrate, is an ice-like, non-stoichiometric, crystalline substance which appears when water (host) molecules, subjected to a particular condition of temperature and pressure, form a cage-like structure around smaller gas (guest) molecules. It is important to point out the fact that hydrate formation process does not involve chemical reaction, rather it involves rearrangement (as shown in Figure 1) of water molecules in such a way as to create cages around the guest molecules. Although there are several types of gas hydrate structure that have been recognised [9], most of the common hydrates can be classified into three main groups namely: structure I (sI), structure II (sII) and structure H (sH) hydrate structures. CO2, for example, forms sI hydrate structure [9].
Can 2-methyl-2-butene and isoprene form clathrate hydrates?
Published in Petroleum Science and Technology, 2018
Kaniki Tumba, Paramespri Naidoo, Amir H. Mohammadi, Deresh Ramjugernath
Gas hydrates, or clathrate hydrates, are defined as non-stoichiometric compounds that form when appropriately sized small molecules (guests, typically gases and some small volatile liquids) are encapsulated into cage-like structures made of hydrogen-bonded water molecules (hosts) (Sloan and Koh 2008, Carroll 2009). Compounds having a molecular size less than 0.9 nm may form hydrates which, depending on the size of the entrapped molecule (s), commonly occur as structures I, II and H [1]. It is known that van der Waals forces between the guest and the host molecules (Sloan and Koh 2008) ensure the stability of the hydrate structure. Clathrate hydrates generally form under conditions of high pressures and low temperatures.
Effects of sorbitan monooleate on the interactions between cyclopentane hydrate particles and water droplets
Published in Journal of Dispersion Science and Technology, 2018
Mingzhong Li, Jinlin Tian, Chenwei Liu, Kaili Geng
Gas clathrate hydrates are crystalline structures consisting of hydrogen bonded water cavities, which entrap suitably sized gas molecules at elevated pressures and low temperatures. Hydrates can accumulate and aggregate in pipelines, which will cause pipeline blockage, resulting in failures of operation and safety issues both in personnel and in equipment.[1] With the development of science technologies, the gas and oil industry is looking at ultra-deep water exploration and production, and hence the risk of hydrate formation increases significantly and is considered to be a major flow assurance issue in oil and gas pipelines.[1]