Evidence of Structure-Performance Relation for Surfactants Used as Antiagglomerants for Hydrate Management

Bui, Tai; Phan, Anh; Monteiro, Deepak; Liu, Qiang; Ceglio, Mark; Acosta, Erick; Krishnamurthy, Pushkala; Striolo, Alberto

doi:10.1021/acs.langmuir.6b04334

Cited by 65 publications

(134 citation statements)

References 48 publications

Supporting

Mentioning

117

Contrasting

Order By: Relevance

“…Although the methane sII hydrate can be thermodynamically stable at large pressures (>100 MPa), a coexistence between sI and sII methane hydrates is generally observed at moderate pressures, as shown by experiments 30 (similar observations hold for CO 2 hydrates 31,32 ) and simulations 33 . We confirmed that in the timescale of our MD simulations the structure of sII methane hydrate remained intact, consistent with our previous study 8 . Moreover, the underlying assumption in our simulations is that the guest molecules in the hydrates do not affect the properties of the aromatics and the AAs films adsorbed on the hydrate.…”

Section: Simulation Methodologysupporting

confidence: 93%

“…This assumption is supported by the fact that the interactions between guest molecules are mainly short ranged and that on the hydrate surface there exists a 'quasi-liquid' layer of water 29,34,35 . The sII hydrate was chosen in the present study because it represents the hydrate structure formed in the rocking cell experiments used to test the performance of AAs 8 .…”

Section: Simulation Methodologymentioning

confidence: 99%

“…We analyse their behaviour at the hydrate-oil interfaces, in terms of density profiles, preferential orientation, etc. As synthetic AAs, we chose a compound, recently developed, which has shown good laboratory performance in preventing hydrate formation in light oils 8 . We quantified how the AAs film at the hydrate-oil interface is affected by the presence of the aromatics.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Synergistic and Antagonistic Effects of Aromatics on the Agglomeration of Gas Hydrates

Bui

Monteiro

et al. 2020

Sci Rep

Self Cite

View full text Add to dashboard Cite

Surfactants are often used to stabilize aqueous dispersions. For example, surfactants can be used to prevent hydrate particles from forming large plugs that can clog, and sometimes rupture pipelines. Changes in oil composition, however dramatically affect the performance of said surfactants. In this work we demonstrate that aromatic compounds, dissolved in the hydrocarbon phase, can have both synergistic and antagonistic effects, depending on their molecular structure, with respect to surfactants developed to prevent hydrate agglomerations. While monocyclic aromatics such as benzene were found to disrupt the structure of surfactant films at low surfactant density, they are expelled from the interfacial film at high surfactant density. On the other hand, polycyclic aromatics, in particular pyrene, are found to induce order and stabilize the surfactant films both at low and high surfactant density. Based on our simulation results, polycyclic aromatics could behave as natural anti-agglomerants and enhance the performance of the specific surfactants considered here, while monocyclic aromatics could, in some cases, negatively affect performance. Although limited to the conditions chosen for the present simulations, the results, explained in terms of molecular features, could be valuable for better understanding synergistic and antagonistic effects relevant for stabilizing aqueous dispersions used in diverse applications, ranging from foodstuff to processing of nanomaterials and advanced manufacturing. Dispersions are found in a variety of applications, from foodstuff to minerals processing, from biotechnology to nanotechnology, from 3D printing to advanced manufacturing. One relevant application in the energy sector concerns flow assurance. In oil and gas pipelines, the simultaneous presence of natural gas and water can lead to the formation of hydrate plugs, which could clog, and sometimes rupture the pipeline. In addition, gas hydrates can form in many offshore energy processes 1. The unintended formation of hydrate plugs can cause disruptions in oil and gas production, as well as large negative environmental consequences 1-3. Among other approaches to manage gas hydrates is the stabilization of hydrate particles in hydrocarbon dispersions. Specifically designed surfactants, known as anti-agglomerants (AAs), are optimized to prevent hydrate plug formation in flow assurance 4,5. AAs are believed to adsorb on hydrate particles by their hydrophilic head groups, while the AAs tail groups are soluble in the hydrocarbon phase. The hydrate particles, as well as water droplets, are expected to be covered by a film of AAs and oil, making them repel each other and disperse 5-9. This rich system offers an ideal platform to test our fundamental understanding regarding the stabilization of dispersions using surfactants. In fact, laboratory and field observations alike show that many phenomena determine the AAs' performance. Small changes in the molecular structure of the surfactants, changes in salt content, and in gas/oil and i...

show abstract

Section: Simulation Methodologysupporting

confidence: 93%

Section: Simulation Methodologymentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Synergistic and Antagonistic Effects of Aromatics on the Agglomeration of Gas Hydrates

Bui

Monteiro

et al. 2020

Sci Rep

Self Cite

View full text Add to dashboard Cite

show abstract

“…The former approach allows us to define unambiguously the Cartesian position of the free methane molecule with respect to the AA layer. [36]. Freezing the AA molecules does not impact the location of global and local minima, Z/Z box = 0.27 and Z/Z box = 0.36, respectively, and the FE ∆F 0 ≈ 8.5 kJ/mol.…”

Section: Thermodynamic Propertiesmentioning

confidence: 90%

Emergent Properties of Antiagglomerant Films Control Methane Transport: Implications for Hydrate Management

et al. 2018

Self Cite

View full text Add to dashboard Cite

The relationship between collective properties and performance of antiagglomerants (AAs) used in hydrate management is handled using molecular dynamics simulations and enhanced sampling techniques. A thin film of AAs adsorbed at the interface between one flat sII methane hydrate substrate and a fluid hydrocarbon mixture containing methane and n-dodecane is studied. The AA considered is a surface-active compound with a complex hydrophilic head that contains both amide and tertiary ammonium cation groups and hydrophobic tails. At a sufficiently high AA density, the interplay between the surfactant layer and the liquid hydrocarbon excludes methane from the interfacial region. In this scenario, we combine metadynamics and umbrella sampling frameworks to study accurately the free-energy landscape and the equilibrium rates associated with the transport of one methane molecule across the AA film. We observe that the local configurational changes of the liquid hydrocarbon packed within the AA film are associated with high free-energy barriers for methane transport. The time scales estimated for the transport of methane across the AA film can be, in some cases, comparable to those reported in the literature for the growth of hydrates, suggesting that one possible mechanism by which AAs delay the formation of hydrate plugs could be providing a barrier to methane transport. Considering the interplay between the structural design and collective properties of AAs might be of relevance to improve their performance in flow assurance.

show abstract

“…[32][33][34] The molecular structure of this AA film is similar to that discussed previously. 9 We expect these ordered interfacial AA films to delay the transport of methane from the hydrocarbon phase to the aqueous film near the growing hydrate, perhaps affecting hydrate growth as suggested by the results shown in Figure 3. Our results confirm that S4 AAs promote faster hydrate growth compared to S1 and S8 AAs at the early stages of growth (less than ~1.5…”

mentioning

confidence: 93%

Antiagglomerants Affect Gas Hydrate Growth

Bui

Sicard

Monteiro

et al. 2018

J. Phys. Chem. Lett.

Self Cite

View full text Add to dashboard Cite

In gas clathrate hydrates, inclusion gas molecules stabilize crystalline water structures. In addition to being fundamentally interesting, gas hydrates attract significant practical attention because of their possible application in various high-tech technologies. However, gas hydrates pose health, safety, and environmental risks when they form within oil and gas pipelines, as well as within hydrocarbon-producing and treatment facilities. Among available strategies to control and sometimes prevent hydrate plug formation is the use of surface-active low-molecular-weight compounds, known as antiagglomerants (AAs). AAs prevent the agglomeration of small hydrate particles into large plugs. It is not clear whether AAs promote or frustrate hydrate growth. We present two molecular mechanisms by which AAs promote and frustrate, respectively, hydrate growth. Our results could lead to innovative methodologies for managing hydrates in high-tech applications, as well as for securing the safety of oil and gas operations.

show abstract

Evidence of Structure-Performance Relation for Surfactants Used as Antiagglomerants for Hydrate Management

Cited by 65 publications

References 48 publications

Synergistic and Antagonistic Effects of Aromatics on the Agglomeration of Gas Hydrates

Synergistic and Antagonistic Effects of Aromatics on the Agglomeration of Gas Hydrates

Emergent Properties of Antiagglomerant Films Control Methane Transport: Implications for Hydrate Management

Antiagglomerants Affect Gas Hydrate Growth

Contact Info

Product

Resources

About