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Clathrate Hydrate (clathrate + hydrate)

Distribution by Scientific Domains
Chemistry66%

Selected Abstracts

Hydrogen Gas Sensor Based on Proton-Conducting Clathrate Hydrate,

ANGEWANDTE CHEMIE, Issue 46 2009
Jong-Ho Cha
Eisiger Detektor: Ein neues, einfaches Konzept für den Aufbau amperometrischer H2 -Sensoren beruht auf der Verwendung eines ionischen Clathrathydrats. Die physikochemischen Eigenschaften des Eis-artigen Me4NOH,5,H2O gewährleisten ein schnelles Ansprechen und kurze Erholungszeiten, selbst bei niedrigeren H2 -Konzentrationen. [source]

Hydrogen in Porous Tetrahydrofuran Clathrate Hydrate

CHEMPHYSCHEM, Issue 9 2008
Fokko M. Mulder Dr.
Abstract The lack of practical methods for hydrogen storage is still a major bottleneck in the realization of an energy economy based on hydrogen as energy carrier.1 Storage within solid-state clathrate hydrates,2,4 and in the clathrate hydrate of tetrahydrofuran (THF), has been recently reported.5,,6 In the latter case, stabilization by THF is claimed to reduce the operation pressure by several orders of magnitude close to room temperature. Here, we apply in situ neutron diffraction to show that,in contrast to previous reports[5,,6],hydrogen (deuterium) occupies the small cages of the clathrate hydrate only to 30,% (at 274 K and 90.5 bar). Such a D2 load is equivalent to 0.27 wt.,% of stored H2. In addition, we show that a surplus of D2O results in the formation of additional D2O ice Ih instead of in the production of sub-stoichiometric clathrate that is stabilized by loaded hydrogen (as was reported in ref. 6). Structure-refinement studies show that [D8]THF is dynamically disordered, while it fills each of the large cages of [D8]THF,17D2O stoichiometrically. Our results show that the clathrate hydrate takes up hydrogen rapidly at pressures between 60 and 90 bar (at about 270 K). At temperatures above ,220 K, the H-storage characteristics of the clathrate hydrate have similarities with those of surface-adsorption materials, such as nanoporous zeolites and metal,organic frameworks,7,,8 but at lower temperatures, the adsorption rates slow down because of reduced D2 diffusion between the small cages. [source]

Reversible Hydrogen Storage in Hydrogel Clathrate Hydrates

ADVANCED MATERIALS, Issue 23 2009
Fabing Su
The use of inexpensive hydrogels as supports to significantly improve H2 enclathration kinetics and capacities in THF,H2O clathrate hydrate with respect to bulk solutions is demonstrated. Polymer hydrogels give rise to significant rate and capacity enhancements for hydrogen clathrate formation with respect to unmixed bulk systems, suggesting potential for accelerated gas-storage kinetics in clathrate-based technologies. [source]

Physicochemical Properties of Ionic Clathrate Hydrates

CHEMISTRY - AN ASIAN JOURNAL, Issue 1 2010
Kyuchul Shin
Abstract Ionic clathrate hydrates are known to be formed by the enclathration of hydrophobic cations or anions into confined cages and the incorporation of counterions into the water framework. As the ionic clathrate hydrates are considered for their potential applicability in various fields, including those that involve solid electrolytes, gas separation, and gas storage, numerous studies of the ionic clathrate hydrates have been reported. This review concentrates on the physicochemical properties of the ionic clathrate hydrates and the notable characteristics of these materials regarding their potential application are addressed. [source]

Adhesion and detachment characteristics of a TBAB hydrate solid on a heat transfer surface (Effect of concentration of TBAB solutions)

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2009
Tadafumi Daitoku
Abstract In air-conditioning systems, it is desirable that the liquid,solid phase change temperature of a cool energy storage material be approximately 10°C, with respect to improving the coefficient of performance (COP). Moreover, a thermal storage material that forms slurry can realize a large heat capacity of the working fluids. A solid that adheres to the heat transfer surface forms a thermal resistance layer and significantly reduces the rate of cold storage; therefore, it is important to avoid the adhesion of a thick solid layer on the surface so as to realize efficient energy storage. Considering a harvest type cooling unit, the force required for removal of the solid phase from the heat transfer surface was investigated. Tetra-n-butylammonium bromide (TBAB) clathrate hydrate was used as a cold storage material and the effect of the TBAB solution concentration on the scraping force required to detach the adhered TBAB hydrate solid from the heat transfer surface was experimentally examined. The TBAB hydrate solids were broadly categorized into two types, and the scraping force required for removal of these two types of TBAB hydrate solid was different. The scraping force required for removal of the solid increased due to the effect of increasing the concentration of the TBAB solution. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20254 [source]

An effect of scraper shapes on detachment of solid adhered to cooling surface for formation of clathrate hydrate slurry

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2007
Tadafumi Daitoku
Abstract In air-conditioning systems, it is desirable that the liquid, solid phase change temperature of a cool energy storage material is approximately 10°C from the perspective of improving the coefficient of performance (COP). Moreover, a thermal storage material that forms slurry can realize large heat capacity of working fluids. Since the solid that adheres to the heat transfer surface forms a thermal resistance layer and remarkably reduces the rate of cold storage, it is important to avoid the adhesion of a thick solid layer on the surface so as to realize efficient energy storage. Considering a harvest type cooling unit, the force required for removing the solid phase from the heat transfer surface was studied. Tetra-n-butylammonium bromide (TBAB) clathrate hydrate was used as a cold storage material. The effect of the scraper shapes on the scraping force for detachment of the adhered solid of TBAB hydrate to the heat transfer surface was examined experimentally. The TBAB hydrate solids were categorized broadly into two kinds of solids. The scraping force of the TBAB hydrate solid on the heat transfer surface was different for the two kinds of the TBAB hydrate solids. And the scraping force of the TBAB hydrate solid formed after scraping was improved by the modifying the scraper shape. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(8): 489, 500, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20179 [source]

Reversible Hydrogen Storage in Hydrogel Clathrate Hydrates

ADVANCED MATERIALS, Issue 23 2009
Fabing Su
The use of inexpensive hydrogels as supports to significantly improve H2 enclathration kinetics and capacities in THF,H2O clathrate hydrate with respect to bulk solutions is demonstrated. Polymer hydrogels give rise to significant rate and capacity enhancements for hydrogen clathrate formation with respect to unmixed bulk systems, suggesting potential for accelerated gas-storage kinetics in clathrate-based technologies. [source]

Comparative study of hydrogen, argon, and xenon uptake into a propane hydrate

AICHE JOURNAL, Issue 10 2010
Joanne A. Abbondondola
Abstract The rate of absorption of hydrogen, argon, and xenon into a Type II propane clathrate hydrate has been studied. The propane hydrate is synthesized from 250-,m ice grains, is estimated to have a porosity of 65% and has roughly the consistency of chalk. Hydrogen is rapidly absorbed by the hydrate sample and approaches the equilibrium vapor pressure in an hour before a very slow residual absorption process ensues. For an initial hydrogen pressure of 1.5 MPa, about 4.5% of the available 512 cages are occupied by hydrogen after 1 h, and 4.9% after 18 h. In contrast, for both argon and xenon significantly more gas is absorbed by the hydrate but at a much slower rate: about 5% as fast for xenon and 1% as fast for argon. We conclude that hydrogen readily diffuses through the propane hydrate microcrystal structure, while argon and xenon are probably absorbed by growing new double hydrate while consuming the propane hydrate. Although considerably higher pressures would be required to store significant quantities of hydrogen in propane hydrate, it appears that the crystal can be loaded and emptied in relatively short times. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source]

Clathrate-hydrate formation by water spraying onto a porous metal plate exuding a hydrophobic liquid coolant

AICHE JOURNAL, Issue 4 2009
Shinya Fujita
Abstract A novel technique for producing a clathrate hydrate from a gaseous guest substance was devised and experimentally tested. This technique employs a horizontally oriented spray nozzle and a vertically oriented porous metal plate placed in opposition to each other in a guest-gas phase. Water is sprayed onto the plate while a precooled hydrophobic liquid coolant is seeping out of the plate to form a continuous film flowing down the plate surface. The coolant film is expected to sweep the heat released by hydrate formation away from the plate surface and, at the same time, to prevent the hydrate crystals from agglomerating on the surface thereby hindering the successive contact of the water spray with the coolant. A series of experiments has been performed to reveal the behavior of hydrate formation in the above scheme of guest-gas/water/coolant contact operations. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Hydrogen in Porous Tetrahydrofuran Clathrate Hydrate

CHEMPHYSCHEM, Issue 9 2008
Fokko M. Mulder Dr.
Abstract The lack of practical methods for hydrogen storage is still a major bottleneck in the realization of an energy economy based on hydrogen as energy carrier.1 Storage within solid-state clathrate hydrates,2,4 and in the clathrate hydrate of tetrahydrofuran (THF), has been recently reported.5,,6 In the latter case, stabilization by THF is claimed to reduce the operation pressure by several orders of magnitude close to room temperature. Here, we apply in situ neutron diffraction to show that,in contrast to previous reports[5,,6],hydrogen (deuterium) occupies the small cages of the clathrate hydrate only to 30,% (at 274 K and 90.5 bar). Such a D2 load is equivalent to 0.27 wt.,% of stored H2. In addition, we show that a surplus of D2O results in the formation of additional D2O ice Ih instead of in the production of sub-stoichiometric clathrate that is stabilized by loaded hydrogen (as was reported in ref. 6). Structure-refinement studies show that [D8]THF is dynamically disordered, while it fills each of the large cages of [D8]THF,17D2O stoichiometrically. Our results show that the clathrate hydrate takes up hydrogen rapidly at pressures between 60 and 90 bar (at about 270 K). At temperatures above ,220 K, the H-storage characteristics of the clathrate hydrate have similarities with those of surface-adsorption materials, such as nanoporous zeolites and metal,organic frameworks,7,,8 but at lower temperatures, the adsorption rates slow down because of reduced D2 diffusion between the small cages. [source]

Physicochemical Properties of Ionic Clathrate Hydrates

CHEMISTRY - AN ASIAN JOURNAL, Issue 1 2010
Kyuchul Shin
Abstract Ionic clathrate hydrates are known to be formed by the enclathration of hydrophobic cations or anions into confined cages and the incorporation of counterions into the water framework. As the ionic clathrate hydrates are considered for their potential applicability in various fields, including those that involve solid electrolytes, gas separation, and gas storage, numerous studies of the ionic clathrate hydrates have been reported. This review concentrates on the physicochemical properties of the ionic clathrate hydrates and the notable characteristics of these materials regarding their potential application are addressed. [source]

Hydrogen in Porous Tetrahydrofuran Clathrate Hydrate

CHEMPHYSCHEM, Issue 9 2008
Fokko M. Mulder Dr.
Abstract The lack of practical methods for hydrogen storage is still a major bottleneck in the realization of an energy economy based on hydrogen as energy carrier.1 Storage within solid-state clathrate hydrates,2,4 and in the clathrate hydrate of tetrahydrofuran (THF), has been recently reported.5,,6 In the latter case, stabilization by THF is claimed to reduce the operation pressure by several orders of magnitude close to room temperature. Here, we apply in situ neutron diffraction to show that,in contrast to previous reports[5,,6],hydrogen (deuterium) occupies the small cages of the clathrate hydrate only to 30,% (at 274 K and 90.5 bar). Such a D2 load is equivalent to 0.27 wt.,% of stored H2. In addition, we show that a surplus of D2O results in the formation of additional D2O ice Ih instead of in the production of sub-stoichiometric clathrate that is stabilized by loaded hydrogen (as was reported in ref. 6). Structure-refinement studies show that [D8]THF is dynamically disordered, while it fills each of the large cages of [D8]THF,17D2O stoichiometrically. Our results show that the clathrate hydrate takes up hydrogen rapidly at pressures between 60 and 90 bar (at about 270 K). At temperatures above ,220 K, the H-storage characteristics of the clathrate hydrate have similarities with those of surface-adsorption materials, such as nanoporous zeolites and metal,organic frameworks,7,,8 but at lower temperatures, the adsorption rates slow down because of reduced D2 diffusion between the small cages. [source]