Observation of two-step nucleation in methane hydrates

Vatamanu, Jenel; Kusalik, Peter G.

doi:10.1039/c0cp00551g

Cited by 199 publications

(375 citation statements)

References 31 publications

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“…The classical nucleation theory that assumes the spontaneous appearance of a fully ordered nucleus has been questioned and a two-stage mechanism has been suggested. Starting with the formation of an intermediate ordered state, referred to liquid-like clusters, the second step involves the structural evolution to the regular crystalline form [50,51].…”

Section: Product Designmentioning

confidence: 99%

Problems, potentials and future of industrial crystallization

Ulrich

Frohberg

2013

Front. Chem. Sci. Eng.

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This review discusses important research developments and arising challenges in the field of industrial crystallization with an emphasis on recent problems. The most relevant areas of research have been identified. These are the prediction of phase diagrams; the prediction of effects of impurities and additives; the design of fluid dynamics; the process control with process analytical technologies (PAT) tools; the polymorph and solvate screening; the stabilization of non-stable phases; and the product design. The potential of industrial crystallization in various areas is outlined and discussed with particular reference to the product quality, process design, and control. On this basis, possible future directions for research and development have been pointed out to highlight the importance of crystallization as an outstanding technique for separation, purification as well as for product design.

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Section: Product Designmentioning

confidence: 99%

Problems, potentials and future of industrial crystallization

Ulrich

Frohberg

2013

Front. Chem. Sci. Eng.

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“…[19][20][21] Theoretically, the nucleation and growth process of methane hydrate have been simulated and explored on the atomic and molecular level through molecular dynamics simulations. [23][24][25][26][27][28][29][30] The interaction between host water cages and guest molecules, 32,41 stability, diffusion and vibrations of guest molecules in water cavities of clathrate hydrates, 31,34,[38][39][40][42][43] and phase transition between ice and methane clathrates have been studied by firstprinciple calculations. 37,44 Experimentally, Raman spectra of hydrocarbon hydrates have demonstrated that the CH stretching frequency of the guest molecule is commonly (but not always) lower when in a large cage than when in a small cage [13][14][15] .…”

Section: Introductionmentioning

confidence: 99%

CH-Stretching Vibrational Trends in Natural Gas Hydrates Studied by Quantum-Chemical Computations

Liu

Ojamäe

2015

J. Phys. Chem. C

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Abstract:Vibrational Raman spectroscopy of hydrocarbon CH stretching vibrations is often used to study natural gas hydrates. In this work, CH stretching vibrational Raman spectra of hydrocarbon molecules (CH4, C2H6, C3H6, C3H8, C4H8, i-C4H10, and n-C4H10) encapsulated in the water cages (D, ID, T, P, H, and I) of the sI, sII, sH, and sK crystal phases are derived from quantum-chemical computations at the ωB97X-D/6-311++G(2d,2p) level of theory. The trends of CH stretching vibrational frequencies of hydrocarbon molecules in NGHs are found to follow the prediction by the "loose cage -tight cage" model: as the size of water cavity increases, the CH frequencies will first decrease and then increase until equal to that in gas phase. In the "tight cage" situation, the frequency will be greater than in the gas phase; in the "loose cage" situation, the frequency will be smaller or asymptotic to that in the gas phase. Furthermore, the OH stretching frequencies are sensitive to the H-bond configuration, and the varying strengths of H-bonds for different configurations are reflected by the frequency distribution in the corresponding sub-spectra.

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“…[28][29][30][31] The nucleation, growth, and dissociation process has been investigated by MD simulations in the last few years. [32][33][34][35][36][37][38] In the quantum-chemical investigations most focus has been on the interaction between host and guest molecules, [39][40] stability and diffusion of guest molecules in water cavities of clathrate hydrates, [41][42][43][44] and phase transitions. [45][46] Liu et al evaluated the performance of twenty density functional theory (DFT) methods for the description of the intermolecular interaction in methane hydrates.…”

Section: Introductionmentioning

confidence: 99%

C–C Stretching Raman Spectra and Stabilities of Hydrocarbon Molecules in Natural Gas Hydrates: A Quantum Chemical Study

Liu

Ojamäe

2014

J. Phys. Chem. A

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Abstract:The presence of specific hydrocarbon gas molecules in various types of water cavities in natural gas hydrates (NGHs) are governed by the relative stabilities of these encapsulated guest molecule ─ water cavity combinations. Using molecular quantum-chemical dispersion-corrected hybrid density functional computations, the interaction energies (ΔEhost-guest) and cohesive energies (ΔEcoh), enthalpies and Gibbs free energies for the complexes of host water cages and hydrocarbon guest molecules are calculated at the ωB97X-D/6-311++G(2d,2p) level of theory. The zero point energy effect of ΔEhost-guest and ΔEcoh is found to be quite substantial. The energetically optimal host-guest combinations for seven hydrocarbon gas molecules (CH4, C2H6, C3H6, C3H8, C4H8, i-C4H10, and n-C4H10) and various water cavities (D, ID, T, P, H and I) in NGHs are found to be CH4@D, C2H6@T, C3H6@T, C3H8@T, C4H8@T/P/H, i-C4H10@H, and n-C4H10@H, as the largest cohesive energy magnitudes will be obtained with these host-guest combinations. The stabilities of various water cavities enclosing hydrocarbon molecules are evaluated from the computed cohesive Gibbs free energies: CH4 prefer to be trapped in a ID cage; C2H6 prefer T cages; C3H6 and C3H8 prefer T and H cages; C4H8 and i-C4H10 prefer H cages; and n-C4H10 prefer I cages. The vibrational frequencies and Raman intensities of the C-C stretching vibrational modes for these seven hydrocarbon molecules enclosed in each water cavity are computed. A blue shift results after the guest molecule is trapped from gas phase into various water cages due to the host-guest interactions between the water cage and hydrocarbon molecule. The frequency shifts to the red as the radius of water cages increases. The model calculations support the view that C-C stretching vibrations of hydrocarbon molecules in the water cavities can be used as a tool to identify the types of crystal phases and guest molecules in NGHs.2

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Observation of two-step nucleation in methane hydrates

Cited by 199 publications

References 31 publications

Problems, potentials and future of industrial crystallization

Problems, potentials and future of industrial crystallization

CH-Stretching Vibrational Trends in Natural Gas Hydrates Studied by Quantum-Chemical Computations

C–C Stretching Raman Spectra and Stabilities of Hydrocarbon Molecules in Natural Gas Hydrates: A Quantum Chemical Study

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