Molecular dynamics study of morpholines at water – Carbon dioxide interfaces

Selvåg, Juri; Kvamme, Bjørn

doi:10.1016/j.fluid.2018.12.004

Cited by 13 publications

(16 citation statements)

References 46 publications

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“…Experimental data for hydrate dissociation are available but there are different types of limitations in these data as discussed elsewhere. , The differences between experimental data reported by various research groups are substantial. The calculated data plotted in Figure is in good agreement with the more recent experimental data, , which also contains detailed information on coordination numbers and other important details.…”

Section: Enthalpy Changes For Hydrate Formation and Hydrate Dissociationsupporting

confidence: 86%

“…10,39 The differences between experimental data reported by various research groups are substantial. The calculated data plotted in Figure 5 is in good agreement with the more recent experimental data, 10,40 which also contains detailed information on coordination numbers and other important details.…”

Section: Enthalpy Changes For Hydrate Formation and Hydrate Dissociationsupporting

confidence: 85%

“…One reason is the relevant (limited price) chemical like, for instance, methanol, which is solvable in water and will partly get lost in the surrounding water. Another reason is that these chemicals normally have a surfactant effect ,, and will even have a hydrate catalyst effect in small concentrations. As such, chemicals like methanol and ethanol might even promote the reformation of hydrate at some point.…”

Section: Discussionmentioning

confidence: 99%

“…Large surfactants will not be a solution to the second problem since they will clog and might also cause blocking. Small surfactants, however, will upconcentrate on the water/CO 2 interface and have three effects. ,, These surfactants will increase the transport rate of hydrate former into the water side of the interface. They will also lead to increased concentration of hydrate formers below the surfactant layer.…”

Section: Hydrate Productionmentioning

confidence: 99%

“…The surfactants need to be small so as to avoid blocking by the accumulation of surfactants. However, the molecules investigated by Selvåg et al , are poisonous and not recommended for use in actual reservoirs. These model components are used to develop reference components, which can serve as references for the desired performances for other surfactants that are environmentally friendly and inexpensive.…”

Section: Kinetics Of Formation Of New Co2/n2 Hydratementioning

confidence: 99%

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Consistent Thermodynamic Calculations for Hydrate Properties and Hydrate Phase Transitions

Kvamme¹

2020

J. Chem. Eng. Data

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Natural gas hydrates in natural sediments are dominated by methane. It is a clean source of hydrocarbon energy compared to conventional oil and gas. Most of these hydrates are created from biogenic degradation of organic material in the upper crust and are almost pure methane hydrates. Production of methane from hydrates can also be combined with steam cracking of CH 4 to H 2 and CO 2 . The produced CO 2 can be used for the continued production of CH 4 in a zero-emission cycle for producing hydrogen from CH 4 hydrates. One of the challenges in theoretical evaluation of various concepts for producing hydrates has traditionally been related to limitations in theoretical descriptions and associated thermodynamic calculations. Any theoretical concept for phase transition dynamics based on physical principles is based on the implicit couplings between thermodynamic control, mass transport dynamics, and associated heat transport dynamics. In this work, I apply a simple theory based on extensions of the classical nucleation theory (CNT). This is used as a basis for illustrating the need for a consistent thermodynamic model for free-energy-related quantities and energy quantities. The model is also utilized to address the thermodynamic control of hydrate phase transitions in various hydrate schemes, as well as in associated energy changes. Specifically, it is argued that the pressure reduction method is limited by low temperature. One of the kinetic bottlenecks in hydrate production is the slow transport of molecules across an interface of strong hydrogen bonds between liquid water and hydrate. Free-energy changes are also limited in the pressure reduction method. Using CO 2 with limited amounts of N 2 is thermodynamically feasible, in terms of both free-energy changes and released enthalpy during the formation of hydrate from the injected CO 2 /N 2 mixture. Addition of limited amounts of low-molecular-weight surfactants is needed to keep the water/CO 2 mixture interface open and not blocked by hydrate films.

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